debugDisableOpacityLayers top-level property
Setting to true will cause all opacity effects from the layer tree to be ignored.
An optimization to not paint the child at all when opacity is 0 will still remain.
Can be used to check whether excessive use of opacity effects is affecting performance.
This will not reduce the number of Layer objects created; the compositing strategy is unaffected. It merely causes the opacity layers to be skipped when building the scene.
Implementation
bool debugDisableOpacityLayers = false;