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1 /*
2  * Mesa 3-D graphics library
3  *
4  * Copyright (C) 2010 LunarG Inc.
5  *
6  * Permission is hereby granted, free of charge, to any person obtaining a
7  * copy of this software and associated documentation files (the "Software"),
8  * to deal in the Software without restriction, including without limitation
9  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
10  * and/or sell copies of the Software, and to permit persons to whom the
11  * Software is furnished to do so, subject to the following conditions:
12  *
13  * The above copyright notice and this permission notice shall be included
14  * in all copies or substantial portions of the Software.
15  *
16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
17  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
20  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
21  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
22  * OTHER DEALINGS IN THE SOFTWARE.
23  *
24  * Authors:
25  *    Chia-I Wu <olv@lunarg.com>
26  */
27 
28 #include "util/u_memory.h"
29 #include "util/u_inlines.h"
30 #include "util/u_atomic.h"
31 #include "state_tracker/st_gl_api.h" /* for st_gl_api_create */
32 #include "pipe/p_state.h"
33 
34 #include "stw_st.h"
35 #include "stw_device.h"
36 #include "stw_framebuffer.h"
37 #include "stw_pixelformat.h"
38 #include "stw_winsys.h"
39 
40 #ifdef GALLIUM_ZINK
41 #include "kopper_interface.h"
42 #endif
43 
44 struct stw_st_framebuffer {
45    struct st_framebuffer_iface base;
46 
47    struct stw_framebuffer *fb;
48    struct st_visual stvis;
49 
50    struct pipe_resource *textures[ST_ATTACHMENT_COUNT];
51    struct pipe_resource *msaa_textures[ST_ATTACHMENT_COUNT];
52    struct pipe_resource *back_texture;
53    bool needs_fake_front;
54    unsigned texture_width, texture_height;
55    unsigned texture_mask;
56 };
57 
58 static uint32_t stwfb_ID = 0;
59 
60 /**
61  * Is the given mutex held by the calling thread?
62  */
63 bool
stw_own_mutex(const CRITICAL_SECTION * cs)64 stw_own_mutex(const CRITICAL_SECTION *cs)
65 {
66    // We can't compare OwningThread with our thread handle/id (see
67    // http://stackoverflow.com/a/12675635 ) but we can compare with the
68    // OwningThread member of a critical section we know we own.
69    CRITICAL_SECTION dummy;
70    InitializeCriticalSection(&dummy);
71    EnterCriticalSection(&dummy);
72    if (0)
73       _debug_printf("%p %p\n", cs->OwningThread, dummy.OwningThread);
74    bool ret = cs->OwningThread == dummy.OwningThread;
75    LeaveCriticalSection(&dummy);
76    DeleteCriticalSection(&dummy);
77    return ret;
78 }
79 
80 static void
stw_pipe_blit(struct pipe_context * pipe,struct pipe_resource * dst,struct pipe_resource * src)81 stw_pipe_blit(struct pipe_context *pipe,
82               struct pipe_resource *dst,
83               struct pipe_resource *src)
84 {
85    struct pipe_blit_info blit;
86 
87    if (!dst || !src)
88       return;
89 
90    /* From the GL spec, version 4.2, section 4.1.11 (Additional Multisample
91     *  Fragment Operations):
92     *
93     *      If a framebuffer object is not bound, after all operations have
94     *      been completed on the multisample buffer, the sample values for
95     *      each color in the multisample buffer are combined to produce a
96     *      single color value, and that value is written into the
97     *      corresponding color buffers selected by DrawBuffer or
98     *      DrawBuffers. An implementation may defer the writing of the color
99     *      buffers until a later time, but the state of the framebuffer must
100     *      behave as if the color buffers were updated as each fragment was
101     *      processed. The method of combination is not specified. If the
102     *      framebuffer contains sRGB values, then it is recommended that the
103     *      an average of sample values is computed in a linearized space, as
104     *      for blending (see section 4.1.7).
105     *
106     * In other words, to do a resolve operation in a linear space, we have
107     * to set sRGB formats if the original resources were sRGB, so don't use
108     * util_format_linear.
