Add private qt_draw_glyphs() API

In some use cases where you use an external font engine and want to
use Qt's font engine for painting, you might need a function which will
give you direct access to the underlying font. A generic API for this
requires a lot of API changes, so in the meantime, we implement an
internal, specialized API to support the use cases where it is
required. The API is considered internal and experimental, and not
guaranteed to be stable or even exist across releases.

This is API which provides several fun ways to shoot yourself in the
foot, but if used properly, it will allow you to paint glyph ids at
precalculated positions.

Task-number: QTBUG-7844
Reviewed-by: Trond

1 files changed, 55 insertions, 0 deletions

diff --git a/src/gui/painting/qpainter.cpp b/src/gui/painting/qpainter.cpp
index 6f5c732..eee3a47 100644
--- a/src/gui/painting/qpainter.cpp
+++ b/src/gui/painting/qpainter.cpp
@@ -5699,6 +5699,61 @@ void QPainter::drawImage(const QRectF &targetRect, const QImage &image, const QR
     d->engine->drawImage(QRectF(x, y, w, h), image, QRectF(sx, sy, sw, sh), flags);
 }
 
+
+void qt_draw_glyphs(QPainter *painter, const quint32 *glyphArray, const QPointF *positionArray,
+                    int glyphCount)
+{
+    QPainterPrivate *painter_d = QPainterPrivate::get(painter);
+    painter_d->drawGlyphs(glyphArray, positionArray, glyphCount);
+}
+
+void QPainterPrivate::drawGlyphs(const quint32 *glyphArray, const QPointF *positionArray,
+                                 int glyphCount)
+{
+    updateState(state);
+
+    QFontEngine *fontEngine = state->font.d->engineForScript(QUnicodeTables::Common);
+
+    QVarLengthArray<QFixedPoint, 128> positions;
+    for (int i=0; i<glyphCount; ++i) {
+        QFixedPoint fp = QFixedPoint::fromPointF(positionArray[i]);
+        positions.append(fp);
+    }
+
+    if (extended != 0) {
+        QStaticTextItem staticTextItem;
+        staticTextItem.color = state->pen.color();
+        staticTextItem.font = state->font;
+        staticTextItem.fontEngine = fontEngine;
+        staticTextItem.numGlyphs = glyphCount;
+        staticTextItem.glyphs = reinterpret_cast<glyph_t *>(const_cast<glyph_t *>(glyphArray));
+        staticTextItem.glyphPositions = positions.data();
+
+        extended->drawStaticTextItem(&staticTextItem);
+    } else {
+        QTextItemInt textItem;
+        textItem.f = &state->font;
+        textItem.fontEngine = fontEngine;
+
+        QVarLengthArray<QFixed, 128> advances(glyphCount);
+        QVarLengthArray<QGlyphJustification, 128> glyphJustifications(glyphCount);
+        QVarLengthArray<HB_GlyphAttributes, 128> glyphAttributes(glyphCount);
+        qMemSet(glyphAttributes.data(), 0, glyphAttributes.size() * sizeof(HB_GlyphAttributes));
+        qMemSet(advances.data(), 0, advances.size() * sizeof(QFixed));
+        qMemSet(glyphJustifications.data(), 0, glyphJustifications.size() * sizeof(QGlyphJustification));
+
+        textItem.glyphs.numGlyphs = glyphCount;
+        textItem.glyphs.glyphs = reinterpret_cast<HB_Glyph *>(const_cast<quint32 *>(glyphArray));
+        textItem.glyphs.offsets = positions.data();
+        textItem.glyphs.advances_x = advances.data();
+        textItem.glyphs.advances_y = advances.data();
+        textItem.glyphs.justifications = glyphJustifications.data();
+        textItem.glyphs.attributes = glyphAttributes.data();
+
+        engine->drawTextItem(QPointF(0, 0), textItem);
+    }
+}
+
 /*!
 
     \fn void QPainter::drawStaticText(const QPoint &position, const QStaticText &staticText)