Fix solid background color opacity (#847)

Since landing the patch adding transparency support to Alacritty,
there's been an issue where othewise solid background cells were also
being rendered partially transparent. Now, all filled background cells
are rendered fully opaque.

Some logic was added to support discarding filled backgrounds which had
the same color as the default background. This means that, if the
default background is #000 and a cell has that background, it will never
be rendered opaque. This may not be correct.

Note that many truecolor vim color schemes print spaces for default
colored background cells. Performance can be dramatically improved by
using ctermbg=NONE guibg=NONE to skip rendering those cells.

1 files changed, 27 insertions, 23 deletions

diff --git a/src/renderer/mod.rs b/src/renderer/mod.rs
index 3db9ccb6..9305e135 100644
--- a/src/renderer/mod.rs
+++ b/src/renderer/mod.rs
@@ -125,8 +125,6 @@ pub struct ShaderProgram {
 
     padding_x: f32,
     padding_y: f32,
-
-    u_bg_opacity: GLint,
 }
 
 
@@ -351,6 +349,7 @@ struct InstanceData {
     bg_r: f32,
     bg_g: f32,
     bg_b: f32,
+    bg_a: f32,
 }
 
 #[derive(Debug)]
@@ -436,6 +435,7 @@ impl Batch {
             bg_r: cell.bg.r as f32,
             bg_g: cell.bg.g as f32,
             bg_b: cell.bg.b as f32,
+            bg_a: cell.bg_alpha,
         });
     }
 
@@ -568,7 +568,7 @@ impl QuadRenderer {
             gl::EnableVertexAttribArray(4);
             gl::VertexAttribDivisor(4, 1);
             // color
-            gl::VertexAttribPointer(5, 3,
+            gl::VertexAttribPointer(5, 4,
                                     gl::FLOAT, gl::FALSE,
                                     size_of::<InstanceData>() as i32,
                                     (13 * size_of::<f32>()) as *const _);
@@ -648,7 +648,6 @@ 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);
@@ -692,17 +691,22 @@ impl QuadRenderer {
     }
 
     pub fn reload_shaders(&mut self, config: &Config, size: Size<Pixels<u32>>) {
-        info!("Reloading shaders");
+        warn!("Reloading shaders ...");
         let program = match ShaderProgram::new(config, size) {
-            Ok(program) => program,
+            Ok(program) => {
+                warn!(" ... OK");
+                program
+            },
             Err(err) => {
                 match err {
                     ShaderCreationError::Io(err) => {
                         error!("Error reading shader file: {}", err);
                     },
                     ShaderCreationError::Compile(path, log) => {
-                        error!("Error compiling shader at {:?}", path);
-                        let _ = io::copy(&mut log.as_bytes(), &mut io::stdout());
+                        error!("Error compiling shader at {:?}\n{}", path, log);
+                    }
+                    ShaderCreationError::Link(log) => {
+                        error!("Error reloading shaders: {}", log);
                     }
                 }
 
@@ -791,6 +795,7 @@ impl<'a> RenderApi<'a> {
                 bg: color,
                 fg: Rgb { r: 0, g: 0, b: 0 },
                 flags: cell::Flags::empty(),
+                bg_alpha: 1.0
             })
             .collect::<Vec<_>>();
 
@@ -957,7 +962,7 @@ impl ShaderProgram {
             gl::FRAGMENT_SHADER,
             frag_source
         )?;
-        let program = ShaderProgram::create_program(vertex_shader, fragment_shader);
+        let program = ShaderProgram::create_program(vertex_shader, fragment_shader)?;
 
         unsafe {
             gl::DeleteShader(vertex_shader);
@@ -980,14 +985,13 @@ impl ShaderProgram {
         }
 
         // get uniform locations
-        let (projection, term_dim, cell_dim, visual_bell, background, bg_opacity) = unsafe {
+        let (projection, term_dim, cell_dim, visual_bell, 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"backgroundPass\0")),
-                gl::GetUniformLocation(program, cptr!(b"bgOpacity\0")),
             )
         };
 
@@ -1002,7 +1006,6 @@ 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);
@@ -1063,13 +1066,7 @@ 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 {
+    fn create_program(vertex: GLuint, fragment: GLuint) -> Result<GLuint, ShaderCreationError> {
         unsafe {
             let program = gl::CreateProgram();
             gl::AttachShader(program, vertex);
@@ -1080,10 +1077,10 @@ impl ShaderProgram {
             gl::GetProgramiv(program, gl::LINK_STATUS, &mut success);
 
             if success != (gl::TRUE as GLint) {
-                error!("{}", get_program_info_log(program));
-                panic!("failed to link shader program");
+                Err(ShaderCreationError::Link(get_program_info_log(program)))
+            } else {
+                Ok(program)
             }
-            program
         }
     }
 
@@ -1198,13 +1195,16 @@ pub enum ShaderCreationError {
 
     /// Error compiling shader
     Compile(PathBuf, String),
+
+    /// Problem linking
+    Link(String),
 }
 
 impl ::std::error::Error for ShaderCreationError {
     fn cause(&self) -> Option<&::std::error::Error> {
         match *self {
             ShaderCreationError::Io(ref err) => Some(err),
-            ShaderCreationError::Compile(_, _) => None,
+            _ => None,
         }
     }
 
@@ -1212,6 +1212,7 @@ impl ::std::error::Error for ShaderCreationError {
         match *self {
             ShaderCreationError::Io(ref err) => err.description(),
             ShaderCreationError::Compile(ref _path, ref s) => s.as_str(),
+            ShaderCreationError::Link(ref s) => s.as_str(),
         }
     }
 }
@@ -1223,6 +1224,9 @@ impl ::std::fmt::Display for ShaderCreationError {
             ShaderCreationError::Compile(ref _path, ref s) => {
                 write!(f, "failed compiling shader: {}", s)
             },
+            ShaderCreationError::Link(ref s) => {
+                write!(f, "failed linking shader: {}", s)
+            },
         }
     }
 }