109     */
110 
111    memset(&blit, 0, sizeof(blit));
112    blit.dst.resource = dst;
113    blit.dst.box.width = dst->width0;
114    blit.dst.box.height = dst->height0;
115    blit.dst.box.depth = 1;
116    blit.dst.format = dst->format;
117    blit.src.resource = src;
118    blit.src.box.width = src->width0;
119    blit.src.box.height = src->height0;
120    blit.src.box.depth = 1;
121    blit.src.format = src->format;
122    blit.mask = PIPE_MASK_RGBA;
123    blit.filter = PIPE_TEX_FILTER_NEAREST;
124 
125    pipe->blit(pipe, &blit);
126 }
127 
128 #ifdef GALLIUM_ZINK
129 static void
stw_st_fill_private_loader_data(struct stw_st_framebuffer * stwfb,struct kopper_loader_info * out)130 stw_st_fill_private_loader_data(struct stw_st_framebuffer *stwfb, struct kopper_loader_info *out)
131 {
132    out->win32.sType = VK_STRUCTURE_TYPE_WIN32_SURFACE_CREATE_INFO_KHR;
133    out->win32.pNext = NULL;
134    out->win32.flags = 0;
135    out->win32.hinstance = GetModuleHandle(NULL);
136    out->win32.hwnd = stwfb->fb->hWnd;
137    out->has_alpha = true;
138 }
139 #endif
140 /**
141  * Remove outdated textures and create the requested ones.
142  */
143 static void
stw_st_framebuffer_validate_locked(struct st_context_iface * stctx,struct st_framebuffer_iface * stfb,unsigned width,unsigned height,unsigned mask)144 stw_st_framebuffer_validate_locked(struct st_context_iface *stctx,
145                                    struct st_framebuffer_iface *stfb,
146                                    unsigned width, unsigned height,
147                                    unsigned mask)
148 {
149    struct stw_st_framebuffer *stwfb = stw_st_framebuffer(stfb);
150    struct pipe_resource templ;
151    unsigned i;
152 
153    memset(&templ, 0, sizeof(templ));
154    templ.target = PIPE_TEXTURE_2D;
155    templ.width0 = width;
156    templ.height0 = height;
157    templ.depth0 = 1;
158    templ.array_size = 1;
159    templ.last_level = 0;
160 
161    /* As of now, the only stw_winsys_framebuffer implementation is
162     * d3d12_wgl_framebuffer and it doesn't support front buffer
163     * drawing. A fake front texture is needed to handle that scenario.
164     * For MSAA, we just need to make sure that the back buffer also
165     * exists, so we can blt to it during flush_frontbuffer. */
166    if (mask & ST_ATTACHMENT_FRONT_LEFT_MASK &&
167        stwfb->fb->winsys_framebuffer) {
168       if (stwfb->stvis.samples <= 1)
169          stwfb->needs_fake_front = true;
170       else
171          mask |= ST_ATTACHMENT_BACK_LEFT_MASK;
172    }
173 
174    /* remove outdated textures */
175    if (stwfb->texture_width != width || stwfb->texture_height != height) {
176       for (i = 0; i < ST_ATTACHMENT_COUNT; i++) {
177          pipe_resource_reference(&stwfb->msaa_textures[i], NULL);
178          pipe_resource_reference(&stwfb->textures[i], NULL);
179       }
180       pipe_resource_reference(&stwfb->back_texture, NULL);
181 
182       if (stwfb->fb->winsys_framebuffer) {
183          templ.nr_samples = templ.nr_storage_samples = 1;
184          templ.format = stwfb->stvis.color_format;
185          stwfb->fb->winsys_framebuffer->resize(stwfb->fb->winsys_framebuffer, stctx->pipe, &templ);
186       }
187    }
188 
189    for (i = 0; i < ST_ATTACHMENT_COUNT; i++) {
190       enum pipe_format format;
191       unsigned bind;
192 
193       /* the texture already exists or not requested */
194       if (stwfb->textures[i] || !(mask & (1 << i))) {
195          /* remember the texture */
196          if (stwfb->textures[i])
197             mask |= (1 << i);
198          continue;
199       }
200 
201       switch (i) {
202       case ST_ATTACHMENT_FRONT_LEFT:
203       case ST_ATTACHMENT_BACK_LEFT:
204          format = stwfb->stvis.color_format;
205          bind = PIPE_BIND_DISPLAY_TARGET |
206                 PIPE_BIND_SAMPLER_VIEW |
207                 PIPE_BIND_RENDER_TARGET;
208 
209 #ifdef GALLIUM_ZINK
210          if (stw_dev->zink) {
211             /* Covers the case where we have already created a drawable that
212              * then got swapped and now we have to make a new back buffer.
