xref: /third_party/mesa3d/src/gallium/frontends/dri/loader_dri3_helper.c

/*
 * Copyright © 2013 Keith Packard
 * Copyright © 2015 Boyan Ding
 *
 * Permission to use, copy, modify, distribute, and sell this software and its
 * documentation for any purpose is hereby granted without fee, provided that
 * the above copyright notice appear in all copies and that both that copyright
 * notice and this permission notice appear in supporting documentation, and
 * that the name of the copyright holders not be used in advertising or
 * publicity pertaining to distribution of the software without specific,
 * written prior permission.  The copyright holders make no representations
 * about the suitability of this software for any purpose.  It is provided "as
 * is" without express or implied warranty.
 *
 * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
 * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
 * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
 * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
 * OF THIS SOFTWARE.
 */

#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>

#include <X11/xshmfence.h>
#include <xcb/xcb.h>
#include <xcb/dri3.h>
#include <xcb/present.h>
#include <xcb/xfixes.h>

#include <X11/Xlib-xcb.h>

#include "loader_dri_helper.h"
#include "loader_dri3_helper.h"
#include "pipe/p_screen.h"
#include "util/log.h"
#include "util/macros.h"
#include "util/simple_mtx.h"
#include "drm-uapi/drm_fourcc.h"
#include "dri_screen.h"
#include "dri_util.h"

/**
 * A cached blit context.
 */
struct loader_dri3_blit_context {
   simple_mtx_t mtx;
   struct dri_context *ctx;
   struct dri_screen *cur_screen;
   const __DRIcoreExtension *core;
};

/* For simplicity we maintain the cache only for a single screen at a time */
static struct loader_dri3_blit_context blit_context = {
   SIMPLE_MTX_INITIALIZER, NULL
};

static void
dri3_flush_present_events(struct loader_dri3_drawable *draw);

static struct loader_dri3_buffer *
dri3_find_back_alloc(struct loader_dri3_drawable *draw);

static xcb_screen_t *
get_screen_for_root(xcb_connection_t *conn, xcb_window_t root)
{
   xcb_screen_iterator_t screen_iter =
   xcb_setup_roots_iterator(xcb_get_setup(conn));

   for (; screen_iter.rem; xcb_screen_next (&screen_iter)) {
      if (screen_iter.data->root == root)
         return screen_iter.data;
   }

   return NULL;
}

/* Error checking helpers for xcb_ functions. Use it to avoid late
 * error handling
 */
__attribute__((format(printf, 3, 4)))
static bool _check_xcb_error(xcb_connection_t *conn, xcb_void_cookie_t cookie, const char *fmt, ...) {
   xcb_generic_error_t *error;

   if ((error = xcb_request_check(conn, cookie))) {
      va_list args;
      va_start(args, fmt);
      mesa_loge_v(fmt, args);
      mesa_loge("X error: %d\n", error->error_code);
      va_end(args);
      free(error);
      return false;
   }
   return true;
}
#define check_xcb_error(cookie, name) _check_xcb_error(draw->conn, cookie, "%s:%d %s failed", __func__, __LINE__, name)

static xcb_visualtype_t *
get_xcb_visualtype_for_depth(struct loader_dri3_drawable *draw, int depth)
{
   xcb_visualtype_iterator_t visual_iter;
   xcb_screen_t *screen = draw->screen;
   xcb_depth_iterator_t depth_iter;

   if (!screen)
      return NULL;

   depth_iter = xcb_screen_allowed_depths_iterator(screen);
   for (; depth_iter.rem; xcb_depth_next(&depth_iter)) {
      if (depth_iter.data->depth != depth)
         continue;

      visual_iter = xcb_depth_visuals_iterator(depth_iter.data);
      if (visual_iter.rem)
         return visual_iter.data;
   }

   return NULL;
}

/* Sets the adaptive sync window property state. */
static void
set_adaptive_sync_property(xcb_connection_t *conn, xcb_drawable_t drawable,
                           uint32_t state)
{
   static char const name[] = "_VARIABLE_REFRESH";
   xcb_intern_atom_cookie_t cookie;
   xcb_intern_atom_reply_t* reply;
   xcb_void_cookie_t check;

   cookie = xcb_intern_atom(conn, 0, strlen(name), name);
   reply = xcb_intern_atom_reply(conn, cookie, NULL);
   if (reply == NULL)
      return;

   if (state)
      check = xcb_change_property_checked(conn, XCB_PROP_MODE_REPLACE,
                                          drawable, reply->atom,
                                          XCB_ATOM_CARDINAL, 32, 1, &state);
   else
      check = xcb_delete_property_checked(conn, drawable, reply->atom);

   xcb_discard_reply(conn, check.sequence);
   free(reply);
}

/* Get red channel mask for given drawable at given depth. */
static unsigned int
dri3_get_red_mask_for_depth(struct loader_dri3_drawable *draw, int depth)
{
   xcb_visualtype_t *visual = get_xcb_visualtype_for_depth(draw, depth);

   if (visual)
      return visual->red_mask;

   return 0;
}

/**
 * Get and lock (for use with the current thread) a dri context associated
 * with the drawable's dri screen. The context is intended to be used with
 * the dri image extension's blitImage method.
 *
 * \param draw[in]  Pointer to the drawable whose dri screen we want a
 * dri context for.
 * \return A dri context or NULL if context creation failed.
 *
 * When the caller is done with the context (even if the context returned was
 * NULL), the caller must call loader_dri3_blit_context_put.
 */
static struct dri_context *
loader_dri3_blit_context_get(struct loader_dri3_drawable *draw)
{
   simple_mtx_lock(&blit_context.mtx);

   if (blit_context.ctx && blit_context.cur_screen != draw->dri_screen_render_gpu) {
      driDestroyContext(blit_context.ctx);
      blit_context.ctx = NULL;
   }

   if (!blit_context.ctx) {
      blit_context.ctx = driCreateNewContext(draw->dri_screen_render_gpu,
                                                           NULL, NULL, NULL);
      blit_context.cur_screen = draw->dri_screen_render_gpu;
   }

   return blit_context.ctx;
}

/**
 * Release (for use with other threads) a dri context previously obtained using
 * loader_dri3_blit_context_get.
 */
static void
loader_dri3_blit_context_put(void)
{
   simple_mtx_unlock(&blit_context.mtx);
}

/**
 * Blit (parts of) the contents of a DRI image to another dri image
 *
 * \param draw[in]  The drawable which owns the images.
 * \param dst[in]  The destination image.
 * \param src[in]  The source image.
 * \param dstx0[in]  Start destination coordinate.
 * \param dsty0[in]  Start destination coordinate.
 * \param width[in]  Blit width.
 * \param height[in] Blit height.
 * \param srcx0[in]  Start source coordinate.
 * \param srcy0[in]  Start source coordinate.
 * \param flush_flag[in]  Image blit flush flag.
 * \return true iff successful.
 */
static bool
loader_dri3_blit_image(struct loader_dri3_drawable *draw,
                       struct dri_image *dst, struct dri_image *src,
                       int dstx0, int dsty0, int width, int height,
                       int srcx0, int srcy0, int flush_flag)
{
   struct dri_context *dri_context;
   bool use_blit_context = false;

   dri_context = draw->vtable->get_dri_context(draw);

   if (!dri_context || !draw->vtable->in_current_context(draw)) {
      dri_context = loader_dri3_blit_context_get(draw);
      use_blit_context = true;
      flush_flag |= __BLIT_FLAG_FLUSH;
   }

   if (dri_context)
      dri2_blit_image(dri_context, dst, src, dstx0, dsty0,
                     width, height, srcx0, srcy0,
                     width, height, flush_flag);

   if (use_blit_context)
      loader_dri3_blit_context_put();

   return dri_context != NULL;
}

static inline void
dri3_fence_reset(xcb_connection_t *c, struct loader_dri3_buffer *buffer)
{
   xshmfence_reset(buffer->shm_fence);
}

static inline void
dri3_fence_set(struct loader_dri3_buffer *buffer)
{
   xshmfence_trigger(buffer->shm_fence);
}

static inline void
dri3_fence_trigger(xcb_connection_t *c, struct loader_dri3_buffer *buffer)
{
   xcb_sync_trigger_fence(c, buffer->sync_fence);
}

static inline void
dri3_fence_await(xcb_connection_t *c, struct loader_dri3_drawable *draw,
                 struct loader_dri3_buffer *buffer)
{
   xcb_flush(c);
   xshmfence_await(buffer->shm_fence);
   if (draw) {
      mtx_lock(&draw->mtx);
      dri3_flush_present_events(draw);
      mtx_unlock(&draw->mtx);
   }
}

static void
dri3_update_max_num_back(struct loader_dri3_drawable *draw)
{
   switch (draw->last_present_mode) {
   case XCB_PRESENT_COMPLETE_MODE_FLIP: {
      if (draw->swap_interval == 0)
         draw->max_num_back = 4;
      else
         draw->max_num_back = 3;

      assert(draw->max_num_back <= LOADER_DRI3_MAX_BACK);
      break;
   }

   case XCB_PRESENT_COMPLETE_MODE_SKIP:
      break;

   default:
      draw->max_num_back = 2;
   }
}

void
loader_dri3_set_swap_interval(struct loader_dri3_drawable *draw, int interval)
{
   /* Wait all previous swap done before changing swap interval.
    *
    * This is for preventing swap out of order in the following cases:
    *   1. Change from sync swap mode (>0) to async mode (=0), so async swap occurs
    *      before previous pending sync swap.
    *   2. Change from value A to B and A > B, so the target_msc for the previous
    *      pending swap may be bigger than newer swap.
    *
    * PS. changing from value A to B and A < B won't cause swap out of order but
    * may still gets wrong target_msc value at the beginning.
    */
   if (draw->swap_interval != interval)
      loader_dri3_swapbuffer_barrier(draw);

   draw->swap_interval = interval;
}

static void
dri3_set_render_buffer(struct loader_dri3_drawable *draw, int buf_id,
                       struct loader_dri3_buffer *buffer)
{
   if (buf_id != LOADER_DRI3_FRONT_ID && !draw->buffers[buf_id])
      draw->cur_num_back++;

