GL: Split GL context creation in two phases

Desktop / GNOME / GTK - Emmanuele Bassi [gnome.org] - 9 February 2015 13:10 UTC

One of the major requests by OpenGL users has been the ability to specify settings when creating a GL context, like the version to use or whether the debug support should be enabled.

We have a couple of requirements in terms of API:

• avoid, if at all possible, the "C arrays of integers with attribute, value pairs", which are hard to write and hard to bind in non-C languages. • allow failing in a recoverable way. • do not make the GL context creation API a mess of arguments.

Looking at prior art, it seems that a common pattern is to split the construction phase in two:

• a first phase that creates a GL context wrapper object and does preliminary checks on the environment. • a second phase that creates the backend-specific GL object.

We adopted a similar pattern:

• gdk_window_create_gl_context() creates a GdkGLContext • gdk_gl_context_realize() creates the underlying resources

Calling gdk_gl_context_make_current() also realizes the context, so simple GL users do not need to care. Advanced users will want to call gdk_window_create_gl_context(), set up the optional requirements, and then call gdk_gl_context_realize(). If either of these two steps fails, it's possible to recover by changing the requirements, or simply creating a new GdkGLContext instance.

https://bugzilla.gnome.org/show_bug.cgi?id=741946

22e6f37 GL: Split GL context creation in two phases
gdk/gdkglcontext.c | 59 +++++-
gdk/gdkglcontext.h | 18 +-
gdk/gdkglcontextprivate.h | 3 +
gdk/gdkwindow.c | 31 ++-
gdk/gdkwindow.h | 1 -
gdk/gdkwindowimpl.h | 4 +-
gdk/wayland/gdkglcontext-wayland.c | 80 +++++---
gdk/x11/gdkglcontext-x11.c | 375 +++++++++++++++++++-----------------
gtk/gtkglarea.c | 17 +-
9 files changed, 363 insertions(+), 225 deletions(-)

Upstream: git.gnome.org

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