Allow arbitrary baseline shift in QTextCharacterFormat

Added 6 new methods in QTextFormat and QTextDocument to
allow setting/getting specific % positioning for baseline and super/
subscript. Modified QTextLayout to honor those new settings.

[ChangeLog][QtGui][QTextLayout,QTextFormat,QTextDocument] Allow text
layout modification based on baseline offset and super/subscript % height
positioning

Fixes: QTBUG-18260
Change-Id: I0796f18224aac8df6baf8359c35022fd98fe64ef
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>

6 files changed, 194 insertions, 5 deletions

diff --git a/src/gui/text/qtextdocument.cpp b/src/gui/text/qtextdocument.cpp
index b95f55451a..f066853792 100644
--- a/src/gui/text/qtextdocument.cpp
+++ b/src/gui/text/qtextdocument.cpp
@@ -1733,6 +1733,93 @@ QFont QTextDocument::defaultFont() const
 }
 
 /*!
+    \fn void QTextDocument::setSuperScriptBaseline(qreal baseline)
+    \since 6.0
+
+    Sets the default superscript's base line as a % of font height to use in the document layout.
+    The default value is 50% (1/2 of height)
+
+    \sa superScriptBaseline(), setSubScriptBaseline(), subScriptBaseline(), setBaselineOffset(), baselineOffset()
+*/
+void QTextDocument::setSuperScriptBaseline(qreal baseline)
+{
+    Q_D(QTextDocument);
+    d->formats.setSuperScriptBaseline(baseline);
+}
+
+/*!
+    \fn qreal QTextDocument::superScriptBaseline() const
+    \since 6.0
+
+    Returns the superscript's base line as a % of font height used in the document layout.
+
+    \sa setSuperScriptBaseline(), setSubScriptBaseline(), subScriptBaseline(), setBaselineOffset(), baselineOffset()
+*/
+qreal QTextDocument::superScriptBaseline() const
+{
+    Q_D(const QTextDocument);
+    return d->formats.defaultTextFormat().superScriptBaseline();
+}
+
+/*!
+    \fn void QTextDocument::setSubScriptBaseline(qreal baseline)
+    \since 6.0
+
+    Sets the default subscript's base line as a % of font height to use in the document layout.
+    The default value is 16.67% (1/6 of height)
+
+    \sa subScriptBaseline(), setSuperScriptBaseline(), superScriptBaseline(), setBaselineOffset(), baselineOffset()
+*/
+void QTextDocument::setSubScriptBaseline(qreal baseline)
+{
+    Q_D(QTextDocument);
+    d->formats.setSubScriptBaseline(baseline);
+}
+
+/*!
+    \fn qreal QTextDocument::subScriptBaseline() const
+    \since 6.0
+
+    Returns the superscript's base line as a % of font height used in the document layout.
+
+    \sa setSubScriptBaseline(), setSuperScriptBaseline(), superScriptBaseline(), setBaselineOffset(), baselineOffset()
+*/
+qreal QTextDocument::subScriptBaseline() const
+{
+    Q_D(const QTextDocument);
+    return d->formats.defaultTextFormat().subScriptBaseline();
+}
+
+/*!
+    \fn void QTextDocument::setBaselineOffset(qreal baseline)
+    \since 6.0
+
+    Sets the baseline (in % of height) to use in the document layout. The default value is 0.
+    A positive value moves up the text, by the corresponding %; a negative value moves it down.
+
+    \sa baselineOffset(), setSubScriptBaseline(), subScriptBaseline(), setSuperScriptBaseline(), superScriptBaseline()
+*/
+void QTextDocument::setBaselineOffset(qreal baseline)
+{
+    Q_D(QTextDocument);
+    d->formats.setBaselineOffset(baseline);
+}
+
+/*!
+    \fn qreal QTextDocument::baselineOffset() const
+    \since 6.0
+
+    Returns the the baseline offset in % used in the document layout.
+
+    \sa setBaselineOffset(), setSubScriptBaseline(), subScriptBaseline(), setSuperScriptBaseline(), superScriptBaseline()
+*/
+qreal QTextDocument::baselineOffset() const
+{
+    Q_D(const QTextDocument);
+    return d->formats.defaultTextFormat().baselineOffset();
+}
+
+/*!
     \fn void QTextDocument::modificationChanged(bool changed)
 
     This signal is emitted whenever the content of the document
diff --git a/src/gui/text/qtextdocument.h b/src/gui/text/qtextdocument.h
index 5de81e683c..0470ad52e9 100644
--- a/src/gui/text/qtextdocument.h
+++ b/src/gui/text/qtextdocument.h
@@ -208,6 +208,15 @@ public:
     void setDefaultFont(const QFont &font);
     QFont defaultFont() const;
 
