Merge "Bowing my head in shame, going back to gamma interpolated gradients"
diff --git a/libs/hwui/FloatColor.h b/libs/hwui/FloatColor.h
index d8afa35..a738ba4 100644
--- a/libs/hwui/FloatColor.h
+++ b/libs/hwui/FloatColor.h
@@ -38,13 +38,14 @@
     }
 
     // "color" is a gamma-encoded sRGB color
-    // After calling this method, the color is stored as a linear color. The color
-    // is not pre-multiplied.
-    void setUnPreMultipliedSRGB(uint32_t color) {
+    // After calling this method, the color is stored as a un-premultiplied linear color
+    // if linear blending is enabled. Otherwise, the color is stored as a un-premultiplied
+    // gamma-encoded sRGB color
+    void setUnPreMultiplied(uint32_t color) {
         a = ((color >> 24) & 0xff) / 255.0f;
-        r = EOCF_sRGB(((color >> 16) & 0xff) / 255.0f);
-        g = EOCF_sRGB(((color >>  8) & 0xff) / 255.0f);
-        b = EOCF_sRGB(((color      ) & 0xff) / 255.0f);
+        r = EOCF(((color >> 16) & 0xff) / 255.0f);
+        g = EOCF(((color >>  8) & 0xff) / 255.0f);
+        b = EOCF(((color      ) & 0xff) / 255.0f);
     }
 
     bool isNotBlack() {
diff --git a/libs/hwui/GradientCache.cpp b/libs/hwui/GradientCache.cpp
index 18bfcc2..dceb285 100644
--- a/libs/hwui/GradientCache.cpp
+++ b/libs/hwui/GradientCache.cpp
@@ -189,9 +189,9 @@
         float amount, uint8_t*& dst) const {
     float oppAmount = 1.0f - amount;
     float a = start.a * oppAmount + end.a * amount;
-    *dst++ = uint8_t(a * OECF_sRGB((start.r * oppAmount + end.r * amount)) * 255.0f);
-    *dst++ = uint8_t(a * OECF_sRGB((start.g * oppAmount + end.g * amount)) * 255.0f);
-    *dst++ = uint8_t(a * OECF_sRGB((start.b * oppAmount + end.b * amount)) * 255.0f);
+    *dst++ = uint8_t(a * OECF(start.r * oppAmount + end.r * amount) * 255.0f);
+    *dst++ = uint8_t(a * OECF(start.g * oppAmount + end.g * amount) * 255.0f);
+    *dst++ = uint8_t(a * OECF(start.b * oppAmount + end.b * amount) * 255.0f);
     *dst++ = uint8_t(a * 255.0f);
 }
 
@@ -201,17 +201,14 @@
     float a = start.a * oppAmount + end.a * amount;
     float* d = (float*) dst;
 #ifdef ANDROID_ENABLE_LINEAR_BLENDING
+    // We want to stay linear
     *d++ = a * (start.r * oppAmount + end.r * amount);
     *d++ = a * (start.g * oppAmount + end.g * amount);
     *d++ = a * (start.b * oppAmount + end.b * amount);
 #else
-    // What we're doing to the alpha channel here is technically incorrect
-    // but reproduces Android's old behavior when the alpha was pre-multiplied
-    // with gamma-encoded colors
-    a = EOCF_sRGB(a);
-    *d++ = a * OECF_sRGB(start.r * oppAmount + end.r * amount);
-    *d++ = a * OECF_sRGB(start.g * oppAmount + end.g * amount);
-    *d++ = a * OECF_sRGB(start.b * oppAmount + end.b * amount);
+    *d++ = a * OECF(start.r * oppAmount + end.r * amount);
+    *d++ = a * OECF(start.g * oppAmount + end.g * amount);
+    *d++ = a * OECF(start.b * oppAmount + end.b * amount);
 #endif
     *d++ = a;
     dst += 4 * sizeof(float);
@@ -232,10 +229,10 @@
     ChannelMixer mix = gMixers[mUseFloatTexture];
 
     FloatColor start;
-    start.setUnPreMultipliedSRGB(colors[0]);
+    start.setUnPreMultiplied(colors[0]);
 
     FloatColor end;
-    end.setUnPreMultipliedSRGB(colors[1]);
+    end.setUnPreMultiplied(colors[1]);
 
     int currentPos = 1;
     float startPos = positions[0];
@@ -250,7 +247,7 @@
 
             currentPos++;
 