   draw->buffers[buf_id] = buffer;
}

/** dri3_free_render_buffer
 *
 * Free everything associated with one render buffer including pixmap, fence
 * stuff and the driver image
 */
static void
dri3_free_render_buffer(struct loader_dri3_drawable *draw,
                        int buf_id)
{
   struct loader_dri3_buffer *buffer = draw->buffers[buf_id];

   if (!buffer)
      return;

   if (buffer->own_pixmap)
      xcb_free_pixmap(draw->conn, buffer->pixmap);
   xcb_sync_destroy_fence(draw->conn, buffer->sync_fence);
   xshmfence_unmap_shm(buffer->shm_fence);
   dri2_destroy_image(buffer->image);
   if (buffer->linear_buffer)
      dri2_destroy_image(buffer->linear_buffer);
   free(buffer);

   draw->buffers[buf_id] = NULL;

   if (buf_id != LOADER_DRI3_FRONT_ID)
      draw->cur_num_back--;
}

void
loader_dri3_drawable_fini(struct loader_dri3_drawable *draw)
{
   int i;

   driDestroyDrawable(draw->dri_drawable);

   for (i = 0; i < ARRAY_SIZE(draw->buffers); i++)
      dri3_free_render_buffer(draw, i);

   if (draw->special_event) {
      xcb_void_cookie_t cookie =
         xcb_present_select_input_checked(draw->conn, draw->eid, draw->drawable,
                                          XCB_PRESENT_EVENT_MASK_NO_EVENT);

      xcb_discard_reply(draw->conn, cookie.sequence);
      xcb_unregister_for_special_event(draw->conn, draw->special_event);
   }

   if (draw->region)
      xcb_xfixes_destroy_region(draw->conn, draw->region);

   cnd_destroy(&draw->event_cnd);
   mtx_destroy(&draw->mtx);
}

int
loader_dri3_drawable_init(xcb_connection_t *conn,
                          xcb_drawable_t drawable,
                          enum loader_dri3_drawable_type type,
                          struct dri_screen *dri_screen_render_gpu,
                          struct dri_screen *dri_screen_display_gpu,
                          bool multiplanes_available,
                          bool prefer_back_buffer_reuse,
                          const struct dri_config *dri_config,
                          const struct loader_dri3_vtable *vtable,
                          struct loader_dri3_drawable *draw)
{
   xcb_get_geometry_cookie_t cookie;
   xcb_get_geometry_reply_t *reply;
   xcb_generic_error_t *error;

   draw->conn = conn;
   draw->vtable = vtable;
   draw->drawable = drawable;
   draw->type = type;
   draw->region = 0;
   draw->dri_screen_render_gpu = dri_screen_render_gpu;
   draw->dri_screen_display_gpu = dri_screen_display_gpu;
   draw->multiplanes_available = multiplanes_available;
   draw->prefer_back_buffer_reuse = prefer_back_buffer_reuse;
   draw->queries_buffer_age = false;

   draw->have_back = 0;
   draw->have_fake_front = 0;
   draw->first_init = true;
   draw->adaptive_sync = false;
   draw->adaptive_sync_active = false;
   draw->block_on_depleted_buffers = false;

   draw->cur_blit_source = -1;
   draw->back_format = DRM_FORMAT_INVALID;
   mtx_init(&draw->mtx, mtx_plain);
   cnd_init(&draw->event_cnd);

   {
      unsigned char adaptive_sync = 0;
      unsigned char block_on_depleted_buffers = 0;

      dri2GalliumConfigQueryb(draw->dri_screen_render_gpu,
                                      "adaptive_sync",
                                      &adaptive_sync);

      draw->adaptive_sync = adaptive_sync;

      dri2GalliumConfigQueryb(draw->dri_screen_render_gpu,
                                      "block_on_depleted_buffers",
                                      &block_on_depleted_buffers);

      draw->block_on_depleted_buffers = block_on_depleted_buffers;
   }

   if (!draw->adaptive_sync)
      set_adaptive_sync_property(conn, draw->drawable, false);

   draw->swap_interval = dri_get_initial_swap_interval(draw->dri_screen_render_gpu);

   dri3_update_max_num_back(draw);

   /* Create a new drawable */
   draw->dri_drawable = dri_create_drawable(dri_screen_render_gpu, dri_config,
                                            type == LOADER_DRI3_DRAWABLE_PIXMAP, draw);

   if (!draw->dri_drawable)
      return 1;

   cookie = xcb_get_geometry(draw->conn, draw->drawable);
   reply = xcb_get_geometry_reply(draw->conn, cookie, &error);
   if (reply == NULL || error != NULL) {
      driDestroyDrawable(draw->dri_drawable);
      return 1;
   }

   draw->screen = get_screen_for_root(draw->conn, reply->root);
   draw->width = reply->width;
   draw->height = reply->height;
   draw->depth = reply->depth;
   draw->vtable->set_drawable_size(draw, draw->width, draw->height);
   free(reply);

   /*
    * Make sure server has the same swap interval we do for the new
    * drawable.
    */
   loader_dri3_set_swap_interval(draw, draw->swap_interval);

   return 0;
}

/* XXX this belongs in presentproto */
#ifndef PresentWindowDestroyed
#define PresentWindowDestroyed (1 << 0)
#endif
/*
 * Process one Present event
 */
static bool
dri3_handle_present_event(struct loader_dri3_drawable *draw,
                          xcb_present_generic_event_t *ge)
{
   switch (ge->evtype) {
   case XCB_PRESENT_CONFIGURE_NOTIFY: {
      xcb_present_configure_notify_event_t *ce = (void *) ge;
      if (ce->pixmap_flags & PresentWindowDestroyed) {
         free(ge);
         return false;
      }

      draw->width = ce->width;
      draw->height = ce->height;
      draw->vtable->set_drawable_size(draw, draw->width, draw->height);
      dri_invalidate_drawable(draw->dri_drawable);
      break;
   }
   case XCB_PRESENT_COMPLETE_NOTIFY: {
      xcb_present_complete_notify_event_t *ce = (void *) ge;

      /* Compute the processed SBC number from the received 32-bit serial number
       * merged with the upper 32-bits of the sent 64-bit serial number while
       * checking for wrap.
       */
      if (ce->kind == XCB_PRESENT_COMPLETE_KIND_PIXMAP) {
         uint64_t recv_sbc = (draw->send_sbc & 0xffffffff00000000LL) | ce->serial;

         /* Only assume wraparound if that results in exactly the previous
          * SBC + 1, otherwise ignore received SBC > sent SBC (those are
          * probably from a previous loader_dri3_drawable instance) to avoid
          * calculating bogus target MSC values in loader_dri3_swap_buffers_msc
          */
         if (recv_sbc <= draw->send_sbc)
            draw->recv_sbc = recv_sbc;
         else if (recv_sbc == (draw->recv_sbc + 0x100000001ULL))
            draw->recv_sbc = recv_sbc - 0x100000000ULL;

         /* When moving from flip to copy, we assume that we can allocate in
          * a more optimal way if we don't need to cater for the display
          * controller.
          */
         if (ce->mode == XCB_PRESENT_COMPLETE_MODE_COPY &&
             draw->last_present_mode == XCB_PRESENT_COMPLETE_MODE_FLIP) {
            for (int b = 0; b < ARRAY_SIZE(draw->buffers); b++) {
               if (draw->buffers[b])
                  draw->buffers[b]->reallocate = true;
            }
         }

         /* If the server tells us that our allocation is suboptimal, we
          * reallocate once.
          */
#ifdef HAVE_X11_DRM
         if (ce->mode == XCB_PRESENT_COMPLETE_MODE_SUBOPTIMAL_COPY &&
             draw->last_present_mode != ce->mode) {
            for (int b = 0; b < ARRAY_SIZE(draw->buffers); b++) {
               if (draw->buffers[b])
                  draw->buffers[b]->reallocate = true;
            }
         }
#endif
         draw->last_present_mode = ce->mode;

         draw->ust = ce->ust;
         draw->msc = ce->msc;
      } else if (ce->serial == draw->eid) {
         draw->notify_ust = ce->ust;
         draw->notify_msc = ce->msc;
      }
      break;
   }
   case XCB_PRESENT_EVENT_IDLE_NOTIFY: {
      xcb_present_idle_notify_event_t *ie = (void *) ge;
      int b;

      for (b = 0; b < ARRAY_SIZE(draw->buffers); b++) {
         struct loader_dri3_buffer *buf = draw->buffers[b];

         if (buf && buf->pixmap == ie->pixmap)
            buf->busy = 0;
      }
      break;
   }
   }
   free(ge);
   return true;
}

static bool
dri3_wait_for_event_locked(struct loader_dri3_drawable *draw,
                           unsigned *full_sequence)
{
   xcb_generic_event_t *ev;
   xcb_present_generic_event_t *ge;

   xcb_flush(draw->conn);

   /* Only have one thread waiting for events at a time */
   if (draw->has_event_waiter) {
      cnd_wait(&draw->event_cnd, &draw->mtx);
      if (full_sequence)
         *full_sequence = draw->last_special_event_sequence;
      /* Another thread has updated the protected info, so retest. */
      return true;
   } else {
      draw->has_event_waiter = true;
      /* Allow other threads access to the drawable while we're waiting. */
      mtx_unlock(&draw->mtx);
      ev = xcb_wait_for_special_event(draw->conn, draw->special_event);
      mtx_lock(&draw->mtx);
      draw->has_event_waiter = false;
      cnd_broadcast(&draw->event_cnd);
   }
   if (!ev)
      return false;
   draw->last_special_event_sequence = ev->full_sequence;
   if (full_sequence)
      *full_sequence = ev->full_sequence;
   ge = (void *) ev;
   return dri3_handle_present_event(draw, ge);
}

/** loader_dri3_wait_for_msc
 *
 * Get the X server to send an event when the target msc/divisor/remainder is
 * reached.
 */
bool
loader_dri3_wait_for_msc(struct loader_dri3_drawable *draw,
                         int64_t target_msc,
                         int64_t divisor, int64_t remainder,
                         int64_t *ust, int64_t *msc, int64_t *sbc)
{
   xcb_void_cookie_t cookie = xcb_present_notify_msc(draw->conn,
                                                     draw->drawable,
                                                     draw->eid,
                                                     target_msc,
                                                     divisor,
                                                     remainder);
   unsigned full_sequence;

   mtx_lock(&draw->mtx);