213              * For Zink, we just alias the front buffer in that case.
214              */
215             if (i == ST_ATTACHMENT_BACK_LEFT && stwfb->textures[ST_ATTACHMENT_FRONT_LEFT])
216                bind &= ~PIPE_BIND_DISPLAY_TARGET;
217          }
218 #endif
219 
220          break;
221       case ST_ATTACHMENT_DEPTH_STENCIL:
222          format = stwfb->stvis.depth_stencil_format;
223          bind = PIPE_BIND_DEPTH_STENCIL;
224          break;
225       default:
226          format = PIPE_FORMAT_NONE;
227          break;
228       }
229 
230       if (format != PIPE_FORMAT_NONE) {
231          templ.format = format;
232 
233          if (bind != PIPE_BIND_DEPTH_STENCIL && stwfb->stvis.samples > 1) {
234             templ.bind = PIPE_BIND_SAMPLER_VIEW | PIPE_BIND_RENDER_TARGET;
235             templ.nr_samples = templ.nr_storage_samples =
236                stwfb->stvis.samples;
237 
238             stwfb->msaa_textures[i] =
239                stw_dev->screen->resource_create(stw_dev->screen, &templ);
240          }
241 
242          templ.bind = bind;
243          templ.nr_samples = templ.nr_storage_samples = 1;
244 
245 #ifdef GALLIUM_ZINK
246          if (stw_dev->zink &&
247              i < ST_ATTACHMENT_DEPTH_STENCIL &&
248              stw_dev->screen->resource_create_drawable) {
249 
250             struct kopper_loader_info loader_info;
251             void *data;
252 
253             if (bind & PIPE_BIND_DISPLAY_TARGET) {
254                stw_st_fill_private_loader_data(stwfb, &loader_info);
255                data = &loader_info;
256             } else
257                data = stwfb->textures[ST_ATTACHMENT_FRONT_LEFT];
258 
259             assert(data);
260             stwfb->textures[i] =
261                stw_dev->screen->resource_create_drawable(stw_dev->screen,
262                                                              &templ,
263                                                              data);
264          } else {
265 #endif
266             if (stwfb->fb->winsys_framebuffer)
267                stwfb->textures[i] = stwfb->fb->winsys_framebuffer->get_resource(
268                   stwfb->fb->winsys_framebuffer, i);
269             else
270                stwfb->textures[i] =
271                   stw_dev->screen->resource_create(stw_dev->screen, &templ);
272 #ifdef GALLIUM_ZINK
273          }
274 #endif
275       }
276    }
277 
278    /* When a fake front buffer is needed for drawing, we use the back buffer
279     * as it reduces the number of blits needed:
280     *
281     *   - When flushing the front buffer, we only need to swap the real buffers
282     *   - When swapping buffers, we can safely overwrite the fake front buffer
283     *     as it is now invalid anyway.
284     *
285     * A new texture is created to store the back buffer content.
