Creative people managed to create an X11 display and a Wayland display
at once, thereby getting EGL and GLX involved in a fight to the death
over the ownership of the glFoo() symbolspace.
A way to force such a fight with available tools here is (on Wayland)
running something like:
GTK_INSPECTOR_DISPLAY=:1 GTK_DEBUG=interactive gtk4-demo
Related: xdg-desktop-portal-gnome#5
Now that we have the display's context to hook into, we can use it to
construct other GL contexts and don't need a GdkSurface vfunc anymore.
This has the added benefit that backends can have different GdkGLContext
classes on the display and get new GLContexts generated from them, so
we get multiple GL backend support per GDK backend for free.
I originally wanted to make this a vfunc on GdkGLContextClass, but
it turns out all the abckends would just call g_object_new() anyway.
Instead of
Display::make_gl_context_current()
we now have
GLContext::clear_current()
GLContext::make_current()
This fits better with the backends (we can actually implement
clearCurrent on macOS now) and makes it easier to implement different GL
backends for backends (like EGL/GLX on X11).
We also pass a surfaceless boolean to make_current() so the calling code
can decide if a surface needs to be bound or not, because the backends
were all doing whatever, which was very counterproductive.
... or more exactly: Only use paint contexts with
gdk_cairo_draw_from_gl().
Instead of paint contexts being the only contexts who call swapBuffer(),
any context can be used for this, when it's used with
begin_frame()/end_frame().
This removes 2 features:
1. We no longer need a big sharing hierarchy. All contexts are now
shared with gdk_display_get_gl_context().
2. There is no longer a difference between attached and non-attached
contexts. All contexts work the same way.
The vfunc is called to initialize GL and it returns a "base" context
that GDK then uses as the context all others are shared with. So the GL
context share tree now looks like:
+ context from init_gl
- context1
- context2
...
So this is a flat tree now, the complexity is gone.
The only caveat is that backends now need to create a GL context when
initializing GL so some refactoring was needed.
Two new functions have been added:
* gdk_display_prepare_gl()
This is public API and can be used to ensure that GL has been
initialized or if not, retrieve an error to display (or debug-print).
* gdk_display_get_gl_context()
This is a private function to retrieve the base context from
init_gl(). It replaces gdk_surface_get_shared_data_context().
If our opaque region is the entire surface, then we can make the OpenGL
context opaque like we do for decorated windows. This improves performance
as the compositor does not need to blend the surface with the contents
behind the window.
We don't need to go through the NSOpenGLContext for these.
We can just use the C API directly. It's also clearer what is using
CGLEnable() vs CGLSetParameter().
Once we figure out what is going on with textures, changes are we'll be
able to let this stay a zero rect. But that is still a bit up in the air right now.
This implements the basics for a GdkGLContext on macOS. Currently, rendering
only is fully working for the GskCairoRenderer case where we read back pixels
into a cairo surface for rendering. More work on synchronization is required for
the GL on GskGLRenderer case.
When we attempt to render a surface itself with GL, the context will ensure that
the new GdkMacosGLView is placed within the NSWindow. In other cases, we
use a dummy NSView and NSWindow for backing the NSOpenGLContext to
ensure that we can get accelerated drawing.
This gets GtkGLArea working when running with GSK_RENDERER=cairo.
This is fairly substantial rewrite of the GDK backend for quartz and
renamed to macOS to allow for a greenfield implementation.
Many things have come across from the quartz implementation fairly
intact such as the eventloop integration design and discovery of
event windows from the NSEvent.
However much has been changed to fit in with the new GDK design and
how removal of child GdkWindow have been completely eliminated.
Furthermore, the new GdkPopup allows for regular NSWindow to be used
to provide popovers unlike the previous implementation.
The object design more closely follows the ideal for a GDK backend.
Views have been broken out into subclasses so that we can support
multiple GSK renderer paths such as GL and Cairo (and Metal in the
future). However mixed mode GL and Cairo will not be supported. Currently
only the Cairo renderer has been implemented.
A new frame clock implementation using CVDisplayLink provides more
accurate information about when to draw drawing the next frame. Some
testing will need to be done here to understand the power implications
of this.
This implementation has also gained edge snapping for CSD windows. Some
work was also done to ensure that CSD windows have opaque regions
registered with the display server.
** This is still very much a work-in-progress **
Some outstanding work that needs to be done:
- Finish a GL context for macOS and alternate NSView for GL rendering
(possibly using speciailized CALayer for OpenGL).
- Input rework to ensure that we don't loose remapping of keys that was
dropped from GDK during GTK 4 development.
- Make sure input methods continue to work.
- Drag-n-Drop is still very much a work in progress
- High resolution input scrolling needs various work in GDK to land
first before we can plumb that to NSEvent.
- gtk/ has a number of things based on GDK_WINDOWING_QUARTZ that need
to be updated to use the macOS backend.
But this is good enough to start playing with and breaking things which
is what I'd like to see.
