Bug 490461

SUMMARY

Editing the Overscan setting of a display is a trial-and-error process because there is currently no interactive feedback on how the screen is going to look like which such setting applied.

Let's say this straight: Nintendo Switch operating system provides an amazing screen for overscan adjustment; you can find it by searching for "Nintendo Switch overscan", for example here: https://www.youtube.com/watch?v=O_h4eexYrqM

So, KScreen in tandem with KWin effects should show some realtime feedback, like those huge 90° angled arrows pointing at the to-be-applied corners of the screen.

There are some concerns though.

First, the overscan values are not standardized, and the meaning of those percents vary between vendors and models. Sounds like it's not a KDE's job to maintain a quirks database for all the GPU models, so it's probably up to the kernel to eventually provide some uniform and well-defined range of values. There are some plans for indeterminate future to implement overscan in KWin internally, which would not suffer from the aforementioned issue.

Second, from graphics point of view, if the cutoff is applied at a driver level, then it would only be possible to preview the shrinking but not the expanding of the drawable area. If an internal overscan is implemented in KWin but not used by default, then it could switch on the fly while the preview effect is active, and then switch back; but that leads us back to non-standardized values as described above.