Fix emojis being blended with background

Fixes #1864.

2 files changed, 28 insertions, 8 deletions

diff --git a/res/text.f.glsl b/res/text.f.glsl
index 70ad3d19..cf477eb0 100644
--- a/res/text.f.glsl
+++ b/res/text.f.glsl
@@ -15,6 +15,7 @@
 in vec2 TexCoords;
 flat in vec3 fg;
 flat in vec4 bg;
+flat in int colored;
 uniform int backgroundPass;
 
 layout(location = 0, index = 0) out vec4 color;
@@ -31,8 +32,22 @@ void main()
         alphaMask = vec4(1.0);
         color = vec4(bg.rgb, 1.0);
     } else {
-        vec3 textColor = texture(mask, TexCoords).rgb;
-        alphaMask = vec4(textColor, textColor.r);
-        color = vec4(fg, 1.0);
+        if (colored != 0) {
+            // Color glyphs, like emojis.
+            vec4 glyphColor = texture(mask, TexCoords);
+            alphaMask = vec4(glyphColor.a);
+
+            // Revert alpha premultiplication.
+            if (glyphColor.a != 0) {
+                glyphColor.rgb = vec3(glyphColor.rgb / glyphColor.a);
+            }
+
+            color = vec4(glyphColor.rgb, 1.0);
+        } else {
+            // Regular text glyphs.
+            vec3 textColor = texture(mask, TexCoords).rgb;
+            alphaMask = vec4(textColor, textColor.r);
+            color = vec4(fg, 1.0);
+        }
     }
 }
diff --git a/res/text.v.glsl b/res/text.v.glsl
index 5189980f..8978c111 100644
--- a/res/text.v.glsl
+++ b/res/text.v.glsl
@@ -12,24 +12,28 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 #version 330 core
-// Cell properties
+// Cell properties.
 layout (location = 0) in vec2 gridCoords;
 
-// glyph properties
+// Glyph properties.
 layout (location = 1) in vec4 glyph;
 
-// uv mapping
+// uv mapping.
 layout (location = 2) in vec4 uv;
 
-// text fg color
+// Text fg color.
 layout (location = 3) in vec3 textColor;
 
-// Background color
+// Background color.
 layout (location = 4) in vec4 backgroundColor;
 
+// Set to 1 if the glyph colors should be kept.
+layout (location = 5) in int coloredGlyph;
+
 out vec2 TexCoords;
 flat out vec3 fg;
 flat out vec4 bg;
+flat out int colored;
 
 // Terminal properties
 uniform vec2 cellDim;
@@ -71,4 +75,5 @@ void main()
 
     bg = vec4(backgroundColor.rgb / 255.0, backgroundColor.a);
     fg = textColor / vec3(255.0, 255.0, 255.0);
+    colored = coloredGlyph;
 }