Cannot center window before showing it on linux

[emersion]

Windows are not centered by default. Calling Show and Center does not work well because the window is first displayed in a corner of the screen and is then centered. Calling Center and Show doesn't work, Center fails.

Provide a way to center the window by default.

[andlabs]

What OS? Center not working before Show is a bug.

[emersion]

Okay. It's happening with GTK:

(Desktop-Bridge:5073): Gdk-CRITICAL **: gdk_window_get_screen: assertion 'GDK_IS_WINDOW (window)' failed

(Desktop-Bridge:5073): Gdk-CRITICAL **: gdk_screen_get_monitor_at_window: assertion 'GDK_IS_SCREEN (screen)' failed

(Desktop-Bridge:5073): Gdk-CRITICAL **: gdk_screen_get_monitor_workarea: assertion 'GDK_IS_SCREEN (screen)' failed

[andlabs]

Yes, the GTK+ window moving is a giant mess right now due to having to deal with how Wayland works, and I'm not yet sure how to solve it. This particular issue might not have a solution; it's ultimately up to the window manager to decide what the initial position of a window is, and the most that's done is there are protocols in place for being able to save and restore window position among session. (For what it's worth, this is how libui works now, especially on Windows.)

[emersion]

On GTK and Windows the default position is not that bad, but on macOS it shows in at the bottom left corner. Is there a way to change this?

[emersion]

Looking at the code, why don't you just use window.set_position(Gtk.WindowPosition.CENTER)? It works before showing the window, and that's the method used by the elementary developer guide.

[andlabs]

I do not fully understand how that function works, namely I do not know if it will work at any time. I can ask about this easily, though. I'll do that later. In the meantime, can you link the relevant portion of the elementary developer guide?

[emersion]

Here: https://elementary.io/docs/code/getting-started#gtk-window-and-gtk-button

Then we tell the window manager that we want to place this window in the center of the screen instead of in the default position (which is usually the top left).

I think you're right, gtk_window_set_position only works when the window is not shown, since the window manager will use it when opening the window. So the fix would be to call gtk_window_set_position when the window is hidden, and use your current code otherwise.