Make visual bell flash color customizable

This addresses the main feedback in jwilm/alacritty/pull/430. I've
decided to go from scratch instead of basing my work on top of what
markandrus has already implemented to keep it as simple as possible.

If there's any stuff that I should take from the other PR, please let me
know. I can also try to send a PR to markandrus.

res/text.f.glsl

@@ -15,6 +15,7 @@
 in vec2 TexCoords;
 in vec3 fg;
 in vec4 bg;
+in vec3 vbc;
 flat in float vb;
 flat in int background;
 
@@ -31,7 +32,11 @@ void main()
             discard;
 
         alphaMask = vec4(1.0);
-        color = vec4(bg.rgb + vb, 1.0);
+        if (vb == 0) {
+            color = vec4(bg.rgb, 1.0);
+        } else {
+            color = vec4(vbc, vb);
+        }
     } else {
         vec3 textColor = texture(mask, TexCoords).rgb;
         alphaMask = vec4(textColor, textColor.r);

res/text.v.glsl

@@ -25,18 +25,21 @@ layout (location = 3) in vec4 uv;
 
 // text fg color
 layout (location = 4) in vec3 textColor;
+
 // Background color
 layout (location = 5) in vec4 backgroundColor;
 
 out vec2 TexCoords;
 out vec3 fg;
 out vec4 bg;
+out vec3 vbc;
 
 // Terminal properties
 uniform vec2 termDim;
 uniform vec2 cellDim;
 
 uniform float visualBell;
+uniform vec3 visualBellColor;
 uniform int backgroundPass;
 
 // Orthographic projection
@@ -74,6 +77,7 @@ void main()
     }
 
     vb = visualBell;
+    vbc = visualBellColor;
     background = backgroundPass;
     bg = vec4(backgroundColor.rgb / 255.0, backgroundColor.a);
     fg = textColor / vec3(255.0, 255.0, 255.0);

src/config.rs

@@ -150,6 +150,10 @@ pub struct VisualBellConfig {
     #[serde(deserialize_with = "deserialize_visual_bell_duration")]
     #[serde(default="default_visual_bell_duration")]
     duration: u16,
+
+    /// Visual bell flash color
+    #[serde(default="default_visual_bell_color", deserialize_with = "rgb_from_hex")]
+    color: Rgb,
 }
 
 fn default_visual_bell_duration() -> u16 {
@@ -168,6 +172,10 @@ fn deserialize_visual_bell_duration<'a, D>(deserializer: D) -> ::std::result::Re
     }
 }
 
+fn default_visual_bell_color() -> Rgb {
+    Rgb { r: 255, g: 255, b: 255 }
+}
+
 impl VisualBellConfig {
     /// Visual bell animation
     #[inline]
@@ -180,6 +188,12 @@ impl VisualBellConfig {
     pub fn duration(&self) -> Duration {
         Duration::from_millis(u64::from(self.duration))
     }
+
+    /// Visual bell flash color
+    #[inline]
+    pub fn color(&self) -> Rgb {
+        self.color
+    }
 }
 
 impl Default for VisualBellConfig {
@@ -187,6 +201,7 @@ impl Default for VisualBellConfig {
         VisualBellConfig {
             animation: VisualBellAnimation::default(),
             duration: default_visual_bell_duration(),
+            color: default_visual_bell_color(),
         }
     }
 }

src/renderer/mod.rs

@@ -118,6 +118,9 @@ pub struct ShaderProgram {
     /// Visual bell
     u_visual_bell: GLint,
 
+    /// Visual bell color
+    u_visual_bell_color: GLint,
+
     /// Background pass flag
     ///
     /// Rendering is split into two passes; 1 for backgrounds, and one for text
@@ -644,10 +647,12 @@ impl QuadRenderer {
             }
         }
 
+        let visual_bell_color = config.visual_bell().color();
+
         unsafe {
             self.program.activate();
             self.program.set_term_uniforms(props);
-            self.program.set_visual_bell(visual_bell_intensity as _);
+            self.program.set_visual_bell(visual_bell_intensity as _, visual_bell_color);
 
             gl::BindVertexArray(self.vao);
             gl::BindBuffer(gl::ELEMENT_ARRAY_BUFFER, self.ebo);
@@ -734,16 +739,21 @@ impl QuadRenderer {
     }
 }
 
+fn mix(x: f32, y: f32, a: f32) -> f32 {
+    x * (1.0 - a) + y * a
+}
+
 impl<'a> RenderApi<'a> {
     pub fn clear(&self, color: Rgb) {
         let alpha = self.config.background_opacity().get();
+        let (flash, intensity) = (self.config.visual_bell().color(), self.visual_bell_intensity);
         unsafe {
             gl::ClearColor(
-                (self.visual_bell_intensity + f32::from(color.r) / 255.0).min(1.0) * alpha,
-                (self.visual_bell_intensity + f32::from(color.g) / 255.0).min(1.0) * alpha,
-                (self.visual_bell_intensity + f32::from(color.b) / 255.0).min(1.0) * alpha,
+                mix(color.r as f32 / 255.0, flash.r as f32 / 255.0, intensity).min(1.0) * alpha,
+                mix(color.g as f32 / 255.0, flash.g as f32 / 255.0, intensity).min(1.0) * alpha,
+                mix(color.b as f32 / 255.0, flash.b as f32 / 255.0, intensity).min(1.0) * alpha,
                 alpha
-                );
+            );
             gl::Clear(gl::COLOR_BUFFER_BIT);
         }
     }
@@ -998,12 +1008,13 @@ impl ShaderProgram {
         }
 
         // get uniform locations
-        let (projection, term_dim, cell_dim, visual_bell, background) = unsafe {
+        let (projection, term_dim, cell_dim, visual_bell, visual_bell_color, background) = unsafe {
             (
                 gl::GetUniformLocation(program, cptr!(b"projection\0")),
                 gl::GetUniformLocation(program, cptr!(b"termDim\0")),
                 gl::GetUniformLocation(program, cptr!(b"cellDim\0")),
                 gl::GetUniformLocation(program, cptr!(b"visualBell\0")),
+                gl::GetUniformLocation(program, cptr!(b"visualBellColor\0")),
                 gl::GetUniformLocation(program, cptr!(b"backgroundPass\0")),
             )
         };
@@ -1016,6 +1027,7 @@ impl ShaderProgram {
             u_term_dim: term_dim,
             u_cell_dim: cell_dim,
             u_visual_bell: visual_bell,
+            u_visual_bell_color: visual_bell_color,
             u_background: background,
             padding_x: config.padding().x.floor(),
             padding_y: config.padding().y.floor(),
@@ -1061,9 +1073,14 @@ impl ShaderProgram {
         }
     }
 
-    fn set_visual_bell(&self, visual_bell: f32) {
+    fn set_visual_bell(&self, visual_bell: f32, vb_color: Rgb) {
         unsafe {
             gl::Uniform1f(self.u_visual_bell, visual_bell);
+            gl::Uniform3f(self.u_visual_bell_color,
+                          vb_color.r as f32 / 255.,
+                          vb_color.g as f32 / 255.,
+                          vb_color.b as f32 / 255.
+            );
         }
     }