+    void setSuperScriptBaseline(qreal baseline);
+    qreal superScriptBaseline() const;
+
+    void setSubScriptBaseline(qreal baseline);
+    qreal subScriptBaseline() const;
+
+    void setBaselineOffset(qreal baseline);
+    qreal baselineOffset() const;
+
     int pageCount() const;
 
     bool isModified() const;
diff --git a/src/gui/text/qtextformat.cpp b/src/gui/text/qtextformat.cpp
index 14b564fc73..faf1765219 100644
--- a/src/gui/text/qtextformat.cpp
+++ b/src/gui/text/qtextformat.cpp
@@ -635,6 +635,10 @@ Q_GUI_EXPORT QDataStream &operator>>(QDataStream &stream, QTextFormat &fmt)
     \value TextOutline
     \value TextUnderlineStyle
     \value TextToolTip Specifies the (optional) tool tip to be displayed for a fragment of text.
+    \value TextSuperScriptBaseline Specifies the baseline (in % of height) of superscript texts.
+    \value TextSubScriptBaseline   Specifies the baseline (in % of height) of subscript texts.
+    \value TextBaselineOffset      Specifies the baseline (in % of height) of text. A positive value moves up the text,
+                                   by the corresponding %; a negative value moves it down.
 
     \value IsAnchor
     \value AnchorHref
@@ -1795,6 +1799,60 @@ void QTextCharFormat::setUnderlineStyle(UnderlineStyle style)
     \sa foreground(), setForeground(), clearBackground()
 */
 
+/*!
+    \fn void QTextCharFormat::setSuperScriptBaseline(qreal baseline)
+    \since 6.0
+
+    Sets the superscript's base line as a % of font height. The default value is 50% (1/2 of height)
+
+    \sa superScriptBaseline(), setSubScriptBaseline(), subScriptBaseline(), setBaselineOffset(), baselineOffset()
+*/
+
+/*!
+    \fn qreal QTextCharFormat::superScriptBaseline() const
+    \since 6.0
+
+    Returns the superscript's base line as a % of font height.
+
+    \sa setSuperScriptBaseline(), setSubScriptBaseline(), subScriptBaseline(), setBaselineOffset(), baselineOffset()
+*/
+
+/*!
+    \fn void QTextCharFormat::setSubScriptBaseline(qreal baseline)
+    \since 6.0
+
+    Sets the subscript's base line as a % of font height. The default value is 16.67% (1/6 of height)
+
+    \sa subScriptBaseline(), setSuperScriptBaseline(), superScriptBaseline(), setBaselineOffset(), baselineOffset()
+*/
+
+/*!
+    \fn qreal QTextCharFormat::subScriptBaseline() const
+    \since 6.0
+
+    Returns the subscript's base line as a % of font height.
+
+    \sa setSubScriptBaseline(), setSuperScriptBaseline(), superScriptBaseline(), setBaselineOffset(), baselineOffset()
+*/
+
+/*!
+    \fn void QTextCharFormat::setBaselineOffset(qreal baseline)
+    \since 6.0
+
+    Sets the baseline (in % of height) of text. A positive value moves up the text, by the corresponding %;
+    a negative value moves it down. The default value is 0.
+
+    \sa baselineOffset(), setSubScriptBaseline(), subScriptBaseline(), setSuperScriptBaseline(), superScriptBaseline()
+*/
+
+/*!
+    \fn qreal QTextCharFormat::baselineOffset() const
+    \since 6.0
+
+    Returns the the baseline offset in %.
+
+    \sa setBaselineOffset(), setSubScriptBaseline(), subScriptBaseline(), setSuperScriptBaseline(), superScriptBaseline()
+*/
 
 /*!
     \fn void QTextCharFormat::setAnchor(bool anchor)
diff --git a/src/gui/text/qtextformat.h b/src/gui/text/qtextformat.h
index e12f033596..9d422786f0 100644
--- a/src/gui/text/qtextformat.h
+++ b/src/gui/text/qtextformat.h
@@ -213,6 +213,9 @@ public:
         TextOutline = 0x2022,
         TextUnderlineStyle = 0x2023,
         TextToolTip = 0x2024,
+        TextSuperScriptBaseline = 0x2025,
+        TextSubScriptBaseline = 0x2026,
+        TextBaselineOffset = 0x2027,
 
         IsAnchor = 0x2030,
         AnchorHref = 0x2031,
@@ -570,6 +573,21 @@ public:
     inline QString toolTip() const
     { return stringProperty(TextToolTip); }
 
