Add default format to QSurfaceFormat

Add defaultFormat() and setDefaultFormat() statics to QSurfaceFormat.
These define the default values for the requestedFormat members of
QOpenGLContext, QWindow and QOpenGLWidget (and implicitly QOpenGLWindow,
QQuickWindow, etc.)

This replaces QQuickWindow::setDefaultFormat() which can now be removed.

The main inspiration here is not the convenience (avoiding setFormat() calls
for all windows/widgets), but robustness: by setting the format once at the start
of the application, all windows and contexts, including the internal share context
used by QOpenGLWidget and QQuickWidget, will use the same format, eliminating
the possibility of failing due to trying to share between incompatible contexts.

Furthermore, since such a functionality is anyway mandatory for QQuickWindow
(due to the possibility of creating windows from QML code), extending it to
QSurfaceFormat and QOpenGLContext/QWindow is the next logical step.

Change-Id: Ie94486adc489d17fecfcebb7050fecedffd2688b
Reviewed-by: Gunnar Sletta <gunnar.sletta@jollamobile.com>

1 files changed, 9 insertions, 1 deletions

diff --git a/src/gui/kernel/qwindow.cpp b/src/gui/kernel/qwindow.cpp
index 8159b7746e..8c0db2c0c7 100644
--- a/src/gui/kernel/qwindow.cpp
+++ b/src/gui/kernel/qwindow.cpp
@@ -224,6 +224,8 @@ void QWindowPrivate::init()
         exit(1);
     }
     QGuiApplicationPrivate::window_list.prepend(q);
+
+    requestedFormat = QSurfaceFormat::defaultFormat();
 }
 
 /*!
@@ -672,7 +674,13 @@ void QWindow::setModality(Qt::WindowModality modality)
     this function after create() has been called will not re-resolve the
     surface format of the native surface.
 
-    \sa create(), destroy()
+    When the format is not explicitly set via this function, the format returned
+    by QSurfaceFormat::defaultFormat() will be used. This means that when having
+    multiple windows, individual calls to this function can be replaced by one
+    single call to QSurfaceFormat::setDefaultFormat() before creating the first
+    window.
+
+    \sa create(), destroy(), QSurfaceFormat::setDefaultFormat()
 */
 void QWindow::setFormat(const QSurfaceFormat &format)
 {