-            end.setUnPreMultipliedSRGB(colors[currentPos]);
+            end.setUnPreMultiplied(colors[currentPos]);
             distance = positions[currentPos] - startPos;
         }
 
diff --git a/libs/hwui/ProgramCache.cpp b/libs/hwui/ProgramCache.cpp
index 3f842e0..38c23e4 100644
--- a/libs/hwui/ProgramCache.cpp
+++ b/libs/hwui/ProgramCache.cpp
@@ -202,23 +202,26 @@
 )__SHADER__";
 const char* gFS_Gradient_Preamble[2] = {
         // Linear framebuffer
-        "\nvec4 dither(const vec4 color) {\n"
-        "    return color + (triangleNoise(gl_FragCoord.xy * screenSize.xy) / 255.0);\n"
-        "}\n"
-        "\nvec4 gammaMix(const vec4 a, const vec4 b, float v) {\n"
-        "    vec4 c = mix(a, b, v);\n"
-        "    c.a = EOTF_sRGB(c.a);\n" // This is technically incorrect but preserves compatibility
-        "    return vec4(OETF_sRGB(c.rgb) * c.a, c.a);\n"
-        "}\n",
+        R"__SHADER__(
+        vec4 dither(const vec4 color) {
+            return color + (triangleNoise(gl_FragCoord.xy * screenSize.xy) / 255.0);
+        }
+        vec4 gradientMix(const vec4 a, const vec4 b, float v) {
+            vec4 c = mix(a, b, v);
+            return vec4(c.rgb * c.a, c.a);
+        }
+        )__SHADER__",
         // sRGB framebuffer
-        "\nvec4 dither(const vec4 color) {\n"
-        "    vec3 dithered = sqrt(color.rgb) + (triangleNoise(gl_FragCoord.xy * screenSize.xy) / 255.0);\n"
-        "    return vec4(dithered * dithered, color.a);\n"
-        "}\n"
-        "\nvec4 gammaMix(const vec4 a, const vec4 b, float v) {\n"
-        "    vec4 c = mix(a, b, v);\n"
-        "    return vec4(c.rgb * c.a, c.a);\n"
-        "}\n"
+        R"__SHADER__(
+        vec4 dither(const vec4 color) {
+            vec3 dithered = sqrt(color.rgb) + (triangleNoise(gl_FragCoord.xy * screenSize.xy) / 255.0);
+            return vec4(dithered * dithered, color.a);
+        }
+        vec4 gradientMixMix(const vec4 a, const vec4 b, float v) {
+            vec4 c = mix(a, b, v);
+            return vec4(c.rgb * c.a, c.a);
+        }
+        )__SHADER__",
 };
 
 // Uses luminance coefficients from Rec.709 to choose the appropriate gamma
@@ -272,19 +275,19 @@
         // Linear
         "    vec4 gradientColor = texture2D(gradientSampler, linear);\n",
 
-        "    vec4 gradientColor = gammaMix(startColor, endColor, clamp(linear, 0.0, 1.0));\n",
+        "    vec4 gradientColor = gradientMix(startColor, endColor, clamp(linear, 0.0, 1.0));\n",
 
         // Circular
         "    vec4 gradientColor = texture2D(gradientSampler, vec2(length(circular), 0.5));\n",
 
-        "    vec4 gradientColor = gammaMix(startColor, endColor, clamp(length(circular), 0.0, 1.0));\n",
+        "    vec4 gradientColor = gradientMix(startColor, endColor, clamp(length(circular), 0.0, 1.0));\n",
 
         // Sweep
         "    highp float index = atan(sweep.y, sweep.x) * 0.15915494309; // inv(2 * PI)\n"
         "    vec4 gradientColor = texture2D(gradientSampler, vec2(index - floor(index), 0.5));\n",
 
         "    highp float index = atan(sweep.y, sweep.x) * 0.15915494309; // inv(2 * PI)\n"
-        "    vec4 gradientColor = gammaMix(startColor, endColor, clamp(index - floor(index), 0.0, 1.0));\n"
+        "    vec4 gradientColor = gradientMix(startColor, endColor, clamp(index - floor(index), 0.0, 1.0));\n"
 };
 const char* gFS_Main_FetchBitmap =
         "    vec4 bitmapColor = OETF(texture2D(bitmapSampler, outBitmapTexCoords));\n";
diff --git a/libs/hwui/SkiaShader.cpp b/libs/hwui/SkiaShader.cpp
index 760c10c..4f7f9d7 100644
--- a/libs/hwui/SkiaShader.cpp
+++ b/libs/hwui/SkiaShader.cpp
@@ -173,8 +173,8 @@
         outData->gradientSampler = 0;
         outData->gradientTexture = nullptr;
 
-        outData->startColor.setUnPreMultipliedSRGB(gradInfo.fColors[0]);
-        outData->endColor.setUnPreMultipliedSRGB(gradInfo.fColors[1]);
+        outData->startColor.setUnPreMultiplied(gradInfo.fColors[0]);
+        outData->endColor.setUnPreMultiplied(gradInfo.fColors[1]);
     }
 
     return true;