1 /* 2 * Copyright 2010 Google Inc. 3 * 4 * Use of this source code is governed by a BSD-style license that can be 5 * found in the LICENSE file. 6 */ 7 8 #ifndef GrClip_DEFINED 9 #define GrClip_DEFINED 10 11 #include "include/core/SkRRect.h" 12 #include "include/core/SkRect.h" 13 #include "src/gpu/ganesh/GrAppliedClip.h" 14 15 class GrDrawOp; 16 namespace skgpu { namespace v1 { class SurfaceDrawContext; }} 17 18 /** 19 * GrClip is an abstract base class for applying a clip. It constructs a clip mask if necessary, and 20 * fills out a GrAppliedClip instructing the caller on how to set up the draw state. 21 */ 22 class GrClip { 23 public: 24 enum class Effect { 25 // The clip conservatively modifies the draw's coverage but doesn't eliminate the draw 26 kClipped, 27 // The clip definitely does not modify the draw's coverage and the draw can be performed 28 // without clipping (beyond the automatic device bounds clip). 29 kUnclipped, 30 // The clip definitely eliminates all of the draw's coverage and the draw can be skipped 31 kClippedOut 32 }; 33 34 struct PreClipResult { 35 Effect fEffect; 36 SkRRect fRRect; // Ignore if 'isRRect' is false 37 GrAA fAA; // Ignore if 'isRRect' is false 38 bool fIsRRect; 39 PreClipResultPreClipResult40 PreClipResult(Effect effect) : fEffect(effect), fIsRRect(false) {} PreClipResultPreClipResult41 PreClipResult(SkRect rect, GrAA aa) : PreClipResult(SkRRect::MakeRect(rect), aa) {} PreClipResultPreClipResult42 PreClipResult(SkRRect rrect, GrAA aa) 43 : fEffect(Effect::kClipped) 44 , fRRect(rrect) 45 , fAA(aa) 46 , fIsRRect(true) {} 47 }; 48 ~GrClip()49 virtual ~GrClip() {} 50 51 /** 52 * Compute a conservative pixel bounds restricted to the given render target dimensions. 53 * The returned bounds represent the limits of pixels that can be drawn; anything outside of the 54 * bounds will be entirely clipped out. 55 */ 56 virtual SkIRect getConservativeBounds() const = 0; 57 58 /** 59 * This computes a GrAppliedClip from the clip which in turn can be used to build a GrPipeline. 60 * To determine the appropriate clipping implementation the GrClip subclass must know whether 61 * the draw will enable HW AA or uses the stencil buffer. On input 'bounds' is a conservative 62 * bounds of the draw that is to be clipped. If kClipped or kUnclipped is returned, the 'bounds' 63 * will have been updated to be contained within the clip bounds (or the device's, for wide-open 64 * clips). If kNoDraw is returned, 'bounds' and the applied clip are in an undetermined state 65 * and should be ignored (and the draw should be skipped). 66 */ 67 virtual Effect apply(GrRecordingContext*, skgpu::v1::SurfaceDrawContext*, GrDrawOp*, GrAAType, 68 GrAppliedClip*, SkRect* bounds) const = 0; 69 70 /** 71 * Perform preliminary, conservative analysis on the draw bounds as if it were provided to 72 * apply(). The results of this are returned the PreClipResults struct, where 'result.fEffect' 73 * corresponds to what 'apply' would return. If this value is kUnclipped or kNoDraw, then it 74 * can be assumed that apply() would also always result in the same Effect. 75 * 76 * If kClipped is returned, apply() may further refine the effect to kUnclipped or kNoDraw, 77 * with one exception. When 'result.fIsRRect' is true, preApply() reports the single round rect 78 * and anti-aliased state that would act as an intersection on the draw geometry. If no further 79 * action is taken to modify the draw, apply() will represent this round rect in the applied 80 * clip. 81 * 82 * When set, 'result.fRRect' will intersect with the render target bounds but may extend 83 * beyond it. If the render target bounds are the only clip effect on the draw, this is reported 84 * as kUnclipped and not as a degenerate rrect that matches the bounds. 