Invalidate text when application fonts are added or removed

We had multiple related issues due to application fonts being added
or removed during the application lifetime.

1. If a text had font family "foo" set, and this font did not
exist at the time, then loading "foo" at a later stage would not
update the text to use the correct font, since the result of
the previous request had been cached.

2. A variation of #1 was if the font "foo" was loaded by a FontLoader
in the scene and referred to by name in the text component. In this
case, there was a race condition, where the font lookup would sometimes
yield different results on the main thread and on the render thread,
and text would be garbled.

3. When a font was removed from the font database, then references to
it would remain in the caches (glyph cache + font cache) in the render
thread. With certain backends (DirectWrite, CoreText) this caused errors
or even crashes, as the cached font engines would be referring to data
that had been removed.

The work-around for #1 and #2 was merely to avoid hardcoding names for
fonts, but instead getting them from the FontLoader. This way, you can
avoid requesting the font family before it is available (and thus avoid
caching the wrong result). However, for #3 there is no known work-around.

This patch fixes all three (together with a smaller patch for qtbase) by
invalidating all text and related caches in Qt Quick when fonts are
either added or removed from the font database. This does add some
overhead if font loading happens during runtime, but the alternative is
broken behavior and dangling pointers.

This is done during the synchronization step. Before synchronization,
the font cache is flushed and all text components are marked for update,
so that fonts are re-requested against the new font database.

After synchronization, we delete all distance field glyph caches which
are not currently in use, to avoid having references to stale application
font data in the list.

[ChangeLog][Text] Fix multiple issues with usage of application fonts when
they are added or removed during the lifetime of the application.

Task-number: QTBUG-100697
Task-number: QDS-1142
Change-Id: Ib309e54e0ee97b6be6d2a7211964043fd51c9ec5
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

20 files changed, 187 insertions, 7 deletions

diff --git a/src/quick/CMakeLists.txt b/src/quick/CMakeLists.txt
index a757ec9afa..e02698f639 100644
--- a/src/quick/CMakeLists.txt
+++ b/src/quick/CMakeLists.txt
@@ -78,6 +78,7 @@ qt_internal_add_qml_module(Quick
         items/qquickstateoperations.cpp items/qquickstateoperations_p.h
         items/qquicktext.cpp items/qquicktext_p.h
         items/qquicktext_p_p.h
+        items/qquicktextinterface_p.h
         items/qquicktextcontrol.cpp items/qquicktextcontrol_p.h
         items/qquicktextcontrol_p_p.h
         items/qquicktextdocument.cpp items/qquicktextdocument.h items/qquicktextdocument_p.h
diff --git a/src/quick/items/qquicktext.cpp b/src/quick/items/qquicktext.cpp
index 66baa7ed7c..fd65028a16 100644
--- a/src/quick/items/qquicktext.cpp
+++ b/src/quick/items/qquicktext.cpp
@@ -3008,6 +3008,13 @@ void QQuickText::hoverLeaveEvent(QHoverEvent *event)
     d->processHoverEvent(event);
 }
 
+void QQuickText::invalidate()
+{
+    Q_D(QQuickText);
+    d->textHasChanged = true;
+    d->updateLayout();
+}
+
 bool QQuickTextPrivate::transformChanged(QQuickItem *transformedItem)
 {
     // If there's a lot of text, we may need QQuickText::updatePaintNode() to call
diff --git a/src/quick/items/qquicktext_p.h b/src/quick/items/qquicktext_p.h
index 13d8579017..aa48467b72 100644
--- a/src/quick/items/qquicktext_p.h
+++ b/src/quick/items/qquicktext_p.h
@@ -52,6 +52,7 @@
 //
 
 #include "qquickimplicitsizeitem_p.h"
+#include "qquicktextinterface_p.h"
 #include <private/qtquickglobal_p.h>
 #include <QtGui/qtextoption.h>
 
@@ -59,9 +60,10 @@ QT_BEGIN_NAMESPACE
 
 class QQuickTextPrivate;
 class QQuickTextLine;
-class Q_QUICK_PRIVATE_EXPORT QQuickText : public QQuickImplicitSizeItem
+class Q_QUICK_PRIVATE_EXPORT QQuickText : public QQuickImplicitSizeItem, public QQuickTextInterface
 {
     Q_OBJECT
+    Q_INTERFACES(QQuickTextInterface)
 
     Q_PROPERTY(QString text READ text WRITE setText NOTIFY textChanged)
     Q_PROPERTY(QFont font READ font WRITE setFont NOTIFY fontChanged)
@@ -274,6 +276,8 @@ public:
     QJSValue fontInfo() const;
     QSizeF advance() const;
 
