Let QPlatformBackingStore handle its own QOpenGLContext

The resources allocated by QPlatformBackingStore are owned by the class,
and should be allocated in a context the class also owns. This removes
the asymmetry of having to pass in a context to composeAndFlush, while
having to make the same context current before destroying the platform
backingstore.

The context owned by QPlatformBackingStore is shared with the associated
window though a new QWindowPrivate::shareContext() API.

The result is that on e.g. iOS, the backingstore does not need to tie
the resource allocation of QPlatformBackingStore to the global share
context, but can instead tie them to the per-window context, and hence
clean them up after each window is closed.

Task-number: QTBUG-56653
Change-Id: Ic1bcae50dafeeafaa8d16a7febd83b840ec6367a
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>

1 files changed, 2 insertions, 4 deletions

diff --git a/src/widgets/kernel/qwidgetbackingstore.cpp b/src/widgets/kernel/qwidgetbackingstore.cpp
index bb421927db..52080fe05f 100644
--- a/src/widgets/kernel/qwidgetbackingstore.cpp
+++ b/src/widgets/kernel/qwidgetbackingstore.cpp
@@ -143,10 +143,8 @@ void QWidgetBackingStore::qt_flush(QWidget *widget, const QRegion &region, QBack
         // WA_TranslucentBackground. Therefore the compositor needs to know whether the app intends
         // to rely on translucency, in order to decide if it should clear to transparent or opaque.
         const bool translucentBackground = widget->testAttribute(Qt::WA_TranslucentBackground);
-        // Use the tlw's context, not widget's. The difference is important with native child
-        // widgets where tlw != widget.
-        backingStore->handle()->composeAndFlush(widget->windowHandle(), effectiveRegion, offset, widgetTextures,
-                                                tlw->d_func()->shareContext(), translucentBackground);
+        backingStore->handle()->composeAndFlush(widget->windowHandle(), effectiveRegion, offset,
+                                                widgetTextures, translucentBackground);
         widget->window()->d_func()->sendComposeStatus(widget->window(), true);
     } else
 #endif