85 */ preApply(const SkRect & drawBounds,GrAA aa)86 virtual PreClipResult preApply(const SkRect& drawBounds, GrAA aa) const { 87 SkIRect pixelBounds = GetPixelIBounds(drawBounds, aa); 88 bool outside = !SkIRect::Intersects(pixelBounds, this->getConservativeBounds()); 89 return outside ? Effect::kClippedOut : Effect::kClipped; 90 } 91 92 /** 93 * This is the maximum distance that a draw may extend beyond a clip's boundary and still count 94 * count as "on the other side". We leave some slack because floating point rounding error is 95 * likely to blame. The rationale for 1e-3 is that in the coverage case (and barring unexpected 96 * rounding), as long as coverage stays within 0.5 * 1/256 of its intended value it shouldn't 97 * have any effect on the final pixel values. 98 */ 99 constexpr static SkScalar kBoundsTolerance = 1e-3f; 100 101 /** 102 * This is the slack around a half-pixel vertex coordinate where we don't trust the GPU's 103 * rasterizer to round consistently. The rounding method is not defined in GPU specs, and 104 * rasterizer precision frequently introduces errors where a fraction < 1/2 still rounds up. 105 * 106 * For non-AA bounds edges, an edge value between 0.45 and 0.55 will round in or round out 107 * depending on what side its on. Outside of this range, the non-AA edge will snap using round() 108 */ 109 constexpr static SkScalar kHalfPixelRoundingTolerance = 5e-2f; 110 111 /** 112 * Returns true if the given draw bounds count as entirely inside the clip. 113 114 * @param innerClipBounds device-space rect fully contained by the clip 115 * @param drawBounds device-space bounds of the query region. 116 */ IsInsideClip(const SkIRect & innerClipBounds,const SkRect & drawBounds,GrAA aa)117 static bool IsInsideClip(const SkIRect& innerClipBounds, const SkRect& drawBounds, GrAA aa) { 118 return innerClipBounds.contains(GetPixelIBounds(drawBounds, aa)); 119 } 120 121 /** 122 * Returns true if the given draw bounds count as entirely outside the clip. 123 124 * @param outerClipBounds device-space rect that contains the clip 125 * @param drawBounds device-space bounds of the query region. 126 * @param aa whether or not the draw will use anti-aliasing 127 */ IsOutsideClip(const SkIRect & outerClipBounds,const SkRect & drawBounds,GrAA aa)128 static bool IsOutsideClip(const SkIRect& outerClipBounds, const SkRect& drawBounds, GrAA aa) { 129 return !SkIRect::Intersects(outerClipBounds, GetPixelIBounds(drawBounds, aa)); 130 } 131 132 // Modifies the behavior of GetPixelIBounds 133 enum class BoundsType { 134 /** 135 * Returns the tightest integer pixel bounding box such that the rasterization of a shape 136 * contained in the analytic 'bounds', using the 'aa' method, will only have non-zero 137 * coverage for pixels inside the returned bounds. Pixels outside the bounds will either 138 * not be touched, or will have 0 coverage that creates no visual change. 139 */ 140 kExterior, 141 /** 142 * Returns the largest integer pixel bounding box such that were 'bounds' to be rendered as 143 * a solid fill using 'aa', every pixel in the returned bounds will have full coverage. 