Prevent overflow in length() in GLCircularRRectEffect

src/gpu/effects/GrRRectEffect.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrRRectEffect.h"
 
 #include "GrConvexPolyEffect.h"
@@ skipping 144 matching lines @@
     const char *rectName;
     const char *radiusPlusHalfName;
     // The inner rect is the rrect bounds inset by the radius. Its left, top, right, and bottom
     // edges correspond to components x, y, z, and w, respectively. When a side of the rrect has
     // only rectangular corners, that side's value corresponds to the rect edge's value outset by
     // half a pixel.
     fInnerRectUniform = uniformHandler->addUniform(GrGLSLUniformHandler::kFragment_Visibility,
                                                    kVec4f_GrSLType, kDefault_GrSLPrecision,
                                                    "innerRect",
                                                    &rectName);
+    // x is (r + .5) and y is 1/(r + .5)
     fRadiusPlusHalfUniform = uniformHandler->addUniform(GrGLSLUniformHandler::kFragment_Visibility,
-                                                        kFloat_GrSLType, kDefault_GrSLPrecision,
+                                                        kVec2f_GrSLType, kDefault_GrSLPrecision,
                                                         "radiusPlusHalf",
                                                         &radiusPlusHalfName);
 
+    // If we're on a device with a "real" mediump then the length calculation could overflow.
+    SkString clampedCircleDistance;
+    if (args.fGLSLCaps->floatPrecisionVaries()) {
+        clampedCircleDistance.printf("clamp(%s.x * (1.0 - length(dxy * %s.y)), 0.0, 1.0);",
+                                     radiusPlusHalfName, radiusPlusHalfName);
+    } else {
+        clampedCircleDistance.printf("clamp(%s.x - length(dxy), 0.0, 1.0);", radiusPlusHalfName);
+    }
+
     GrGLSLFragmentBuilder* fragBuilder = args.fFragBuilder;
     const char* fragmentPos = fragBuilder->fragmentPosition();
     // At each quarter-circle corner we compute a vector that is the offset of the fragment position
     // from the circle center. The vector is pinned in x and y to be in the quarter-plane relevant
     // to that corner. This means that points near the interior near the rrect top edge will have
     // a vector that points straight up for both the TL left and TR corners. Computing an
     // alpha from this vector at either the TR or TL corner will give the correct result. Similarly,
     // fragments near the other three edges will get the correct AA. Fragments in the interior of
     // the rrect will have a (0,0) vector at all four corners. So long as the radius > 0.5 they will
     // correctly produce an alpha value of 1 at all four corners. We take the min of all the alphas.
     // The code below is a simplified version of the above that performs maxs on the vector
     // components before computing distances and alpha values so that only one distance computation
     // need be computed to determine the min alpha.
     //
     // For the cases where one half of the rrect is rectangular we drop one of the x or y
     // computations, compute a separate rect edge alpha for the rect side, and mul the two computed
     // alphas together.
     switch (crre.getCircularCornerFlags()) {
         case CircularRRectEffect::kAll_CornerFlags:
-            fragBuilder->codeAppendf("\t\tvec2 dxy0 = %s.xy - %s.xy;\n", rectName, fragmentPos);
-            fragBuilder->codeAppendf("\t\tvec2 dxy1 = %s.xy - %s.zw;\n", fragmentPos, rectName);
-            fragBuilder->codeAppend("\t\tvec2 dxy = max(max(dxy0, dxy1), 0.0);\n");
-            fragBuilder->codeAppendf("\t\tfloat alpha = clamp(%s - length(dxy), 0.0, 1.0);\n",
-                                   radiusPlusHalfName);
+            fragBuilder->codeAppendf("vec2 dxy0 = %s.xy - %s.xy;", rectName, fragmentPos);
+            fragBuilder->codeAppendf("vec2 dxy1 = %s.xy - %s.zw;", fragmentPos, rectName);
+            fragBuilder->codeAppend("vec2 dxy = max(max(dxy0, dxy1), 0.0);");
+            fragBuilder->codeAppendf("float alpha = %s;", clampedCircleDistance.c_str());
             break;
         case CircularRRectEffect::kTopLeft_CornerFlag:
-            fragBuilder->codeAppendf("\t\tvec2 dxy = max(%s.xy - %s.xy, 0.0);\n",
+            fragBuilder->codeAppendf("vec2 dxy = max(%s.xy - %s.xy, 0.0);",
                                      rectName, fragmentPos);
-            fragBuilder->codeAppendf("\t\tfloat rightAlpha = clamp(%s.z - %s.x, 0.0, 1.0);\n",