   /* Wait for the event */
   do {
      if (!dri3_wait_for_event_locked(draw, &full_sequence)) {
         mtx_unlock(&draw->mtx);
         return false;
      }
   } while (full_sequence != cookie.sequence || draw->notify_msc < target_msc);

   *ust = draw->notify_ust;
   *msc = draw->notify_msc;
   *sbc = draw->recv_sbc;
   mtx_unlock(&draw->mtx);

   return true;
}

/** loader_dri3_wait_for_sbc
 *
 * Wait for the completed swap buffer count to reach the specified
 * target. Presumably the application knows that this will be reached with
 * outstanding complete events, or we're going to be here awhile.
 */
int
loader_dri3_wait_for_sbc(struct loader_dri3_drawable *draw,
                         int64_t target_sbc, int64_t *ust,
                         int64_t *msc, int64_t *sbc)
{
   /* From the GLX_OML_sync_control spec:
    *
    *     "If <target_sbc> = 0, the function will block until all previous
    *      swaps requested with glXSwapBuffersMscOML for that window have
    *      completed."
    */
   mtx_lock(&draw->mtx);
   if (!target_sbc)
      target_sbc = draw->send_sbc;

   while (draw->recv_sbc < target_sbc) {
      if (!dri3_wait_for_event_locked(draw, NULL)) {
         mtx_unlock(&draw->mtx);
         return 0;
      }
   }

   *ust = draw->ust;
   *msc = draw->msc;
   *sbc = draw->recv_sbc;
   mtx_unlock(&draw->mtx);
   return 1;
}

/** loader_dri3_find_back
 *
 * Find an idle back buffer. If there isn't one, then
 * wait for a present idle notify event from the X server
 */
static int
dri3_find_back(struct loader_dri3_drawable *draw, bool prefer_a_different)
{
   struct loader_dri3_buffer *buffer;
   int b;
   int max_num;
   int best_id = -1;
   uint64_t best_swap = 0;

   mtx_lock(&draw->mtx);

   if (!prefer_a_different) {
      /* Increase the likelyhood of reusing current buffer */
      dri3_flush_present_events(draw);

      /* Reuse current back buffer if it's idle */
      buffer = draw->buffers[draw->cur_back];
      if (buffer && !buffer->busy) {
         best_id = draw->cur_back;
         goto unlock;
      }
   }

   /* Check whether we need to reuse the current back buffer as new back.
    * In that case, wait until it's not busy anymore.
    */
   if (draw->cur_blit_source != -1) {
      max_num = 1;
      draw->cur_blit_source = -1;
   } else {
      max_num = LOADER_DRI3_MAX_BACK;
   }

   /* In a DRI_PRIME situation, if prefer_a_different is true, we first try
    * to find an idle buffer that is not the last used one.
    * This is useful if we receive a XCB_PRESENT_EVENT_IDLE_NOTIFY event
    * for a pixmap but it's not actually idle (eg: the DRI_PRIME blit is
    * still in progress).
    * Unigine Superposition hits this and this allows to use 2 back buffers
    * instead of reusing the same one all the time, causing the next frame
    * to wait for the copy to finish.
    */
   int current_back_id = draw->cur_back;
   do {
      /* Find idle buffer with lowest buffer age, or an unallocated slot */
      for (b = 0; b < max_num; b++) {
         int id = LOADER_DRI3_BACK_ID((b + current_back_id) % LOADER_DRI3_MAX_BACK);

         buffer = draw->buffers[id];
         if (buffer) {
            if (!buffer->busy &&
                (!prefer_a_different || id != current_back_id) &&
                (best_id == -1 || buffer->last_swap > best_swap)) {
               best_id = id;
               best_swap = buffer->last_swap;
            }
         } else if (best_id == -1 &&
                    draw->cur_num_back < draw->max_num_back) {
            best_id = id;
         }
      }

      /* Prefer re-using the same buffer over blocking */
      if (prefer_a_different && best_id == -1 &&
          !draw->buffers[LOADER_DRI3_BACK_ID(current_back_id)]->busy)
         best_id = current_back_id;
   } while (best_id == -1 && dri3_wait_for_event_locked(draw, NULL));

   if (best_id != -1)
      draw->cur_back = best_id;

unlock:
   mtx_unlock(&draw->mtx);
   return best_id;
}

static xcb_gcontext_t
dri3_drawable_gc(struct loader_dri3_drawable *draw)
{
   if (!draw->gc) {
      uint32_t v = 0;
      xcb_create_gc(draw->conn,
                    (draw->gc = xcb_generate_id(draw->conn)),
                    draw->drawable,
                    XCB_GC_GRAPHICS_EXPOSURES,
                    &v);
   }
   return draw->gc;
}


static struct loader_dri3_buffer *
dri3_back_buffer(struct loader_dri3_drawable *draw)
{
   return draw->buffers[LOADER_DRI3_BACK_ID(draw->cur_back)];
}

static struct loader_dri3_buffer *
dri3_front_buffer(struct loader_dri3_drawable *draw)
{
   return draw->buffers[LOADER_DRI3_FRONT_ID];
}

static void
dri3_copy_area(xcb_connection_t *c,
               xcb_drawable_t    src_drawable,
               xcb_drawable_t    dst_drawable,
               xcb_gcontext_t    gc,
               int16_t           src_x,
               int16_t           src_y,
               int16_t           dst_x,
               int16_t           dst_y,
               uint16_t          width,
               uint16_t          height)
{
   xcb_void_cookie_t cookie;

   cookie = xcb_copy_area_checked(c,
                                  src_drawable,
                                  dst_drawable,
                                  gc,
                                  src_x,
                                  src_y,
                                  dst_x,
                                  dst_y,
                                  width,
                                  height);
   xcb_discard_reply(c, cookie.sequence);
}

/**
 * Asks the driver to flush any queued work necessary for serializing with the
 * X command stream, and optionally the slightly more strict requirement of
 * glFlush() equivalence (which would require flushing even if nothing had
 * been drawn to a window system framebuffer, for example).
 */
void
loader_dri3_flush(struct loader_dri3_drawable *draw,
                  unsigned flags,
                  enum __DRI2throttleReason throttle_reason)
{
   /* NEED TO CHECK WHETHER CONTEXT IS NULL */
   struct dri_context *dri_context = draw->vtable->get_dri_context(draw);

   if (dri_context) {
      dri_flush(dri_context, draw->dri_drawable, flags, throttle_reason);
   }
}

void
loader_dri3_copy_sub_buffer(struct loader_dri3_drawable *draw,
                            int x, int y,
                            int width, int height,
                            bool flush)
{
   struct loader_dri3_buffer *back;
   unsigned flags = __DRI2_FLUSH_DRAWABLE;

   /* Check we have the right attachments */
   if (!draw->have_back || draw->type != LOADER_DRI3_DRAWABLE_WINDOW)
      return;

   if (flush)
      flags |= __DRI2_FLUSH_CONTEXT;
   loader_dri3_flush(draw, flags, __DRI2_THROTTLE_COPYSUBBUFFER);

   back = dri3_find_back_alloc(draw);
   if (!back)
      return;

   y = draw->height - y - height;

   if (draw->dri_screen_render_gpu != draw->dri_screen_display_gpu) {
      /* Update the linear buffer part of the back buffer
       * for the dri3_copy_area operation
       */
      (void) loader_dri3_blit_image(draw,
                                    back->linear_buffer,
                                    back->image,
                                    0, 0, back->width, back->height,
                                    0, 0, __BLIT_FLAG_FLUSH);
   }

   loader_dri3_swapbuffer_barrier(draw);
   dri3_fence_reset(draw->conn, back);
   dri3_copy_area(draw->conn,
                  back->pixmap,
                  draw->drawable,
                  dri3_drawable_gc(draw),
                  x, y, x, y, width, height);
   dri3_fence_trigger(draw->conn, back);
   /* Refresh the fake front (if present) after we just damaged the real
    * front.
    */
   if (draw->have_fake_front &&
       !loader_dri3_blit_image(draw,
                               dri3_front_buffer(draw)->image,
                               back->image,
                               x, y, width, height,
                               x, y, __BLIT_FLAG_FLUSH) &&
       draw->dri_screen_render_gpu == draw->dri_screen_display_gpu) {
      dri3_fence_reset(draw->conn, dri3_front_buffer(draw));
      dri3_copy_area(draw->conn,
                     back->pixmap,
                     dri3_front_buffer(draw)->pixmap,
                     dri3_drawable_gc(draw),
                     x, y, x, y, width, height);
      dri3_fence_trigger(draw->conn, dri3_front_buffer(draw));
      dri3_fence_await(draw->conn, NULL, dri3_front_buffer(draw));
   }
   dri3_fence_await(draw->conn, draw, back);
}

void
loader_dri3_copy_drawable(struct loader_dri3_drawable *draw,
                          xcb_drawable_t dest,
                          xcb_drawable_t src)
{
   loader_dri3_flush(draw, __DRI2_FLUSH_DRAWABLE, __DRI2_THROTTLE_COPYSUBBUFFER);

   struct loader_dri3_buffer *front = dri3_front_buffer(draw);
   if (front)
      dri3_fence_reset(draw->conn, front);

   dri3_copy_area(draw->conn,
                  src, dest,
                  dri3_drawable_gc(draw),
                  0, 0, 0, 0, draw->width, draw->height);

   if (front) {
      dri3_fence_trigger(draw->conn, front);
      dri3_fence_await(draw->conn, draw, front);
   }
}

void
loader_dri3_wait_x(struct loader_dri3_drawable *draw)
{
   struct loader_dri3_buffer *front;

   if (draw == NULL || !draw->have_fake_front)
      return;

   front = dri3_front_buffer(draw);

   loader_dri3_copy_drawable(draw, front->pixmap, draw->drawable);