+    inline void setSuperScriptBaseline(qreal baseline)
+    { setProperty(TextSuperScriptBaseline, baseline); }
+    inline qreal superScriptBaseline() const
+    { return hasProperty(TextSuperScriptBaseline) ? doubleProperty(TextSuperScriptBaseline) : 50.0; }
+
+    inline void setSubScriptBaseline(qreal baseline)
+    { setProperty(TextSubScriptBaseline, baseline); }
+    inline qreal subScriptBaseline() const
+    { return hasProperty(TextSubScriptBaseline) ? doubleProperty(TextSubScriptBaseline) : 100.0 / 6.0; }
+
+    inline void setBaselineOffset(qreal baseline)
+    { setProperty(TextBaselineOffset, baseline); }
+    inline qreal baselineOffset() const
+    { return hasProperty(TextBaselineOffset) ? doubleProperty(TextBaselineOffset) : 0.0; }
+
     inline void setAnchor(bool anchor)
     { setProperty(IsAnchor, anchor); }
     inline bool isAnchor() const
diff --git a/src/gui/text/qtextformat_p.h b/src/gui/text/qtextformat_p.h
index 862ef18e65..13815d06b3 100644
--- a/src/gui/text/qtextformat_p.h
+++ b/src/gui/text/qtextformat_p.h
@@ -101,8 +101,15 @@ public:
     inline QFont defaultFont() const { return defaultFnt; }
     void setDefaultFont(const QFont &f);
 
+    inline void setSuperScriptBaseline(qreal baseline) { defaultFormat.setSuperScriptBaseline(baseline); }
+    inline void setSubScriptBaseline(qreal baseline) { defaultFormat.setSubScriptBaseline(baseline); }
+    inline void setBaselineOffset(qreal baseline) { defaultFormat.setBaselineOffset(baseline); }
+
+    inline QTextCharFormat defaultTextFormat() const { return defaultFormat; }
+
 private:
     QFont defaultFnt;
+    QTextCharFormat defaultFormat;
 
     Q_DISABLE_COPY_MOVE(QTextFormatCollection)
 };
diff --git a/src/gui/text/qtextlayout.cpp b/src/gui/text/qtextlayout.cpp
index ec4270ea9c..cd064364d5 100644
--- a/src/gui/text/qtextlayout.cpp
+++ b/src/gui/text/qtextlayout.cpp
@@ -2511,6 +2511,8 @@ void QTextLine::draw(QPainter *p, const QPointF &pos, const QTextLayout::FormatR
 
     const QFixed y = QFixed::fromReal(pos.y()) + line.y + lineBase;
 
+    const QTextFormatCollection *formatCollection = eng->formatCollection();
+
     bool suppressColors = (eng->option.flags() & QTextOption::SuppressColors);
     while (!iterator.atEnd()) {
         QScriptItem &si = iterator.next();
@@ -2525,10 +2527,12 @@ void QTextLine::draw(QPainter *p, const QPointF &pos, const QTextLayout::FormatR
         QFixed itemBaseLine = y;
         QFont f = eng->font(si);
         QTextCharFormat format;
+        if (formatCollection != nullptr)
+            format = formatCollection->defaultTextFormat();
 
+        if (eng->hasFormats() || selection || formatCollection) {
+            format.merge(eng->format(&si));
 
-        if (eng->hasFormats() || selection) {
-            format = eng->format(&si);
             if (suppressColors) {
                 format.clearForeground();
                 format.clearBackground();
@@ -2540,14 +2544,20 @@ void QTextLine::draw(QPainter *p, const QPointF &pos, const QTextLayout::FormatR
             setPenAndDrawBackground(p, pen, format, QRectF(iterator.x.toReal(), (y - lineBase).toReal(),
                                                            iterator.itemWidth.toReal(), line.height().toReal()));
 
+            const qreal baseLineOffset = format.baselineOffset() / 100.0;
             QTextCharFormat::VerticalAlignment valign = format.verticalAlignment();
-            if (valign == QTextCharFormat::AlignSuperScript || valign == QTextCharFormat::AlignSubScript) {
+            if (valign == QTextCharFormat::AlignSuperScript
+                || valign == QTextCharFormat::AlignSubScript
+                || !qFuzzyIsNull(baseLineOffset))
+            {
                 QFontEngine *fe = f.d->engineForScript(si.analysis.script);
                 QFixed height = fe->ascent() + fe->descent();
+                itemBaseLine -= height * QFixed::fromReal(baseLineOffset);
+
                 if (valign == QTextCharFormat::AlignSubScript)
-                    itemBaseLine += height / 6;
+                    itemBaseLine += height * QFixed::fromReal(format.subScriptBaseline() / 100.0);
                 else if (valign == QTextCharFormat::AlignSuperScript)
-                    itemBaseLine -= height / 2;
+                    itemBaseLine -= height * QFixed::fromReal(format.superScriptBaseline() / 100.0);
             }
         }