+            fragBuilder->codeAppendf("float rightAlpha = clamp(%s.z - %s.x, 0.0, 1.0);",
                                      rectName, fragmentPos);
-            fragBuilder->codeAppendf("\t\tfloat bottomAlpha = clamp(%s.w - %s.y, 0.0, 1.0);\n",
+            fragBuilder->codeAppendf("float bottomAlpha = clamp(%s.w - %s.y, 0.0, 1.0);",
                                      rectName, fragmentPos);
-            fragBuilder->codeAppendf(
-                "\t\tfloat alpha = bottomAlpha * rightAlpha * clamp(%s - length(dxy), 0.0, 1.0);\n",
-                radiusPlusHalfName);
+            fragBuilder->codeAppendf("float alpha = bottomAlpha * rightAlpha * %s;",
+                                     clampedCircleDistance.c_str());
             break;
         case CircularRRectEffect::kTopRight_CornerFlag:
-            fragBuilder->codeAppendf("\t\tvec2 dxy = max(vec2(%s.x - %s.z, %s.y - %s.y), 0.0);\n",
+            fragBuilder->codeAppendf("vec2 dxy = max(vec2(%s.x - %s.z, %s.y - %s.y), 0.0);",
                                      fragmentPos, rectName, rectName, fragmentPos);
-            fragBuilder->codeAppendf("\t\tfloat leftAlpha = clamp(%s.x - %s.x, 0.0, 1.0);\n",
+            fragBuilder->codeAppendf("float leftAlpha = clamp(%s.x - %s.x, 0.0, 1.0);",
                                      fragmentPos, rectName);
-            fragBuilder->codeAppendf("\t\tfloat bottomAlpha = clamp(%s.w - %s.y, 0.0, 1.0);\n",
+            fragBuilder->codeAppendf("float bottomAlpha = clamp(%s.w - %s.y, 0.0, 1.0);",
                                      rectName, fragmentPos);
-            fragBuilder->codeAppendf(
-                "\t\tfloat alpha = bottomAlpha * leftAlpha * clamp(%s - length(dxy), 0.0, 1.0);\n",
-                radiusPlusHalfName);
+            fragBuilder->codeAppendf("float alpha = bottomAlpha * leftAlpha * %s;",
+                                     clampedCircleDistance.c_str());
             break;
         case CircularRRectEffect::kBottomRight_CornerFlag:
-            fragBuilder->codeAppendf("\t\tvec2 dxy = max(%s.xy - %s.zw, 0.0);\n",
+            fragBuilder->codeAppendf("vec2 dxy = max(%s.xy - %s.zw, 0.0);",
                                      fragmentPos, rectName);
-            fragBuilder->codeAppendf("\t\tfloat leftAlpha = clamp(%s.x - %s.x, 0.0, 1.0);\n",
+            fragBuilder->codeAppendf("float leftAlpha = clamp(%s.x - %s.x, 0.0, 1.0);",
                                      fragmentPos, rectName);
-            fragBuilder->codeAppendf("\t\tfloat topAlpha = clamp(%s.y - %s.y, 0.0, 1.0);\n",
+            fragBuilder->codeAppendf("float topAlpha = clamp(%s.y - %s.y, 0.0, 1.0);",
                                      fragmentPos, rectName);
-            fragBuilder->codeAppendf(
-                "\t\tfloat alpha = topAlpha * leftAlpha * clamp(%s - length(dxy), 0.0, 1.0);\n",
-                radiusPlusHalfName);
+            fragBuilder->codeAppendf("float alpha = topAlpha * leftAlpha * %s;",
+                                     clampedCircleDistance.c_str());
             break;
         case CircularRRectEffect::kBottomLeft_CornerFlag:
-            fragBuilder->codeAppendf("\t\tvec2 dxy = max(vec2(%s.x - %s.x, %s.y - %s.w), 0.0);\n",
+            fragBuilder->codeAppendf("vec2 dxy = max(vec2(%s.x - %s.x, %s.y - %s.w), 0.0);",
                                      rectName, fragmentPos, fragmentPos, rectName);
-            fragBuilder->codeAppendf("\t\tfloat rightAlpha = clamp(%s.z - %s.x, 0.0, 1.0);\n",
+            fragBuilder->codeAppendf("float rightAlpha = clamp(%s.z - %s.x, 0.0, 1.0);",
                                      rectName, fragmentPos);
-            fragBuilder->codeAppendf("\t\tfloat topAlpha = clamp(%s.y - %s.y, 0.0, 1.0);\n",
+            fragBuilder->codeAppendf("float topAlpha = clamp(%s.y - %s.y, 0.0, 1.0);",
                                      fragmentPos, rectName);
-            fragBuilder->codeAppendf(
-                "\t\tfloat alpha = topAlpha * rightAlpha * clamp(%s - length(dxy), 0.0, 1.0);\n",
-                radiusPlusHalfName);
+            fragBuilder->codeAppendf("float alpha = topAlpha * rightAlpha * %s;",
+                                     clampedCircleDistance.c_str());
             break;
         case CircularRRectEffect::kLeft_CornerFlags:
-            fragBuilder->codeAppendf("\t\tvec2 dxy0 = %s.xy - %s.xy;\n", rectName, fragmentPos);
-            fragBuilder->codeAppendf("\t\tfloat dy1 = %s.y - %s.w;\n", fragmentPos, rectName);
