Paint() called from OpenGL thread

nfonseca2011 · December 3, 2018, 6:13pm

I’m having this strange behaviour, with asserts from JUCE being fired, because my paint() method is being called from OpenGL thread.

The assert is being called in juce::Font::getStringWidthFloat(), which is called indirectly from a Component::paint() call, all on the OpenGL thread.

What am I doing wrong?
Any ideas?

|#0| juce::Font::getStringWidthFloat(juce::String const&)
|#1| juce::Font::getStringWidth(juce::String const&)
|#2| SpDrawText::neededRect(juce::String, bool, juce::String, float)
|#3| SpDrawText::neededRect(juce::String)
|#4| SpDrawText::neededRect()
|#5| SpDrawText::draw()
|#6| InspectorPanel::draw()
|#7| ParticleGroupAudioFilesView::draw()
|#8| BaseViewExt::paint(juce::Graphics&)
|#9| juce::Component::paintComponentAndChildren(juce::Graphics&)
|#10| juce::Component::paintEntireComponent(juce::Graphics&, bool)
|#11| juce::Component::paintWithinParentContext(juce::Graphics&)
|#12| juce::Component::paintComponentAndChildren(juce::Graphics&)
|#13| juce::Component::paintEntireComponent(juce::Graphics&, bool)
|#14| juce::Component::paintWithinParentContext(juce::Graphics&)
|#15| juce::Component::paintComponentAndChildren(juce::Graphics&)
|#16| juce::Component::paintEntireComponent(juce::Graphics&, bool)
|#17| juce::Component::paintWithinParentContext(juce::Graphics&)
|#18| juce::Component::paintComponentAndChildren(juce::Graphics&)
|#19| juce::Component::paintEntireComponent(juce::Graphics&, bool)
|#20| juce::Component::paintWithinParentContext(juce::Graphics&)
|#21| juce::Component::paintComponentAndChildren(juce::Graphics&)
|#22| juce::Component::paintEntireComponent(juce::Graphics&, bool)
|#23| juce::Component::paintWithinParentContext(juce::Graphics&)
|#24| juce::Component::paintComponentAndChildren(juce::Graphics&)
|#25| juce::Component::paintEntireComponent(juce::Graphics&, bool)
|#26| juce::Component::paintWithinParentContext(juce::Graphics&)
|#27| juce::Component::paintComponentAndChildren(juce::Graphics&)
|#28| juce::Component::paintEntireComponent(juce::Graphics&, bool)
|#29| juce::Component::paintWithinParentContext(juce::Graphics&)
|#30| juce::Component::paintComponentAndChildren(juce::Graphics&)
|#31| juce::Component::paintEntireComponent(juce::Graphics&, bool)
|#32| juce::ComponentPeer::handlePaint(juce::LowLevelGraphicsContext&)
|#33| juce::NSViewComponentPeer::invokePaint(juce::LowLevelGraphicsContext&)
|#34| juce::NSViewComponentPeer::drawRect(CGContext*, CGRect, float)
|#35| juce::NSViewComponentPeer::drawRect(CGRect)
|#36| juce::JuceNSViewClass::drawRect(objc_object*, objc_selector*, CGRect)
|#37| _NSViewDrawRect ()|
|#38| -[NSView(NSInternal) _recursive:displayRectIgnoringOpacity:inContext:shouldChangeFontReferenceColor:stopAtLayerBackedViews:] ()|
|#39| __46-[NSView(NSLayerKitGlue) drawLayer:inContext:]_block_invoke ()|
|#40| -[NSView(NSLayerKitGlue) drawViewBackingLayer:inContext:drawingHandler:] ()|
|#41| CABackingStoreUpdate ()|
|#42| ___ZN2CA5Layer8display_Ev_block_invoke ()|
|#43| -[CALayer _display] ()|
|#44| _NSBackingLayerDisplay ()|
|#45| -[_NSViewBackingLayer display] ()|
|#46| CA::Layer::display_if_needed(CA::Transaction*) ()|
|#47| CA::Context::commit_transaction(CA::Transaction*) ()|
|#48| CA::Transaction::commit() ()|
|#49| NSPerformVisuallyAtomicChange ()|
|#50| -[NSOpenGLContext setView:] ()|
|#51| juce::OpenGLContext::NativeContext::makeActive() |#52| juce::OpenGLContext::makeActive()
|#53| juce::OpenGLContext::CachedImage::initialiseOnThread()
|#54| juce::OpenGLContext::CachedImage::runJob()
|#55| juce::ThreadPool::runNextJob(juce::ThreadPool::ThreadPoolThread&)
|#56| juce::ThreadPool::ThreadPoolThread::run()
|#57| juce::threadEntryPoint()
|#58| juce::juce_threadEntryPoint(void*)
|#59| juce::threadEntryProc(void*)
|#60| _pthread_body ()|
|#61| _pthread_start ()|
|#62| thread_start ()|

