metal: Fix compilation when using older Apple SDKs (bug #4828).
diff --git a/src/render/metal/SDL_render_metal.m b/src/render/metal/SDL_render_metal.m
index 8d59dcb..bdf7ed1 100644
--- a/src/render/metal/SDL_render_metal.m
+++ b/src/render/metal/SDL_render_metal.m
@@ -271,7 +271,7 @@ MakePipelineState(METAL_RenderData *data, METAL_PipelineCache *cache,
case SDL_METAL_VERTEX_SOLID:
/* position (float2) */
vertdesc.layouts[0].stride = sizeof(float) * 2;
- vertdesc.layouts[0].stepFunction = MTLStepFunctionPerVertex;
+ vertdesc.layouts[0].stepFunction = MTLVertexStepFunctionPerVertex;
vertdesc.attributes[0].format = MTLVertexFormatFloat2;
vertdesc.attributes[0].offset = 0;
@@ -280,7 +280,7 @@ MakePipelineState(METAL_RenderData *data, METAL_PipelineCache *cache,
case SDL_METAL_VERTEX_COPY:
/* position (float2), texcoord (float2) */
vertdesc.layouts[0].stride = sizeof(float) * 4;
- vertdesc.layouts[0].stepFunction = MTLStepFunctionPerVertex;
+ vertdesc.layouts[0].stepFunction = MTLVertexStepFunctionPerVertex;
vertdesc.attributes[0].format = MTLVertexFormatFloat2;
vertdesc.attributes[0].offset = 0;