Metal: Make GLSL shader source MSL compliant also

Metal shading language follows the C++ 14 standard and in some cases requires a greater level of explicitness than GLSL. There are also some small language differences:

- Explicit type-casts (C++ requirements)
- Explicit constant values (C++ requirements, e.g. floating point values using 0.0 instead of 0).
- Metal/OpenGL compatibility paths
- GLSL Function prototypes
- Explicit accessors for vector types when sampling textures.

Authored by Apple: Michael Parkin-White

Ref T96261

Reviewed By: fclem

Maniphest Tasks: T96261

Differential Revision: https://developer.blender.org/D14378

1 files changed, 27 insertions, 0 deletions

diff --git a/source/blender/gpu/shaders/gpu_shader_2D_image_rect_vert.glsl b/source/blender/gpu/shaders/gpu_shader_2D_image_rect_vert.glsl
index d9a5aeeef46..903c602c5d6 100644
--- a/source/blender/gpu/shaders/gpu_shader_2D_image_rect_vert.glsl
+++ b/source/blender/gpu/shaders/gpu_shader_2D_image_rect_vert.glsl
@@ -15,6 +15,32 @@ void main()
 {
   vec2 uv;
   vec2 co;
+
+#ifdef GPU_METAL
+/* Metal API does not support Triangle fan primitive topology.
+ * When this shader is called using Triangle-Strip, vertex ID's
+ * are in a different order. */
+#  define GPU_PRIM_TRI_STRIP
+#endif
+
+#ifdef GPU_PRIM_TRI_STRIP
+  if (gl_VertexID == 0) {
+    co = rect_geom.xw;
+    uv = rect_icon.xw;
+  }
+  else if (gl_VertexID == 1) {
+    co = rect_geom.xy;
+    uv = rect_icon.xy;
+  }
+  else if (gl_VertexID == 2) {
+    co = rect_geom.zw;
+    uv = rect_icon.zw;
+  }
+  else {
+    co = rect_geom.zy;
+    uv = rect_icon.zy;
+  }
+#else
   if (gl_VertexID == 0) {
     co = rect_geom.xy;
     uv = rect_icon.xy;
@@ -31,6 +57,7 @@ void main()
     co = rect_geom.zy;
     uv = rect_icon.zy;
   }
+#endif
 
   gl_Position = ModelViewProjectionMatrix * vec4(co, 0.0f, 1.0f);
   texCoord_interp = uv;