if (mOffScreen) mCleanupContext->DestroyDrawingSurface(mOffScreen);  if (mOffScreenWhite) mCleanupContext->DestroyDrawingSurface(mOffScreenWhite);
BlendingBuffers::~BlendingBuffers() {  if (mOffScreen)    mCleanupContext->DestroyDrawingSurface(mOffScreen);  if (mOffScreenWhite)    mCleanupContext->DestroyDrawingSurface(mOffScreenWhite);  if (mWhite)    mCleanupContext->DestroyDrawingSurface(mWhite);  if (mBlack)    mCleanupContext->DestroyDrawingSurface(mBlack);}