286     */
287    if (stwfb->needs_fake_front) {
288       if (!stwfb->back_texture) {
289          templ.format = stwfb->stvis.color_format;
290          templ.bind = PIPE_BIND_SAMPLER_VIEW | PIPE_BIND_RENDER_TARGET;
291          templ.nr_samples = templ.nr_storage_samples = 1;
292 
293          stwfb->back_texture =
294             stw_dev->screen->resource_create(stw_dev->screen, &templ);
295 
296          /* TODO Only blit if there is something currently drawn on the back buffer */
297          stw_pipe_blit(stctx->pipe,
298                        stwfb->back_texture,
299                        stwfb->textures[ST_ATTACHMENT_BACK_LEFT]);
300       }
301 
302       /* Copying front texture content to fake front texture (back texture) */
303       stw_pipe_blit(stctx->pipe,
304                     stwfb->textures[ST_ATTACHMENT_BACK_LEFT],
305                     stwfb->textures[ST_ATTACHMENT_FRONT_LEFT]);
306    }
307 
308    stwfb->texture_width = width;
309    stwfb->texture_height = height;
310    stwfb->texture_mask = mask;
311 }
312 
313 static bool
stw_st_framebuffer_validate(struct st_context_iface * stctx,struct st_framebuffer_iface * stfb,const enum st_attachment_type * statts,unsigned count,struct pipe_resource ** out)314 stw_st_framebuffer_validate(struct st_context_iface *stctx,
315                             struct st_framebuffer_iface *stfb,
316                             const enum st_attachment_type *statts,
317                             unsigned count,
318                             struct pipe_resource **out)
319 {
320    struct stw_st_framebuffer *stwfb = stw_st_framebuffer(stfb);
321    unsigned statt_mask, i;
322 
323    statt_mask = 0x0;
324    for (i = 0; i < count; i++)
325       statt_mask |= 1 << statts[i];
326 
327    stw_framebuffer_lock(stwfb->fb);
328 
329    if (stwfb->fb->must_resize || stwfb->needs_fake_front || (statt_mask & ~stwfb->texture_mask)) {
330       stw_st_framebuffer_validate_locked(stctx, &stwfb->base,
331             stwfb->fb->width, stwfb->fb->height, statt_mask);
332       stwfb->fb->must_resize = FALSE;
333    }
334 
335    struct pipe_resource **textures =
336       stwfb->stvis.samples > 1 ? stwfb->msaa_textures
337                                : stwfb->textures;
338 
339    for (i = 0; i < count; i++) {
340       struct pipe_resource *texture = NULL;
341 
342       if (stwfb->needs_fake_front) {
343          if (statts[i] == ST_ATTACHMENT_FRONT_LEFT)
344             texture = textures[ST_ATTACHMENT_BACK_LEFT]; /* Fake front buffer */
345          else if (statts[i] == ST_ATTACHMENT_BACK_LEFT)
346             texture = stwfb->back_texture;
347       } else {
348          texture = textures[statts[i]];
349       }
350       pipe_resource_reference(&out[i], texture);
351    }
352 
353    stw_framebuffer_unlock(stwfb->fb);
354 
355    return true;
356 }
357 
358 struct notify_before_flush_cb_args {
359    struct st_context_iface *stctx;
360    struct stw_st_framebuffer *stwfb;
361    unsigned flags;
362 };
363 
364 static void
notify_before_flush_cb(void * _args)365 notify_before_flush_cb(void* _args)
366 {
367    struct notify_before_flush_cb_args *args = (struct notify_before_flush_cb_args *) _args;
368    struct st_context_iface *st = args->stctx;
369    struct pipe_context *pipe = st->pipe;
370 
371    if (args->stwfb->stvis.samples > 1) {
372       /* Resolve the MSAA back buffer. */
373       stw_pipe_blit(pipe,
374                     args->stwfb->textures[ST_ATTACHMENT_BACK_LEFT],
375                     args->stwfb->msaa_textures[ST_ATTACHMENT_BACK_LEFT]);
376 
377       /* FRONT_LEFT is resolved in flush_frontbuffer. */
378    } else if (args->stwfb->back_texture) {
379       /* Fake front texture is dirty ?? */
380       stw_pipe_blit(pipe,
381                     args->stwfb->textures[ST_ATTACHMENT_BACK_LEFT],
382                     args->stwfb->back_texture);
383    }
384 
385    if (args->stwfb->textures[ST_ATTACHMENT_BACK_LEFT])
386       pipe->flush_resource(pipe, args->stwfb->textures[ST_ATTACHMENT_BACK_LEFT]);
387 }
388 
389 void
stw_st_flush(struct st_context_iface * stctx,struct st_framebuffer_iface * stfb,unsigned flags)390 stw_st_flush(struct st_context_iface *stctx,
391              struct st_framebuffer_iface *stfb,
392              unsigned flags)
393 {
394    struct stw_st_framebuffer *stwfb = stw_st_framebuffer(stfb);
395    struct notify_before_flush_cb_args args;
396    struct pipe_fence_handle **pfence = NULL;
397    struct pipe_fence_handle *fence = NULL;
398 
399    args.stctx = stctx;
400    args.stwfb = stwfb;
401    args.flags = flags;
402 
403    if (flags & ST_FLUSH_END_OF_FRAME && !stwfb->fb->winsys_framebuffer)
404       flags |= ST_FLUSH_WAIT;
405 
406    if (flags & ST_FLUSH_WAIT)
407       pfence = &fence;
408    stctx->flush(stctx, flags, pfence, notify_before_flush_cb, &args);
409 }
410 
411 /**
412  * Present an attachment of the framebuffer.