   /* In the psc->is_different_gpu case, the linear buffer has been updated,
    * but not yet the tiled buffer.
    * Copy back to the tiled buffer we use for rendering.
    * Note that we don't need flushing.
    */
   if (draw->dri_screen_render_gpu != draw->dri_screen_display_gpu)
      (void) loader_dri3_blit_image(draw,
                                    front->image,
                                    front->linear_buffer,
                                    0, 0, front->width, front->height,
                                    0, 0, 0);
}

void
loader_dri3_wait_gl(struct loader_dri3_drawable *draw)
{
   struct loader_dri3_buffer *front;

   if (draw == NULL || !draw->have_fake_front)
      return;

   front = dri3_front_buffer(draw);
   /* TODO: `front` is not supposed to be NULL here, fix the actual bug
    * https://gitlab.freedesktop.org/mesa/mesa/-/issues/8982
    */
   if (!front)
      return;

   /* In the psc->is_different_gpu case, we update the linear_buffer
    * before updating the real front.
    */
   if (draw->dri_screen_render_gpu != draw->dri_screen_display_gpu)
      (void) loader_dri3_blit_image(draw,
                                    front->linear_buffer,
                                    front->image,
                                    0, 0, front->width, front->height,
                                    0, 0, __BLIT_FLAG_FLUSH);
   loader_dri3_swapbuffer_barrier(draw);
   loader_dri3_copy_drawable(draw, draw->drawable, front->pixmap);
}

/** dri3_flush_present_events
 *
 * Process any present events that have been received from the X server
 */
static void
dri3_flush_present_events(struct loader_dri3_drawable *draw)
{
   /* Check to see if any configuration changes have occurred
    * since we were last invoked
    */
   if (draw->has_event_waiter)
      return;

   if (draw->special_event) {
      xcb_generic_event_t    *ev;

      while ((ev = xcb_poll_for_special_event(draw->conn,
                                              draw->special_event)) != NULL) {
         xcb_present_generic_event_t *ge = (void *) ev;
         if (!dri3_handle_present_event(draw, ge))
            break;
      }
   }
}

/** loader_dri3_swap_buffers_msc
 *
 * Make the current back buffer visible using the present extension
 */
int64_t
loader_dri3_swap_buffers_msc(struct loader_dri3_drawable *draw,
                             int64_t target_msc, int64_t divisor,
                             int64_t remainder, unsigned flush_flags,
                             const int *rects, int n_rects,
                             bool force_copy)
{
   struct loader_dri3_buffer *back;
   int64_t ret = 0;
   bool wait_for_next_buffer = false;

   /* GLX spec:
    *   void glXSwapBuffers(Display *dpy, GLXDrawable draw);
    *   This operation is a no-op if draw was created with a non-double-buffered
    *   GLXFBConfig, or if draw is a GLXPixmap.
    *   ...
    *   GLX pixmaps may be created with a config that includes back buffers and
    *   stereoscopic buffers. However, glXSwapBuffers is ignored for these pixmaps.
    *   ...
    *   It is possible to create a pbuffer with back buffers and to swap the
    *   front and back buffers by calling glXSwapBuffers.
    *
    * EGL spec:
    *   EGLBoolean eglSwapBuffers(EGLDisplay dpy, EGLSurface surface);
    *   If surface is a back-buffered window surface, then the color buffer is
    *   copied to the native window associated with that surface. If surface is
    *   a single-buffered window, pixmap, or pbuffer surface, eglSwapBuffers has
    *   no effect.
    *
    * SwapBuffer effect:
    *       |           GLX             |           EGL            |
    *       | window | pixmap | pbuffer | window | pixmap | pbuffer|
    *-------+--------+--------+---------+--------+--------+--------+
    * single|  nop   |  nop   |   nop   |  nop   |  nop   |   nop  |
    * double|  swap  |  nop   |   swap  |  swap  |  NA    |   NA   |
    */
   if (!draw->have_back || draw->type == LOADER_DRI3_DRAWABLE_PIXMAP)
      return ret;

   draw->vtable->flush_drawable(draw, flush_flags);

   back = dri3_find_back_alloc(draw);
   /* Could only happen when error case, like display is already closed. */
   if (!back)
      return ret;

   mtx_lock(&draw->mtx);

   if (draw->adaptive_sync && !draw->adaptive_sync_active) {
      set_adaptive_sync_property(draw->conn, draw->drawable, true);
      draw->adaptive_sync_active = true;
   }

   if (draw->dri_screen_render_gpu != draw->dri_screen_display_gpu) {
      /* Update the linear buffer before presenting the pixmap */
      (void) loader_dri3_blit_image(draw,
                                    back->linear_buffer,
                                    back->image,
                                    0, 0, back->width, back->height,
                                    0, 0, __BLIT_FLAG_FLUSH);
   }

   /* If we need to preload the new back buffer, remember the source.
    * The force_copy parameter is used by EGL to attempt to preserve
    * the back buffer across a call to this function.
    */
   if (force_copy)
      draw->cur_blit_source = LOADER_DRI3_BACK_ID(draw->cur_back);

   /* Exchange the back and fake front. Even though the server knows about these
    * buffers, it has no notion of back and fake front.
    */
   if (draw->have_fake_front) {
      struct loader_dri3_buffer *tmp;

      tmp = dri3_front_buffer(draw);
      draw->buffers[LOADER_DRI3_FRONT_ID] = back;
      draw->buffers[LOADER_DRI3_BACK_ID(draw->cur_back)] = tmp;

      if (force_copy)
         draw->cur_blit_source = LOADER_DRI3_FRONT_ID;
   }

   dri3_flush_present_events(draw);

   if (draw->type == LOADER_DRI3_DRAWABLE_WINDOW) {
      dri3_fence_reset(draw->conn, back);

      /* Compute when we want the frame shown by taking the last known
       * successful MSC and adding in a swap interval for each outstanding swap
       * request. target_msc=divisor=remainder=0 means "Use glXSwapBuffers()
       * semantic"
       */
      ++draw->send_sbc;
      if (target_msc == 0 && divisor == 0 && remainder == 0)
         target_msc = draw->msc + abs(draw->swap_interval) *
                      (draw->send_sbc - draw->recv_sbc);
      else if (divisor == 0 && remainder > 0) {
         /* From the GLX_OML_sync_control spec:
          *     "If <divisor> = 0, the swap will occur when MSC becomes
          *      greater than or equal to <target_msc>."
          *
          * Note that there's no mention of the remainder.  The Present
          * extension throws BadValue for remainder != 0 with divisor == 0, so
          * just drop the passed in value.
          */
         remainder = 0;
      }

      /* From the GLX_EXT_swap_control spec
       * and the EGL 1.4 spec (page 53):
       *
       *     "If <interval> is set to a value of 0, buffer swaps are not
       *      synchronized to a video frame."
       *
       * From GLX_EXT_swap_control_tear:
       *
       *     "If <interval> is negative, the minimum number of video frames
       *      between buffer swaps is the absolute value of <interval>. In this
       *      case, if abs(<interval>) video frames have already passed from
       *      the previous swap when the swap is ready to be performed, the
       *      swap will occur without synchronization to a video frame."
       *
       * Implementation note: It is possible to enable triple buffering
       * behaviour by not using XCB_PRESENT_OPTION_ASYNC, but this should not be
       * the default.
       */
      uint32_t options = XCB_PRESENT_OPTION_NONE;
      if (draw->swap_interval <= 0)
         options |= XCB_PRESENT_OPTION_ASYNC;

      /* If we need to populate the new back, but need to reuse the back
       * buffer slot due to lack of local blit capabilities, make sure
       * the server doesn't flip and we deadlock.
       */
      if (draw->cur_blit_source != -1)
         options |= XCB_PRESENT_OPTION_COPY;
#ifdef HAVE_X11_DRM
      if (draw->multiplanes_available)
         options |= XCB_PRESENT_OPTION_SUBOPTIMAL;
#endif
      back->busy = 1;
      back->last_swap = draw->send_sbc;

      if (!draw->region) {
         draw->region = xcb_generate_id(draw->conn);
         xcb_xfixes_create_region(draw->conn, draw->region, 0, NULL);
      }

      xcb_xfixes_region_t region = 0;
      xcb_rectangle_t xcb_rects[64];

      if (n_rects > 0 && n_rects <= ARRAY_SIZE(xcb_rects)) {
         for (int i = 0; i < n_rects; i++) {
            const int *rect = &rects[i * 4];
            xcb_rects[i].x = rect[0];
            xcb_rects[i].y = draw->height - rect[1] - rect[3];
            xcb_rects[i].width = rect[2];
            xcb_rects[i].height = rect[3];
         }

         region = draw->region;
         xcb_xfixes_set_region(draw->conn, region, n_rects, xcb_rects);
      }

      xcb_present_pixmap(draw->conn,
                         draw->drawable,
                         back->pixmap,
                         (uint32_t) draw->send_sbc,
                         0,                                    /* valid */
                         region,                               /* update */
                         0,                                    /* x_off */
                         0,                                    /* y_off */
                         None,                                 /* target_crtc */
                         None,
                         back->sync_fence,
                         options,
                         target_msc,
                         divisor,
                         remainder, 0, NULL);
   } else {
      /* This can only be reached by double buffered GLXPbuffer. */
      assert(draw->type == LOADER_DRI3_DRAWABLE_PBUFFER);
      /* GLX does not have damage regions. */
      assert(n_rects == 0);

      /* For wait and buffer age usage. */
      draw->send_sbc++;
      draw->recv_sbc = back->last_swap = draw->send_sbc;

      /* Pixmap is imported as front buffer image when same GPU case, so just
       * locally blit back buffer image to it is enough. Otherwise front buffer
       * is a fake one which needs to be synced with pixmap by xserver remotely.
       */
      if (draw->dri_screen_render_gpu != draw->dri_screen_display_gpu ||
          !loader_dri3_blit_image(draw,
                                  dri3_front_buffer(draw)->image,
                                  back->image,
                                  0, 0, draw->width, draw->height,
                                  0, 0, __BLIT_FLAG_FLUSH)) {
         dri3_copy_area(draw->conn, back->pixmap,
                        draw->drawable,
                        dri3_drawable_gc(draw),
                        0, 0, 0, 0, draw->width, draw->height);
      }
   }

   ret = (int64_t) draw->send_sbc;

