Line spacing fixes

QTextEdit (via QTextLayout) and QPlainTextEdit in Qt used to ignore
any font leading but added one extra pixel in QFontMetrics. With many
freetype fonts,  this resulted in a "spacy" text layout.

The necessary fixes on X11 and Windows were to take (positive) leading
into account, to make the font database convert point sizes to pixel
sizes without rounding to plain integer values, and to subtract the
extra pixel from QFontMetrics from the font engines' descent value.

The change also fixes several places in styles and widgets, where
QFontMetrics::lineSpacing() was wrongly used instead of
QFontMetrics::height().

Ideally we should also handle negative leading, which would require
additional and bigger code changes in QTextLayout and QPlainTextEdit.
In addition, all other editors we have tested seem to ignore leading on
X11. If we choose to believe the values provided by freetype, our text
layout would be one pixel smaller than everybody else's.

On the Mac, this change does nothing. There our layout is still too spacy,
and for smaller fonts quite ugly compared to native Mac applications.

Done with mae.

Reviewed-by: mae

1 files changed, 12 insertions, 5 deletions

diff --git a/src/gui/text/qtextengine_p.h b/src/gui/text/qtextengine_p.h
index 85c6928..a1d363b 100644
--- a/src/gui/text/qtextengine_p.h
+++ b/src/gui/text/qtextengine_p.h
@@ -345,11 +345,11 @@ struct Q_AUTOTEST_EXPORT QScriptItem
 {
     inline QScriptItem()
         : position(0),
-          num_glyphs(0), descent(-1), ascent(-1), width(-1),
+          num_glyphs(0), descent(-1), ascent(-1), leading(-1), width(-1),
           glyph_data_offset(0) {}
     inline QScriptItem(int p, const QScriptAnalysis &a)
         : position(p), analysis(a),
-          num_glyphs(0), descent(-1), ascent(-1), width(-1),
+          num_glyphs(0), descent(-1), ascent(-1), leading(-1), width(-1),
           glyph_data_offset(0) {}
 
     int position;
@@ -357,6 +357,7 @@ struct Q_AUTOTEST_EXPORT QScriptItem
     unsigned short num_glyphs;
     QFixed descent;
     QFixed ascent;
+    QFixed leading;
     QFixed width;
     int glyph_data_offset;
     QFixed height() const { return ascent + descent + 1; }
@@ -373,9 +374,10 @@ struct Q_AUTOTEST_EXPORT QScriptLine
     QScriptLine()
         : from(0), length(0),
         justified(0), gridfitted(0),
-        hasTrailingSpaces(0) {}
+        hasTrailingSpaces(0), leadingIncluded(0) {}
     QFixed descent;
     QFixed ascent;
+    QFixed leading;
     QFixed x;
     QFixed y;
     QFixed width;
@@ -385,7 +387,11 @@ struct Q_AUTOTEST_EXPORT QScriptLine
     mutable uint justified : 1;
     mutable uint gridfitted : 1;
     uint hasTrailingSpaces : 1;
-    QFixed height() const { return ascent + descent + 1; }
+    uint leadingIncluded : 1;
+    QFixed height() const { return ascent + descent + 1
+                            + (leadingIncluded?  qMax(QFixed(),leading) : QFixed()); }
+    QFixed base() const { return ascent
+                          + (leadingIncluded ? qMax(QFixed(),leading) : QFixed()); }
     void setDefaultHeight(QTextEngine *eng);
     void operator+=(const QScriptLine &other);
 };
@@ -394,6 +400,7 @@ Q_DECLARE_TYPEINFO(QScriptLine, Q_PRIMITIVE_TYPE);
 
 inline void QScriptLine::operator+=(const QScriptLine &other)
 {
+    leading= qMax(leading + ascent, other.leading + other.ascent) - qMax(ascent, other.ascent);
     descent = qMax(descent, other.descent);
     ascent = qMax(ascent, other.ascent);
     textWidth += other.textWidth;
@@ -476,7 +483,7 @@ public:
         return end - si->position;
     }
 
-    QFontEngine *fontEngine(const QScriptItem &si, QFixed *ascent = 0, QFixed *descent = 0) const;
+    QFontEngine *fontEngine(const QScriptItem &si, QFixed *ascent = 0, QFixed *descent = 0, QFixed *leading = 0) const;
     QFont font(const QScriptItem &si) const;
     inline QFont font() const { return fnt; }