Fix alpha fading on subpixel text.

webrender/res/ps_text_run.glsl

@@ -89,10 +89,10 @@ void main(void) {
             modulate_color = alpha * vColor;
             break;
         case MODE_SUBPX_PASS0:
-            modulate_color = vec4(alpha);
+            modulate_color = vec4(alpha) * vColor.a;
             break;
         case MODE_SUBPX_PASS1:
-            modulate_color = vColor;
+            modulate_color = alpha * vColor;
             break;
     }
 

webrender/src/frame_builder.rs

@@ -1162,7 +1162,7 @@ impl FrameBuilder {
             font.variations.clone(),
             font.synthetic_italics,
         );
-        let mut prim = TextRunPrimitiveCpu {
+        let prim = TextRunPrimitiveCpu {
             font: prim_font,
             glyph_range,
             glyph_count,
@@ -1187,12 +1187,6 @@ impl FrameBuilder {
             if shadow.blur_radius == 0.0 {
                 let mut text_prim = prim.clone();
                 text_prim.font.color = shadow.color.into();
-                // If we have translucent text, we need to ensure it won't go
-                // through the subpixel blend mode, which doesn't work with
-                // traditional alpha blending.
-                if shadow.color.a != 1.0 {
-                    text_prim.font.render_mode = text_prim.font.render_mode.limit_by(FontRenderMode::Alpha);
-                }
                 text_prim.offset += shadow.offset;
                 fast_shadow_prims.push((idx, text_prim));
             }
@@ -1211,12 +1205,6 @@ impl FrameBuilder {
             self.shadow_prim_stack[idx].1.push((prim_index, clip_and_scroll));
         }
 
-        // We defer this until after fast-shadows so that shadows of transparent text
-        // get subpixel-aa
-        if color.a != 1.0 {
-            prim.font.render_mode = prim.font.render_mode.limit_by(FontRenderMode::Alpha);
-        }
-
         // Create (and add to primitive store) the primitive that will be
         // used for both the visual element and also the shadow(s).
         let prim_index = self.create_primitive(

wrench/reftests/text/colors.yaml

@@ -163,7 +163,7 @@ root:
       origin: 20 410
       size: 32
       font: "FreeSans.ttf"
-      color: [50, 50, 50, 0.1]
+      color: [50, 50, 50, 0.5]
 
     - type: rect
       bounds: [270, 370, 250, 50]
@@ -172,7 +172,7 @@ root:
       origin: 280 410
       size: 32
       font: "FreeSans.ttf"
-      color: [50, 50, 50, 0.1]
+      color: [50, 50, 50, 0.5]
 
     - type: rect
       bounds: [530, 370, 250, 50]
@@ -181,7 +181,7 @@ root:
       origin: 540 410
       size: 32
       font: "FreeSans.ttf"
-      color: [50, 50, 50, 0.1]
+      color: [50, 50, 50, 0.5]
 
     - type: rect
       bounds: [10, 430, 250, 50]
@@ -190,7 +190,7 @@ root:
       origin: 20 470
       size: 32
       font: "FreeSans.ttf"
-      color: [50, 50, 50, 0.1]
+      color: [50, 50, 50, 0.5]
 
     - type: rect
       bounds: [270, 430, 250, 50]
@@ -199,7 +199,7 @@ root:
       origin: 280 470
       size: 32
       font: "FreeSans.ttf"
-      color: [50, 50, 50, 0.1]
+      color: [50, 50, 50, 0.5]
 
     - type: rect
       bounds: [530, 430, 250, 50]
@@ -208,4 +208,4 @@ root:
       origin: 540 470
       size: 32
       font: "FreeSans.ttf"
-      color: [50, 50, 50, 0.1]
+      color: [50, 50, 50, 0.5]

wrench/reftests/text/reftest.list

@@ -28,8 +28,10 @@ options(disable-subpixel) == ahem.yaml ahem-ref.yaml
 platform(linux) == isolated-text.yaml isolated-text.png
 platform(mac) == white-opacity.yaml white-opacity.png
 fuzzy(1,4) platform(linux) options(disable-subpixel) == colors.yaml colors-alpha.png
-fuzzy(1,2) platform(linux) == colors.yaml colors-subpx.png
+fuzzy(1,4) platform(linux) == colors.yaml colors-subpx.png
 platform(linux) options(disable-subpixel) == border-radius.yaml border-radius-alpha.png
 platform(linux) == border-radius.yaml border-radius-subpx.png
 options(disable-aa) == transparent-no-aa.yaml transparent-no-aa-ref.yaml
 != diacritics.yaml diacritics-ref.yaml
+fuzzy(1,1) platform(linux) options(disable-subpixel) == text-masking.yaml text-masking-alpha.png
+fuzzy(1,44) platform(linux) == text-masking.yaml text-masking-subpx.png

wrench/reftests/text/text-masking.yaml

@@ -0,0 +1,28 @@
+---
+root:
+  items:
+    - bounds: [0, 0, 750, 100]
+      "clip-rect": [0, 0, 750, 100]
+      "clip-and-scroll": 0
+      type: rect
+      color: [180, 180, 180]
+    - bounds: [0, 0, 750, 100]
+      "clip-rect": [0, 0, 750, 100]
+      type: clip
+      id: 1
+      "content-size": [750, 100]
+      "image-mask":
+        image: "text-masking-mask.png"
+        rect: [0, 0, 750, 100]
+        repeat: false
+    - text: "Cats making all the muffins knock over christmas tree"
+      origin: 40 40
+      size: 20
+      "clip-and-scroll": 1
+      font: "FreeSans.ttf"
+    - text: "Cats making all the muffins knock over christmas tree"
+      origin: 40 80
+      size: 20
+      color: white
+      "clip-and-scroll": 1
+      font: "FreeSans.ttf"