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Drop SGI_video_sync based method for vsync

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With the new compositing timing, we want to start compositing some time
later after a vsync event. This doesn't go along with the video sync
based method to synchronize buffer swaps with vblank.

Since practically all drivers nowadays provide support for the swap
control extensions (GLX_EXT_swap_control, GLX_SGI_swap_control, or
GLX_MESA_swap_control), it's safe to rely on them for the purpose of
synchronizing buffer swaps to vblank.
This commit is contained in:
Vlad Zahorodnii 2020-11-18 15:49:25 +02:00
parent 7a3fa88f02
commit 4f3adbb520
2 changed files with 5 additions and 38 deletions
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40
plugins/platforms/x11/standalone/glxbackend.cpp
View file

@ -100,7 +100,6 @@ GlxBackend::GlxBackend(Display *display)
, glxWindow(None)
, ctx(nullptr)
, m_bufferAge(0)
, haveSwapInterval(false)
, m_x11Display(display)
{
// Force initialization of GLX integration in the Qt's xcb backend
@ -204,7 +203,7 @@ void GlxBackend::init()
glXSelectEvent(display(), glxWindow, GLX_BUFFER_SWAP_COMPLETE_INTEL_MASK);
}
haveSwapInterval = m_haveMESASwapControl || m_haveEXTSwapControl || m_haveSGISwapControl;
bool haveSwapInterval = m_haveMESASwapControl || m_haveEXTSwapControl || m_haveSGISwapControl;
setSupportsBufferAge(false);
@ -216,21 +215,14 @@ void GlxBackend::init()
}
setSyncsToVBlank(false);
haveWaitSync = false;
const bool wantSync = options->glPreferBufferSwap() != Options::NoSwapEncourage;
if (wantSync && glXIsDirect(display(), ctx)) {
if (haveSwapInterval) { // glXSwapInterval is preferred being more reliable
setSwapInterval(1);
setSyncsToVBlank(true);
} else if (hasExtension(QByteArrayLiteral("GLX_SGI_video_sync"))) {
unsigned int sync;
if (glXGetVideoSyncSGI(&sync) == 0 && glXWaitVideoSyncSGI(1, 0, &sync) == 0) {
setSyncsToVBlank(true);
haveWaitSync = true;
} else
qCWarning(KWIN_X11STANDALONE) << "NO VSYNC! glXSwapInterval is not supported, glXWaitVideoSync is supported but broken";
} else
qCWarning(KWIN_X11STANDALONE) << "NO VSYNC! neither glSwapInterval nor glXWaitVideoSync are supported";
} else {
qCWarning(KWIN_X11STANDALONE) << "glSwapInterval is unsupported";
}
} else {
// disable v-sync (if possible)
setSwapInterval(0);
@ -671,23 +663,6 @@ void GlxBackend::setSwapInterval(int interval)
glXSwapIntervalSGI(interval);
}
void GlxBackend::waitSync()
{
// NOTE that vsync has no effect with indirect rendering
if (haveWaitSync) {
uint sync;
#if 0
// TODO: why precisely is this important?
// the sync counter /can/ perform multiple steps during glXGetVideoSync & glXWaitVideoSync
// but this only leads to waiting for two frames??!?
glXGetVideoSync(&sync);
glXWaitVideoSync(2, (sync + 1) % 2, &sync);
#else
glXWaitVideoSyncSGI(1, 0, &sync);
#endif
}
}
void GlxBackend::present(const QRegion &damage)
{
if (damage.isEmpty()) {
@ -702,12 +677,7 @@ void GlxBackend::present(const QRegion &damage)
if (m_haveINTELSwapEvent)
Compositor::self()->aboutToSwapBuffers();
if (haveSwapInterval) {
glXSwapBuffers(display(), glxWindow);
} else {
waitSync();
glXSwapBuffers(display(), glxWindow);
}
glXSwapBuffers(display(), glxWindow);
if (supportsBufferAge()) {
glXQueryDrawable(display(), glxWindow, GLX_BACK_BUFFER_AGE_EXT, (GLuint *) &m_bufferAge);
}

3
plugins/platforms/x11/standalone/glxbackend.h
View file

@ -73,7 +73,6 @@ private:
bool initBuffer();
bool checkVersion();
void initExtensions();
void waitSync();
bool initRenderingContext();
bool initFbConfig();
void initVisualDepthHashTable();
@ -102,8 +101,6 @@ private:
bool m_haveEXTSwapControl = false;
bool m_haveSGISwapControl = false;
bool m_haveINTELSwapEvent = false;
bool haveSwapInterval = false;
bool haveWaitSync = false;
Display *m_x11Display;
friend class GlxTexture;
};