Re-draw issue on resize

[aytey]

What Operating System(s) are you seeing this problem on?

Windows

WezTerm version

wezterm 20211024-192045-f4ee31fe

Did you try the latest nightly build to see if the issue is better (or worse!) than your current version?

Using local build from main @ f4ee31f

Describe the bug

While writing-up #1263 I noticed that I have some "redraw" issues after resizing.

Step 1:

• Start with a file cat'd to the screen and in full screen

Step 2:

• Shrink the window to whatever the default size is

Step 3:

• Maximise the window

So there are two issues here:

1. It would be great if maximised -> shrunk -> maximised left what was on the screen alone (i.e., if I have a full screen of text before shrinking, and then I shrink/remaximise, it should have the same screen as before)
2. The cursor is "floating" in the middle of nowhere (I think it is at its position in the "shrunk" window size)

To Reproduce

• cat a large file to the screen when the window is maximised
• shrink the window
• maximise the window again

Configuration

no config

Expected Behavior

It would be great if maximised -> shrunk -> maximised left what was on the screen alone

Logs

No response

Anything else?

No response

[davidrios]

I have this same issue. Something very similar also happens in Windows Terminal, and since this problem doesn't appear in other platforms, I thinks it's likely an issue with ConPTY.

[wez]

There's a lot of bugs around resizing in conpty:

• [Scenario] 2 Resize 2 Reflow microsoft/terminal#5800
• ConPTY sends two WINDOW_BUFFER_SIZE_EVENT messages when the window is restored from maximize microsoft/terminal#1765 (which may be extra on top for this particular situation)

The most problematic aspect of it is that the cursor moves up and then conpty decides to repaint the screen at that position, corrupting the output.

wezterm has a quirk mode for conpty to push the screen contents into the scrollback as part of resizing, in order to preserve the existing output, but it is still frustrating to deal with the fallout as the cursor position doesn't seem to agree in all cases.

I think we're waiting for this to land in conpty to bypass that layer:

• ConPTY Passthrough mode  microsoft/terminal#1173

I've learned to live with this when working in pwsh or cmd, but try to avoid conpty when I'm working in a unix environment by using either wezterm ssh or wezterm connect to bypass conpty and talk directly to the unix pty implementation.

I just pushed 53c4714 to disable the resize quirk mode for those bypass cases: previously it was hard coded to enabled for the windows GUI. Now it is only enabled when we know that we started ConPTY for a given pane.