Use getResourceDesc instead of GetDesc, See #1239 (#2260)

* Use getResourceDesc instead of GetDesc, See #1239

* Fix MSAA on d3d12

src/renderer_d3d12.cpp

@@ -2078,17 +2078,19 @@ namespace bgfx { namespace d3d12
 						? s_textureFormat[m_resolution.format].m_fmtSrgb
 						: s_textureFormat[m_resolution.format].m_fmt;
 
-					if (1 < m_backBufferColor[ii]->GetDesc().DepthOrArraySize)
+					if (1 < getResourceDesc(m_backBufferColor[ii]).DepthOrArraySize)
 					{
-						rtvDesc.ViewDimension = D3D12_RTV_DIMENSION_TEXTURE2DARRAY;
+						rtvDesc.ViewDimension = (NULL == m_msaaRt) ?
+							D3D12_RTV_DIMENSION_TEXTURE2DARRAY : D3D12_RTV_DIMENSION_TEXTURE2DMSARRAY;
 						rtvDesc.Texture2DArray.FirstArraySlice = 0;
-						rtvDesc.Texture2DArray.ArraySize = m_backBufferColor[ii]->GetDesc().DepthOrArraySize;
+						rtvDesc.Texture2DArray.ArraySize = getResourceDesc(m_backBufferColor[ii]).DepthOrArraySize;
 						rtvDesc.Texture2DArray.MipSlice = 0;
 						rtvDesc.Texture2DArray.PlaneSlice = 0;
 					}
 					else
 					{
-						rtvDesc.ViewDimension = D3D12_RTV_DIMENSION_TEXTURE2D;
+						rtvDesc.ViewDimension = (NULL == m_msaaRt) ?
+							D3D12_RTV_DIMENSION_TEXTURE2D : D3D12_RTV_DIMENSION_TEXTURE2DMS;
 						rtvDesc.Texture2D.MipSlice = 0;
 						rtvDesc.Texture2D.PlaneSlice = 0;
 					}