alassandro · December 3, 2018, 6:18pm

If you’re calling Component::paint() explicitly (rather than using OpenGLContext::setComopnentPaintingEnabled(true)) you’ll run into problems because there are quite a few things that should only be run on the main thread (in this case, Font related methods)

Note though that acquiring a message thread lock in renderOpenGL() might not be viable:

nfonseca2011 · December 3, 2018, 6:27pm

I’m not calling paint() explicitly - the entire call stack bellow paint() is either JUCE or system.

alassandro · December 3, 2018, 6:55pm

Is the OpenGLContext just attached normally with attachTo() and component painting enabled? The context will handle locking the main thread when painting components via OpenGL, otherwise it just runs the OpenGLRenderer (if one is set)

I haven’t run into this issue on macOS 10.13.6

matkatmusic · December 3, 2018, 9:15pm

You’re supposed to use triggerRepaint, not repaint with the openGL context approach

alassandro · December 3, 2018, 9:24pm

The behavior is somewhat similar since the OpenGLContext is implemented via a CachedComponentImage. Calling repaint on a component invalidates the cache (in this case just a saved rectangle) which then results in a call to OpenGLContext::triggerRepaint(). If you manually call triggerRepaint() it seems it will run the internal OpenGLContext::paintComponent() but may skip over updating the actual component texture if validArea hasn’t changed

github.com

WeAreROLI/JUCE/blob/master/modules/juce_gui_basics/components/juce_Component.cpp#L1794




void Component::internalRepaintUnchecked (Rectangle<int> area, bool isEntireComponent)

{

// if component methods are being called from threads other than the message

// thread, you'll need to use a MessageManagerLock object to make sure it's thread-safe.

JUCE_ASSERT_MESSAGE_MANAGER_IS_LOCKED



if (flags.visibleFlag)

{

    if (cachedImage != nullptr)

        if (! (isEntireComponent ? cachedImage->invalidateAll()

                                 : cachedImage->invalidate (area)))

            return;



    if (flags.hasHeavyweightPeerFlag)

    {

        if (auto* peer = getPeer())

        {

            // Tweak the scaling so that the component's integer size exactly aligns with the peer's scaled size

            auto peerBounds = peer->getBounds();

            auto scaled = area * Point<float> (peerBounds.getWidth()  / (float) getWidth(),

github.com

WeAreROLI/JUCE/blob/master/modules/juce_opengl/opengl/juce_OpenGLContext.cpp#L151


    if (renderThread != nullptr)

        renderThread->addJob (this, false);

}



//==============================================================================

void paint (Graphics&) override

{

    updateViewportSize (false);

}



bool invalidateAll() override

{

    validArea.clear();

    triggerRepaint();

    return false;

}



bool invalidate (const Rectangle<int>& area) override

{

    validArea.subtract (area.toFloat().transformedBy (transform).getSmallestIntegerContainer());

    triggerRepaint();

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Paint() called from OpenGL thread

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