I am currently trying to learn video compositing and editing in blender, using 2.80. Whenever I'm masking within the image editor, the compositor does its processing on every single interaction with the mask. That is, every single mouse move while dragging a control point.
This causes everything to lag and I cannot edit the mask smoothly at all. The same thing happens in blender 2.79 except that the actual mask editing is not affected by the processing in the compositor, I can edit smoothly even if it is constantly doing its compositing.
I understand that it is a good feature to update the compositor in real-time so that any processing using the mask is instant, and you can see the results in a viewer node immediately. However, I think you should be able to turn this off, so that it only updates on mouse release. Also, I kind of think it is an unreasonable amount of lag - only a movie input and a viewer are needed in the compositor to replicate this.
Something to note is that this same lag does not happen when masking using the movie clip editor, but it does happen in the image editor no matter what the background image is. Also, checking off "use nodes" in the compositor does not affect the lag.
Should I report this as a bug? Seems like a bug to me that the masking interaction is completely destroyed just as a result of having a movie clip in the compositor.