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, 8 insertions, 0 deletions

diff --git a/src/widgets/kernel/qwidgetwindow.cpp b/src/widgets/kernel/qwidgetwindow.cpp
index d30154410c..319eccf223 100644
--- a/src/widgets/kernel/qwidgetwindow.cpp
+++ b/src/widgets/kernel/qwidgetwindow.cpp
@@ -96,6 +96,7 @@ public:
     }
 
     QRectF closestAcceptableGeometry(const QRectF &rect) const Q_DECL_OVERRIDE;
+    QOpenGLContext *shareContext() const override;
 };
 
 QRectF QWidgetWindowPrivate::closestAcceptableGeometry(const QRectF &rect) const
@@ -127,6 +128,13 @@ QRectF QWidgetWindowPrivate::closestAcceptableGeometry(const QRectF &rect) const
     return result;
 }
 
+QOpenGLContext *QWidgetWindowPrivate::shareContext() const
+{
+    Q_Q(const QWidgetWindow);
+    const QWidgetPrivate *widgetPrivate = QWidgetPrivate::get(q->widget());
+    return widgetPrivate->shareContext();
+}
+
 QWidgetWindow::QWidgetWindow(QWidget *widget)
     : QWindow(*new QWidgetWindowPrivate(), 0)
     , m_widget(widget)