413  */
414 static bool
stw_st_framebuffer_present_locked(HDC hdc,struct st_context_iface * stctx,struct st_framebuffer_iface * stfb,enum st_attachment_type statt)415 stw_st_framebuffer_present_locked(HDC hdc,
416                                   struct st_context_iface *stctx,
417                                   struct st_framebuffer_iface *stfb,
418                                   enum st_attachment_type statt)
419 {
420    struct stw_st_framebuffer *stwfb = stw_st_framebuffer(stfb);
421    struct pipe_resource *resource;
422 
423    assert(stw_own_mutex(&stwfb->fb->mutex));
424 
425    resource = stwfb->textures[statt];
426    if (resource) {
427       stw_framebuffer_present_locked(hdc, stwfb->fb, resource);
428    }
429    else {
430       stw_framebuffer_unlock(stwfb->fb);
431    }
432 
433    assert(!stw_own_mutex(&stwfb->fb->mutex));
434 
435    return true;
436 }
437 
438 static bool
stw_st_framebuffer_flush_front(struct st_context_iface * stctx,struct st_framebuffer_iface * stfb,enum st_attachment_type statt)439 stw_st_framebuffer_flush_front(struct st_context_iface *stctx,
440                                struct st_framebuffer_iface *stfb,
441                                enum st_attachment_type statt)
442 {
443    struct stw_st_framebuffer *stwfb = stw_st_framebuffer(stfb);
444    struct pipe_context *pipe = stctx->pipe;
445    bool ret;
446    HDC hDC;
447    bool need_swap_textures = false;
448 
449    if (statt != ST_ATTACHMENT_FRONT_LEFT)
450       return false;
451 
452    stw_framebuffer_lock(stwfb->fb);
453 
454    /* Resolve the front buffer. */
455    if (stwfb->stvis.samples > 1) {
456       enum st_attachment_type blit_target = statt;
457       if (stwfb->fb->winsys_framebuffer) {
458          blit_target = ST_ATTACHMENT_BACK_LEFT;
459          need_swap_textures = true;
460       }
461 
462       stw_pipe_blit(pipe, stwfb->textures[blit_target],
463                     stwfb->msaa_textures[statt]);
464    } else if (stwfb->needs_fake_front) {
465       /* fake front texture is now invalid */
466       p_atomic_inc(&stwfb->base.stamp);
467       need_swap_textures = true;
468    }
469 
470    if (need_swap_textures) {
471       struct pipe_resource *ptex = stwfb->textures[ST_ATTACHMENT_FRONT_LEFT];
472       stwfb->textures[ST_ATTACHMENT_FRONT_LEFT] = stwfb->textures[ST_ATTACHMENT_BACK_LEFT];
473       stwfb->textures[ST_ATTACHMENT_BACK_LEFT] = ptex;
474    }
475 
476    if (stwfb->textures[statt])
477       pipe->flush_resource(pipe, stwfb->textures[statt]);
478 
479    pipe->flush(pipe, NULL, 0);
480 
481    /* We must not cache HDCs anywhere, as they can be invalidated by the
482     * application, or screen resolution changes. */
483 
484    hDC = GetDC(stwfb->fb->hWnd);
485 
486    ret = stw_st_framebuffer_present_locked(hDC, stctx, &stwfb->base, statt);
487 
488    ReleaseDC(stwfb->fb->hWnd, hDC);
489 
490    return ret;
491 }
492 
493 /**
494  * Create a framebuffer interface.