+    void invalidate() override;
+
 Q_SIGNALS:
     void textChanged(const QString &text);
     void linkActivated(const QString &link);
diff --git a/src/quick/items/qquicktextedit.cpp b/src/quick/items/qquicktextedit.cpp
index f739474908..814522394e 100644
--- a/src/quick/items/qquicktextedit.cpp
+++ b/src/quick/items/qquicktextedit.cpp
@@ -435,6 +435,18 @@ void QQuickTextEdit::setText(const QString &text)
     setFlag(QQuickItem::ItemObservesViewport, text.size() > QQuickTextEditPrivate::largeTextSizeThreshold);
 }
 
+void QQuickTextEdit::invalidate()
+{
+    Q_D(QQuickTextEdit);
+    if (isComponentComplete()) {
+        if (d->document != nullptr)
+            d->document->markContentsDirty(0, d->document->characterCount());
+        invalidateFontCaches();
+        d->updateType = QQuickTextEditPrivate::UpdateAll;
+        update();
+    }
+}
+
 /*!
     \qmlproperty string QtQuick::TextEdit::preeditText
     \readonly
@@ -2078,20 +2090,25 @@ QSGNode *QQuickTextEdit::updatePaintNode(QSGNode *oldNode, UpdatePaintNodeData *
     Q_UNUSED(updatePaintNodeData);
     Q_D(QQuickTextEdit);
 
-    if (d->updateType != QQuickTextEditPrivate::UpdatePaintNode && oldNode != nullptr) {
+    if (d->updateType != QQuickTextEditPrivate::UpdatePaintNode
+          && d->updateType != QQuickTextEditPrivate::UpdateAll
+          && oldNode != nullptr) {
         // Update done in preprocess() in the nodes
         d->updateType = QQuickTextEditPrivate::UpdateNone;
         return oldNode;
     }
 
-    d->updateType = QQuickTextEditPrivate::UpdateNone;
+    if (!oldNode || d->updateType == QQuickTextEditPrivate::UpdateAll) {
+        delete oldNode;
+        oldNode = nullptr;
 
-    if (!oldNode) {
         // If we had any QQuickTextNode node references, they were deleted along with the root node
         // But here we must delete the Node structures in textNodeMap
         d->textNodeMap.clear();
     }
 
+    d->updateType = QQuickTextEditPrivate::UpdateNone;
+
     RootNode *rootNode = static_cast<RootNode *>(oldNode);
     TextNodeIterator nodeIterator = d->textNodeMap.begin();
     while (nodeIterator != d->textNodeMap.end() && !nodeIterator->dirty())
diff --git a/src/quick/items/qquicktextedit_p.h b/src/quick/items/qquicktextedit_p.h
index 7b43a847c1..77f19c1cfa 100644
--- a/src/quick/items/qquicktextedit_p.h
+++ b/src/quick/items/qquicktextedit_p.h
@@ -52,6 +52,7 @@
 //
 
 #include "qquickimplicitsizeitem_p.h"
+#include "qquicktextinterface_p.h"
 
 #include <QtGui/qtextoption.h>
 
@@ -61,9 +62,10 @@ class QQuickTextDocument;
 class QQuickTextEditPrivate;
 class QTextBlock;
 
-class Q_QUICK_PRIVATE_EXPORT QQuickTextEdit : public QQuickImplicitSizeItem
+class Q_QUICK_PRIVATE_EXPORT QQuickTextEdit : public QQuickImplicitSizeItem, public QQuickTextInterface
 {
     Q_OBJECT
+    Q_INTERFACES(QQuickTextInterface)
 
     Q_PROPERTY(QString text READ text WRITE setText NOTIFY textChanged)
     Q_PROPERTY(QColor color READ color WRITE setColor NOTIFY colorChanged)
@@ -303,6 +305,8 @@ public:
     int tabStopDistance() const;
     void setTabStopDistance(qreal distance);
 
+    void invalidate() override;
+
 Q_SIGNALS:
     void textChanged();
     Q_REVISION(2, 7) void preeditTextChanged();
diff --git a/src/quick/items/qquicktextedit_p_p.h b/src/quick/items/qquicktextedit_p_p.h
index 2381b46a05..da62fe8c99 100644
--- a/src/quick/items/qquicktextedit_p_p.h
+++ b/src/quick/items/qquicktextedit_p_p.h
@@ -197,7 +197,8 @@ public:
     enum UpdateType {
         UpdateNone,
         UpdateOnlyPreprocess,
-        UpdatePaintNode
+        UpdatePaintNode,
+        UpdateAll
     };
 
