GPUShader: Add optionnal single shader stage interface for in and out

This makes optionnal the use of a different interface for the geometry
shader stage output. When the vertex and geometry interface instance name
matches, a `_in` and `_out` suffix is added to the end of the instance name.

This makes it easier to have optional geometry shader stages.

# Conflicts:
#	source/blender/gpu/intern/gpu_shader_create_info.hh

1 files changed, 6 insertions, 1 deletions

diff --git a/source/blender/gpu/intern/gpu_shader_create_info.hh b/source/blender/gpu/intern/gpu_shader_create_info.hh
index 02c303fb8fa..6fe6d7676fb 100644
--- a/source/blender/gpu/intern/gpu_shader_create_info.hh
+++ b/source/blender/gpu/intern/gpu_shader_create_info.hh
@@ -380,7 +380,12 @@ struct ShaderCreateInfo {
     return *(Self *)this;
   }
 
-  /* Only needed if geometry shader is enabled. */
+  /**
+   * Only needed if geometry shader is enabled.
+   * IMPORTANT: Input and output instance name will have respectively "_in" and "_out" suffix
+   * appended in the geometry shader IF AND ONLY IF the vertex_out interface instance name matches
+   * the geometry_out interface instance name.
+   */
   Self &geometry_out(StageInterfaceInfo &interface)
   {
     geometry_out_interfaces_.append(&interface);