495  */
496 struct st_framebuffer_iface *
stw_st_create_framebuffer(struct stw_framebuffer * fb)497 stw_st_create_framebuffer(struct stw_framebuffer *fb)
498 {
499    struct stw_st_framebuffer *stwfb;
500 
501    stwfb = CALLOC_STRUCT(stw_st_framebuffer);
502    if (!stwfb)
503       return NULL;
504 
505    stwfb->fb = fb;
506    stwfb->stvis = fb->pfi->stvis;
507    stwfb->base.ID = p_atomic_inc_return(&stwfb_ID);
508    stwfb->base.state_manager = stw_dev->smapi;
509 
510    stwfb->base.visual = &stwfb->stvis;
511    p_atomic_set(&stwfb->base.stamp, 1);
512    stwfb->base.flush_front = stw_st_framebuffer_flush_front;
513    stwfb->base.validate = stw_st_framebuffer_validate;
514 
515    return &stwfb->base;
516 }
517 
518 /**
519  * Destroy a framebuffer interface.
520  */
521 void
stw_st_destroy_framebuffer_locked(struct st_framebuffer_iface * stfb)522 stw_st_destroy_framebuffer_locked(struct st_framebuffer_iface *stfb)
523 {
524    struct stw_st_framebuffer *stwfb = stw_st_framebuffer(stfb);
525    int i;
526 
527    for (i = 0; i < ST_ATTACHMENT_COUNT; i++) {
528       pipe_resource_reference(&stwfb->msaa_textures[i], NULL);
529       pipe_resource_reference(&stwfb->textures[i], NULL);
530    }
531    pipe_resource_reference(&stwfb->back_texture, NULL);
532 
533    /* Notify the st manager that the framebuffer interface is no
534     * longer valid.
535     */
536    stw_dev->stapi->destroy_drawable(stw_dev->stapi, &stwfb->base);
537 
538    FREE(stwfb);
539 }
540 
541 /**
542  * Swap the buffers of the given framebuffer.
543  */
544 bool
stw_st_swap_framebuffer_locked(HDC hdc,struct st_context_iface * stctx,struct st_framebuffer_iface * stfb)545 stw_st_swap_framebuffer_locked(HDC hdc, struct st_context_iface *stctx,
546                                struct st_framebuffer_iface *stfb)
547 {
548    struct stw_st_framebuffer *stwfb = stw_st_framebuffer(stfb);
549    unsigned front = ST_ATTACHMENT_FRONT_LEFT, back = ST_ATTACHMENT_BACK_LEFT;
550    struct pipe_resource *ptex;
551    unsigned mask;
552 
553    /* swap the textures */
554    ptex = stwfb->textures[front];
555    stwfb->textures[front] = stwfb->textures[back];
556    stwfb->textures[back] = ptex;
557 
558    /* swap msaa_textures */
559    ptex = stwfb->msaa_textures[front];
560    stwfb->msaa_textures[front] = stwfb->msaa_textures[back];
561    stwfb->msaa_textures[back] = ptex;
562 
563 
564    /* Fake front texture is now dirty */
565    if (stwfb->needs_fake_front)
566       p_atomic_inc(&stwfb->base.stamp);
567 
568    /* convert to mask */
569    front = 1 << front;
570    back = 1 << back;
571 
572    /* swap the bits in mask */
573    mask = stwfb->texture_mask & ~(front | back);
574    if (stwfb->texture_mask & front)
575       mask |= back;
576    if (stwfb->texture_mask & back)
577       mask |= front;
578    stwfb->texture_mask = mask;
579 
580    front = ST_ATTACHMENT_FRONT_LEFT;
581    return stw_st_framebuffer_present_locked(hdc, stctx, &stwfb->base, front);
582 }
583 
584 
585 /**
586  * Return the pipe_resource that correspond to given buffer.
587  */
588 struct pipe_resource *
stw_get_framebuffer_resource(struct st_framebuffer_iface * stfb,enum st_attachment_type att)589 stw_get_framebuffer_resource(struct st_framebuffer_iface *stfb,
590                              enum st_attachment_type att)
591 {
592    struct stw_st_framebuffer *stwfb = stw_st_framebuffer(stfb);
593    return stwfb->textures[att];
594 }
595 
596 
597 /**
598  * Create an st_api of the gallium frontend.
599  */
600 struct st_api *
stw_st_create_api(void)601 stw_st_create_api(void)
602 {
603    return st_gl_api_create();
604 }
605