windowscodecs: More complete implementation of DdsFrameDecode_CopyPixels().

dlls/windowscodecs/ddsformat.c

@@ -607,9 +607,7 @@ static HRESULT WINAPI DdsFrameDecode_CopyPixels(IWICBitmapFrameDecode *iface,
     if (!prc) {
         if (cbStride < frame_stride) return E_INVALIDARG;
         if (cbBufferSize < frame_size) return WINCODEC_ERR_INSUFFICIENTBUFFER;
-        return S_OK;
-    }
-
+    } else {
         x = prc->X;
         y = prc->Y;
         width = prc->Width;
@@ -621,6 +619,7 @@ static HRESULT WINAPI DdsFrameDecode_CopyPixels(IWICBitmapFrameDecode *iface,
         }
         if (cbStride < width * bpp / 8) return E_INVALIDARG;
         if (cbBufferSize < cbStride * height) return WINCODEC_ERR_INSUFFICIENTBUFFER;
+    }
 
     EnterCriticalSection(&This->lock);
 
@@ -632,6 +631,9 @@ static HRESULT WINAPI DdsFrameDecode_CopyPixels(IWICBitmapFrameDecode *iface,
         }
     }
 
+    hr = copy_pixels(bpp, This->pixel_data, This->info.width, This->info.height, frame_stride,
+                     prc, cbStride, cbBufferSize, pbBuffer);
+
 end:
     LeaveCriticalSection(&This->lock);