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x11: Properly detect whether swap events have to disabled

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qEnvironmentVariableIntValue() will return 0 if the specified variable
is not set.

This means that swap events will be disabled on AMD GPUs unless the env
var is set explicitly to 1.
This commit is contained in:
Vlad Zahorodnii 2021-02-18 12:22:28 +02:00
parent 892b8cf6cb
commit cf2486d643
2 changed files with 15 additions and 15 deletions
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29
src/plugins/platforms/x11/standalone/glxbackend.cpp
View file

@ -200,14 +200,25 @@ void GlxBackend::init()
glPlatform->printResults();
initGL(&getProcAddress);
const bool swapEventSwitch = qEnvironmentVariableIntValue("KWIN_USE_INTEL_SWAP_EVENT");
bool supportsSwapEvent = false;
if (hasExtension(QByteArrayLiteral("GLX_INTEL_swap_event"))) {
if (qEnvironmentVariableIsSet("KWIN_USE_INTEL_SWAP_EVENT")) {
supportsSwapEvent = qEnvironmentVariable("KWIN_USE_INTEL_SWAP_EVENT") != QLatin1String("0");
} else {
// Don't use swap events on Intel. The issue with Intel GPUs is that they are not as
// powerful as discrete GPUs. Therefore, it's better to push frames as often as vblank
// notifications are received. This, however, may increase latency. If the swap events
// are enabled explicitly by setting the environment variable, honor that choice.
supportsSwapEvent = !glPlatform->isIntel();
}
}
// Check whether certain features are supported
m_haveMESACopySubBuffer = hasExtension(QByteArrayLiteral("GLX_MESA_copy_sub_buffer"));
m_haveMESASwapControl = hasExtension(QByteArrayLiteral("GLX_MESA_swap_control"));
m_haveEXTSwapControl = hasExtension(QByteArrayLiteral("GLX_EXT_swap_control"));
m_haveSGISwapControl = hasExtension(QByteArrayLiteral("GLX_SGI_swap_control"));
m_haveINTELSwapEvent = hasExtension(QByteArrayLiteral("GLX_INTEL_swap_event")) && swapEventSwitch;
bool haveSwapInterval = m_haveMESASwapControl || m_haveEXTSwapControl || m_haveSGISwapControl;
@ -223,17 +234,7 @@ void GlxBackend::init()
// If the buffer age extension is unsupported, glXSwapBuffers() is not guaranteed to
// be called. Therefore, there is no point for creating the swap event filter.
if (!supportsBufferAge()) {
m_haveINTELSwapEvent = false;
}
// Don't use swap events on Intel. The issue with Intel GPUs is that they are not as
// powerful as discrete GPUs. Therefore, it's better to push frames as often as vblank
// notifications are received. This, however, may increase latency. If the swap events
// are enabled explicitly by setting the environment variable, honor that choice.
if (glPlatform->isIntel()) {
if (!swapEventSwitch) {
m_haveINTELSwapEvent = false;
}
supportsSwapEvent = false;
}
if (haveSwapInterval) {
@ -249,7 +250,7 @@ void GlxBackend::init()
glXQueryDrawable = nullptr;
}
if (m_haveINTELSwapEvent) {
if (supportsSwapEvent) {
// Nice, the GLX_INTEL_swap_event extension is available. We are going to receive
// the presentation timestamp (UST) after glXSwapBuffers() via the X command stream.
m_swapEventFilter = std::make_unique<SwapEventFilter>(window, glxWindow);

1
src/plugins/platforms/x11/standalone/glxbackend.h
View file

@ -104,7 +104,6 @@ private:
bool m_haveMESASwapControl = false;
bool m_haveEXTSwapControl = false;
bool m_haveSGISwapControl = false;
bool m_haveINTELSwapEvent = false;
Display *m_x11Display;
X11StandalonePlatform *m_backend;
VsyncMonitor *m_vsyncMonitor = nullptr;