click-to-focus on window should focus the pane under the mouse cursor

[wez]

Discussed in #880

^{Originally posted by mivok June 17, 2021}
Hi.

I currently have wezterm running with multiple panes in a single window. If I have another window focused, and click on the wezterm window, but over an inactive pane, I need to click a second time in order to focus the pane as well. Is it possible to have the pane be immediately focused on the first click that activates the window?

I do have pane_focus_follows_mouse = true, which almost does what I want. Unfortunately, if I click the window to focus it, and don't also move the mouse after clicking, then the pane under the cursor never actually gets focused. I also have swallow_mouse_click_on_pane_focus = false (or rather I have it left at the default), but that doesn't appear to be what I'm looking for either.

[wez]

I looked at this a bit tonight; on macOS at least, the click that focuses the window isn't reported as a mouse event. This is potentially tricky; the internal focus event plumbing needs to include/infer information about the focus event so that we don't do something annoying like implicitly focusing the pane that was under the mouse prior to CMD-tabing away and back again, but does focus the the pane under the mouse when the focus was due to a mouse click.

[mivok]

It looks like you might be able to set acceptsFirstMouse on an NSView to get it to show up as an event: https://developer.apple.com/documentation/appkit/nsview/1483410-acceptsfirstmouse/. I took a brief look at the code and immediately got very very lost, but I think something similar to what you did with accepts_first_responder would be how it would need to be done in https://github.com/wez/wezterm/blob/main/window/src/os/macos/window.rs

[wez]

Thanks for the lead! I've pushed a commit that implements this. The mac builds typically take about 30 minutes to build out after a push; please try it when it's built and let me know how well this works for you!

[mivok]

I just did a quick test with nightly and it appears to work perfectly. Thank you!

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