CGContextRef gfxQuartzNativeDrawing::BeginNativeDrawing() { NS_ASSERTION(!mCGContext, "BeginNativeDrawing called when drawing already in progress"); DrawTarget *dt = mDrawTarget; if (dt->IsDualDrawTarget() || dt->IsTiledDrawTarget() || dt->GetBackendType() != BackendType::SKIA || dt->IsRecording()) { // We need a DrawTarget that we can get a CGContextRef from: Matrix transform = dt->GetTransform(); mNativeRect = transform.TransformBounds(mNativeRect); mNativeRect.RoundOut(); if (mNativeRect.IsEmpty()) { return nullptr; } mTempDrawTarget = Factory::CreateDrawTarget(BackendType::SKIA, IntSize::Truncate(mNativeRect.width, mNativeRect.height), SurfaceFormat::B8G8R8A8); if (!mTempDrawTarget) { return nullptr; } transform.PostTranslate(-mNativeRect.x, -mNativeRect.y); mTempDrawTarget->SetTransform(transform); dt = mTempDrawTarget; } else { // Clip the DT in case BorrowedCGContext needs to create a new layer. // This prevents it from creating a new layer the size of the window. // But make sure that this clip is device pixel aligned. Matrix transform = dt->GetTransform(); Rect deviceRect = transform.TransformBounds(mNativeRect); deviceRect.RoundOut(); mNativeRect = transform.Inverse().TransformBounds(deviceRect); mDrawTarget->PushClipRect(mNativeRect); } MOZ_ASSERT(dt->GetBackendType() == BackendType::SKIA); mCGContext = mBorrowedContext.Init(dt); if (NS_WARN_IF(!mCGContext)) { // Failed borrowing CG context, so we need to clean up. if (!mTempDrawTarget) { mDrawTarget->PopClip(); } return nullptr; } return mCGContext; }