Re: GtkGLArea

[Bill Kelly <billk cts com>]

Emmanuele Bassi wrote:
> > Our primary goal was to embed GTK widgets into Native views,
> > and we now have that working, via:
> >
> >   GtkWin32EmbedWidget   // This already existed, but wasn't publicly exposed
> >   GtkQuartzEmbedWidget  // New, using our GDK Foreign Window additions for OSX
> >
> > So far, so good.
>
> Not really, because GTK+ does not really like rendering outside of its
> rendering pipeline.
>
> I expect, for instance, that you had to disable double buffering,
> which is a deprecated operation because a) it's not portable b) it's a
> workaround to using native surfaces with out-of-frame rendering
> cycles. Additionally, you'll notice that you won't be able to handle
> things like overlaid popovers, or semi-transparent windows on top of
> the native window.

Interesting.  To the best of my knowledge, our changes didn't affect
double buffering; and popovers seem to be working.

GDK was already rendering to an NSView (via GdkQuartzView) and we
didn't need to change that, structurally.

Mainly our modifications addressed how GDK identifies a toplevel
window, and how events are dispatched.

(Our resident OSX-pert adds: "Their popovers end up creating a
borderless NSWindow that contains a content view that the drawing
appears within."  So, indeed, our changes should be compatible
with popovers.)

To clarify: What we're doing is embedding the GdkQuartzView associated
with a GTK widget into a native NSWindow.  We're not doing the converse
(i.e. /not/ embedding Native controls *inside* a GTK widget.)


> The whole "let's embed an external windowing surface into GTK+ and
> expect it to render at the same time as the rest of the application"
> use case is untenable in modern graphics stack, and it's something
> we're (as a toolkit) dropping from the next major API version. It's
> basically impossible for the toolkit to optimise, it's also a typical
> scenario where there cannot be any expectation of portability. Either
> GTK+ is in control of what it should render, or it's not — in which
> case you get rendering artefacts, tearing, or obscene performance.

Fair enough.

(In our case, this is an application that has been under continuous
development for 15 years, so being able begin an incremental transition
toward GTK has been crucial for us.)


> [...] we are switching
> to OpenGL (and Vulkan) as *the* rendering API for GTK+.

That sounds excellent!


Regards,

Bill