   /* Schedule a server-side back-preserving blit if necessary.
    * This happens iff all conditions below are satisfied:
    * a) We have a fake front,
    * b) We need to preserve the back buffer,
    * c) We don't have local blit capabilities.
    */
   if (draw->cur_blit_source != -1 &&
       draw->cur_blit_source != LOADER_DRI3_BACK_ID(draw->cur_back)) {
      struct loader_dri3_buffer *new_back = dri3_back_buffer(draw);
      struct loader_dri3_buffer *src = draw->buffers[draw->cur_blit_source];

      dri3_fence_reset(draw->conn, new_back);
      dri3_copy_area(draw->conn, src->pixmap,
                     new_back->pixmap,
                     dri3_drawable_gc(draw),
                     0, 0, 0, 0, draw->width, draw->height);
      dri3_fence_trigger(draw->conn, new_back);
      new_back->last_swap = src->last_swap;
   }

   xcb_flush(draw->conn);
   if (draw->stamp)
      ++(*draw->stamp);

   /* Waiting on a buffer is only sensible if all buffers are in use and the
    * client doesn't use the buffer age extension. In this case a client is
    * relying on it receiving back control immediately.
    *
    * As waiting on a buffer can at worst make us miss a frame the option has
    * to be enabled explicitly with the block_on_depleted_buffers DRI option.
    */
   wait_for_next_buffer = draw->cur_num_back == draw->max_num_back &&
      !draw->queries_buffer_age && draw->block_on_depleted_buffers;

   mtx_unlock(&draw->mtx);

   dri_invalidate_drawable(draw->dri_drawable);

   /* Clients that use up all available buffers usually regulate their drawing
    * through swapchain contention backpressure. In such a scenario the client
    * draws whenever control returns to it. Its event loop is slowed down only
    * by us waiting on buffers becoming available again.
    *
    * By waiting here on a new buffer and only then returning back to the client
    * we ensure the client begins drawing only when the next buffer is available
    * and not draw first and then wait a refresh cycle on the next available
    * buffer to show it. This way we can reduce the latency between what is
    * being drawn by the client and what is shown on the screen by one frame.
    */
   if (wait_for_next_buffer)
      dri3_find_back(draw, draw->prefer_back_buffer_reuse);

   return ret;
}

int
loader_dri3_query_buffer_age(struct loader_dri3_drawable *draw)
{
   struct loader_dri3_buffer *back = dri3_find_back_alloc(draw);
   int ret = 0;

   mtx_lock(&draw->mtx);
   draw->queries_buffer_age = true;
   if (back && back->last_swap != 0)
      ret = draw->send_sbc - back->last_swap + 1;
   mtx_unlock(&draw->mtx);

   return ret;
}

static uint32_t
dri3_cpp_for_fourcc(uint32_t format) {
   switch (format) {
   case DRM_FORMAT_R8:
      return 1;
   case DRM_FORMAT_ARGB1555:
   case DRM_FORMAT_RGB565:
   case DRM_FORMAT_GR88:
      return 2;
   case DRM_FORMAT_XRGB8888:
   case DRM_FORMAT_ARGB8888:
   case DRM_FORMAT_ABGR8888:
   case DRM_FORMAT_XBGR8888:
   case DRM_FORMAT_XRGB2101010:
   case DRM_FORMAT_ARGB2101010:
   case DRM_FORMAT_XBGR2101010:
   case DRM_FORMAT_ABGR2101010:
   case __DRI_IMAGE_FORMAT_SARGB8:
   case __DRI_IMAGE_FORMAT_SABGR8:
   case __DRI_IMAGE_FORMAT_SXRGB8:
      return 4;
   case DRM_FORMAT_ABGR16161616:
   case DRM_FORMAT_XBGR16161616:
   case DRM_FORMAT_XBGR16161616F:
   case DRM_FORMAT_ABGR16161616F:
      return 8;
   case DRM_FORMAT_INVALID:
   default:
      return 0;
   }
}

/* Map format of render buffer to corresponding format for the linear_buffer
 * used for sharing with the display gpu of a Prime setup (== is_different_gpu).
 * Usually linear_format == format, except for depth >= 30 formats, where
 * different gpu vendors have different preferences wrt. color channel ordering.
 */
static uint32_t
dri3_linear_format_for_format(struct loader_dri3_drawable *draw, uint32_t format)
{
   switch (format) {
      case  __DRI_IMAGE_FORMAT_XRGB2101010:
      case  __DRI_IMAGE_FORMAT_XBGR2101010:
         /* Different preferred formats for different hw */
         if (dri3_get_red_mask_for_depth(draw, 30) == 0x3ff)
            return __DRI_IMAGE_FORMAT_XBGR2101010;
         else
            return __DRI_IMAGE_FORMAT_XRGB2101010;

      case  __DRI_IMAGE_FORMAT_ARGB2101010:
      case  __DRI_IMAGE_FORMAT_ABGR2101010:
         /* Different preferred formats for different hw */
         if (dri3_get_red_mask_for_depth(draw, 30) == 0x3ff)
            return __DRI_IMAGE_FORMAT_ABGR2101010;
         else
            return __DRI_IMAGE_FORMAT_ARGB2101010;

      default:
         return format;
   }
}

#ifdef HAVE_X11_DRM
static bool
has_supported_modifier(struct loader_dri3_drawable *draw, unsigned int format,
                       uint64_t *modifiers, uint32_t count)
{
   uint64_t *supported_modifiers;
   int32_t supported_modifiers_count;
   bool found = false;
   int i, j;

   if (!dri_query_dma_buf_modifiers(draw->dri_screen_render_gpu,
                                               format, 0, NULL, NULL,
                                               &supported_modifiers_count) ||
       supported_modifiers_count == 0)
      return false;

   supported_modifiers = malloc(supported_modifiers_count * sizeof(uint64_t));
   if (!supported_modifiers)
      return false;

   dri_query_dma_buf_modifiers(draw->dri_screen_render_gpu, format,
                                          supported_modifiers_count,
                                          supported_modifiers, NULL,
                                          &supported_modifiers_count);

   for (i = 0; !found && i < supported_modifiers_count; i++) {
      for (j = 0; !found && j < count; j++) {
         if (supported_modifiers[i] == modifiers[j])
            found = true;
      }
   }

   free(supported_modifiers);
   return found;
}
#endif

/** loader_dri3_alloc_render_buffer
 *
 * Use the driver createImage function to construct a struct dri_image, then
 * get a file descriptor for that and create an X pixmap from that
 *
 * Allocate an xshmfence for synchronization
 */
static struct loader_dri3_buffer *
dri3_alloc_render_buffer(struct loader_dri3_drawable *draw, unsigned int fourcc,
                         int width, int height, int depth)
{
   struct loader_dri3_buffer *buffer;
   struct dri_image *pixmap_buffer = NULL, *linear_buffer_display_gpu = NULL;
   int format = loader_fourcc_to_image_format(fourcc);
   xcb_pixmap_t pixmap;
   xcb_sync_fence_t sync_fence;
   struct xshmfence *shm_fence;
   int buffer_fds[4], fence_fd;
   int num_planes = 0;
   uint64_t *modifiers = NULL;
   uint32_t count = 0;
   int i, mod;
   int ret;

   /* Create an xshmfence object and
    * prepare to send that to the X server
    */

   fence_fd = xshmfence_alloc_shm();
   if (fence_fd < 0)
      return NULL;

   shm_fence = xshmfence_map_shm(fence_fd);
   if (shm_fence == NULL)
      goto no_shm_fence;

   /* Allocate the image from the driver
    */
   buffer = calloc(1, sizeof *buffer);
   if (!buffer)
      goto no_buffer;

   buffer->cpp = dri3_cpp_for_fourcc(fourcc);
   if (!buffer->cpp)
      goto no_image;

   if (draw->dri_screen_render_gpu == draw->dri_screen_display_gpu) {
#ifdef HAVE_X11_DRM
      if (draw->multiplanes_available && draw->dri_screen_render_gpu->base.screen->resource_create_with_modifiers) {
         xcb_dri3_get_supported_modifiers_cookie_t mod_cookie;
         xcb_dri3_get_supported_modifiers_reply_t *mod_reply;
         xcb_generic_error_t *error = NULL;

         mod_cookie = xcb_dri3_get_supported_modifiers(draw->conn,
                                                       draw->window,
                                                       depth, buffer->cpp * 8);
         mod_reply = xcb_dri3_get_supported_modifiers_reply(draw->conn,
                                                            mod_cookie,
                                                            &error);
         if (!mod_reply)
            goto no_image;

         if (mod_reply->num_window_modifiers) {
            count = mod_reply->num_window_modifiers;
            modifiers = malloc(count * sizeof(uint64_t));
            if (!modifiers) {
               free(mod_reply);
               goto no_image;
            }

            memcpy(modifiers,
                   xcb_dri3_get_supported_modifiers_window_modifiers(mod_reply),
                   count * sizeof(uint64_t));

            if (!has_supported_modifier(draw, fourcc, modifiers, count)) {
               free(modifiers);
               count = 0;
               modifiers = NULL;
            }
         }

         if (mod_reply->num_screen_modifiers && modifiers == NULL) {
            count = mod_reply->num_screen_modifiers;
            modifiers = malloc(count * sizeof(uint64_t));
            if (!modifiers) {
               free(mod_reply);
               goto no_image;
            }

            memcpy(modifiers,
                   xcb_dri3_get_supported_modifiers_screen_modifiers(mod_reply),
                   count * sizeof(uint64_t));
         }

         free(mod_reply);
      }
#endif
      buffer->image = dri_create_image_with_modifiers(draw->dri_screen_render_gpu,
                                              width, height, format,
                                              __DRI_IMAGE_USE_SHARE |
                                              __DRI_IMAGE_USE_SCANOUT |
                                              __DRI_IMAGE_USE_BACKBUFFER |
                                              (draw->is_protected_content ?
                                               __DRI_IMAGE_USE_PROTECTED : 0),
                                              modifiers, count, buffer);
      free(modifiers);

      pixmap_buffer = buffer->image;

      if (!buffer->image)
         goto no_image;
   } else {
      buffer->image =
         dri_create_image(draw->dri_screen_render_gpu,
                                       width, height, format,
                                       NULL, 0, 0, buffer);

      if (!buffer->image)
         goto no_image;

