Port the tint shader

kitty/shaders/tint.slang

@@ -0,0 +1,32 @@
+#language slang 2026
+// Copyright (C) 2026 Kovid Goyal <kovid at kovidgoyal.net>
+// Distributed under terms of the GPLv3 license.
+
+// Main Vertex Shader Entry Point
+[shader("vertex")]
+float4 vertex_main(
+    uint vertex_id : SV_VertexID,
+    uniform float4 edges, // [ left, top, right, bottom ]
+) : SV_Position {
+    // Extract boundaries from the edges vector
+    float left   = edges[0];
+    float top    = edges[1];
+    float right  = edges[2];
+    float bottom = edges[3];
+
+    // Static mapping table for vertex positions
+    const float2 pos_map[4] = {
+        float2(left, top),
+        float2(left, bottom),
+        float2(right, bottom),
+        float2(right, top)
+    };
+
+    // Calculate final position
+    return float4(pos_map[vertex_id], 0.0, 1.0);
+}
+
+[shader("fragment")]
+float4 fragment_main(uniform float4 tint_color) : SV_Target {
+    return tint_color;
+}