Change QStaticText::setMaximumSize() to setTextWidth()

To avoid having to precalculate the height of the laid out text, we
now only supply a maximum text width to QStaticText. The only usage of
the maximum height would be to clip the results, and clipping should be
set separately from the QStaticText call, since this has no impact on
the layout of the glyphs. The tests have been updated to reflect the
change in logic.

We also need a consistent way of specifying the position of the text.
Before, the position meant "baseline position" for unbroken text and
"top left position" for text with a specified layout width. We want
to be consistent, and since baseline position makes no sense for
multiline text, we standardize on top left position.

Task-number: QTBUG-9029
Reviewed-by: Gunnar

3 files changed, 55 insertions, 44 deletions

diff --git a/src/gui/text/qstatictext.cpp b/src/gui/text/qstatictext.cpp
index f433c78..977355e 100644
--- a/src/gui/text/qstatictext.cpp
+++ b/src/gui/text/qstatictext.cpp
@@ -143,11 +143,10 @@ QStaticText::QStaticText()
 
     If an invalid size is passed for \a size the text will be unbounded.
 */
-QStaticText::QStaticText(const QString &text, const QSizeF &size)
+QStaticText::QStaticText(const QString &text)
     : data(new QStaticTextPrivate)
 {    
     data->text = text;
-    data->maximumSize = size;
     data->init();
 }
 
@@ -209,7 +208,7 @@ QStaticText &QStaticText::operator=(const QStaticText &other)
 }
 
 /*!
-    Compares \a other to this QStaticText. Returns true if the texts, fonts and maximum sizes
+    Compares \a other to this QStaticText. Returns true if the texts, fonts and text widths
     are equal.
 */
 bool QStaticText::operator==(const QStaticText &other) const
@@ -217,7 +216,7 @@ bool QStaticText::operator==(const QStaticText &other) const
     return (data == other.data
             || (data->text == other.data->text
                 && data->font == other.data->font
-                && data->maximumSize == other.data->maximumSize));
+                && data->textWidth == other.data->textWidth));
 }
 
 /*!
@@ -315,33 +314,39 @@ QStaticText::PerformanceHint QStaticText::performanceHint() const
 }
 
 /*!
-    Sets the maximum size of the QStaticText to \a size.
+    Sets the preferred width for this QStaticText. If the text is wider than the specified width,
+    it will be broken into multiple lines and grow vertically. If the text cannot be split into
+    multiple lines, it will be larger than the specified \a textWidth.
+
+    Setting the preferred text width to a negative number will cause the text to be unbounded.
+
+    Use size() to get the actual size of the text.
 
     \note This function will cause the layout of the text to be recalculated.
 
-    \sa maximumSize(), size()
+    \sa textWidth(), size()
 */
-void QStaticText::setMaximumSize(const QSizeF &size)
+void QStaticText::setTextWidth(qreal textWidth)
 {
     detach();
-    data->maximumSize = size;
+    data->textWidth = textWidth;
     data->init();
 }
 
 /*!
-    Returns the maximum size of the QStaticText.
+    Returns the preferred width for this QStaticText.
 
-    \sa setMaximumSize()
+    \sa setTextWidth()
 */
-QSizeF QStaticText::maximumSize() const
+qreal QStaticText::textWidth() const
 {
-    return data->maximumSize;
+    return data->textWidth;
 }
 
 /*!
   Returns the size of the bounding rect for this QStaticText.
 
-  \sa maximumSize()
+  \sa textWidth()
 */
 QSizeF QStaticText::size() const
 {
@@ -349,14 +354,14 @@ QSizeF QStaticText::size() const
 }
 
 QStaticTextPrivate::QStaticTextPrivate()
-        : items(0), itemCount(0), glyphPool(0), positionPool(0), needsClipRect(false),
+        : items(0), itemCount(0), glyphPool(0), positionPool(0), textWidth(-1.0),
           useBackendOptimizations(false), textFormat(Qt::AutoText)
 {
 }
 
 QStaticTextPrivate::QStaticTextPrivate(const QStaticTextPrivate &other)
-    : text(other.text), font(other.font), maximumSize(other.maximumSize), matrix(other.matrix),
-      items(0), itemCount(0), glyphPool(0), positionPool(0), needsClipRect(false),
+    : text(other.text), font(other.font), textWidth(other.textWidth), matrix(other.matrix),
+      items(0), itemCount(0), glyphPool(0), positionPool(0),
       useBackendOptimizations(other.useBackendOptimizations), textFormat(other.textFormat)
 {
 }
@@ -539,43 +544,50 @@ namespace {
     };
 }
 
