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, 17 insertions, 5 deletions

diff --git a/src/renderer/mod.rs b/src/renderer/mod.rs
index 3cad4a01..0dad716e 100644
--- a/src/renderer/mod.rs
+++ b/src/renderer/mod.rs
@@ -119,6 +119,8 @@ pub struct ShaderProgram {
 
     padding_x: f32,
     padding_y: f32,
+
+    u_bg_opacity: GLint,
 }
 
 
@@ -604,6 +606,7 @@ impl QuadRenderer {
             self.program.activate();
             self.program.set_term_uniforms(props);
             self.program.set_visual_bell(visual_bell_intensity as _);
+            self.program.set_bg_opacity(config.background_opacity().get());
 
             gl::BindVertexArray(self.vao);
             gl::BindBuffer(gl::ELEMENT_ARRAY_BUFFER, self.ebo);
@@ -685,12 +688,13 @@ impl QuadRenderer {
 
 impl<'a> RenderApi<'a> {
     pub fn clear(&self, color: Rgb) {
+        let alpha = self.config.background_opacity().get();
         unsafe {
             gl::ClearColor(
-                (self.visual_bell_intensity + color.r as f32 / 255.0).min(1.0),
-                (self.visual_bell_intensity + color.g as f32 / 255.0).min(1.0),
-                (self.visual_bell_intensity + color.b as f32 / 255.0).min(1.0),
-                1.0
+                (self.visual_bell_intensity + color.r as f32 / 255.0).min(1.0) * alpha,
+                (self.visual_bell_intensity + color.g as f32 / 255.0).min(1.0) * alpha,
+                (self.visual_bell_intensity + color.b as f32 / 255.0).min(1.0) * alpha,
+                alpha
                 );
             gl::Clear(gl::COLOR_BUFFER_BIT);
         }
@@ -916,13 +920,14 @@ impl ShaderProgram {
         }
 
         // get uniform locations
-        let (projection, term_dim, cell_dim, visual_bell, background) = unsafe {
+        let (projection, term_dim, cell_dim, visual_bell, background, bg_opacity) = 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"backgroundPass\0")),
+                gl::GetUniformLocation(program, cptr!(b"bgOpacity\0")),
             )
         };
 
@@ -937,6 +942,7 @@ impl ShaderProgram {
             u_background: background,
             padding_x: config.padding().x.floor(),
             padding_y: config.padding().y.floor(),
+            u_bg_opacity: bg_opacity,
         };
 
         shader.update_projection(*size.width as f32, *size.height as f32);
@@ -997,6 +1003,12 @@ impl ShaderProgram {
         }
     }
 
+    fn set_bg_opacity(&self, bg_opacity: f32) {
+        unsafe {
+            gl::Uniform1f(self.u_bg_opacity, bg_opacity);
+        }
+    }
+
     fn create_program(vertex: GLuint, fragment: GLuint) -> GLuint {
         unsafe {
             let program = gl::CreateProgram();