Make it possible to create distance field with specific size

The distance field size calculation is floating point math
and  sensitive to numerical errors. When used in Qt Quick,
it is vital that the allocated memory is the same as what
we calculate in the cache, otherwise we will get memory
corruption. In certain cases, numerical errors would cause
a qCeil() to round what was actually an integer up, and
we would end up with an allocated size that was off by one.

To avoid this, we allow the user to specify the size to
allocate, so that we can do the calculation in a single
place.

Pick-to: 5.15 6.2 6.5 6.7 6.8
Task-number: QTBUG-124572
Change-Id: I14e381952fdf331286f1ae4b51bb5fef9e39d704
Reviewed-by: Eirik Aavitsland <[email protected]>

src/gui/text/qdistancefield.cpp

@@ -839,14 +839,9 @@ QDistanceFieldData *QDistanceFieldData::create(const QSize &size)
     return data;
 }
 
-QDistanceFieldData *QDistanceFieldData::create(const QPainterPath &path, bool doubleResolution)
+QDistanceFieldData *QDistanceFieldData::create(QSize size, const QPainterPath &path, bool doubleResolution)
 {
-    int dfMargin = QT_DISTANCEFIELD_RADIUS(doubleResolution) / QT_DISTANCEFIELD_SCALE(doubleResolution);
-    int glyphWidth = qCeil(path.boundingRect().width() / QT_DISTANCEFIELD_SCALE(doubleResolution)) + dfMargin * 2;
-    int glyphHeight = qCeil(path.boundingRect().height() / QT_DISTANCEFIELD_SCALE(doubleResolution)) + dfMargin * 2;
-
-    QDistanceFieldData *data = create(QSize(glyphWidth, glyphHeight));
-
+    QDistanceFieldData *data = create(size);
     makeDistanceField(data,
                       path,
                       QT_DISTANCEFIELD_SCALE(doubleResolution),
@@ -855,6 +850,16 @@ QDistanceFieldData *QDistanceFieldData::create(const QPainterPath &path, bool do
 }
 
 
+QDistanceFieldData *QDistanceFieldData::create(const QPainterPath &path, bool doubleResolution)
+{
+    int dfMargin = QT_DISTANCEFIELD_RADIUS(doubleResolution) / QT_DISTANCEFIELD_SCALE(doubleResolution);
+    int glyphWidth = qCeil(path.boundingRect().width() / QT_DISTANCEFIELD_SCALE(doubleResolution)) + dfMargin * 2;
+    int glyphHeight = qCeil(path.boundingRect().height() / QT_DISTANCEFIELD_SCALE(doubleResolution)) + dfMargin * 2;
+
+    return create(QSize(glyphWidth, glyphHeight), path, doubleResolution);
+}
+
+
 QDistanceField::QDistanceField()
     : d(new QDistanceFieldData)
 {
@@ -875,6 +880,16 @@ QDistanceField::QDistanceField(QFontEngine *fontEngine, glyph_t glyph, bool doub
     setGlyph(fontEngine, glyph, doubleResolution);
 }
 
+QDistanceField::QDistanceField(QSize size, const QPainterPath &path, glyph_t glyph, bool doubleResolution)
+{
+    QPainterPath dfPath = path;
+    dfPath.translate(-dfPath.boundingRect().topLeft());
+    dfPath.setFillRule(Qt::WindingFill);
+
+    d = QDistanceFieldData::create(size, dfPath, doubleResolution);
+    d->glyph = glyph;
+}
+
 QDistanceField::QDistanceField(const QPainterPath &path, glyph_t glyph, bool doubleResolution)
 {
     QPainterPath dfPath = path;

src/gui/text/qdistancefield_p.h

@@ -42,6 +42,7 @@ class Q_GUI_EXPORT QDistanceFieldData : public QSharedData
 
     static QDistanceFieldData *create(const QSize &size);
     static QDistanceFieldData *create(const QPainterPath &path, bool doubleResolution);
+    static QDistanceFieldData *create(QSize size, const QPainterPath &path, bool doubleResolution);
 
     glyph_t glyph;
     int width;
@@ -58,6 +59,7 @@ class Q_GUI_EXPORT QDistanceField
     QDistanceField(const QRawFont &font, glyph_t glyph, bool doubleResolution = false);
     QDistanceField(QFontEngine *fontEngine, glyph_t glyph, bool doubleResolution = false);
     QDistanceField(const QPainterPath &path, glyph_t glyph, bool doubleResolution = false);
+    QDistanceField(QSize size, const QPainterPath &path, glyph_t glyph, bool doubleResolution = false);
 
     bool isNull() const;