add background pass

shaders/cell.f.glsl

@@ -2,18 +2,21 @@
 
 in vec2 glyph_tex_coords;
 
-/// The background color for this cell.
+// The color for this cell. If this is a background pass this is the
-flat in vec4 bg_color;
+// background color. Otherwise, this is the foreground color.
+flat in vec4 color;
 
-/// Font texture
+// Font texture
 uniform sampler2D text;
 
+// Background or foreground pass.
+uniform int background;
+
 void main() {
-    int background = 0;
     if (background == 1) {
-        gl_FragColor = bg_color;
+        gl_FragColor = color;
     } else {
         float a = texture(text, glyph_tex_coords).r;
-        gl_FragColor = vec4(bg_color.rgb, bg_color.a*a);
+        gl_FragColor = vec4(color.rgb, color.a*a);
     }
 }

shaders/cell.v.glsl

@@ -13,10 +13,14 @@ layout (location = 2) in vec2 glyph_size;
 layout (location = 3) in vec2 glyph_offset;
 
 // The background color for this cell in RGBA (0 to 1.0)
-layout (location = 4) in vec4 bg_color_in;
+layout (location = 4) in vec4 fg_color_in;
 
 // The background color for this cell in RGBA (0 to 1.0)
-flat out vec4 bg_color;
+layout (location = 5) in vec4 bg_color_in;
+
+// The background or foreground color for the fragment, depending on
+// whether this is a background or foreground pass.
+flat out vec4 color;
 
 // The x/y coordinate for the glyph representing the font.
 out vec2 glyph_tex_coords;
@@ -25,6 +29,10 @@ uniform sampler2D text;
 uniform vec2 cell_size;
 uniform mat4 projection;
 
+// non-zero if this is a background pass where we draw the background
+// of the cell. We do a background pass followed by a foreground pass.
+uniform int background;
+
 void main() {
     // Top-left cell coordinates converted to world space
     // Example: (1,0) with a 30 wide cell is converted to (30,0)
@@ -44,7 +52,6 @@ void main() {
     position.x = (gl_VertexID == 0 || gl_VertexID == 1) ? 1. : 0.;
     position.y = (gl_VertexID == 0 || gl_VertexID == 3) ? 0. : 1.;
 
-    int background = 0;
     if (background == 1) {
         // Calculate the final position of our cell in world space.
         // We have to add our cell size since our vertices are offset
@@ -52,7 +59,7 @@ void main() {
         cell_pos = cell_pos + cell_size * position;
 
         gl_Position = projection * vec4(cell_pos, 0.0, 1.0);
-        bg_color = vec4(bg_color_in.rgb / 255.0, 1.0);
+        color = bg_color_in / 255.0;
     } else {
         // TODO: why?
         vec2 glyph_offset_calc = glyph_offset;
@@ -67,7 +74,7 @@ void main() {
         vec2 glyph_tex_size = glyph_size / text_size.xy;
         glyph_tex_coords = glyph_pos + glyph_tex_size * position;
 
-        // This is used to color the font for now.
+        // Set our foreground color output
-        bg_color = vec4(bg_color_in.rgb / 255.0, 1.0);
+        color = fg_color_in / 255.;
     }
 }

src/Grid.zig

@@ -52,6 +52,12 @@ const GPUCell = struct {
     glyph_offset_x: i32,
     glyph_offset_y: i32,
 
+    /// vec4 fg_color_in
+    fg_r: u8,
+    fg_g: u8,
+    fg_b: u8,
+    fg_a: u8,
+
     /// vec4 bg_color_in
     bg_r: u8,
     bg_g: u8,
@@ -140,16 +146,20 @@ pub fn init(alloc: Allocator) !Grid {
     try vbobind.attributeAdvanced(3, 2, gl.c.GL_INT, false, @sizeOf(GPUCell), offset);
     offset += 2 * @sizeOf(i32);
     try vbobind.attributeAdvanced(4, 4, gl.c.GL_UNSIGNED_BYTE, false, @sizeOf(GPUCell), offset);
+    offset += 4 * @sizeOf(u8);
+    try vbobind.attributeAdvanced(5, 4, gl.c.GL_UNSIGNED_BYTE, false, @sizeOf(GPUCell), offset);
     try vbobind.enableAttribArray(0);
     try vbobind.enableAttribArray(1);
     try vbobind.enableAttribArray(2);
     try vbobind.enableAttribArray(3);
     try vbobind.enableAttribArray(4);
+    try vbobind.enableAttribArray(5);
     try vbobind.attributeDivisor(0, 1);
     try vbobind.attributeDivisor(1, 1);
     try vbobind.attributeDivisor(2, 1);
     try vbobind.attributeDivisor(3, 1);
     try vbobind.attributeDivisor(4, 1);
+    try vbobind.attributeDivisor(5, 1);
 
     // Build our texture
     const tex = try gl.Texture.create();
@@ -246,10 +256,14 @@ pub fn updateCells(self: *Grid, term: Terminal) !void {
                 .glyph_height = glyph.height,
                 .glyph_offset_x = glyph.offset_x,
                 .glyph_offset_y = glyph.offset_y,
-                .bg_r = 0xFF,
+                .fg_r = 0xFF,
+                .fg_g = 0xA5,
+                .fg_b = 0,
+                .fg_a = 255,
+                .bg_r = 0x0,
                 .bg_g = 0xA5,
                 .bg_b = 0,
-                .bg_a = 255,
+                .bg_a = 0,
             });
         }
     }
@@ -304,6 +318,15 @@ pub fn render(self: Grid) !void {
     var texbind = try self.texture.bind(.@"2D");
     defer texbind.unbind();
 
+    try self.program.setUniform("background", 1);
+    try gl.drawElementsInstanced(
+        gl.c.GL_TRIANGLES,
+        6,
+        gl.c.GL_UNSIGNED_BYTE,
+        self.cells.items.len,
+    );
+
+    try self.program.setUniform("background", 0);
     try gl.drawElementsInstanced(
         gl.c.GL_TRIANGLES,
         6,

src/opengl/Program.zig

@@ -82,6 +82,7 @@ pub inline fn setUniform(p: Program, n: [:0]const u8, value: anytype) !void {
 
     // Perform the correct call depending on the type of the value.
     switch (@TypeOf(value)) {
+        comptime_int => c.glUniform1i(loc, value),
         @Vector(2, f32) => c.glUniform2f(loc, value[0], value[1]),
         @Vector(3, f32) => c.glUniform3f(loc, value[0], value[1], value[2]),
         @Vector(4, f32) => c.glUniform4f(loc, value[0], value[1], value[2], value[3]),