     QQuickTextEdit::HAlignment hAlign;
diff --git a/src/quick/items/qquicktextinput.cpp b/src/quick/items/qquicktextinput.cpp
index 2a136bf8d4..b209fabf14 100644
--- a/src/quick/items/qquicktextinput.cpp
+++ b/src/quick/items/qquicktextinput.cpp
@@ -136,6 +136,13 @@ QString QQuickTextInput::text() const
     return (res.isNull() ? QString::fromLatin1("") : res);
 }
 
+void QQuickTextInput::invalidate()
+{
+    Q_D(QQuickTextInput);
+    d->updateLayout();
+    invalidateFontCaches();
+}
+
 void QQuickTextInput::setText(const QString &s)
 {
     Q_D(QQuickTextInput);
diff --git a/src/quick/items/qquicktextinput_p.h b/src/quick/items/qquicktextinput_p.h
index 031b4780db..24c27868de 100644
--- a/src/quick/items/qquicktextinput_p.h
+++ b/src/quick/items/qquicktextinput_p.h
@@ -52,6 +52,7 @@
 //
 
 #include "qquickimplicitsizeitem_p.h"
+#include "qquicktextinterface_p.h"
 #include <QtGui/qtextoption.h>
 #include <QtGui/qvalidator.h>
 
@@ -59,9 +60,10 @@ QT_BEGIN_NAMESPACE
 
 class QQuickTextInputPrivate;
 class QValidator;
-class Q_QUICK_PRIVATE_EXPORT QQuickTextInput : public QQuickImplicitSizeItem
+class Q_QUICK_PRIVATE_EXPORT QQuickTextInput : public QQuickImplicitSizeItem, public QQuickTextInterface
 {
     Q_OBJECT
+    Q_INTERFACES(QQuickTextInterface)
 
     Q_PROPERTY(QString text READ text WRITE setText NOTIFY textChanged)
     Q_PROPERTY(int length READ length NOTIFY textChanged)
@@ -311,6 +313,8 @@ public:
     void setBottomPadding(qreal padding);
     void resetBottomPadding();
 
+    void invalidate() override;
+
 Q_SIGNALS:
     void textChanged();
     void cursorPositionChanged();
diff --git a/src/quick/items/qquicktextinterface_p.h b/src/quick/items/qquicktextinterface_p.h
new file mode 100644
index 0000000000..da2c123abf
--- /dev/null
+++ b/src/quick/items/qquicktextinterface_p.h
@@ -0,0 +1,67 @@
+/****************************************************************************
+**
+** Copyright (C) 2022 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtQuick module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QQUICKTEXTINTERFACE_P_H
+#define QQUICKTEXTINTERFACE_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+QT_BEGIN_NAMESPACE
+
+class Q_QUICK_PRIVATE_EXPORT QQuickTextInterface
+{
+public:
+    virtual void invalidate() = 0;
+};
+
+#define QQuickTextInterface_iid "org.qt-project.Qt.QQuickTextInterface"
+Q_DECLARE_INTERFACE(QQuickTextInterface, QQuickTextInterface_iid)
+
+QT_END_NAMESPACE
+
+#endif // QQUICKTEXTINTERFACE_P_H
diff --git a/src/quick/items/qquickwindow.cpp b/src/quick/items/qquickwindow.cpp
index 6e9c258fd7..c172f0ec53 100644
--- a/src/quick/items/qquickwindow.cpp
+++ b/src/quick/items/qquickwindow.cpp
@@ -53,6 +53,7 @@
 #include <private/qquickrendercontrol_p.h>
 #include <private/qquickanimatorcontroller_p.h>
 #include <private/qquickprofiler_p.h>
+#include <private/qquicktextinterface_p.h>
 
 #include <private/qguiapplication_p.h>
 
@@ -436,6 +437,12 @@ void QQuickWindow::physicalDpiChanged()
         updatePixelRatioHelper(d->contentItem, newPixelRatio);
 }
 
+void QQuickWindow::handleFontDatabaseChanged()
+{
+    Q_D(QQuickWindow);
+    d->pendingFontUpdate = true;
+}
+
 void QQuickWindow::handleScreenChanged(QScreen *screen)
 {
     Q_D(QQuickWindow);
@@ -504,6 +511,17 @@ void QQuickWindowRenderTarget::reset(QRhi *rhi)
     owns = false;
 }
 
