Screen.Clear — Flickering on Windows

[rivo]

Following up on this comment, I noticed that calling Screen.Clear() prior to Screen.Show() (and after drawing other elements) leads to full-screen flickering on Windows. It's as if the call to Clear() immediately clears the screen instead of deferring it to Show(). The comment above illustrates this with a video. Here is the relevant code in tview. If I remove the call to Clear(), there is no flickering anymore (but this has other unintended side effects, so I would like to keep Clear() there).

Is this the intended behaviour? If so, what's the best way to clear the screen buffer at the beginning of a drawing cycle?

[gdamore]

Ok, I just reviewed the code... the implementation of Clear() on current versions is literally Fill(). So there should be no flickering. Is it possible that you are using a version of Tcell that does not include a642547 (i.e. I think this report is probably a duplicate of #576 )

[gdamore]

So 576 only fixed POSIX. The fix is simple. Stay tuned.

[rivo]

Thanks, @gdamore! Looks like this solves the problem.

(As a minor note, it looks like the cursor still flickers on Windows even when the screen content remains the same and the cursor's position doesn't change. But I haven't looked into this in detail so I don't know if this is a tcell problem.)

[gdamore]

I suspect that we need to hide the cursor when drawing. In the past we drew using a direct API, but now that we're using the escape codes to do this, we probably need to add the logic to hide the cursor for a redraw.