Add QGlyphRun::SplitLigature flag

If the glyph run is generated based on characters which split a
ligature glyph, it needs to include the ligature glyph in the run,
and when painting, we need to clip the painter to the reported
bounding rect of the run in order to avoid painting too much of
the ligature. To make it possible to reduce clipping to a
minimum, we need a flag to inform of whether the glyph run contains
a split ligature or not.

Change-Id: Id787e0bec6d6e8e06cc818700ae0fca22cf81e98
Reviewed-by: Jiang Jiang <jiang.jiang@nokia.com>

3 files changed, 49 insertions, 28 deletions

diff --git a/src/gui/text/qglyphrun.cpp b/src/gui/text/qglyphrun.cpp
index a4e9048678..0457202a18 100644
--- a/src/gui/text/qglyphrun.cpp
+++ b/src/gui/text/qglyphrun.cpp
@@ -100,6 +100,14 @@ QT_BEGIN_NAMESPACE
   \value RightToLeft Indicates that the glyphs are ordered right to left. This can affect the
   positioning of other screen elements that are relative to the glyph run, such as an inline
   text object.
+  \value SplitLigature Indicates that the glyph run splits a ligature glyph. This means
+  that a ligature glyph is included in the run, but the characters represented by it corresponds
+  only to part of that ligature. The glyph run's boundingRect() function can in this case be used
+  to retrieve the area covered by glyphs that correspond to the characters represented by the
+  glyph run. When visualizing the glyphs, care needs to be taken to clip to this bounding rect to
+  ensure that only the corresponding part of the ligature is painted. In particular, this can be
+  the case when retrieving a glyph run from a QTextLayout for a specific character range, e.g.
+  when retrieving the selected area of a QTextLayout.
 */
 
 /*!
diff --git a/src/gui/text/qglyphrun.h b/src/gui/text/qglyphrun.h
index 5a55eacbcb..22fb5ff395 100644
--- a/src/gui/text/qglyphrun.h
+++ b/src/gui/text/qglyphrun.h
@@ -60,10 +60,11 @@ class Q_GUI_EXPORT QGlyphRun
 {
 public:
     enum GlyphRunFlag {
-        Overline    = 0x1,
-        Underline   = 0x2,
-        StrikeOut   = 0x4,
-        RightToLeft = 0x8
+        Overline        = 0x01,
+        Underline       = 0x02,
+        StrikeOut       = 0x04,
+        RightToLeft     = 0x08,
+        SplitLigature   = 0x10,
     };
     Q_DECLARE_FLAGS(GlyphRunFlags, GlyphRunFlag)
 
diff --git a/src/gui/text/qtextlayout.cpp b/src/gui/text/qtextlayout.cpp
index 3e7c0ad4ab..d3f8cb7cde 100644
--- a/src/gui/text/qtextlayout.cpp
+++ b/src/gui/text/qtextlayout.cpp
@@ -1015,15 +1015,7 @@ QList<QGlyphRun> QTextLayout::glyphRuns(int from, int length) const
                 QRawFont rawFont = glyphRun.rawFont();
 
                 QFontEngine *fontEngine = rawFont.d->fontEngine;
-                QTextItem::RenderFlags flags;
-                if (glyphRun.underline())
-                    flags |= QTextItem::Underline;
-                if (glyphRun.overline())
-                    flags |= QTextItem::Overline;
-                if (glyphRun.strikeOut())
-                    flags |= QTextItem::StrikeOut;
-                if (glyphRun.isRightToLeft())
-                    flags |= QTextItem::RightToLeft;
+                QGlyphRun::GlyphRunFlags flags = glyphRun.flags();
                 QPair<QFontEngine *, int> key(fontEngine, int(flags));
                 // merge the glyph runs using the same font
                 if (glyphRunHash.contains(key)) {
@@ -2106,7 +2098,7 @@ static void setPenAndDrawBackground(QPainter *p, const QPen &defaultPen, const Q
 
 #if !defined(QT_NO_RAWFONT)
 static QGlyphRun glyphRunWithInfo(QFontEngine *fontEngine, const QGlyphLayout &glyphLayout,
-                                  const QPointF &pos, const QTextItem::RenderFlags &flags,
+                                  const QPointF &pos, const QGlyphRun::GlyphRunFlags &flags,
                                   const QFixed &selectionX, const QFixed &selectionWidth)
 {
     QGlyphRun glyphRun;
@@ -2137,7 +2129,17 @@ static QGlyphRun glyphRunWithInfo(QFontEngine *fontEngine, const QGlyphLayout &g
     QVarLengthArray<glyph_t> glyphsArray;
     QVarLengthArray<QFixedPoint> positionsArray;
 
