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>
 

3 files changed, 7 insertions, 4 deletions

diff --git a/src/plugins/platforms/xcb/gl_integrations/xcb_glx/qglxintegration.cpp b/src/plugins/platforms/xcb/gl_integrations/xcb_glx/qglxintegration.cpp
index 4adf662152..f26f698e76 100644
--- a/src/plugins/platforms/xcb/gl_integrations/xcb_glx/qglxintegration.cpp
+++ b/src/plugins/platforms/xcb/gl_integrations/xcb_glx/qglxintegration.cpp
@@ -204,7 +204,6 @@ QGLXContext::QGLXContext(QXcbScreen *screen, const QSurfaceFormat &format, QPlat
     , m_shareContext(0)
     , m_format(format)
     , m_isPBufferCurrent(false)
-    , m_swapInterval(-1)
     , m_ownsContext(nativeHandle.isNull())
     , m_getGraphicsResetStatus(0)
     , m_lost(false)
@@ -567,9 +566,9 @@ bool QGLXContext::makeCurrent(QPlatformSurface *surface)
 
     if (success && surfaceClass == QSurface::Window) {
         int interval = surface->format().swapInterval();
+        QXcbWindow *window = static_cast<QXcbWindow *>(surface);
         QXcbScreen *screen = screenForPlatformSurface(surface);
-        if (interval >= 0 && m_swapInterval != interval && screen) {
-            m_swapInterval = interval;
+        if (interval >= 0 && interval != window->swapInterval() && screen) {
             typedef void (*qt_glXSwapIntervalEXT)(Display *, GLXDrawable, int);
             typedef void (*qt_glXSwapIntervalMESA)(unsigned int);
             static qt_glXSwapIntervalEXT glXSwapIntervalEXT = 0;
@@ -588,6 +587,7 @@ bool QGLXContext::makeCurrent(QPlatformSurface *surface)
                 glXSwapIntervalEXT(m_display, glxDrawable, interval);
             else if (glXSwapIntervalMESA)
                 glXSwapIntervalMESA(interval);
+            window->setSwapInterval(interval);
         }
     }
 
diff --git a/src/plugins/platforms/xcb/gl_integrations/xcb_glx/qglxintegration.h b/src/plugins/platforms/xcb/gl_integrations/xcb_glx/qglxintegration.h
index be9d3f5dcb..2a88fd6e59 100644
--- a/src/plugins/platforms/xcb/gl_integrations/xcb_glx/qglxintegration.h
+++ b/src/plugins/platforms/xcb/gl_integrations/xcb_glx/qglxintegration.h
@@ -87,7 +87,6 @@ private:
     GLXContext m_shareContext;
     QSurfaceFormat m_format;
     bool m_isPBufferCurrent;
-    int m_swapInterval;
     bool m_ownsContext;
     GLenum (APIENTRY * m_getGraphicsResetStatus)();
     bool m_lost;
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