Re: gtk3 public API requests

[Jonas Ådahl <jadahl gmail com>]

On Thu, Apr 05, 2018 at 01:25:04AM -0700, Christian Hergert wrote:
> Hey everyone,
>
> I'm lobbying to make 2 functions public API in the stable branch (3.x)
> that would help me be able do some fancy things in Builder/Dazzle (which
> I can make work fine on Xorg already).
>
> If there are objections, I'd like to hear from people so I can find a
> way to make forward progress.
>
> The functions I'd like to see made public:
>
>   - gtk_window_set_use_subsurface()
>   - gdk_window_move_to_rect()
>
> The Gdk function is currently accessible if you're compiling Gtk since
> it can access the private API vtable. Widgets like GtkMenu use this to
> do positioning. It didn't make it to public API in time for 3.22, but
> had we continued to do a 3.24, it seems likely that would have happened.
>
> The gtk_window_set_use_subsurface() is basically only useful when on
> Wayland, but it helps ensure that we get a subsurface for transient
> popup windows. I'm open to other ways to solve the problem, like
> GDK_WINDOW_SUBSURFACE, if they allow me to ensure that my window is
> backed by a subsurface on Wayland.

For the gdk_window_move_to_rect() I think making it public is a good
idea, and it has been requested before on behalf of Firefox[0]. The
gtk_window_set_use_subsurface() however, I'm not so sure about.
Eventually I want to move away from using subsurfaces for things like
tooltips (anything that will extend outside the parent window really),
and while I haven't investigated further whether this is possible on
gtk-3, exposing _set_use_subsurface() might hinder such improvements.

The reason for moving away from using subsurfaces for various things is
that they cannot be positioned properly when they extend outside the
parent window (they tend to sometimes go partly off-screen), and should
rather use xdg_popup+xdg_positioner instead.


Jonas


[0] https://bugzilla.gnome.org/show_bug.cgi?id=791845

> Again, this API is available internally to Gtk so widgets like ComboBox
> can use it, but if you're not a GtkWidget, you're outta luck.
>
> Thoughts?
>
> -- Christian
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