From 5dd94b75e37930e9941aaea06497d7e41c9c921f Mon Sep 17 00:00:00 2001
From: Laszlo Agocs <laszlo.agocs@digia.com>
Date: Wed, 6 Nov 2013 16:00:23 +0100
Subject: Add swapInterval to QSurfaceFormat

Implement swap interval support for EGL, GLX and WGL.

The environment variable QT_QPA_EGLFS_SWAPINTERVAL is renamed to
QT_QPA_EGL_SWAPINTERVAL and can be used to override the applications'
setting of the swap interval.

Task-number: QTBUG-31939

Change-Id: I644325d5d3306b7604bffd7efccda3c00ed37d36
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
Reviewed-by: Gunnar Sletta <gunnar.sletta@digia.com>
---
 src/gui/kernel/qsurfaceformat.cpp | 49 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 47 insertions(+), 2 deletions(-)

(limited to 'src/gui/kernel/qsurfaceformat.cpp')

diff --git a/src/gui/kernel/qsurfaceformat.cpp b/src/gui/kernel/qsurfaceformat.cpp
index ebfd71b4d3..b8fe55adc0 100644
--- a/src/gui/kernel/qsurfaceformat.cpp
+++ b/src/gui/kernel/qsurfaceformat.cpp
@@ -72,6 +72,7 @@ public:
         , profile(QSurfaceFormat::NoProfile)
         , major(2)
         , minor(0)
+        , swapInterval(1) // default to vsync
     {
     }
 
@@ -89,7 +90,8 @@ public:
           renderableType(other->renderableType),
           profile(other->profile),
           major(other->major),
-          minor(other->minor)
+          minor(other->minor),
+          swapInterval(other->swapInterval)
     {
     }
 
@@ -107,6 +109,7 @@ public:
     QSurfaceFormat::OpenGLContextProfile profile;
     int major;
     int minor;
+    int swapInterval;
 };
 
 /*!
@@ -675,6 +678,46 @@ void QSurfaceFormat::setVersion(int major, int minor)
     }
 }
 
+/*!
+    Sets the preferred swap interval. The swap interval specifies the
+    minimum number of video frames that are displayed before a buffer
+    swap occurs. This can be used to sync the GL drawing into a window
+    to the vertical refresh of the screen.
+
+    Setting an \a interval value of 0 will turn the vertical refresh
+    syncing off, any value higher than 0 will turn the vertical
+    syncing on. Setting \a interval to a higher value, for example 10,
+    results in having 10 vertical retraces between every buffer swap.
+
+    The default interval is 1.
+
+    Changing the swap interval may not be supported by the underlying
+    platform. In this case, the request will be silently ignored.
+
+    \since 5.3
+
+    \sa swapInterval()
+ */
+void QSurfaceFormat::setSwapInterval(int interval)
+{
+    if (d->swapInterval != interval) {
+        detach();
+        d->swapInterval = interval;
+    }
+}
+
+/*!
+    Returns the swap interval.
+
+    \since 5.3
+
+    \sa setSwapInterval()
+*/
+int QSurfaceFormat::swapInterval() const
+{
+    return d->swapInterval;
+}
+
 /*!
     Returns \c true if all the options of the two QSurfaceFormat objects
     \a a and \a b are equal.
@@ -694,7 +737,8 @@ bool operator==(const QSurfaceFormat& a, const QSurfaceFormat& b)
         && a.d->swapBehavior == b.d->swapBehavior
         && a.d->profile == b.d->profile
         && a.d->major == b.d->major
-        && a.d->minor == b.d->minor);
+        && a.d->minor == b.d->minor
+        && a.d->swapInterval == b.d->swapInterval);
 }
 
 /*!
@@ -724,6 +768,7 @@ QDebug operator<<(QDebug dbg, const QSurfaceFormat &f)
                   << ", stencilBufferSize " << d->stencilSize
                   << ", samples " << d->numSamples
                   << ", swapBehavior " << d->swapBehavior
+                  << ", swapInterval " << d->swapInterval
                   << ", profile  " << d->profile
                   << ')';
 
-- 
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