-            fragBuilder->codeAppend("\t\tvec2 dxy = max(vec2(dxy0.x, max(dxy0.y, dy1)), 0.0);\n");
-            fragBuilder->codeAppendf("\t\tfloat rightAlpha = clamp(%s.z - %s.x, 0.0, 1.0);\n",
+            fragBuilder->codeAppendf("vec2 dxy0 = %s.xy - %s.xy;", rectName, fragmentPos);
+            fragBuilder->codeAppendf("float dy1 = %s.y - %s.w;", fragmentPos, rectName);
+            fragBuilder->codeAppend("vec2 dxy = max(vec2(dxy0.x, max(dxy0.y, dy1)), 0.0);");
+            fragBuilder->codeAppendf("float rightAlpha = clamp(%s.z - %s.x, 0.0, 1.0);",
                                      rectName, fragmentPos);
-            fragBuilder->codeAppendf(
-                "\t\tfloat alpha = rightAlpha * clamp(%s - length(dxy), 0.0, 1.0);\n",
-                radiusPlusHalfName);
+            fragBuilder->codeAppendf("float alpha = rightAlpha * %s;",
+                                     clampedCircleDistance.c_str());
             break;
         case CircularRRectEffect::kTop_CornerFlags:
-            fragBuilder->codeAppendf("\t\tvec2 dxy0 = %s.xy - %s.xy;\n", rectName, fragmentPos);
-            fragBuilder->codeAppendf("\t\tfloat dx1 = %s.x - %s.z;\n", fragmentPos, rectName);
-            fragBuilder->codeAppend("\t\tvec2 dxy = max(vec2(max(dxy0.x, dx1), dxy0.y), 0.0);\n");
-            fragBuilder->codeAppendf("\t\tfloat bottomAlpha = clamp(%s.w - %s.y, 0.0, 1.0);\n",
+            fragBuilder->codeAppendf("vec2 dxy0 = %s.xy - %s.xy;", rectName, fragmentPos);
+            fragBuilder->codeAppendf("float dx1 = %s.x - %s.z;", fragmentPos, rectName);
+            fragBuilder->codeAppend("vec2 dxy = max(vec2(max(dxy0.x, dx1), dxy0.y), 0.0);");
+            fragBuilder->codeAppendf("float bottomAlpha = clamp(%s.w - %s.y, 0.0, 1.0);",
                                      rectName, fragmentPos);
-            fragBuilder->codeAppendf(
-                "\t\tfloat alpha = bottomAlpha * clamp(%s - length(dxy), 0.0, 1.0);\n",
-                radiusPlusHalfName);
+            fragBuilder->codeAppendf("float alpha = bottomAlpha * %s;",
+                                     clampedCircleDistance.c_str());
             break;
         case CircularRRectEffect::kRight_CornerFlags:
-            fragBuilder->codeAppendf("\t\tfloat dy0 = %s.y - %s.y;\n", rectName, fragmentPos);
-            fragBuilder->codeAppendf("\t\tvec2 dxy1 = %s.xy - %s.zw;\n", fragmentPos, rectName);
-            fragBuilder->codeAppend("\t\tvec2 dxy = max(vec2(dxy1.x, max(dy0, dxy1.y)), 0.0);\n");
-            fragBuilder->codeAppendf("\t\tfloat leftAlpha = clamp(%s.x - %s.x, 0.0, 1.0);\n",
+            fragBuilder->codeAppendf("float dy0 = %s.y - %s.y;", rectName, fragmentPos);
+            fragBuilder->codeAppendf("vec2 dxy1 = %s.xy - %s.zw;", fragmentPos, rectName);
+            fragBuilder->codeAppend("vec2 dxy = max(vec2(dxy1.x, max(dy0, dxy1.y)), 0.0);");
+            fragBuilder->codeAppendf("float leftAlpha = clamp(%s.x - %s.x, 0.0, 1.0);",
                                      fragmentPos, rectName);
-            fragBuilder->codeAppendf(
-                "\t\tfloat alpha = leftAlpha * clamp(%s - length(dxy), 0.0, 1.0);\n",
-                radiusPlusHalfName);
+            fragBuilder->codeAppendf("float alpha = leftAlpha * %s;",
+                                     clampedCircleDistance.c_str());
             break;
         case CircularRRectEffect::kBottom_CornerFlags:
-            fragBuilder->codeAppendf("\t\tfloat dx0 = %s.x - %s.x;\n", rectName, fragmentPos);
-            fragBuilder->codeAppendf("\t\tvec2 dxy1 = %s.xy - %s.zw;\n", fragmentPos, rectName);
-            fragBuilder->codeAppend("\t\tvec2 dxy = max(vec2(max(dx0, dxy1.x), dxy1.y), 0.0);\n");
-            fragBuilder->codeAppendf("\t\tfloat topAlpha = clamp(%s.y - %s.y, 0.0, 1.0);\n",
+            fragBuilder->codeAppendf("float dx0 = %s.x - %s.x;", rectName, fragmentPos);
+            fragBuilder->codeAppendf("vec2 dxy1 = %s.xy - %s.zw;", fragmentPos, rectName);
+            fragBuilder->codeAppend("vec2 dxy = max(vec2(max(dx0, dxy1.x), dxy1.y), 0.0);");
+            fragBuilder->codeAppendf("float topAlpha = clamp(%s.y - %s.y, 0.0, 1.0);",
                                      fragmentPos, rectName);
-            fragBuilder->codeAppendf(
-                "\t\tfloat alpha = topAlpha * clamp(%s - length(dxy), 0.0, 1.0);\n",
-                radiusPlusHalfName);
+            fragBuilder->codeAppendf("float alpha = topAlpha * %s;",
+                                     clampedCircleDistance.c_str());
             break;
     }
 