      /* if driver name is same only then dri_screen_display_gpu is set.
       * This check is needed because for simplicity render gpu image extension
       * is also used for display gpu.
       */
      if (draw->dri_screen_display_gpu) {
         linear_buffer_display_gpu =
           dri_create_image(draw->dri_screen_display_gpu,
                                         width, height,
                                         dri3_linear_format_for_format(draw, format),
                                         NULL, 0,
                                         __DRI_IMAGE_USE_SHARE |
                                         __DRI_IMAGE_USE_LINEAR |
                                         __DRI_IMAGE_USE_BACKBUFFER |
                                         __DRI_IMAGE_USE_SCANOUT,
                                         buffer);
         pixmap_buffer = linear_buffer_display_gpu;
      }

      if (!pixmap_buffer) {
         buffer->linear_buffer =
           dri_create_image(draw->dri_screen_render_gpu,
                                        width, height,
                                        dri3_linear_format_for_format(draw, format),
                                        NULL, 0,
                                        __DRI_IMAGE_USE_SHARE |
                                        __DRI_IMAGE_USE_LINEAR |
                                        __DRI_IMAGE_USE_BACKBUFFER |
                                        __DRI_IMAGE_USE_SCANOUT |
                                        __DRI_IMAGE_USE_PRIME_BUFFER,
                                        buffer);

         pixmap_buffer = buffer->linear_buffer;
         if (!buffer->linear_buffer) {
            goto no_linear_buffer;
         }
      }
   }

   /* X want some information about the planes, so ask the image for it
    */
   if (!dri2_query_image(pixmap_buffer, __DRI_IMAGE_ATTRIB_NUM_PLANES,
                                     &num_planes))
      num_planes = 1;

   for (i = 0; i < num_planes; i++) {
      struct dri_image *image = dri2_from_planar(pixmap_buffer, i, NULL);

      if (!image) {
         assert(i == 0);
         image = pixmap_buffer;
      }

      buffer_fds[i] = -1;

      ret = dri2_query_image(image, __DRI_IMAGE_ATTRIB_FD,
                                         &buffer_fds[i]);
      ret &= dri2_query_image(image, __DRI_IMAGE_ATTRIB_STRIDE,
                                          &buffer->strides[i]);
      ret &= dri2_query_image(image, __DRI_IMAGE_ATTRIB_OFFSET,
                                          &buffer->offsets[i]);
      if (image != pixmap_buffer)
         dri2_destroy_image(image);

      if (!ret)
         goto no_buffer_attrib;
   }

   ret = dri2_query_image(pixmap_buffer,
                                     __DRI_IMAGE_ATTRIB_MODIFIER_UPPER, &mod);
   buffer->modifier = (uint64_t) mod << 32;
   ret &= dri2_query_image(pixmap_buffer,
                                       __DRI_IMAGE_ATTRIB_MODIFIER_LOWER, &mod);
   buffer->modifier |= (uint64_t)(mod & 0xffffffff);

   if (!ret)
      buffer->modifier = DRM_FORMAT_MOD_INVALID;

   if (draw->dri_screen_render_gpu != draw->dri_screen_display_gpu &&
       draw->dri_screen_display_gpu && linear_buffer_display_gpu) {
      /* The linear buffer was created in the display GPU's vram, so we
       * need to make it visible to render GPU
       */
      buffer->linear_buffer =
         dri2_from_dma_bufs(draw->dri_screen_render_gpu,
                                                  width,
                                                  height,
                                                  fourcc,
                                                  DRM_FORMAT_MOD_INVALID,
                                                  &buffer_fds[0], num_planes,
                                                  &buffer->strides[0],
                                                  &buffer->offsets[0],
                                                  0, 0, 0, 0, __DRI_IMAGE_PRIME_LINEAR_BUFFER,
                                                  NULL, buffer);
      if (!buffer->linear_buffer)
         goto no_buffer_attrib;

      dri2_destroy_image(linear_buffer_display_gpu);
   }

   pixmap = xcb_generate_id(draw->conn);

   xcb_void_cookie_t cookie_pix, cookie_fence;
#ifdef HAVE_X11_DRM
   if (draw->multiplanes_available &&
       buffer->modifier != DRM_FORMAT_MOD_INVALID) {
      cookie_pix = xcb_dri3_pixmap_from_buffers_checked(draw->conn,
                                                        pixmap,
                                                        draw->window,
                                                        num_planes,
                                                        width, height,
                                                        buffer->strides[0], buffer->offsets[0],
                                                        buffer->strides[1], buffer->offsets[1],
                                                        buffer->strides[2], buffer->offsets[2],
                                                        buffer->strides[3], buffer->offsets[3],
                                                        depth, buffer->cpp * 8,
                                                        buffer->modifier,
                                                        buffer_fds);
   } else
#endif
   {
      cookie_pix = xcb_dri3_pixmap_from_buffer_checked(draw->conn,
                                                       pixmap,
                                                       draw->drawable,
                                                       buffer->size,
                                                       width, height, buffer->strides[0],
                                                       depth, buffer->cpp * 8,
                                                       buffer_fds[0]);
   }
   cookie_fence = xcb_dri3_fence_from_fd_checked(draw->conn,
                                                 pixmap,
                                                 (sync_fence = xcb_generate_id(draw->conn)),
                                                 false,
                                                 fence_fd);
   /* Group error checking to limit round-trips. */
   if (!check_xcb_error(cookie_pix, "xcb_dri3_pixmap_from_buffer[s]"))
      goto no_buffer_attrib;
   if (!check_xcb_error(cookie_fence, "xcb_dri3_fence_from_fd"))
      goto no_buffer_attrib;

   buffer->pixmap = pixmap;
   buffer->own_pixmap = true;
   buffer->sync_fence = sync_fence;
   buffer->shm_fence = shm_fence;
   buffer->width = width;
   buffer->height = height;

   /* Mark the buffer as idle
    */
   dri3_fence_set(buffer);

   return buffer;

no_buffer_attrib:
   do {
      if (buffer_fds[i] != -1)
         close(buffer_fds[i]);
   } while (--i >= 0);
   dri2_destroy_image(pixmap_buffer);
no_linear_buffer:
   if (draw->dri_screen_render_gpu != draw->dri_screen_display_gpu)
      dri2_destroy_image(buffer->image);
no_image:
   free(buffer);
no_buffer:
   xshmfence_unmap_shm(shm_fence);
no_shm_fence:
   close(fence_fd);
   return NULL;
}

static bool
dri3_detect_drawable_is_window(struct loader_dri3_drawable *draw)
{
   /* Try to select for input on the window.
    *
    * If the drawable is a window, this will get our events
    * delivered.
    *
    * Otherwise, we'll get a BadWindow error back from this request which
    * will let us know that the drawable is a pixmap instead.
    */

   xcb_void_cookie_t cookie =
      xcb_present_select_input_checked(draw->conn, draw->eid, draw->drawable,
                                       XCB_PRESENT_EVENT_MASK_CONFIGURE_NOTIFY |
                                       XCB_PRESENT_EVENT_MASK_COMPLETE_NOTIFY |
                                       XCB_PRESENT_EVENT_MASK_IDLE_NOTIFY);

   /* Check to see if our select input call failed. If it failed with a
    * BadWindow error, then assume the drawable is a pixmap.
    */
   xcb_generic_error_t *error = xcb_request_check(draw->conn, cookie);

   if (error) {
      if (error->error_code != BadWindow) {
         free(error);
         return false;
      }
      free(error);

      /* pixmap can't get here, see driFetchDrawable(). */
      draw->type = LOADER_DRI3_DRAWABLE_PBUFFER;
      return true;
   }

   draw->type = LOADER_DRI3_DRAWABLE_WINDOW;
   return true;
}

static bool
dri3_setup_present_event(struct loader_dri3_drawable *draw)
{
   /* No need to setup for pixmap drawable. */
   if (draw->type == LOADER_DRI3_DRAWABLE_PIXMAP ||
       draw->type == LOADER_DRI3_DRAWABLE_PBUFFER)
      return true;

   draw->eid = xcb_generate_id(draw->conn);

   if (draw->type == LOADER_DRI3_DRAWABLE_WINDOW) {
      xcb_present_select_input(draw->conn, draw->eid, draw->drawable,
                               XCB_PRESENT_EVENT_MASK_CONFIGURE_NOTIFY |
                               XCB_PRESENT_EVENT_MASK_COMPLETE_NOTIFY |
                               XCB_PRESENT_EVENT_MASK_IDLE_NOTIFY);
   } else {
      assert(draw->type == LOADER_DRI3_DRAWABLE_UNKNOWN);

      if (!dri3_detect_drawable_is_window(draw))
         return false;

      if (draw->type != LOADER_DRI3_DRAWABLE_WINDOW)
         return true;
   }

   /* Create an XCB event queue to hold present events outside of the usual
    * application event queue
    */
   draw->special_event = xcb_register_for_special_xge(draw->conn,
                                                      &xcb_present_id,
                                                      draw->eid,
                                                      draw->stamp);
   return true;
}

/** loader_dri3_update_drawable
 *
 * Called the first time we use the drawable and then
 * after we receive present configure notify events to
 * track the geometry of the drawable
 */
static int
dri3_update_drawable(struct loader_dri3_drawable *draw)
{
   mtx_lock(&draw->mtx);
   if (draw->first_init) {
      xcb_get_geometry_cookie_t                 geom_cookie;
      xcb_get_geometry_reply_t                  *geom_reply;
      xcb_window_t                               root_win;

      draw->first_init = false;

      if (!dri3_setup_present_event(draw)) {
         mtx_unlock(&draw->mtx);
         return false;
      }

      geom_cookie = xcb_get_geometry(draw->conn, draw->drawable);

      geom_reply = xcb_get_geometry_reply(draw->conn, geom_cookie, NULL);

      if (!geom_reply) {
         mtx_unlock(&draw->mtx);
         return false;
      }
      draw->width = geom_reply->width;
      draw->height = geom_reply->height;
      draw->depth = geom_reply->depth;
      draw->vtable->set_drawable_size(draw, draw->width, draw->height);
      root_win = geom_reply->root;

      free(geom_reply);

      if (draw->type != LOADER_DRI3_DRAWABLE_WINDOW)
         draw->window = root_win;
      else
         draw->window = draw->drawable;
   }
   dri3_flush_present_events(draw);
   mtx_unlock(&draw->mtx);
   return true;
}

struct dri_image *
loader_dri3_create_image(xcb_connection_t *c,
                         xcb_dri3_buffer_from_pixmap_reply_t *bp_reply,
                         unsigned int fourcc,
                         struct dri_screen *dri_screen,
                         void *loaderPrivate)
{
   int                                  *fds;
   struct dri_image                           *image_planar, *ret;
   int                                  stride, offset;

