sokol_gfx.h mtl: allow binding multisampled textured

sokol_gfx.h

@@ -3948,6 +3948,7 @@ typedef struct sg_frame_stats {
     _SG_LOGITEM_XMACRO(VALIDATE_ABND_EXPECTED_IMAGE_BINDING, "sg_apply_bindings: image binding is missing or the image handle is invalid") \
     _SG_LOGITEM_XMACRO(VALIDATE_ABND_IMG_EXISTS, "sg_apply_bindings: bound image no longer alive") \
     _SG_LOGITEM_XMACRO(VALIDATE_ABND_IMAGE_TYPE_MISMATCH, "sg_apply_bindings: type of bound image doesn't match shader desc") \
+    _SG_LOGITEM_XMACRO(VALIDATE_ABND_EXPECTED_MULTISAMPLED_IMAGE, "sg_apply_bindings: expected image with sample_count > 1") \
     _SG_LOGITEM_XMACRO(VALIDATE_ABND_IMAGE_MSAA, "sg_apply_bindings: cannot bind image with sample_count>1") \
     _SG_LOGITEM_XMACRO(VALIDATE_ABND_EXPECTED_FILTERABLE_IMAGE, "sg_apply_bindings: filterable image expected") \
     _SG_LOGITEM_XMACRO(VALIDATE_ABND_EXPECTED_DEPTH_IMAGE, "sg_apply_bindings: depth image expected") \
@@ -12607,7 +12608,7 @@ _SOKOL_PRIVATE void _sg_mtl_init_texdesc_rt(MTLTextureDescriptor* mtl_desc, _sg_
 // initialize MTLTextureDescriptor with MSAA attributes
 _SOKOL_PRIVATE void _sg_mtl_init_texdesc_rt_msaa(MTLTextureDescriptor* mtl_desc, _sg_image_t* img) {
     SOKOL_ASSERT(img->cmn.sample_count > 1);
-    mtl_desc.usage = MTLTextureUsageRenderTarget;
+    mtl_desc.usage = MTLTextureUsageShaderRead | MTLTextureUsageRenderTarget;
     mtl_desc.resourceOptions = MTLResourceStorageModePrivate;
     mtl_desc.textureType = MTLTextureType2DMultisample;
     mtl_desc.sampleCount = (NSUInteger)img->cmn.sample_count;
@@ -17238,7 +17239,10 @@ _SOKOL_PRIVATE bool _sg_validate_apply_bindings(const sg_bindings* bindings) {
                     _SG_VALIDATE(img != 0, VALIDATE_ABND_IMG_EXISTS);
                     if (img && img->slot.state == SG_RESOURCESTATE_VALID) {
                         _SG_VALIDATE(img->cmn.type == shd->cmn.images[i].image_type, VALIDATE_ABND_IMAGE_TYPE_MISMATCH);
-                        _SG_VALIDATE(img->cmn.sample_count == 1, VALIDATE_ABND_IMAGE_MSAA);
+//                        _SG_VALIDATE(img->cmn.sample_count == 1, VALIDATE_ABND_IMAGE_MSAA);
+                        if (shd->cmn.images[0].multisampled) {
+                            _SG_VALIDATE(img->cmn.sample_count > 1, VALIDATE_ABND_EXPECTED_MULTISAMPLED_IMAGE);
+                        }
                         const _sg_pixelformat_info_t* info = &_sg.formats[img->cmn.pixel_format];
                         switch (shd->cmn.images[i].sample_type) {
                             case SG_IMAGESAMPLETYPE_FLOAT: