Bug 1594128 - Add brush_mix_blend to the multi-brush infrastructure. r=gw

Differential Revision: https://phabricator.services.mozilla.com/D53994

--HG--
extra : moz-landing-system : lando

gfx/wr/webrender/res/brush.glsl

@@ -225,6 +225,12 @@ void main(void) {
             blend_brush_vs(BRUSH_VS_PARAMS);
             break;
         #endif
+
+        #ifdef WR_FEATURE_MIX_BLEND_BRUSH
+        case BRUSH_KIND_MIX_BLEND:
+            mix_blend_brush_vs(BRUSH_VS_PARAMS);
+            break;
+        #endif
     }
 
 #else
@@ -279,6 +285,12 @@ void main(void) {
             frag = blend_brush_fs();
             break;
         }
+#endif
+#ifdef WR_FEATURE_MIX_BLEND_BRUSH
+        case BRUSH_KIND_MIX_BLEND: {
+            frag = mix_blend_brush_fs();
+            break;
+        }
 #endif
     }
 #else

gfx/wr/webrender/res/brush_mix_blend.glsl

@@ -10,9 +10,13 @@
 
 #include shared,prim_shared,brush
 
-varying vec3 vSrcUv;
-varying vec3 vBackdropUv;
-flat varying int vOp;
+#define V_SRC_UV            varying_vec4_0.xy
+#define V_SRC_LAYER         varying_vec4_0.w
+
+#define V_BACKDROP_UV       varying_vec4_1.xy
+#define V_BACKDROP_LAYER    varying_vec4_1.w
+
+#define V_OP                flat_varying_ivec4_0.x
 
 #ifdef WR_VERTEX_SHADER
 
@@ -35,19 +39,21 @@ void mix_blend_brush_vs(
 ) {
     vec2 snapped_device_pos = snap_device_pos(vi, pic_task.device_pixel_scale);
     vec2 texture_size = vec2(textureSize(sPrevPassColor, 0));
-    vOp = prim_user_data.x;
+    V_OP = prim_user_data.x;
 
     PictureTask src_task = fetch_picture_task(prim_user_data.z);
     vec2 src_uv = snapped_device_pos +
                   src_task.common_data.task_rect.p0 -
                   src_task.content_origin;
-    vSrcUv = vec3(src_uv / texture_size, src_task.common_data.texture_layer_index);
+    V_SRC_UV = src_uv / texture_size;
+    V_SRC_LAYER = src_task.common_data.texture_layer_index;
 
     RenderTaskCommonData backdrop_task = fetch_render_task_common_data(prim_user_data.y);
     vec2 backdrop_uv = snapped_device_pos +
                        backdrop_task.task_rect.p0 -
                        src_task.content_origin;
-    vBackdropUv = vec3(backdrop_uv / texture_size, backdrop_task.texture_layer_index);
+    V_BACKDROP_UV = backdrop_uv / texture_size;
+    V_BACKDROP_LAYER = backdrop_task.texture_layer_index;
 }
 #endif
 
@@ -210,8 +216,8 @@ const int MixBlendMode_Color       = 14;
 const int MixBlendMode_Luminosity  = 15;
 
 Fragment mix_blend_brush_fs() {
-    vec4 Cb = textureLod(sPrevPassColor, vBackdropUv, 0.0);
-    vec4 Cs = textureLod(sPrevPassColor, vSrcUv, 0.0);
+    vec4 Cb = textureLod(sPrevPassColor, vec3(V_BACKDROP_UV, V_BACKDROP_LAYER), 0.0);
+    vec4 Cs = textureLod(sPrevPassColor, vec3(V_SRC_UV, V_SRC_LAYER), 0.0);
 
     // The mix-blend-mode functions assume no premultiplied alpha
     if (Cb.a != 0.0) {
@@ -225,7 +231,7 @@ Fragment mix_blend_brush_fs() {
     // Return yellow if none of the branches match (shouldn't happen).
     vec4 result = vec4(1.0, 1.0, 0.0, 1.0);
 
-    switch (vOp) {
+    switch (V_OP) {
         case MixBlendMode_Multiply:
             result.rgb = Multiply(Cb.rgb, Cs.rgb);
             break;
@@ -289,3 +295,10 @@ Fragment mix_blend_brush_fs() {
     return Fragment(result);
 }
 #endif
+
+// Undef macro names that could be re-defined by other shaders.
+#undef V_SRC_UV
+#undef V_SRC_LAYER
+#undef V_BACKDROP_UV
+#undef V_BACKDROP_LAYER
+#undef V_OP

gfx/wr/webrender/res/brush_multi.glsl

@@ -28,6 +28,14 @@ int vecs_per_brush(int brush_kind);
 #include brush_blend
 #endif
 
+#undef VECS_PER_SPECIFIC_BRUSH
+#undef WR_BRUSH_VS_FUNCTION
+#undef WR_BRUSH_FS_FUNCTION
+
+#ifdef WR_FEATURE_MIX_BLEND_BRUSH
+#include brush_mix_blend
+#endif
+
 int vecs_per_brush(int brush_kind) {
     int result;
     switch (brush_kind) {
@@ -48,6 +56,12 @@ int vecs_per_brush(int brush_kind) {
             result = VECS_PER_BLEND_BRUSH;
             break;
         #endif
+
+        #ifdef WR_FEATURE_MIX_BLEND_BRUSH
+        case BRUSH_KIND_MIX_BLEND:
+            result = VECS_PER_MIX_BLEND_BRUSH;
+            break;
+        #endif
     }
 
     return result;