   /* Get an FD for the pixmap object
    */
   fds = xcb_dri3_buffer_from_pixmap_reply_fds(c, bp_reply);

   stride = bp_reply->stride;
   offset = 0;

   /* createImageFromDmaBufs creates a wrapper struct dri_image structure which
    * can deal with multiple planes for things like Yuv images. So, once
    * we've gotten the planar wrapper, pull the single plane out of it and
    * discard the wrapper.
    */
   image_planar = dri2_from_dma_bufs(dri_screen,
                                       bp_reply->width,
                                       bp_reply->height,
                                       fourcc,
                                       DRM_FORMAT_MOD_INVALID,
                                       fds, 1,
                                       &stride, &offset,
                                       0, 0, 0, 0, 0,
                                       NULL, loaderPrivate);
   close(fds[0]);
   if (!image_planar)
      return NULL;

   ret = dri2_from_planar(image_planar, 0, loaderPrivate);

   if (!ret)
      ret = image_planar;
   else
      dri2_destroy_image(image_planar);

   return ret;
}

#ifdef HAVE_X11_DRM
struct dri_image *
loader_dri3_create_image_from_buffers(xcb_connection_t *c,
                                      xcb_dri3_buffers_from_pixmap_reply_t *bp_reply,
                                      unsigned int fourcc,
                                      struct dri_screen *dri_screen,
                                      void *loaderPrivate)
{
   struct dri_image                           *ret;
   int                                  *fds;
   uint32_t                             *strides_in, *offsets_in;
   int                                   strides[4], offsets[4];
   unsigned                              error;
   int                                   i;

   if (bp_reply->nfd > 4)
      return NULL;

   fds = xcb_dri3_buffers_from_pixmap_reply_fds(c, bp_reply);
   strides_in = xcb_dri3_buffers_from_pixmap_strides(bp_reply);
   offsets_in = xcb_dri3_buffers_from_pixmap_offsets(bp_reply);
   for (i = 0; i < bp_reply->nfd; i++) {
      strides[i] = strides_in[i];
      offsets[i] = offsets_in[i];
   }

   ret = dri2_from_dma_bufs(dri_screen,
                                       bp_reply->width,
                                       bp_reply->height,
                                       fourcc,
                                       bp_reply->modifier,
                                       fds, bp_reply->nfd,
                                       strides, offsets,
                                       0, 0, 0, 0, /* UNDEFINED */
                                       0, &error, loaderPrivate);

   for (i = 0; i < bp_reply->nfd; i++)
      close(fds[i]);

   return ret;
}
#endif

struct dri_image *
loader_dri3_get_pixmap_buffer(xcb_connection_t *conn, xcb_drawable_t pixmap, struct dri_screen *screen,
                              unsigned fourcc, bool multiplanes_available,
                              int *width, int *height, void *loader_data)
{
   struct dri_image *image;
#ifdef HAVE_X11_DRM
   if (multiplanes_available) {
      xcb_dri3_buffers_from_pixmap_cookie_t bps_cookie;
      xcb_dri3_buffers_from_pixmap_reply_t *bps_reply;

      bps_cookie = xcb_dri3_buffers_from_pixmap(conn, pixmap);
      bps_reply = xcb_dri3_buffers_from_pixmap_reply(conn, bps_cookie,
                                                     NULL);
      if (!bps_reply)
         return NULL;
      image = loader_dri3_create_image_from_buffers(conn, bps_reply, fourcc,
                                                    screen, loader_data);
      *width = bps_reply->width;
      *height = bps_reply->height;
      free(bps_reply);
   } else
#endif
   {
      xcb_dri3_buffer_from_pixmap_cookie_t bp_cookie;
      xcb_dri3_buffer_from_pixmap_reply_t *bp_reply;

      bp_cookie = xcb_dri3_buffer_from_pixmap(conn, pixmap);
      bp_reply = xcb_dri3_buffer_from_pixmap_reply(conn, bp_cookie, NULL);
      if (!bp_reply)
         return NULL;

      image = loader_dri3_create_image(conn, bp_reply, fourcc, screen,
                                               loader_data);
      *width = bp_reply->width;
      *height = bp_reply->height;
      free(bp_reply);
   }
   return image;
}

/** dri3_get_pixmap_buffer
 *
 * Get the DRM object for a pixmap from the X server and
 * wrap that with a struct dri_image structure using createImageFromDmaBufs
 */
static struct loader_dri3_buffer *
dri3_get_pixmap_buffer(struct dri_drawable *driDrawable, unsigned int fourcc,
                       enum loader_dri3_buffer_type buffer_type,
                       struct loader_dri3_drawable *draw)
{
   int                                  buf_id = loader_dri3_pixmap_buf_id(buffer_type);
   struct loader_dri3_buffer            *buffer = draw->buffers[buf_id];
   xcb_drawable_t                       pixmap;
   xcb_void_cookie_t                    cookie;
   xcb_sync_fence_t                     sync_fence;
   struct xshmfence                     *shm_fence;
   int                                  width;
   int                                  height;
   int                                  fence_fd;
   struct dri_screen                          *cur_screen;

   if (buffer)
      return buffer;

   pixmap = draw->drawable;

   buffer = calloc(1, sizeof *buffer);
   if (!buffer)
      goto no_buffer;

   fence_fd = xshmfence_alloc_shm();
   if (fence_fd < 0)
      goto no_fence;
   shm_fence = xshmfence_map_shm(fence_fd);
   if (shm_fence == NULL) {
      close (fence_fd);
      goto no_fence;
   }

   /* Get the currently-bound screen or revert to using the drawable's screen if
    * no contexts are currently bound. The latter case is at least necessary for
    * obs-studio, when using Window Capture (Xcomposite) as a Source.
    */
   cur_screen = draw->vtable->get_dri_screen();
   if (!cur_screen) {
       cur_screen = draw->dri_screen_render_gpu;
   }

   cookie = xcb_dri3_fence_from_fd_checked(draw->conn,
                                           pixmap,
                                           (sync_fence = xcb_generate_id(draw->conn)),
                                           false,
                                           fence_fd);
   if (!check_xcb_error(cookie, "xcb_dri3_fence_from_fd"))
      goto no_image;

   buffer->image = loader_dri3_get_pixmap_buffer(draw->conn, pixmap, cur_screen, fourcc,
                                                 draw->multiplanes_available, &width, &height, buffer);

   if (!buffer->image)
      goto no_image;

   buffer->pixmap = pixmap;
   buffer->own_pixmap = false;
   buffer->width = width;
   buffer->height = height;
   buffer->shm_fence = shm_fence;
   buffer->sync_fence = sync_fence;

   dri3_set_render_buffer(draw, buf_id, buffer);

   return buffer;

no_image:
   xcb_sync_destroy_fence(draw->conn, sync_fence);
   xshmfence_unmap_shm(shm_fence);
no_fence:
   free(buffer);
no_buffer:
   return NULL;
}

/** dri3_get_buffer
 *
 * Find a front or back buffer, allocating new ones as necessary
 */
static struct loader_dri3_buffer *
dri3_get_buffer(struct dri_drawable *driDrawable,
                unsigned int fourcc,
                enum loader_dri3_buffer_type buffer_type,
                struct loader_dri3_drawable *draw)
{
   struct loader_dri3_buffer *buffer;
   bool fence_await = buffer_type == loader_dri3_buffer_back;
   int buf_id;

   if (buffer_type == loader_dri3_buffer_back) {
      draw->back_format = fourcc;

      buf_id = dri3_find_back(draw, !draw->prefer_back_buffer_reuse);

      if (buf_id < 0)
         return NULL;
   } else {
      buf_id = LOADER_DRI3_FRONT_ID;
   }

   buffer = draw->buffers[buf_id];

   /* Allocate a new buffer if there isn't an old one, if that
    * old one is the wrong size, or if it's suboptimal
    */
   if (!buffer || buffer->width != draw->width ||
       buffer->height != draw->height ||
       buffer->reallocate) {
      struct loader_dri3_buffer *new_buffer;

      /* Allocate the new buffers
       */
      new_buffer = dri3_alloc_render_buffer(draw,
                                            fourcc,
                                            draw->width,
                                            draw->height,
                                            draw->depth);
      if (!new_buffer)
         return NULL;

      /* When resizing, copy the contents of the old buffer, waiting for that
       * copy to complete using our fences before proceeding
       */
      if ((buffer_type == loader_dri3_buffer_back ||
           (buffer_type == loader_dri3_buffer_front && draw->have_fake_front))
          && buffer) {

