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rhi: metal: macOS: Set presentsWithTransaction during resize

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...when presenting from the main thread.

Make resizing nice and smooth in application that render and present
on the main thread. This includes Qt Quick applications when ran
with QSG_RENDER_LOOP=basic, as well as QQuickWidget-based widget apps
and anything using the QRhi-based backingstore flushing, and plain
QWindow apps that use QRhi on the main thread.

Allow opting out with an environment variable (QT_MTL_NO_TRANSACTION),
following the existing patterns of some of the other backends (such as
QT_D3D_NO_xxxx). This can be handy in case it turns out setting
presentsWithTransaction is not desired in some very specific case.

Task-number: QTBUG-107198
Change-Id: Id0f4e5a509076dd24c03d243c4f098ddb139d7af
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
This commit is contained in:
Laszlo Agocs 2023-03-10 17:02:48 +01:00
parent fb70893dd5
commit 401edea982
1 changed files with 60 additions and 25 deletions
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85
src/gui/rhi/qrhimetal.mm
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@ -417,6 +417,11 @@ struct QMetalSwapChainData
id<MTLTexture> msaaTex[QMTL_FRAMES_IN_FLIGHT];
QRhiTexture::Format rhiColorFormat;
MTLPixelFormat colorFormat;
#ifdef Q_OS_MACOS
bool liveResizeObserverSet = false;
QMacNotificationObserver liveResizeStartObserver;
QMacNotificationObserver liveResizeEndObserver;
#endif
};
QRhiMetal::QRhiMetal(QRhiMetalInitParams *params, QRhiMetalNativeHandles *importDevice)
@ -2291,26 +2296,29 @@ QRhi::FrameOpResult QRhiMetal::endFrame(QRhiSwapChain *swapChain, QRhi::EndFrame
QMetalSwapChain *swapChainD = QRHI_RES(QMetalSwapChain, swapChain);
Q_ASSERT(currentSwapChain == swapChainD);
__block int thisFrameSlot = currentFrameSlot;
[swapChainD->cbWrapper.d->cb addCompletedHandler: ^(id<MTLCommandBuffer>) {
dispatch_semaphore_signal(swapChainD->d->sem[thisFrameSlot]);
}];
const bool needsPresent = !flags.testFlag(QRhi::SkipPresent);
if (needsPresent) {
// beginFrame-endFrame without a render pass inbetween means there is no
// drawable, handle this gracefully because presentDrawable does not like
// null arguments.
if (id<CAMetalDrawable> drawable = swapChainD->d->curDrawable) {
// QTBUG-103415: while the docs suggest the following two approaches are
// equivalent, there is a difference in case a frame is recorded earlier than
// (i.e. not in response to) the next CVDisplayLink callback. Therefore, stick
// with presentDrawable, which gives results identical to OpenGL, and all other
// platforms, i.e. throttles to vsync as expected, meaning constant 15-17 ms with
// a 60 Hz screen, no jumps with smaller intervals, regardless of when the frame
// is submitted by the app)
#if 1
const bool presentsWithTransaction = swapChainD->d->layer.presentsWithTransaction;
if (!presentsWithTransaction && needsPresent) {
// beginFrame-endFrame without a render pass inbetween means there is no drawable.
if (id<CAMetalDrawable> drawable = swapChainD->d->curDrawable)
[swapChainD->cbWrapper.d->cb presentDrawable: drawable];
#else
[swapChainD->cbWrapper.d->cb addScheduledHandler:^(id<MTLCommandBuffer>) {
[drawable present];
}];
#endif
}
[swapChainD->cbWrapper.d->cb commit];
if (presentsWithTransaction && needsPresent) {
// beginFrame-endFrame without a render pass inbetween means there is no drawable.
if (id<CAMetalDrawable> drawable = swapChainD->d->curDrawable) {
// The layer has presentsWithTransaction set to true to avoid flicker on resizing,
// so here it is important to follow what the Metal docs say when it comes to the
// issuing the present.
[swapChainD->cbWrapper.d->cb waitUntilScheduled];
[drawable present];
}
}
@ -2318,13 +2326,6 @@ QRhi::FrameOpResult QRhiMetal::endFrame(QRhiSwapChain *swapChain, QRhi::EndFrame
[swapChainD->d->curDrawable release];
swapChainD->d->curDrawable = nil;
__block int thisFrameSlot = currentFrameSlot;
[swapChainD->cbWrapper.d->cb addCompletedHandler: ^(id<MTLCommandBuffer>) {
dispatch_semaphore_signal(swapChainD->d->sem[thisFrameSlot]);
}];
[swapChainD->cbWrapper.d->cb commit];
[d->captureScope endScope];
if (needsPresent)
@ -5974,6 +5975,12 @@ void QMetalSwapChain::destroy()
d->msaaTex[i] = nil;
}
#ifdef Q_OS_MACOS
d->liveResizeStartObserver.remove();
d->liveResizeEndObserver.remove();
d->liveResizeObserverSet = false;
#endif
d->layer = nullptr;
[d->curDrawable release];
@ -6163,6 +6170,34 @@ bool QMetalSwapChain::createOrResize()
[d->layer setDevice: rhiD->d->dev];
#ifdef Q_OS_MACOS
// Can only use presentsWithTransaction (to get smooth resizing) when
// presenting from the main (gui) thread. We predict that based on the
// thread this function is called on since if the QRhiSwapChain is
// initialied on a given thread then that's almost certainly the thread on
// which the QRhi renders and presents.
const bool canUsePresentsWithTransaction = NSThread.isMainThread;
// Have an env.var. just in case it turns out presentsWithTransaction is
// not desired in some specific case.
static bool allowPresentsWithTransaction = !qEnvironmentVariableIntValue("QT_MTL_NO_TRANSACTION");
if (allowPresentsWithTransaction && canUsePresentsWithTransaction && !d->liveResizeObserverSet) {
d->liveResizeObserverSet = true;
NSView *view = reinterpret_cast<NSView *>(window->winId());
NSWindow *window = view.window;
if (window) {
qCDebug(QRHI_LOG_INFO, "will set presentsWithTransaction during live resize");
d->liveResizeStartObserver = QMacNotificationObserver(window, NSWindowWillStartLiveResizeNotification, [this] {
d->layer.presentsWithTransaction = true;
});
d->liveResizeEndObserver = QMacNotificationObserver(window, NSWindowDidEndLiveResizeNotification, [this] {
d->layer.presentsWithTransaction = false;
});
}
}
#endif
[d->curDrawable release];
d->curDrawable = nil;