This is not really needed. The gl context is totally tied to the
window it is created from by virtue of sharing the context with the
paint context of that window and that context always has the visual
of the window (which we already can get).
Also, all user visible contexts are essentially offscreen contexts, so
a visual doesn't make sense for them. They only use FBOs which have
whatever format that the users sets up.
This adds the new type GdkGLContext that wraps an OpenGL context for a
particular native window. It also adds support for the gdk paint
machinery to use OpenGL to draw everything. As soon as anyone creates
a GL context for a native window we create a "paint context" for that
GdkWindow and switch to using GL for painting it.
This commit contains only an implementation for X11 (using GLX).
The way painting works is that all client gl contexts draw into
offscreen buffers rather than directly to the back buffer, and the
way something gets onto the window is by using gdk_cairo_draw_from_gl()
to draw part of that buffer onto the draw cairo context.
As a fallback (if we're doing redirected drawing or some effect like a
cairo_push_group()) we read back the gl buffer into memory and composite
using cairo. This means that GL rendering works in all cases, including
rendering to a PDF. However, this is not particularly fast.
In the *typical* case, where we're drawing directly to the window in
the regular paint loop we hit the fast path. The fast path uses opengl
to draw the buffer to the window back buffer, either by blitting or
texturing. Then we track the region that was drawn, and when the draw
ends we paint the normal cairo surface to the window (using
texture-from-pixmap in the X11 case, or texture from cairo image
otherwise) in the regions where there is no gl painted.
There are some complexities wrt layering of gl and cairo areas though:
* We track via gdk_window_mark_paint_from_clip() whenever gtk is
painting over a region we previously rendered with opengl
(flushed_region). This area (needs_blend_region) is blended
rather than copied at the end of the frame.
* If we're drawing a gl texture with alpha we first copy the current
cairo_surface inside the target region to the back buffer before
we blend over it.
These two operations allow us full stacking of transparent gl and cairo
regions.
This is a new function that gets called every time we're drawing
some area in the Gtk paint machinery. It is a no-op right now, but
it will be required later to keep track of what areas which
we previously rendered with GL was overwritten with cairo contents.
Add gdk_device_get_last_event_window(), and use to implement the window
tracking we need for synthesizing crossing events for sensitivity changes
and gtk grabs, rather than keeping the information in qdata and updating
it based when GTK+ gets events.
https://bugzilla.gnome.org/show_bug.cgi?id=726187
And deprecate the X11-specific version of it.
We call this new API _set_shadow_width() and not _set_frame_extents()
because we already have a gdk_window_get_frame_extents() with a
different meaning and different type of value.
https://bugzilla.gnome.org/show_bug.cgi?id=720374
Setting event compression to false will allow inter-frame
mouse motion events to be delivered, which are necessary
for painting applications to produce smooth strokes.
https://bugzilla.gnome.org/show_bug.cgi?id=702392
GtkPlug directly handles X KeyPress/Release events, instead of using
translation in GDK (which expects XI2 events for XI2). When this
was done, the handling of the group was stubbed out and never replaced.
Export gdk_keymap_x11_group_for_state() and gdk_keymap_x11_is_modifier()
so we can fill out the fields correctly.
https://bugzilla.gnome.org/show_bug.cgi?id=675167
