Fetch Monitor Index

[meanbeanmachine]

What problem does this solve or what need does it fill?

Prior to 0.9, it was possible to have "window persistence" for a multi-monitor setup. By window persistence I mean that the app will boot in the exact place you left it when you closed it. This was achieved by saving the window position to a file before app exit, then loading that file on app boot and injecting the saved window position coordinates with WindowPlugin.

As of 0.9+, this is no longer possible on a multi-monitor setup because of the introduction of 'MonitorSelection'. It looks like window position is no longer considered a global/desktop "area", and instead uses monitor index along with the coordinates. This means you now have to manually set the Monitor Index for a multi-monitor setup.

Setting the Monitor Index makes sense and is now possible with MonitorSelection, however, there doesn't seem to be a way to actually GET the Monitor Index. window::Window::position() only returns the Vec2 coordinates, and I don't see a new method related to fetching the monitor index. With this change, window persistence only works on single monitor setups; it no longer works on multi-monitor setups because you have no idea what to set the Monitor Index to.

What solution would you like?

create window::Window::monitor() => returns Monitor Index

or

window::Window::position() now returns Monitor Index in addition to the Vec2 coordinates

What alternative(s) have you considered?

There is no alternative solution unless you decide to build window persistence into Bevy core and make it an optional feature, and of course works on multi-monitor setups.

Additional context

Here is an example repo of window persistence. The Monitor stuff is commented out because there is no point setting the index if there is no way to fetch it and save it.

[tim-blackbird]

Window::position() returns the position of the window in "desktop space", ie. not relative to the monitor the window is on.

(In X11 at least) the origin of the window position is relative to the first monitor, so the following code works:

window.set_position(MonitorSelection::Index(0), position);

I'll open a PR that makes monitor selection optional for set_position.

[meanbeanmachine]

(In X11 at least) the origin of the window position is relative to the first monitor, so the following code works:

window.set_position(MonitorSelection::Index(0), position);

This does not work for dual monitors. The window is set to the same position, but on the wrong monitor.

I start the app, move it to my side monitor and close it. The following coords are printed: IVec2(44, 279)

I check the file the coords were saved to: IVec2(44, 279)

I restart the app, it pops up on my main monitor, not my side monitor, with the following coords: IVec2(1964, 279)

The window.x is off by 1920px, i.e. my entire side monitor. This happens no matter what I set 'WindowPlugin.window.monitor' to, or even if I don't set it at all. This was not an issue prior to 0.90 when MonitorSelection did not exist.

[alice-i-cecile]

I'd happily accept a PR for this.

[tim-blackbird]

Sorry for forgetting about this. I'll open a PR that makes monitor selection optional for set_position tomorrow (like I said I would two weeks ago, oops). It's a simple change and will allow you to do what you want again.
We currently don't have any way to fetch info about monitors in Bevy. I'll look into that afterwards, if I find the time :)

[meanbeanmachine]

I'll open a PR that makes monitor selection optional for set_position tomorrow

Will that fix this issue tho? I don't think we are on the same page here. I am using the WindowPlugin to setup the position/monitor on app start. If I set monitor to index 0 like you suggested, the app starts on my main monitor even though I closed it on my side monitor. If I don't set monitor at all, it will default to Current, which is also my main monitor. The only way to get the app to start on my side monitor where I closed it is to use Index 1. So at the end of the day, if a user moves and closes my app, I have no idea what monitor to boot it to, since there is currently no way to know what monitor it was on when it closed.

This was not a problem prior to 0.9 before this MonitorSelection was added....I don't understand why you would introduce the ability to set the monitor if you don't provide us a way to actually fetch the monitor the app is on. Because of this, support for multi-monitor setups is broken in regards to window persistence, since it's a complete guessing game for setting the monitor index. And again, not setting the monitor just defaults to Current, and doesn't solve the issue.