144 * 145 * This effectively determines the pixels that are definitely covered by a draw or clip. It 146 * effectively performs the opposite operations as GetOuterPixelBounds. It rounds in instead 147 * of out for coverage AA and non-AA near pixel centers. 148 */ 149 kInterior 150 }; 151 152 /** 153 * Convert the analytic bounds of a shape into an integer pixel bounds, where the given aa type 154 * is used when the shape is rendered. The bounds mode can be used to query exterior or interior 155 * pixel boundaries. Interior bounds only make sense when its know that the analytic bounds 156 * are filled completely. 157 * 158 * NOTE: When using kExterior_Bounds, some coverage-AA rendering methods may still touch a pixel 159 * center outside of these bounds but will evaluate to 0 coverage. This is visually acceptable, 160 * but an additional outset of 1px should be used for dst proxy access. 161 */ 162 static SkIRect GetPixelIBounds(const SkRect& bounds, GrAA aa, 163 BoundsType mode = BoundsType::kExterior) { 164 auto roundLow = [aa](float v) { 165 v += kBoundsTolerance; 166 return aa == GrAA::kNo ? SkScalarRoundToInt(v - kHalfPixelRoundingTolerance) 167 : SkScalarFloorToInt(v); 168 }; 169 auto roundHigh = [aa](float v) { 170 v -= kBoundsTolerance; 171 return aa == GrAA::kNo ? SkScalarRoundToInt(v + kHalfPixelRoundingTolerance) 172 : SkScalarCeilToInt(v); 173 }; 174 175 if (bounds.isEmpty()) { 176 return SkIRect::MakeEmpty(); 177 } 178 179 if (mode == BoundsType::kExterior) { 180 return SkIRect::MakeLTRB(roundLow(bounds.fLeft), roundLow(bounds.fTop), 181 roundHigh(bounds.fRight), roundHigh(bounds.fBottom)); 182 } else { 183 return SkIRect::MakeLTRB(roundHigh(bounds.fLeft), roundHigh(bounds.fTop), 184 roundLow(bounds.fRight), roundLow(bounds.fBottom)); 185 } 186 } 187 188 /** 189 * Returns true if the given rect counts as aligned with pixel boundaries. 190 */ IsPixelAligned(const SkRect & rect)191 static bool IsPixelAligned(const SkRect& rect) { 192 return SkScalarAbs(SkScalarRoundToScalar(rect.fLeft) - rect.fLeft) <= kBoundsTolerance && 193 SkScalarAbs(SkScalarRoundToScalar(rect.fTop) - rect.fTop) <= kBoundsTolerance && 194 SkScalarAbs(SkScalarRoundToScalar(rect.fRight) - rect.fRight) <= kBoundsTolerance && 195 SkScalarAbs(SkScalarRoundToScalar(rect.fBottom) - rect.fBottom) <= kBoundsTolerance; 196 } 197 }; 198 199 200 /** 201 * GrHardClip never uses coverage FPs. It can only enforce the clip using the already-existing 202 * stencil buffer contents and/or fixed-function state like scissor. Always aliased if MSAA is off. 203 */ 204 class GrHardClip : public GrClip { 205 public: 206 /** 207 * Sets the appropriate hardware state modifications on GrAppliedHardClip that will implement 208 * the clip. On input 'bounds' is a conservative bounds of the draw that is to be clipped. After 209 * return 'bounds' has been intersected with a conservative bounds of the clip. 210 */ 211 virtual Effect apply(GrAppliedHardClip* out, SkIRect* bounds) const = 0; 212 213 private: apply(GrRecordingContext *,skgpu::v1::SurfaceDrawContext *,GrDrawOp *,GrAAType aa,GrAppliedClip * out,SkRect * bounds)214 Effect apply(GrRecordingContext*, 215 skgpu::v1::SurfaceDrawContext*, 216 GrDrawOp*, 217 GrAAType aa, 218 GrAppliedClip* out, 219 SkRect* bounds) const final { 220 SkIRect pixelBounds = GetPixelIBounds(*bounds, GrAA(aa != GrAAType::kNone)); 221 Effect effect = this->apply(&out->hardClip(), &pixelBounds); 222 bounds->intersect(SkRect::Make(pixelBounds)); 223 return effect; 224 } 225 }; 226 227 #endif 228