Track swap interval in QXcbWindow

As per GLX_EXT_swap_control, the GLX swap interval is specified on a
per-drawable basis. However, QGLXContext only tracks it per-context
using the m_swapInterval member. If a new drawable is made current to a
context, it is still necessary to call glXSwapIntervalEXT to change the
swap interval, even if it has been previously called for the same
context with a different drawable.  However, currently,
QGLXContext::makeCurrent doesn't do this if its m_swapInterval field
matches the new swap interval. This change removes m_swapInterval from
QGLXContext, instead tracking it in QXcbWindow. This still avoids
unnecessary calls to glXSwapIntervalEXT, while ensuring the swap
interval is always set for new window drawables.

Change-Id: Idc34101476c6af618059f6f3d8925dee743994a3
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>
 

1 files changed, 4 insertions, 0 deletions

diff --git a/src/plugins/platforms/xcb/qxcbwindow.h b/src/plugins/platforms/xcb/qxcbwindow.h
index f98cd8a74d..8258cc2dfa 100644
--- a/src/plugins/platforms/xcb/qxcbwindow.h
+++ b/src/plugins/platforms/xcb/qxcbwindow.h
@@ -184,6 +184,9 @@ public:
     static void setWindowTitle(const QXcbConnection *conn, xcb_window_t window, const QString &title);
     static QString windowTitle(const QXcbConnection *conn, xcb_window_t window);
 
+    int swapInterval() const { return m_swapInterval; }
+    void setSwapInterval(int swapInterval) { m_swapInterval = swapInterval; }
+
 public Q_SLOTS:
     void updateSyncRequestCounter();
 
@@ -276,6 +279,7 @@ protected:
     SyncState m_syncState = NoSyncNeeded;
 
     QXcbSyncWindowRequest *m_pendingSyncRequest = nullptr;
+    int m_swapInterval = -1;
 };
 
 class QXcbForeignWindow : public QXcbWindow