Improve hash strategy for font caches

We were using a string key for font lookups instead of
creating a proper type for this. This was a quick fix
which has grown over time and is inconvenient and slow.
Instead we now introduce a FontKey type which uses
Qt 6's qHashMulti() for this, also making it
automatically adapt to changes in the FaceId as well.

Change-Id: I32dfe3b809710e3d76896a5ddef03649bb4da0d5
Reviewed-by: Eskil Abrahamsen Blomfeldt <[email protected]>

4 files changed, 48 insertions, 27 deletions

diff --git a/src/quick/scenegraph/qsgcontext.cpp b/src/quick/scenegraph/qsgcontext.cpp
index 76c521dfd1..01e0707556 100644
--- a/src/quick/scenegraph/qsgcontext.cpp
+++ b/src/quick/scenegraph/qsgcontext.cpp
@@ -292,6 +292,20 @@ private:
     QElapsedTimer m_wallTime;
 };
 
+QSGRenderContext::FontKey::FontKey(const QRawFont &font, int quality)
+{
+    QFontEngine *fe = QRawFontPrivate::get(font)->fontEngine;
+    if (fe != nullptr)
+        faceId = fe->faceId();
+    style = font.style();
+    weight = font.weight();
+    renderTypeQuality = quality;
+    if (faceId.filename.isEmpty()) {
+        familyName = font.familyName();
+        styleName = font.styleName();
+    }
+}
+
 /*!
     \class QSGContext
 
diff --git a/src/quick/scenegraph/qsgcontext_p.h b/src/quick/scenegraph/qsgcontext_p.h
index 6f124c52dd..252dd5f7fd 100644
--- a/src/quick/scenegraph/qsgcontext_p.h
+++ b/src/quick/scenegraph/qsgcontext_p.h
@@ -24,6 +24,7 @@
 
 #include <private/qtquickglobal_p.h>
 #include <private/qrawfont_p.h>
+#include <private/qfontengine_p.h>
 
 #include <QtQuick/qsgnode.h>
 #include <QtQuick/qsgrendererinterface.h>
@@ -190,19 +191,48 @@ public Q_SLOTS:
     void textureFactoryDestroyed(QObject *o);
 
 protected:
+    struct FontKey {
+        FontKey(const QRawFont &font, int renderTypeQuality);
+
+        QFontEngine::FaceId faceId;
+        QFont::Style style;
+        int weight;
+        int renderTypeQuality;
+        QString familyName;
+        QString styleName;
+    };
+    friend bool operator==(const QSGRenderContext::FontKey &f1, const QSGRenderContext::FontKey &f2);
+    friend size_t qHash(const QSGRenderContext::FontKey &f, size_t seed);
+
     // Hold m_sg with QPointer in the rare case it gets deleted before us.
     QPointer<QSGContext> m_sg;
 
     QMutex m_mutex;
     QHash<QObject *, QSGTexture *> m_textures;
     QSet<QSGTexture *> m_texturesToDelete;
-    QHash<QString, QSGDistanceFieldGlyphCache *> m_glyphCaches;
+    QHash<FontKey, QSGDistanceFieldGlyphCache *> m_glyphCaches;
 
     // 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;
 };
 
+inline bool operator ==(const QSGRenderContext::FontKey &f1, const QSGRenderContext::FontKey &f2)
+{
+    return f1.faceId == f2.faceId
+        && f1.style == f2.style
+        && f1.weight == f2.weight
+        && f1.renderTypeQuality == f2.renderTypeQuality
+        && f1.familyName == f2.familyName
+        && f1.styleName == f2.styleName;
+}
+
+inline size_t qHash(const QSGRenderContext::FontKey &f, size_t seed = 0)
+{
+    return qHashMulti(seed, f.faceId, f.renderTypeQuality, f.familyName, f.styleName, f.style, f.weight);
+}
+
+
 QT_END_NAMESPACE
 
