6 files changed, 48 insertions, 16 deletions
diff --git a/src/quick/scenegraph/adaptations/software/qsgsoftwarecontext.cpp b/src/quick/scenegraph/adaptations/software/qsgsoftwarecontext.cpp
index 0c0ee5e579..4fd0003e54 100644
--- a/src/quick/scenegraph/adaptations/software/qsgsoftwarecontext.cpp
+++ b/src/quick/scenegraph/adaptations/software/qsgsoftwarecontext.cpp
@@ -113,8 +113,7 @@ void QSGSoftwareRenderContext::invalidate()
     qDeleteAll(m_textures);
     m_textures.clear();
 
-    qDeleteAll(m_fontEnginesToClean);
-    m_fontEnginesToClean.clear();
+    Q_ASSERT(m_fontEnginesToClean.isEmpty());
 
     qDeleteAll(m_glyphCaches);
     m_glyphCaches.clear();
diff --git a/src/quick/scenegraph/qsgcontext.cpp b/src/quick/scenegraph/qsgcontext.cpp
index be7c934fd7..7668db7a69 100644
--- a/src/quick/scenegraph/qsgcontext.cpp
+++ b/src/quick/scenegraph/qsgcontext.cpp
@@ -475,7 +475,13 @@ void QSGRenderContext::invalidateGlyphCaches()
 void QSGRenderContext::registerFontengineForCleanup(QFontEngine *engine)
 {
     engine->ref.ref();
-    m_fontEnginesToClean << engine;
+    m_fontEnginesToClean[engine]++;
+}
+
+void QSGRenderContext::unregisterFontengineForCleanup(QFontEngine *engine)
+{
+    m_fontEnginesToClean[engine]--;
+    Q_ASSERT(m_fontEnginesToClean.value(engine) >= 0);
 }
 
 QRhi *QSGRenderContext::rhi() const
diff --git a/src/quick/scenegraph/qsgcontext_p.h b/src/quick/scenegraph/qsgcontext_p.h
index 299b003716..19585c6f4b 100644
--- a/src/quick/scenegraph/qsgcontext_p.h
+++ b/src/quick/scenegraph/qsgcontext_p.h
@@ -166,6 +166,7 @@ public:
 
     virtual int maxTextureSize() const = 0;
 
+    void unregisterFontengineForCleanup(QFontEngine *engine);
     void registerFontengineForCleanup(QFontEngine *engine);
 
     virtual QRhi *rhi() const;
@@ -187,7 +188,9 @@ protected:
     QSet<QSGTexture *> m_texturesToDelete;
     QHash<QString, QSGDistanceFieldGlyphCache *> m_glyphCaches;
 
-    QSet<QFontEngine *> m_fontEnginesToClean;
+    // References to font engines that are currently in use by native rendering glyph nodes
+    // and which must be kept alive as long as they are used in the render thread.
+    QHash<QFontEngine *, int> m_fontEnginesToClean;
 };
 
 QT_END_NAMESPACE
diff --git a/src/quick/scenegraph/qsgdefaultglyphnode_p.cpp b/src/quick/scenegraph/qsgdefaultglyphnode_p.cpp
index e9e6c26d88..f10dbd4bc6 100644
--- a/src/quick/scenegraph/qsgdefaultglyphnode_p.cpp
+++ b/src/quick/scenegraph/qsgdefaultglyphnode_p.cpp
@@ -322,6 +322,8 @@ QSGTextMaskMaterial::QSGTextMaskMaterial(QSGRenderContext *rc, const QVector4D &
 
 QSGTextMaskMaterial::~QSGTextMaskMaterial()
 {
+    if (m_retainedFontEngine != nullptr)
+        m_rc->unregisterFontengineForCleanup(m_retainedFontEngine);
     delete m_texture;
 }
 
@@ -385,6 +387,12 @@ void QSGTextMaskMaterial::updateCache(QFontEngine::GlyphFormat glyphFormat)
         if (!m_glyphCache || int(m_glyphCache->glyphFormat()) != glyphFormat) {
             m_glyphCache = new QSGRhiTextureGlyphCache(m_rc, glyphFormat, glyphCacheTransform, color);
             fontEngine->setGlyphCache(cacheKey, m_glyphCache.data());
+            if (m_retainedFontEngine != nullptr)
+                m_rc->unregisterFontengineForCleanup(m_retainedFontEngine);
+
+            // Note: This is reference counted by the render context, so it will stay alive until
+            // we release that reference
+            m_retainedFontEngine = fontEngine;
             m_rc->registerFontengineForCleanup(fontEngine);
         }
     }
diff --git a/src/quick/scenegraph/qsgdefaultglyphnode_p_p.h b/src/quick/scenegraph/qsgdefaultglyphnode_p_p.h
index e77e2715cd..d3b919c275 100644
--- a/src/quick/scenegraph/qsgdefaultglyphnode_p_p.h
+++ b/src/quick/scenegraph/qsgdefaultglyphnode_p_p.h
@@ -69,6 +69,7 @@ private:
     QSGPlainTexture *m_texture;
     QExplicitlySharedDataPointer<QFontEngineGlyphCache> m_glyphCache;
     QRawFont m_font;
+    QFontEngine *m_retainedFontEngine = nullptr;
     QRhi *m_rhi;
     QVector4D m_color;
     QSize m_size;
diff --git a/src/quick/scenegraph/qsgdefaultrendercontext.cpp b/src/quick/scenegraph/qsgdefaultrendercontext.cpp
index 462196927b..73f4bec27f 100644
--- a/src/quick/scenegraph/qsgdefaultrendercontext.cpp
+++ b/src/quick/scenegraph/qsgdefaultrendercontext.cpp
@@ -59,13 +59,29 @@ void QSGDefaultRenderContext::initialize(const QSGRenderContext::InitParams *par
 
 void QSGDefaultRenderContext::invalidateGlyphCaches()
 {
-    auto it = m_glyphCaches.begin();
-    while (it != m_glyphCaches.end()) {
-        if (!(*it)->isActive()) {
-            delete *it;
-            it = m_glyphCaches.erase(it);
-        } else {
-            ++it;
+    {
+        auto it = m_glyphCaches.begin();
+        while (it != m_glyphCaches.end()) {
+            if (!(*it)->isActive()) {
+                delete *it;
+                it = m_glyphCaches.erase(it);
+            } else {
+                ++it;
+            }
+        }
+    }
+
+    {
+        auto it = m_fontEnginesToClean.begin();
+        while (it != m_fontEnginesToClean.end()) {
+            if (it.value() == 0) {
+                it.key()->clearGlyphCache(this);
+                if (!it.key()->ref.deref())
+                    delete it.key();
+                it = m_fontEnginesToClean.erase(it);
+            } else {
+                ++it;
+            }
         }
     }
 }
@@ -108,11 +124,10 @@ void QSGDefaultRenderContext::invalidate()
     // code is only called from QQuickWindow's shutdown which is called
     // only when the GUI is blocked, and multiple threads will call it in
     // sequence. (see qsgdefaultglyphnode_p.cpp's init())
-    for (QSet<QFontEngine *>::const_iterator it = m_fontEnginesToClean.constBegin(),
-         end = m_fontEnginesToClean.constEnd(); it != end; ++it) {
-        (*it)->clearGlyphCache(this);
-        if (!(*it)->ref.deref())
-            delete *it;
+    for (auto it = m_fontEnginesToClean.constBegin(); it != m_fontEnginesToClean.constEnd(); ++it) {
+        it.key()->clearGlyphCache(this);
+        if (!it.key()->ref.deref())
+            delete it.key();
     }
     m_fontEnginesToClean.clear();