+void QQuickWindowPrivate::invalidateFontData(QQuickItem *item)
+{
+    QQuickTextInterface *textItem = qobject_cast<QQuickTextInterface *>(item);
+    if (textItem != nullptr)
+        textItem->invalidate();
+
+    QList<QQuickItem *> children = item->childItems();
+    for (QQuickItem *child : children)
+        invalidateFontData(child);
+}
+
 void QQuickWindowPrivate::ensureCustomRenderTarget()
 {
     // resolve() can be expensive when importing an existing native texture, so
@@ -547,6 +565,12 @@ void QQuickWindowPrivate::syncSceneGraph()
 
     emit q->beforeSynchronizing();
     runAndClearJobs(&beforeSynchronizingJobs);
+
+    if (pendingFontUpdate) {
+        QFont::cleanup();
+        invalidateFontData(contentItem);
+    }
+
     if (!renderer) {
         forceUpdate(contentItem);
 
@@ -573,6 +597,11 @@ void QQuickWindowPrivate::syncSceneGraph()
 
     renderer->setVisualizationMode(visualizationMode);
 
+    if (pendingFontUpdate) {
+        context->invalidateGlyphCaches();
+        pendingFontUpdate = false;
+    }
+
     emit q->afterSynchronizing();
     runAndClearJobs(&afterSynchronizingJobs);
 }
@@ -748,6 +777,11 @@ void QQuickWindowPrivate::init(QQuickWindow *c, QQuickRenderControl *control)
 
     Q_ASSERT(windowManager || renderControl);
 
+    QObject::connect(static_cast<QGuiApplication *>(QGuiApplication::instance()),
+                     &QGuiApplication::fontDatabaseChanged,
+                     q,
+                     &QQuickWindow::handleFontDatabaseChanged);
+
     if (QScreen *screen = q->screen()) {
         lastReportedItemDevicePixelRatio = q->effectiveDevicePixelRatio();
         // if the screen changes, then QQuickWindow::handleScreenChanged disconnects
diff --git a/src/quick/items/qquickwindow.h b/src/quick/items/qquickwindow.h
index 48878b057d..2d5b18dbcf 100644
--- a/src/quick/items/qquickwindow.h
+++ b/src/quick/items/qquickwindow.h
@@ -259,6 +259,7 @@ private Q_SLOTS:
     void setTransientParent_helper(QQuickWindow *window);
     void runJobsAfterSwap();
     void handleApplicationStateChanged(Qt::ApplicationState state);
+    void handleFontDatabaseChanged();
 private:
 #ifndef QT_NO_DEBUG_STREAM
     inline friend QQmlInfo operator<<(QQmlInfo info, const QQuickWindow *window)
diff --git a/src/quick/items/qquickwindow_p.h b/src/quick/items/qquickwindow_p.h
index 0fd09a1e33..20f4743481 100644
--- a/src/quick/items/qquickwindow_p.h
+++ b/src/quick/items/qquickwindow_p.h
@@ -168,6 +168,7 @@ public:
 
     void polishItems();
     void forcePolish();
+    void invalidateFontData(QQuickItem *item);
     void syncSceneGraph();
     void renderSceneGraph(const QSize &size, const QSize &surfaceSize = QSize());
 
@@ -295,6 +296,7 @@ public:
     uint hasActiveSwapchain : 1;
     uint hasRenderableSwapchain : 1;
     uint swapchainJustBecameRenderable : 1;
+    bool pendingFontUpdate = false;
     bool windowEventDispatch = false;
 
 private:
diff --git a/src/quick/scenegraph/qsgadaptationlayer.cpp b/src/quick/scenegraph/qsgadaptationlayer.cpp
index 9d18868c58..a35c1dc5a6 100644
--- a/src/quick/scenegraph/qsgadaptationlayer.cpp
+++ b/src/quick/scenegraph/qsgadaptationlayer.cpp
@@ -170,6 +170,11 @@ void QSGDistanceFieldGlyphCache::release(const QVector<glyph_t> &glyphs)
     releaseGlyphs(unusedGlyphs);
 }
 
+bool QSGDistanceFieldGlyphCache::isActive() const
+{
+    return true;
+}
+
 void QSGDistanceFieldGlyphCache::update()
 {
     m_populatingGlyphs.clear();
diff --git a/src/quick/scenegraph/qsgadaptationlayer_p.h b/src/quick/scenegraph/qsgadaptationlayer_p.h
index 03b3889322..d7c5bebbf7 100644
--- a/src/quick/scenegraph/qsgadaptationlayer_p.h
+++ b/src/quick/scenegraph/qsgadaptationlayer_p.h
@@ -495,6 +495,7 @@ public:
 
     virtual bool eightBitFormatIsAlphaSwizzled() const = 0;
     virtual bool screenSpaceDerivativesSupported() const = 0;
+    virtual bool isActive() const;
 
 protected:
     struct GlyphPosition {
diff --git a/src/quick/scenegraph/qsgcontext.cpp b/src/quick/scenegraph/qsgcontext.cpp
index 695af6b127..a5e0e5e035 100644
--- a/src/quick/scenegraph/qsgcontext.cpp
+++ b/src/quick/scenegraph/qsgcontext.cpp
@@ -432,6 +432,10 @@ QSGDistanceFieldGlyphCache *QSGRenderContext::distanceFieldGlyphCache(const QRaw
     return nullptr;
 }
 