 #endif // QSGCONTEXT_H
diff --git a/src/quick/scenegraph/qsgdefaultrendercontext.cpp b/src/quick/scenegraph/qsgdefaultrendercontext.cpp
index a81366b401..1b0753e9ae 100644
--- a/src/quick/scenegraph/qsgdefaultrendercontext.cpp
+++ b/src/quick/scenegraph/qsgdefaultrendercontext.cpp
@@ -227,27 +227,6 @@ QSGTexture *QSGDefaultRenderContext::compressedTextureForFactory(const QSGCompre
     return nullptr;
 }
 
-QString QSGDefaultRenderContext::fontKey(const QRawFont &font, int renderTypeQuality)
-{
-    QFontEngine *fe = QRawFontPrivate::get(font)->fontEngine;
-    if (fe && !fe->faceId().filename.isEmpty()) {
-        QByteArray keyName =
-                fe->faceId().filename + ' ' + QByteArray::number(fe->faceId().index)
-                + (font.style() != QFont::StyleNormal ? QByteArray(" I") : QByteArray())
-                + (font.weight() != QFont::Normal ? ' ' + QByteArray::number(font.weight()) : QByteArray())
-                + ' ' + QByteArray::number(renderTypeQuality)
-                + QByteArray(" DF");
-        return QString::fromUtf8(keyName);
-    } else {
-        return QString::fromLatin1("%1_%2_%3_%4_%5")
-            .arg(font.familyName())
-            .arg(font.styleName())
-            .arg(font.weight())
-            .arg(font.style())
-            .arg(renderTypeQuality);
-    }
-}
-
 void QSGDefaultRenderContext::initializeRhiShader(QSGMaterialShader *shader, QShader::Variant shaderVariant)
 {
     QSGMaterialShaderPrivate::get(shader)->prepare(shaderVariant);
@@ -263,7 +242,7 @@ void QSGDefaultRenderContext::preprocess()
 
 QSGCurveGlyphAtlas *QSGDefaultRenderContext::curveGlyphAtlas(const QRawFont &font)
 {
-    QString key = fontKey(font, 0);
+    FontKey key = FontKey(font, 0);
     QSGCurveGlyphAtlas *atlas = m_curveGlyphAtlases.value(key, nullptr);
     if (atlas == nullptr) {
         atlas = new QSGCurveGlyphAtlas(font);
@@ -275,7 +254,7 @@ QSGCurveGlyphAtlas *QSGDefaultRenderContext::curveGlyphAtlas(const QRawFont &fon
 
 QSGDistanceFieldGlyphCache *QSGDefaultRenderContext::distanceFieldGlyphCache(const QRawFont &font, int renderTypeQuality)
 {
-    QString key = fontKey(font, renderTypeQuality);
+    FontKey key(font, renderTypeQuality);
     QSGDistanceFieldGlyphCache *cache = m_glyphCaches.value(key, 0);
     if (!cache && font.isValid()) {
         cache = new QSGRhiDistanceFieldGlyphCache(this, font, renderTypeQuality);
diff --git a/src/quick/scenegraph/qsgdefaultrendercontext_p.h b/src/quick/scenegraph/qsgdefaultrendercontext_p.h
index 1743ea35b7..766c628ae0 100644
--- a/src/quick/scenegraph/qsgdefaultrendercontext_p.h
+++ b/src/quick/scenegraph/qsgdefaultrendercontext_p.h
@@ -108,8 +108,6 @@ public:
     void resetGlyphCacheResources();
 
 protected:
-    static QString fontKey(const QRawFont &font, int renderTypeQuality);
-
     InitParams m_initParams;
     QRhi *m_rhi;
     int m_maxTextureSize;
@@ -120,7 +118,7 @@ protected:
     bool m_useDepthBufferFor2D;
     QRhiResourceUpdateBatch *m_glyphCacheResourceUpdates;
     QSet<QRhiTexture *> m_pendingGlyphCacheTextures;
-    QHash<QString, QSGCurveGlyphAtlas *> m_curveGlyphAtlases;
+    QHash<FontKey, QSGCurveGlyphAtlas *> m_curveGlyphAtlases;
 };
 
 QT_END_NAMESPACE