     if (kInverseFillAA_GrProcessorEdgeType == crre.getEdgeType()) {
-        fragBuilder->codeAppend("\t\talpha = 1.0 - alpha;\n");
+        fragBuilder->codeAppend("alpha = 1.0 - alpha;");
     }
 
-    fragBuilder->codeAppendf("\t\t%s = %s;\n", args.fOutputColor,
+    fragBuilder->codeAppendf("%s = %s;", args.fOutputColor,
                              (GrGLSLExpr4(args.fInputColor) * GrGLSLExpr1("alpha")).c_str());
 }
 
 void GLCircularRRectEffect::GenKey(const GrProcessor& processor, const GrGLSLCaps&,
                                    GrProcessorKeyBuilder* b) {
     const CircularRRectEffect& crre = processor.cast<CircularRRectEffect>();
     GR_STATIC_ASSERT(kGrProcessorEdgeTypeCnt <= 8);
     b->add32((crre.getCircularCornerFlags() << 3) | crre.getEdgeType());
 }
 
@@ skipping 64 matching lines @@
                 radius = rrect.radii(SkRRect::kLowerLeft_Corner).fX;
                 rect.fLeft += radius;
                 rect.fTop -= 0.5f;
                 rect.fRight -= radius;
                 rect.fBottom -= radius;
                 break;
             default:
                 SkFAIL("Should have been one of the above cases.");
         }
         pdman.set4f(fInnerRectUniform, rect.fLeft, rect.fTop, rect.fRight, rect.fBottom);
-        pdman.set1f(fRadiusPlusHalfUniform, radius + 0.5f);
+        radius += 0.5f;
+        pdman.set2f(fRadiusPlusHalfUniform, radius, 1.f / radius);
         fPrevRRect = rrect;
     }
 }
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 
 void CircularRRectEffect::onGetGLSLProcessorKey(const GrGLSLCaps& caps,
                                                 GrProcessorKeyBuilder* b) const {
     GLCircularRRectEffect::GenKey(*this, caps, b);
 }
@@ skipping 345 matching lines @@
                 if (rrect.isNinePatch()) {
                     return EllipticalRRectEffect::Create(edgeType, rrect);
                 }
                 return nullptr;
             }
         }
     }
 
     return nullptr;
 }