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From fbf34883dfc23c109aa03d0df04a07bfd3be59e6 Mon Sep 17 00:00:00 2001
From: Erik Kurzinger <ekurzinger@nvidia.com>
Date: Mon, 10 Jun 2019 14:50:40 -0700
Subject: [PATCH] Remove m_swapInterval from QGLXContext

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 m_swapInterval matches the
new swap interval. This change removes m_swapInterval, forcing the swap
interval to be set every time and relying on the OpenGL implementation
to optimize away unnecessary calls.

Change-Id: Idc34101476c6af618059f6f3d8925dee743994a3
---

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 4adf662..01517eb 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 @@
     , m_shareContext(0)
     , m_format(format)
     , m_isPBufferCurrent(false)
-    , m_swapInterval(-1)
     , m_ownsContext(nativeHandle.isNull())
     , m_getGraphicsResetStatus(0)
     , m_lost(false)
@@ -568,8 +567,7 @@
     if (success && surfaceClass == QSurface::Window) {
         int interval = surface->format().swapInterval();
         QXcbScreen *screen = screenForPlatformSurface(surface);
-        if (interval >= 0 && m_swapInterval != interval && screen) {
-            m_swapInterval = interval;
+        if (interval >= 0 && screen) {
             typedef void (*qt_glXSwapIntervalEXT)(Display *, GLXDrawable, int);
             typedef void (*qt_glXSwapIntervalMESA)(unsigned int);
             static qt_glXSwapIntervalEXT glXSwapIntervalEXT = 0;
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 be9d3f5..2a88fd6 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 @@
     GLXContext m_shareContext;
     QSurfaceFormat m_format;
     bool m_isPBufferCurrent;
-    int m_swapInterval;
     bool m_ownsContext;
     GLenum (APIENTRY * m_getGraphicsResetStatus)();
     bool m_lost;