eglfs: Fix raster windows

Also sanitize the initial WebAssembly hack. Both eglfs and wasm lack the concept
of true raster windows. A QWindow with RasterSurface is rendered with OpenGL
no matter what. The two platforms took two different approaches to work around
the rest of the machinery:

- wasm disabled the QOpenGLContext warning for non-OpenGL QWindows,

- eglfs forced the QWindow surfaceType to OpenGLSurface whenever it was
  originally set to RasterSurface.

Now, the latter breaks since c4e9eabc309a275efc222f4127f31ba4677259b7, leaving
all raster window applications failing on eglfs, because flush in the backingstore
is now checking the surface type and disallows OpenGLSurface windows. (just like
how QOpenGLContext disallows RasterSurface windows)

To solve all this correctly, introduce a new platform capability,
OpenGLOnRasterSurface, and remove the special handling in the platform plugins.

Change-Id: I7785dfb1c955577bbdccdc14ebaaac5babdec57c
Fixes: QTBUG-77100
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
(cherry picked from commit 53a6f7b7836ef5084106ed63f6745c20d663affa)
Reviewed-by: Jukka Jokiniva <jukka.jokiniva@qt.io>

1 files changed, 3 insertions, 0 deletions

diff --git a/src/gui/kernel/qplatformintegration.cpp b/src/gui/kernel/qplatformintegration.cpp
index 490cfc6178..b3d3db0751 100644
--- a/src/gui/kernel/qplatformintegration.cpp
+++ b/src/gui/kernel/qplatformintegration.cpp
@@ -244,6 +244,9 @@ QPlatformServices *QPlatformIntegration::services() const
     \value TopStackedNativeChildWindows The platform supports native child windows via
     QWindowContainer without having to punch a transparent hole in the
     backingstore. (since 5.10)
+
+    \value OpenGLOnRasterSurface The platform supports making a QOpenGLContext current
+    in combination with a QWindow of type RasterSurface.
  */
 
 /*!