Show/Hide Window Programmatically

[newcomb-luke]

This pull request closes issue #2089.
You can now hide and show a window programmatically. This is done by a new hide() method on WindowHandle, and by a new command Selector called HIDE_WINDOW. This has been implemented on the x11, GTK+, Windows, and macOS backends. Wayland does not yet seem to support hiding/showing windows through their own protocol, and window managers seem to be currently just falling back to the x11 protocol, so Wayland implementation was held off.
HIDE_WINDOW leaves the macOS only HIDE_APPLICATION Selector alone in that HIDE_WINDOW does what it says, and only hides a specific window.
The Window can be shown again by the command SHOW_WINDOW which calls the WindowHandle's bring_to_front_and_focus method, which still works as intended when the window is already shown, but when it is hidden, it shows the window again, and brings it to the front and focuses it.

[newcomb-luke]

Seems to still work well with all of the new code changes that have been going on.

[yim7]

Thanks, I used your code.

hide feature works perfectly, but i can't show window after hiding it.
The deferred_queue cannot be processed because the window does not receive events after hiding. We should call the window display function directly.
And ShowWindow don't bring the window into foreground. We can use SetForegroundWindow to implement bring_to_front_and_focus

[newcomb-luke]

Thanks, I used your code.

hide feature works perfectly, but i can't show window after hiding it. The deferred_queue cannot be processed because the window does not receive events after hiding. We should call the window display function directly. And ShowWindow don't bring the window into foreground. We can use SetForegroundWindow to implement bring_to_front_and_focus

What version of Windows are you trying to run it on? Maybe it is being treated differently. I've tested it on Windows 10.

How did you try to show the window? When I spawn a thread and run handle.submit_command(druid::commands::SHOW_WINDOW, (), Target::Window(window_id)), it works perfectly, and shows the window again. The program would crash when I tried to ShowWindow in a non-deferred way.

I will implement SetForegroundWindow however, to make it bring the window to the front.

[newcomb-luke]

"An application cannot force a window to the foreground while the user is working with another window. Instead, Windows flashes the taskbar button of the window to notify the user. " here

[newcomb-luke]

I've added SetForegroundWindow, and everything should be up to date with master.

[xStrom]

Really sorry this has been sitting for so long. Please merge master once again so we can pass CI. I will then review.

[newcomb-luke]

Synced with master.

[xStrom]

This looks reasonable, thanks for your effort!