-    fontEngine->getGlyphPositions(glyphLayout, QTransform(), flags, glyphsArray,
+    QTextItem::RenderFlags renderFlags;
+    if (flags.testFlag(QGlyphRun::Overline))
+        renderFlags |= QTextItem::Overline;
+    if (flags.testFlag(QGlyphRun::Underline))
+        renderFlags |= QTextItem::Underline;
+    if (flags.testFlag(QGlyphRun::StrikeOut))
+        renderFlags |= QTextItem::StrikeOut;
+    if (flags.testFlag(QGlyphRun::RightToLeft))
+        renderFlags |= QTextItem::RightToLeft;
+
+    fontEngine->getGlyphPositions(glyphLayout, QTransform(), renderFlags, glyphsArray,
                                   positionsArray);
     Q_ASSERT(glyphsArray.size() == positionsArray.size());
 
@@ -2164,12 +2166,7 @@ static QGlyphRun glyphRunWithInfo(QFontEngine *fontEngine, const QGlyphLayout &g
 
     glyphRun.setGlyphIndexes(glyphs);
     glyphRun.setPositions(positions);
-
-    glyphRun.setOverline(flags.testFlag(QTextItem::Overline));
-    glyphRun.setUnderline(flags.testFlag(QTextItem::Underline));
-    glyphRun.setStrikeOut(flags.testFlag(QTextItem::StrikeOut));
-    if (flags.testFlag(QTextItem::RightToLeft))
-        glyphRun.setRightToLeft(true);
+    glyphRun.setFlags(flags);
     glyphRun.setRawFont(font);
 
     glyphRun.setBoundingRect(QRectF(selectionX.toReal(), minY, selectionWidth.toReal(), height));
@@ -2229,17 +2226,17 @@ QList<QGlyphRun> QTextLine::glyphRuns(int from, int length) const
 
         QFont font = eng->font(si);
 
-        QTextItem::RenderFlags flags;
+        QGlyphRun::GlyphRunFlags flags;
         if (font.overline())
-            flags |= QTextItem::Overline;
+            flags |= QGlyphRun::Overline;
         if (font.underline())
-            flags |= QTextItem::Underline;
+            flags |= QGlyphRun::Underline;
         if (font.strikeOut())
-            flags |= QTextItem::StrikeOut;
+            flags |= QGlyphRun::StrikeOut;
 
         bool rtl = false;
         if (si.analysis.bidiLevel % 2) {
-            flags |= QTextItem::RightToLeft;
+            flags |= QGlyphRun::RightToLeft;
             rtl = true;
         }
 
@@ -2251,6 +2248,9 @@ QList<QGlyphRun> QTextLine::glyphRuns(int from, int length) const
         int glyphsEnd = (relativeTo == eng->length(&si))
                          ? si.num_glyphs - 1
                          : logClusters[relativeTo];
+        bool startsInsideLigature = relativeFrom > 0 && logClusters[relativeFrom - 1] == glyphsStart;
+        bool endsInsideLigature = relativeTo < eng->length(&si) - 1
+                               && logClusters[relativeTo + 1] == glyphsEnd;
 
         int itemGlyphsStart = logClusters[iterator.itemStart - si.position];
         int itemGlyphsEnd = logClusters[iterator.itemEnd - 1 - si.position];
@@ -2294,8 +2294,13 @@ QList<QGlyphRun> QTextLine::glyphRuns(int from, int length) const
 
                     QGlyphLayout subLayout = glyphLayout.mid(start, end - start);
                     multiFontEngine->ensureEngineAt(which);
+
+                    QGlyphRun::GlyphRunFlags subFlags = flags;
+                    if (start == 0 && startsInsideLigature)
+                        subFlags |= QGlyphRun::SplitLigature;
+
                     glyphRuns.append(glyphRunWithInfo(multiFontEngine->engine(which),
-                                                      subLayout, pos, flags, x, width));
+                                                      subLayout, pos, subFlags, x, width));
                     for (int i = 0; i < subLayout.numGlyphs; i++) {
                         pos += QPointF(subLayout.advances_x[i].toReal(),
                                        subLayout.advances_y[i].toReal());
@@ -2307,11 +2312,18 @@ QList<QGlyphRun> QTextLine::glyphRuns(int from, int length) const
 
                 QGlyphLayout subLayout = glyphLayout.mid(start, end - start);
                 multiFontEngine->ensureEngineAt(which);
+
+                QGlyphRun::GlyphRunFlags subFlags = flags;
+                if ((start == 0 && startsInsideLigature) || endsInsideLigature)
+                    subFlags |= QGlyphRun::SplitLigature;
+
                 QGlyphRun glyphRun = glyphRunWithInfo(multiFontEngine->engine(which),
-                                                      subLayout, pos, flags, x, width);
+                                                      subLayout, pos, subFlags, x, width);
                 if (!glyphRun.isEmpty())
                     glyphRuns.append(glyphRun);
             } else {
+                if (startsInsideLigature || endsInsideLigature)
+                    flags |= QGlyphRun::SplitLigature;
                 QGlyphRun glyphRun = glyphRunWithInfo(mainFontEngine, glyphLayout, pos, flags, x,
                                                       width);
                 if (!glyphRun.isEmpty())