The subsurfaces example creates a subsurface widget and uses EGL to
render to it directly rather than using the cairo context from the
widget. In theory this shouldn't cause any problems because the westoy
window code lazily creates the cairo surface when an application
creates a cairo context. However commit fdca95c7 changed the behaviour
to force the lazy creation at the beginning of each surface redraw.
This ends up making the triangle surface get two attaches – one from
Cairo and one from the direct EGL.
It looks like it would be difficult to reinstate the lazy surface
creation behaviour whilst still maintaining the error handling for
surface creation because none of the redraw handlers in the example
clients are designed to cope with that. Instead, this patch adds an
explicit option on a widget to disable creating the Cairo surface and
the subsurface example now uses that.
Closes: https://bugs.freedesktop.org/show_bug.cgi?id=72854
when using cairo-glesv2 subsurface rendering code
implicitly calls eglMakeCurrent(dpy, NULL, NULL, ctx)
(since EGL_KHR_surfaceless_context is used), thus,
triangle_frame_callback:eglSwapBuffers returns EGL_BAD_SURFACE
error for all invocations other that the first one
Add a demo program with:
- a main surface (green)
- a Cairo-image sub-surface (red)
- a raw GLESv2 widget (triangle)
Sub-surface input region is set empty to avoid problems in toytoolkit.
If Cairo links to libGL, then we will end up with also libGLESv2 linked
to subsurfaces program, and both libs getting really used, which leads
to disaster.
Do not build subsurfaces demo, if Cairo links to libGL and cairo-egl is
usable.
The GL rendering loop is not tied to the toytoolkit or the widget, but
runs directly from its own frame callback. Therefore it runs
independent of the rest of the application. This also relies on one of
two things:
- eglSwapInterval(0) is implemented, and therefore eglSwapBuffers never
blocks indefinitely, or
- toytoolkit has a workaround, that guarantees that eglSwapBuffers will
return soon, when we force a repaint on resize.
Otherwise the demo will deadlock.
The code is separated into three sections:
1. The library component, using only EGL, GLESv2, and libwayland-client
APIs, and not aware of any toolkit details of the parent application.
This runs independently until the parent application tells otherwise.
2. The glue code: a toytoolkit application widget, who has its own
rendering machinery.
3. The application written in toytoolkit.
This patch also adds new toytoolkit interfaces:
- widget_get_wl_surface()
- widget_get_last_time()
- widget_input_region_add()
Toytoolkit applications have not had a possibility to change the input
region. The frame widget (decorations) set the input region on its own
when used, otherwise the default input region of everything has been
used. If a window does not have a frame widget, it can now use
widget_input_region_add() to set a custom input region.
These are not window methods, because a widget may lie on a different
wl_surface (sub-surface) than the window.
Changes in v3:
- replace set_commit_mode with set_sync and set_desync
Signed-off-by: Pekka Paalanen <ppaalanen@gmail.com>
