view: do not render monitor for tearing if it's blocked

[vaxerski]

If tearing is blocked, we cannot start rendering. We'll start fucking the log and wasting resources

[epsilonshmepsilon]

This breaks tearing for me.
First of all in CMonitor::isTearingBlocked I'm not sure if

if (!m_tearingState.nextRenderTorn) {
  reasons |= TC_NOT_TORN;
  if (!full)
    return reasons;
}

is useful. It's not really a reason for blocking tearing. I think the problem now is that to render a torn frame m_tearingState.nextRenderTorn needs to be true, or else isTearingBlocked is always true and

    if (PMONITOR && PMONITOR->m_solitaryClient.lock() == m_self.lock() && canBeTorn() && PMONITOR->m_tearingState.canTear && wlSurface()->resource()->m_current.texture &&
        !PMONITOR->isTearingBlocked()) {

will never be true in CWindow::commitWindow(), so no torn frame can be rendered.
But to get m_tearingState.nextRenderTorn to be true the only place to get it is in CMonitorFrameScheduler::onFrame().

 if (PMONITOR->m_tearingState.activelyTearing && ...) {
...
        PMONITOR->m_tearingState.nextRenderTorn          = true;

But m_tearingState.activelyTearing is only set here (if I'm correct):

bool CMonitor::updateTearing() {
    m_tearingState.activelyTearing = !isTearingBlocked();
    m_tearingState.nextRenderTorn  = false;
    return m_tearingState.activelyTearing;
}

But this uses isTearingBlocked() again which might be always true again because of

    if (!m_tearingState.nextRenderTorn) {
        reasons |= TC_NOT_TORN;
        if (!full)
            return reasons;
    }

So, also activelyTearing is always false.

So getting rid of

    if (!m_tearingState.nextRenderTorn) {
        reasons |= TC_NOT_TORN;
        if (!full)
            return reasons;
    }

in CMonitor::isTearingBlocked might be something to consider.

Also

    if (!m_tearingState.canTear) {
        reasons |= TC_SUPPORT;
        if (!full) {
            Log::logger->log(Log::WARN, "Tearing commit requested but monitor doesn't support it, ignoring");
            return reasons;
        }
    }

is in CMonitor::isTearingBlocked. So is canBeTorn() in

    if (PMONITOR && PMONITOR->m_solitaryClient.lock() == m_self.lock() && canBeTorn() && PMONITOR->m_tearingState.canTear && wlSurface()->resource()->m_current.texture &&
        !PMONITOR->isTearingBlocked()) {

still needed?

[gulafaran]

This breaks tearing for me. First of all in CMonitor::isTearingBlocked I'm not sure if

if (!m_tearingState.nextRenderTorn) {
  reasons |= TC_NOT_TORN;
  if (!full)
    return reasons;
}

is useful. It's not really a reason for blocking tearing. I think the problem now is that to render a torn frame m_tearingState.nextRenderTorn needs to be true, or else isTearingBlocked is always true and

    if (PMONITOR && PMONITOR->m_solitaryClient.lock() == m_self.lock() && canBeTorn() && PMONITOR->m_tearingState.canTear && wlSurface()->resource()->m_current.texture &&
        !PMONITOR->isTearingBlocked()) {

will never be true in CWindow::commitWindow(), so no torn frame can be rendered. But to get m_tearingState.nextRenderTorn to be true the only place to get it is in CMonitorFrameScheduler::onFrame().

 if (PMONITOR->m_tearingState.activelyTearing && ...) {
...
        PMONITOR->m_tearingState.nextRenderTorn          = true;

But m_tearingState.activelyTearing is only set here (if I'm correct):

bool CMonitor::updateTearing() {
    m_tearingState.activelyTearing = !isTearingBlocked();
    m_tearingState.nextRenderTorn  = false;
    return m_tearingState.activelyTearing;
}

But this uses isTearingBlocked() again which might be always true again because of

    if (!m_tearingState.nextRenderTorn) {
        reasons |= TC_NOT_TORN;
        if (!full)
            return reasons;
    }

So, also activelyTearing is always false.

So getting rid of

    if (!m_tearingState.nextRenderTorn) {
        reasons |= TC_NOT_TORN;
        if (!full)
            return reasons;
    }

in CMonitor::isTearingBlocked might be something to consider.

Also

    if (!m_tearingState.canTear) {
        reasons |= TC_SUPPORT;
        if (!full) {
            Log::logger->log(Log::WARN, "Tearing commit requested but monitor doesn't support it, ignoring");
            return reasons;
        }
    }

is in CMonitor::isTearingBlocked. So is canBeTorn() in

    if (PMONITOR && PMONITOR->m_solitaryClient.lock() == m_self.lock() && canBeTorn() && PMONITOR->m_tearingState.canTear && wlSurface()->resource()->m_current.texture &&
        !PMONITOR->isTearingBlocked()) {

still needed?

will be reverted in #15580 but requires that AQ pr to not reintroduce the artifacts that caused this commit.

[realm2100]

this PR seems to have broken tearing for me as well, downgrading to 0.56.0 fixed the issue.