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Calling wglMakeCurrent on an already current context gives 100% cpu load

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The problem occurs at least with nvidia cards when vsync is enabled
in the control panel.

Task-number: QTBUG-29686
Change-Id: I6fd2a3560a5baeeac7c3fe0440db85904c45026d
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
This commit is contained in:
Gunnar Sletta 2013-04-17 08:38:19 +02:00 committed by The Qt Project
parent bcc14954d3
commit 7c791171a1
1 changed files with 9 additions and 1 deletions
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10
src/plugins/platforms/windows/qwindowsglcontext.cpp
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@ -1052,8 +1052,16 @@ bool QWindowsGLContext::makeCurrent(QPlatformSurface *surface)
// Do we already have a DC entry for that window?
QWindowsWindow *window = static_cast<QWindowsWindow *>(surface);
const HWND hwnd = window->handle();
if (const QOpenGLContextData *contextData = findByHWND(m_windowContexts, hwnd))
if (const QOpenGLContextData *contextData = findByHWND(m_windowContexts, hwnd)) {
// Repeated calls to wglMakeCurrent when vsync is enabled in the driver will
// often result in 100% cpuload. This check is cheap and avoids the problem.
// This is reproducable on NVidia cards and Intel onboard chips.
if (wglGetCurrentContext() == contextData->renderingContext
&& wglGetCurrentDC() == contextData->hdc) {
return true;
}
return wglMakeCurrent(contextData->hdc, contextData->renderingContext);
}
// Create a new entry.
const QOpenGLContextData newContext(m_renderingContext, hwnd, GetDC(hwnd));
if (!newContext.hdc)