From be4f939b268b7569633dc3968a2cfe8898978781 Mon Sep 17 00:00:00 2001
From: CJ van den Berg <cj@vdbonline.com>
Date: Fri, 10 Apr 2026 13:50:19 +0200
Subject: [PATCH] refactor(gui): fill background outside of grid

---
 src/gui/gpu/builtin.glsl.zig | 6 +++++-
 src/gui/gpu/gpu.zig          | 1 +
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/gui/gpu/builtin.glsl.zig b/src/gui/gpu/builtin.glsl.zig
index eb1b3873..5a89dcf4 100644
--- a/src/gui/gpu/builtin.glsl.zig
+++ b/src/gui/gpu/builtin.glsl.zig
@@ -23,6 +23,8 @@ pub const FsParams = extern struct {
     cursor_color: [4]f32, // RGBA normalized [0,1]
     // Secondary cursor colour (positions encoded in ShaderCell._pad)
     sec_cursor_color: [4]f32, // RGBA normalized [0,1]
+    // Background fill for border area outside the cell grid
+    bg_color: [4]f32, // RGBA normalized [0,1]
 };
 
 const vs_src =
@@ -48,6 +50,7 @@ const fs_src =
     \\uniform int cursor_vis;
     \\uniform vec4 cursor_color;
     \\uniform vec4 sec_cursor_color;
+    \\uniform vec4 bg_color;
     \\uniform sampler2D glyph_tex_glyph_smp;
     \\uniform usampler2D cell_tex_cell_smp;
     \\out vec4 frag_color;
@@ -69,7 +72,7 @@ const fs_src =
     \\    int row = py / cell_size_y;
     \\
     \\    if (col >= col_count || row >= row_count || row < 0 || col < 0) {
-    \\        frag_color = vec4(0.0, 0.0, 0.0, 1.0);
+    \\        frag_color = vec4(bg_color.rgb, 1.0);
     \\        return;
     \\    }
     \\
@@ -142,6 +145,7 @@ pub fn shaderDesc(backend: sg.Backend) sg.ShaderDesc {
             desc.uniform_blocks[0].glsl_uniforms[8] = .{ .type = .INT, .glsl_name = "cursor_vis" };
             desc.uniform_blocks[0].glsl_uniforms[9] = .{ .type = .FLOAT4, .glsl_name = "cursor_color" };
             desc.uniform_blocks[0].glsl_uniforms[10] = .{ .type = .FLOAT4, .glsl_name = "sec_cursor_color" };
+            desc.uniform_blocks[0].glsl_uniforms[11] = .{ .type = .FLOAT4, .glsl_name = "bg_color" };
 
             // Glyph atlas texture: R8 → sample_type = FLOAT
             desc.views[0].texture = .{
diff --git a/src/gui/gpu/gpu.zig b/src/gui/gpu/gpu.zig
index fb23273e..66860182 100644
--- a/src/gui/gpu/gpu.zig
+++ b/src/gui/gpu/gpu.zig
@@ -463,6 +463,7 @@ pub fn paint(
         .cursor_vis = if (cursor.vis) 1 else 0,
         .cursor_color = cursor.color.to_vec4(),
         .sec_cursor_color = sec_color.to_vec4(),
+        .bg_color = global.background.to_vec4(),
     };
     sg.applyUniforms(0, .{
         .ptr = &fs_params,