         /* Fill the new buffer with data from an old buffer */
         if (!loader_dri3_blit_image(draw,
                                     new_buffer->image,
                                     buffer->image,
                                     0, 0,
                                     MIN2(buffer->width, new_buffer->width),
                                     MIN2(buffer->height, new_buffer->height),
                                     0, 0, 0) &&
             !buffer->linear_buffer) {
            dri3_fence_reset(draw->conn, new_buffer);
            dri3_copy_area(draw->conn,
                           buffer->pixmap,
                           new_buffer->pixmap,
                           dri3_drawable_gc(draw),
                           0, 0, 0, 0,
                           draw->width, draw->height);
            dri3_fence_trigger(draw->conn, new_buffer);
            fence_await = true;
         }
         dri3_free_render_buffer(draw, buf_id);
      } else if (buffer_type == loader_dri3_buffer_front) {
         /* Fill the new fake front with data from a real front */
         loader_dri3_swapbuffer_barrier(draw);
         dri3_fence_reset(draw->conn, new_buffer);
         dri3_copy_area(draw->conn,
                        draw->drawable,
                        new_buffer->pixmap,
                        dri3_drawable_gc(draw),
                        0, 0, 0, 0,
                        draw->width, draw->height);
         dri3_fence_trigger(draw->conn, new_buffer);

         if (new_buffer->linear_buffer) {
            dri3_fence_await(draw->conn, draw, new_buffer);
            (void) loader_dri3_blit_image(draw,
                                          new_buffer->image,
                                          new_buffer->linear_buffer,
                                          0, 0, draw->width, draw->height,
                                          0, 0, 0);
         } else
            fence_await = true;
      }
      buffer = new_buffer;
      dri3_set_render_buffer(draw, buf_id, buffer);
   }

   if (fence_await)
      dri3_fence_await(draw->conn, draw, buffer);

   /*
    * Do we need to preserve the content of a previous buffer?
    *
    * Note that this blit is needed only to avoid a wait for a buffer that
    * is currently in the flip chain or being scanned out from. That's really
    * a tradeoff. If we're ok with the wait we can reduce the number of back
    * buffers to 1 for SWAP_EXCHANGE, and 1 for SWAP_COPY,
    * but in the latter case we must disallow page-flipping.
    */
   if (buffer_type == loader_dri3_buffer_back &&
       draw->cur_blit_source != -1 &&
       draw->buffers[draw->cur_blit_source] &&
       buffer != draw->buffers[draw->cur_blit_source]) {

      struct loader_dri3_buffer *source = draw->buffers[draw->cur_blit_source];

      /* Avoid flushing here. Will propably do good for tiling hardware. */
      (void) loader_dri3_blit_image(draw,
                                    buffer->image,
                                    source->image,
                                    0, 0, draw->width, draw->height,
                                    0, 0, 0);
      buffer->last_swap = source->last_swap;
      draw->cur_blit_source = -1;
   }
   /* Return the requested buffer */
   return buffer;
}

/** dri3_free_buffers
 *
 * Free the front bufffer or all of the back buffers. Used
 * when the application changes which buffers it needs
 */
static void
dri3_free_buffers(struct dri_drawable *driDrawable,
                  enum loader_dri3_buffer_type buffer_type,
                  struct loader_dri3_drawable *draw)
{
   int first_id;
   int n_id;
   int buf_id;

   switch (buffer_type) {
   case loader_dri3_buffer_back:
      first_id = LOADER_DRI3_BACK_ID(0);
      n_id = LOADER_DRI3_MAX_BACK;
      draw->cur_blit_source = -1;
      break;
   case loader_dri3_buffer_front:
      first_id = LOADER_DRI3_FRONT_ID;
      /* Don't free a fake front holding new backbuffer content. */
      n_id = (draw->cur_blit_source == LOADER_DRI3_FRONT_ID) ? 0 : 1;
      break;
   default:
      unreachable("unhandled buffer_type");
   }

   for (buf_id = first_id; buf_id < first_id + n_id; buf_id++)
      dri3_free_render_buffer(draw, buf_id);
}

/** loader_dri3_get_buffers
 *
 * The published buffer allocation API.
 * Returns all of the necessary buffers, allocating
 * as needed.
 */
int
loader_dri3_get_buffers(struct dri_drawable *driDrawable,
                        unsigned int format,
                        uint32_t *stamp,
                        void *loaderPrivate,
                        uint32_t buffer_mask,
                        struct __DRIimageList *buffers)
{
   struct loader_dri3_drawable *draw = loaderPrivate;
   struct loader_dri3_buffer   *front, *back;
   int fourcc = loader_image_format_to_fourcc(format);
   int buf_id;

   buffers->image_mask = 0;
   buffers->front = NULL;
   buffers->back = NULL;

   if (!dri3_update_drawable(draw))
      return false;

   dri3_update_max_num_back(draw);

   /* Free no longer needed back buffers */
   for (buf_id = 0; buf_id < LOADER_DRI3_MAX_BACK; buf_id++) {
      int buffer_age;

      back = draw->buffers[buf_id];
      if (!back || !back->last_swap || draw->cur_blit_source == buf_id)
         continue;

      buffer_age = draw->send_sbc - back->last_swap + 1;
      if (buffer_age > 200)
         dri3_free_render_buffer(draw, buf_id);
   }

   /* pixmaps always have front buffers.
    */
   if (draw->type != LOADER_DRI3_DRAWABLE_WINDOW)
      buffer_mask |= __DRI_IMAGE_BUFFER_FRONT;

   if (buffer_mask & __DRI_IMAGE_BUFFER_FRONT) {
      /* All pixmaps are owned by the server gpu.
       * When we use a different gpu, we can't use the pixmap
       * as buffer since it is potentially tiled a way
       * our device can't understand. In this case, use
       * a fake front buffer. Hopefully the pixmap
       * content will get synced with the fake front
       * buffer.
       */
      if (draw->type != LOADER_DRI3_DRAWABLE_WINDOW &&
          draw->dri_screen_render_gpu == draw->dri_screen_display_gpu)
         front = dri3_get_pixmap_buffer(driDrawable,
                                        fourcc,
                                        loader_dri3_buffer_front,
                                        draw);
      else
         front = dri3_get_buffer(driDrawable,
                                 fourcc,
                                 loader_dri3_buffer_front,
                                 draw);

      if (!front)
         return false;
   } else {
      dri3_free_buffers(driDrawable, loader_dri3_buffer_front, draw);
      draw->have_fake_front = 0;
      front = NULL;
   }

   if (buffer_mask & __DRI_IMAGE_BUFFER_BACK) {
      back = dri3_get_buffer(driDrawable,
                             fourcc,
                             loader_dri3_buffer_back,
                             draw);
      if (!back)
         return false;
      draw->have_back = 1;
   } else {
      dri3_free_buffers(driDrawable, loader_dri3_buffer_back, draw);
      draw->have_back = 0;
      back = NULL;
   }

   if (front) {
      buffers->image_mask |= __DRI_IMAGE_BUFFER_FRONT;
      buffers->front = front->image;
      draw->have_fake_front =
         draw->dri_screen_render_gpu != draw->dri_screen_display_gpu ||
         draw->type == LOADER_DRI3_DRAWABLE_WINDOW;
   }

   if (back) {
      buffers->image_mask |= __DRI_IMAGE_BUFFER_BACK;
      buffers->back = back->image;
   }

   draw->stamp = stamp;

   return true;
}

/** loader_dri3_update_drawable_geometry
 *
 * Get the current drawable geometry.
 */
void
loader_dri3_update_drawable_geometry(struct loader_dri3_drawable *draw)
{
   xcb_get_geometry_cookie_t geom_cookie;
   xcb_get_geometry_reply_t *geom_reply;

   geom_cookie = xcb_get_geometry(draw->conn, draw->drawable);

   geom_reply = xcb_get_geometry_reply(draw->conn, geom_cookie, NULL);

   if (geom_reply) {
      bool changed = draw->width != geom_reply->width || draw->height != geom_reply->height;
      draw->width = geom_reply->width;
      draw->height = geom_reply->height;
      if (changed) {
         draw->vtable->set_drawable_size(draw, draw->width, draw->height);
         dri_invalidate_drawable(draw->dri_drawable);
      }

      free(geom_reply);
   }
}

/**
 * Make sure the server has flushed all pending swap buffers to hardware
 * for this drawable. Ideally we'd want to send an X protocol request to
 * have the server block our connection until the swaps are complete. That
 * would avoid the potential round-trip here.
 */
void
loader_dri3_swapbuffer_barrier(struct loader_dri3_drawable *draw)
{
   int64_t ust, msc, sbc;

   (void) loader_dri3_wait_for_sbc(draw, 0, &ust, &msc, &sbc);
}

/**
 * Perform any cleanup associated with a close screen operation.
 * \param dri_screen[in,out] Pointer to struct dri_screen about to be closed.
 *
 * This function destroys the screen's cached swap context if any.
 */
void
loader_dri3_close_screen(struct dri_screen *dri_screen)
{
   simple_mtx_lock(&blit_context.mtx);
   if (blit_context.ctx && blit_context.cur_screen == dri_screen) {
      driDestroyContext(blit_context.ctx);
      blit_context.ctx = NULL;
   }
   simple_mtx_unlock(&blit_context.mtx);
}

/**
 * Find a backbuffer slot - potentially allocating a back buffer
 *
 * \param draw[in,out]  Pointer to the drawable for which to find back.
 * \return Pointer to a new back buffer or NULL if allocation failed or was
 * not mandated.
 *
 * Find a potentially new back buffer, and if it's not been allocated yet and
 * in addition needs initializing, then try to allocate and initialize it.
 */
static struct loader_dri3_buffer *
dri3_find_back_alloc(struct loader_dri3_drawable *draw)
{
   struct loader_dri3_buffer *back;
   int id;

   id = dri3_find_back(draw, false);
   if (id < 0)
      return NULL;

   back = draw->buffers[id];
   /* Allocate a new back if we haven't got one */
   if (!back && draw->back_format != DRM_FORMAT_INVALID &&
       dri3_update_drawable(draw))
      back = dri3_alloc_render_buffer(draw, draw->back_format,
                                      draw->width, draw->height, draw->depth);

   if (!back)
      return NULL;

   dri3_set_render_buffer(draw, id, back);

   /* If necessary, prefill the back with data. */
   if (draw->cur_blit_source != -1 &&
       draw->buffers[draw->cur_blit_source] &&
       back != draw->buffers[draw->cur_blit_source]) {
      struct loader_dri3_buffer *source = draw->buffers[draw->cur_blit_source];

      dri3_fence_await(draw->conn, draw, source);
      dri3_fence_await(draw->conn, draw, back);
      (void) loader_dri3_blit_image(draw,
                                    back->image,
                                    source->image,
                                    0, 0, draw->width, draw->height,
                                    0, 0, 0);
      back->last_swap = source->last_swap;
      draw->cur_blit_source = -1;
   }

   return back;
}