Add background_opacity option to set terminal transparency (#331)

The option is an Alpha struct that ensures that the contained float is
between 0.0 and 1.0. Background colors are multiplied by the opacity
to properly alpha blend them.

1 files changed, 5 insertions, 3 deletions

diff --git a/res/text.f.glsl b/res/text.f.glsl
index 70d50b38..dd60333c 100644
--- a/res/text.f.glsl
+++ b/res/text.f.glsl
@@ -21,15 +21,17 @@ flat in int background;
 layout(location = 0, index = 0) out vec4 color;
 layout(location = 0, index = 1) out vec4 alphaMask;
 
+uniform float bgOpacity;
 uniform sampler2D mask;
 
 void main()
 {
     if (background != 0) {
-        alphaMask = vec4(1.0, 1.0, 1.0, 1.0);
-        color = vec4(bg + vb, 1.0);
+        alphaMask = vec4(1.0);
+        color = vec4(bg + vb, 1.0) * bgOpacity;
     } else {
-        alphaMask = vec4(texture(mask, TexCoords).rgb, 1.0);
+        vec3 textColor = texture(mask, TexCoords).rgb;
+        alphaMask = vec4(textColor, textColor.r);
         color = vec4(fg, 1.0);
     }
 }