+void QSGRenderContext::invalidateGlyphCaches()
+{
+
+}
 
 void QSGRenderContext::registerFontengineForCleanup(QFontEngine *engine)
 {
diff --git a/src/quick/scenegraph/qsgcontext_p.h b/src/quick/scenegraph/qsgcontext_p.h
index 1c6b5c3205..39a3051fe2 100644
--- a/src/quick/scenegraph/qsgcontext_p.h
+++ b/src/quick/scenegraph/qsgcontext_p.h
@@ -198,6 +198,7 @@ public:
     virtual void endSync();
 
     virtual void preprocess();
+    virtual void invalidateGlyphCaches();
     virtual QSGDistanceFieldGlyphCache *distanceFieldGlyphCache(const QRawFont &font, int renderTypeQuality);
     QSGTexture *textureForFactory(QQuickTextureFactory *factory, QQuickWindow *window);
 
diff --git a/src/quick/scenegraph/qsgdefaultrendercontext.cpp b/src/quick/scenegraph/qsgdefaultrendercontext.cpp
index a4337a58ca..508870fbd5 100644
--- a/src/quick/scenegraph/qsgdefaultrendercontext.cpp
+++ b/src/quick/scenegraph/qsgdefaultrendercontext.cpp
@@ -94,6 +94,19 @@ void QSGDefaultRenderContext::initialize(const QSGRenderContext::InitParams *par
     emit initialized();
 }
 
+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;
+        }
+    }
+}
+
 void QSGDefaultRenderContext::invalidate()
 {
     if (!m_rhi)
diff --git a/src/quick/scenegraph/qsgdefaultrendercontext_p.h b/src/quick/scenegraph/qsgdefaultrendercontext_p.h
index a97347eaf0..e233c4c3bd 100644
--- a/src/quick/scenegraph/qsgdefaultrendercontext_p.h
+++ b/src/quick/scenegraph/qsgdefaultrendercontext_p.h
@@ -111,6 +111,7 @@ public:
     void endNextRhiFrame(QSGRenderer *renderer) override;
 
     void preprocess() override;
+    void invalidateGlyphCaches() override;
     QSGDistanceFieldGlyphCache *distanceFieldGlyphCache(const QRawFont &font, int renderTypeQuality) override;
 
     QSGTexture *createTexture(const QImage &image, uint flags) const override;
diff --git a/src/quick/scenegraph/qsgrhidistancefieldglyphcache.cpp b/src/quick/scenegraph/qsgrhidistancefieldglyphcache.cpp
index b139c3428a..50a3091c55 100644
--- a/src/quick/scenegraph/qsgrhidistancefieldglyphcache.cpp
+++ b/src/quick/scenegraph/qsgrhidistancefieldglyphcache.cpp
@@ -147,6 +147,11 @@ void QSGRhiDistanceFieldGlyphCache::requestGlyphs(const QSet<glyph_t> &glyphs)
     markGlyphsToRender(glyphsToRender);
 }
 
+bool QSGRhiDistanceFieldGlyphCache::isActive() const
+{
+    return m_unusedGlyphs.size() != m_glyphsTexture.size();
+}
+
 void QSGRhiDistanceFieldGlyphCache::storeGlyphs(const QList<QDistanceField> &glyphs)
 {
     typedef QHash<TextureInfo *, QVector<glyph_t> > GlyphTextureHash;
diff --git a/src/quick/scenegraph/qsgrhidistancefieldglyphcache_p.h b/src/quick/scenegraph/qsgrhidistancefieldglyphcache_p.h
index 965b496e48..47bf59e3d7 100644
--- a/src/quick/scenegraph/qsgrhidistancefieldglyphcache_p.h
+++ b/src/quick/scenegraph/qsgrhidistancefieldglyphcache_p.h
@@ -72,6 +72,7 @@ public:
 
     bool useTextureResizeWorkaround() const;
     bool createFullSizeTextures() const;
+    bool isActive() const override;
     int maxTextureSize() const;
 
     void setMaxTextureCount(int max) { m_maxTextureCount = max; }