This happens in the real world when using the inspector to look at a
node recording of a GStreamer video while the video is still playing.
GStreamer will use the GL context in a different thread while we are
busy trying to download it.
A test is included.
1. The download via gdk_cairo_draw_from_gl() was broken sometimes
2. We get easy conversion on fallback by chaining up and using
download_texture().
3. One more place where Cairo is no longer necessary.
1. It avoids Cairo, and in particular conversion to Cairo.
2. Keeping a texture allows easy chaining in the vfuncs.
3. Using a texture means releasing will work for HDR formats
too, once we add them.
A private vfunc that downloads a texture as a GdkMemoryTexture in
whatever format the texture deems best.
There are multiple reasons for this:
* GLES cannot download the Cairo format. But it can download some
format and then just delegate to the GdkMemoryTexture implementation.
* All the other download vfuncs (including the ones still coming) can
be implemented via download_texture() and delegation, making the
interface easier.
* We want to implement image loading and saving support. By using
download_texture(), we can save in the actual format of the texture.
* A potential GdkCompressedTexture could be implemented by just
providing this one vfunc as a compress() step.
It seems these are sent with `xwindow` set to the root window, so this
was failing to find a surface and get the screen from that.
I'm not sure if there's a reason not to get the screen this way
elsewhere in the function, but it seems this should be correct.
This fixes the behavior of `gdk_x11_display_get_monitors()`, which
wasn't correctly changing when monitors were added or removed. For
instance, this python code was always showing the same number of
monitors when one was turned off and on, but updates correctly with this
change applied:
```python
import gi
gi.require_version("GLib", "2.0")
gi.require_version("Gdk", "4.0")
gi.require_version("Gtk", "4.0")
from gi.repository import GLib, Gdk, Gtk
def f():
print(len(Gdk.Display.get_default().get_monitors()))
return True
GLib.timeout_add_seconds(1, f)
GLib.MainLoop().run()
```
_gdk_macos_event_source_new() calls g_source_set_static_name(), which
for GLib versions before 2.69.1 is a macro defined in gdk-private.h.
Fixes#4195
modified: gdk/macos/gdkmacoseventsource.c
Goals:
1. Provide as much information as possible in the error message, so
users can try to fix their system themselves.
2. Try to formulate the error message in a way that explains that this
is not something GTK can fix, but a lower layer problem.
Related: #4193
