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This note is a conclusion description of the group chat yesterday. Includes Chuyu-Team members and me and more anonymous people. Thanks!

Restore?

If your app is like Game Launcher or Login Dialog, has fixed size, then it's recommended to be placed in the center. Or it's usually better to store/restore the window state.

Restore what?

Referring to popular apps and os, we recommend always restore the size (width,height) as the best practice. You'd better remember to restore the "maximized" state.

To go further, you can also store the scale factor and reset the size if you notice a scale/resolution change. Of course you can also do sophisticated calculations to make the app keep a reasonable size even after the scale change, but I don't think this is reliable or standard practice.

However there are many details to consider when restore the window position (x,y).

For all platforms, does the position of the new window opening cover the smaller windows of other apps? In desktop such as windows, system will automatically set a "reasonable" position if it's not specified, usually a little to the right down of the currently focused window, so new window appears nicely and allows the previous window to still be adjustable by dragging the title bar.

For Windows, should we exclude Snap Windows (left-right/quad split screen) from the position store? Explorer excluded, Chromium, QQ and others does not. If you don't exclude it, your window will looks like splitted (similar size and position) but the system doesn't think so (the Snap Windows features doesn't work), it's fucking weird. In Win11, splitted windows use square corners instead of rounded one. And the fast adjustment of neighbors, as well as the auto window fill, will not work.

On windows, some apps will use the new WinAPI to support Snap Windows (some of which are still undocumented), but have you noticed, this is the trap! Back in the days of Win7, Snap Windows only supported left/right split, which caused some apps to store and restore to the basic left/right split after being switched to quad split, three split, or more complex states on Win10, Win11! This is completely wrong, even worse than not restore, so weird.

On GNOME, most GNOME apps have size restore,but not position restore.

Multi-monitor support has been the massive problem for all platforms, and if you store a position, it's best to judge whether it causes the window part to appear outside the monitor? Does it cause the coordinates to be negative (although allowed under windows, but not recommended)?

Also, if the position is restored, is the monitor the window is on when it opens, the one the user wants? I'm not a dual-monitors user, but I've observed that they often run into the situation where they click on an icon on monitor A, and the window appears on monitor B, and they have to drag it back. Of course, desktop environments have a tricky way around this problem by only showing the taskbar, dock, or whatever on the primary monitor, which ensures that you can only click on an icon to launch an application on the primary monitor, and then, to launch the application only on the primary monitor, you just need to eliminate the need to memorize the location of the window on the secondary monitor... So why not just drop the store?

More and more people are using cross-platform GUI these days, but much of the above requires native code to provide support. This would be a disaster for most mediocre app development teams, I'm afraid, and how do you anticipate that more relevant features will be added to the desktop environment afterwards? Will your old apps look so out of place in the new environment that the user experience is not as good as not adapting?

To summarize, here I give the simplest, robust, but not full featured approach: Restore window size, reset after scaling or resolution change, restore maximized state, no restore window position and split-screen state.

Where to store?

Most projects writes to a config file and reads it at startup. For example https://github.com/mawie81/electron-window-state . Some projects under Linux write to dconf, some projects under windows use the Registry, but if we look at it from a cross-platform point of view, it's probably safer and more consistent to use a config file instead of windows registry / Linux dconf. Besides, some Linux desktop environments don't have dconf.

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