-void QStaticTextPrivate::paintText(const QPointF &pos, QPainter *p)
+void QStaticTextPrivate::paintText(const QPointF &topLeftPosition, QPainter *p)
 {
     bool preferRichText = textFormat == Qt::RichText
                           || (textFormat == Qt::AutoText && Qt::mightBeRichText(text));
 
     if (!preferRichText) {
-        if (maximumSize.isValid()) {
-            QRectF boundingRect;
-            p->drawText(QRectF(pos, maximumSize), Qt::TextWordWrap, text, &boundingRect);
-
-            actualSize = boundingRect.size();
-            needsClipRect = boundingRect.width() > maximumSize.width()
-                            || boundingRect.height() > maximumSize.height();
-        } else {
-            p->drawText(pos, text);
-            needsClipRect = false;
-
-            QFontMetrics fm(font);
-            actualSize = fm.boundingRect(text).size();
+        QTextLayout textLayout;
+        textLayout.setText(text);
+        textLayout.setFont(font);
+
+        qreal leading = QFontMetricsF(font).leading();
+        qreal height = -leading;
+
+        textLayout.beginLayout();
+        while (1) {
+            QTextLine line = textLayout.createLine();
+            if (!line.isValid())
+                break;
+
+            if (textWidth >= 0.0)
+                line.setLineWidth(textWidth);
+            height += leading;
+            line.setPosition(QPointF(0.0, height));
+            height += line.height();
         }
+        textLayout.endLayout();
+
+        actualSize = textLayout.boundingRect().size();
+        textLayout.draw(p, topLeftPosition);
     } else {
         QTextDocument document;
         document.setDefaultFont(font);
         document.setDocumentMargin(0.0);
+        if (textWidth >= 0.0)
+            document.setTextWidth(textWidth);
         document.setHtml(text);
 
-        QPointF adjustedPos = pos - QPointF(0, QFontMetricsF(font).ascent());
-        QRectF rect = maximumSize.isValid() ? QRectF(adjustedPos, maximumSize) : QRectF();
         document.adjustSize();
         p->save();
-        p->translate(adjustedPos);
-        document.drawContents(p, rect);        
+        p->translate(topLeftPosition);
+        document.drawContents(p);
         p->restore();
+
         actualSize = document.size();
-        needsClipRect = maximumSize.isValid()
-                        && (actualSize.width() > maximumSize.width()
-                            || actualSize.height() > maximumSize.height());
     }
 }
 
diff --git a/src/gui/text/qstatictext.h b/src/gui/text/qstatictext.h
index 00d42e0..c37194c 100644
--- a/src/gui/text/qstatictext.h
+++ b/src/gui/text/qstatictext.h
@@ -66,7 +66,7 @@ public:
     };
 
     QStaticText();
-    QStaticText(const QString &text, const QSizeF &maximumSize = QSizeF());
+    QStaticText(const QString &text);
     QStaticText(const QStaticText &other);
     ~QStaticText();
 
@@ -76,8 +76,8 @@ public:
     void setTextFormat(Qt::TextFormat textFormat);
     Qt::TextFormat textFormat() const;
 
-    void setMaximumSize(const QSizeF &maximumSize);
-    QSizeF maximumSize() const;
+    void setTextWidth(qreal textWidth);
+    qreal textWidth() const;
 
     QSizeF size() const;
 
diff --git a/src/gui/text/qstatictext_p.h b/src/gui/text/qstatictext_p.h
index e758244..3bbc61f 100644
--- a/src/gui/text/qstatictext_p.h
+++ b/src/gui/text/qstatictext_p.h
@@ -122,7 +122,7 @@ public:
 
     QString text;                        // 4 bytes per text
     QFont font;                          // 8 bytes per text
-    QSizeF maximumSize;                  // 16 bytes per text
+    qreal textWidth;                     // 8 bytes per text
     QSizeF actualSize;                   // 16 bytes per text
     QPointF position;                    // 16 bytes per text
 
@@ -132,11 +132,10 @@ public:
     glyph_t *glyphPool;                  // 4 bytes per text
     QFixedPoint *positionPool;           // 4 bytes per text
 
-    unsigned char needsClipRect           : 1;    // 1 byte per text
-    unsigned char useBackendOptimizations : 1;
+    unsigned char useBackendOptimizations : 1; // 1 byte per text
     unsigned char textFormat              : 2;
                                          // ================
-                                         // 171 bytes per text
+                                         // 163 bytes per text
 
     static QStaticTextPrivate *get(const QStaticText *q);
 };