Best practices for saving and restoring window layout

[Pekka Paalanen]

On Fri, 5 Jun 2020 02:06:00 +1000
Brad Robinson <brobinson at toptensoftware.com> wrote:

> Hi All,
> 
> First post here...
> 
> I'm looking into porting an existing UI library to Gtk+ and I'm struggling
> to solve a couple of problems related to window positioning when using
> Wayland as the backend.
> 
> I've read through the posts on this list's archive about window positioning
> and it's clear that a global coordinate system isn't something that Wayland
> supports - fair enough and I understand the reasons why.
> 
> However, I'm wondering what the recommendations are for applications with
> complicated user-controllable layouts that need to be persisted not only
> across application runs, but also between documents and across application
> modes.
> 
> For example:
> 
> * my application is a music app where the user might have many plugin
> windows carefully positioned across multiple monitors.
> * each document file has a different set of plugins loaded and those plugin
> windows need to be restored to their previous location.
> * the app can be in "Live" mode or "Edit" mode and switching between modes
> saves and restores the plugin window locations for each mode.
> 
> How should such an app be handled under Wayland?
> 
> Note: the app doesn't need to be able to explicitly position windows. It
> just needs a way to capture and restore a window's position.  An opaque
> string or data structure that the app can save and use to later reposition
> a window back to that same place would be perfect.  It would need to be
> client persistable though - eg: giving a window an id that the window
> manager can use to store previous geometry probably wouldn't suffice.

Hi,

I believe the above is the consensus: ask the server to give you a
token that records the current state, including position, of the
window. You store the token, or any number of tokens. When you want to
recall old state, you pass the token back to the compositor.

The problem is that I don't remember seeing an extension spec for this.
It has been talked about, sure, but at least wayland-protocols does not
seem to have anything for it.


Thanks,
pq

> I'm about to refactor a big part of the code that handles this and now is
> the time I can make conceptual changes that could better cater for Wayland
> as a back end. I've seen comments in the archive about how a global
> coordinate system isn't necessary and that issues related to a lack of one
> can be better solved by other means but I'm not sure what those other means
> are and I'm struggling to see a way forward with this.
> 
> Any thoughts, suggestions, recommendations greatly appreciated.
> 
> Brad

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