1fb96180f4
Fixes hiding a wxGLCanvas on Wayland, either directly (`->Show(false)`)
or indirectly (e.g. when it is contained in a wxNotebook).
On Wayland, unlike on X11, to show the canvas on the screen, we need to
create a Wayland subsurface. This subsurface is detached from the GTK
widget associated to the canvas, thus it is not automatically mapped or
unmapped when the associated GTK widget is.
Rather, we need to manually keep it in sync with the widget's state.
Knowing what has to be done to map and unmap the canvas, while dealing
with edge cases properly, is not easy to someone not used to Wayland.
When the canvas is mapped, we have this graph of resources:
EGL Surface (m_surface)
|
|
v
wl_egl window (m_wlEGLWindow)
|
|
v
Canvas wl_surface GDK's toplevel window wl_surface
(m_wlSurface) (gdk_wayland_window_get_wl_surface(w))
\ which is shown to the user
\ ^
\ /
\ /
v /
Subsurface (m_wlSubsurface) to overlay
the canvas onto the toplevel window
A simple way would be to destroy everything (m_surface, m_wlEGLWindow,
m_wlSurface, m_wlSubsurface) on unmap, and re-create it again on map.
Inefficiencies aside, this mostly works. However, it can mess with the
current OpenGL context. For example, suppose we have a (fragile)
program that places a canvas inside one of wxNotebook's tabs, and makes
the OpenGL context current only once at startup (e.g. on wxEVT_SHOW).
Switching between tabs will destroy and re-create the EGL Surface, so
the canvas will not be properly rendered when going back to its tab.
So we need to be smarter, and find some way to hide the subsurface
instead. The obvious way would be to unmap the canvas wl_surface
(m_wlSurface), as according to the Wayland spec., "a sub-surface is
hidden [...] if a NULL wl_buffer is applied [to the canvas surface]."
(https://wayland.freedesktop.org/docs/html/apa.html#protocol-spec-wl_subsurface)
However, as far as I can tell, this can't be done. There's no API to
hide an wl_egl window, and directly applying a NULL wl_buffer to the
canvas surface initially hides it, but seems to breaks the associated
window so that it crashes when one attempts to show it again.
So what remains, is destroying the overlay subsurface (m_wlSubsurface).
When doing it, to the spec, "the wl_surface is unmapped immediately.".
And not only does this work, but it also deals with the annoying fact
that on current GTK3 versions, when the GDK's toplevel window is
unmapped, its wl_surface is not just unmapped, but entirely destroyed.
(Side note: This may not have been intended, and has been changed for
GTK4, see: https://gitlab.gnome.org/GNOME/gtk/-/commit/5d3cec5441ca)
So we'd have to re-create the subsurface because of this anyway.
So, this works nicely, and as far as I can tell (documentation is a bit
scarce), there's no problem to leaving m_wlSurface (and its associated
m_wlEGLWindow and m_surface) unmapped in this way.
See #22580, #23835.
(cherry picked from commit 952de605f622cc7a3c30257365046ecd1a307808)
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| art | ||
| build | ||
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| include | ||
| interface | ||
| lib | ||
| locale | ||
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| samples | ||
| src | ||
| tests | ||
| utils | ||
| .cirrus.yml | ||
| .editorconfig | ||
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| acinclude.m4 | ||
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| mkinstalldirs | ||
| README-GIT.md | ||
| README.md | ||
| regen | ||
| setup.h_vms | ||
| setup.h.in | ||
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| wx-config-inplace.in | ||
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