Fix too fast zooming in QTextEdit with smooth scrolling events

Do not zoom 1pt on every single wheel-event, but instead scale
the zoom with the size of the angle delta.

Change-Id: Idbe17356c7845ebd0039f655d3e611e71c6f0dd6
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>

src/widgets/widgets/qplaintextedit.cpp

@@ -2276,11 +2276,8 @@ void QPlainTextEdit::wheelEvent(QWheelEvent *e)
     Q_D(QPlainTextEdit);
     if (!(d->control->textInteractionFlags() & Qt::TextEditable)) {
         if (e->modifiers() & Qt::ControlModifier) {
-            const int delta = e->delta();
-            if (delta < 0)
-                zoomOut();
-            else if (delta > 0)
-                zoomIn();
+            float delta = e->angleDelta().y() / 120.f;
+            zoomInF(delta);
             return;
         }
     }
@@ -2300,12 +2297,7 @@ void QPlainTextEdit::wheelEvent(QWheelEvent *e)
 */
 void QPlainTextEdit::zoomIn(int range)
 {
-    QFont f = font();
-    const int newSize = f.pointSize() + range;
-    if (newSize <= 0)
-        return;
-    f.setPointSize(newSize);
-    setFont(f);
+    zoomInF(range);
 }
 
 /*!
@@ -2321,7 +2313,22 @@ void QPlainTextEdit::zoomIn(int range)
 */
 void QPlainTextEdit::zoomOut(int range)
 {
-    zoomIn(-range);
+    zoomInF(-range);
+}
+
+/*!
+    \internal
+*/
+void QPlainTextEdit::zoomInF(float range)
+{
+    if (range == 0.f)
+        return;
+    QFont f = font();
+    const float newSize = f.pointSizeF() + range;
+    if (newSize <= 0)
+        return;
+    f.setPointSizeF(newSize);
+    setFont(f);
 }
 
 #ifndef QT_NO_CONTEXTMENU

src/widgets/widgets/qplaintextedit.h

@@ -271,6 +271,7 @@ protected:
     QRectF blockBoundingGeometry(const QTextBlock &block) const;
     QAbstractTextDocumentLayout::PaintContext getPaintContext() const;
 
+    void zoomInF(float range);
 
 private:
     Q_DISABLE_COPY(QPlainTextEdit)

src/widgets/widgets/qtextedit.cpp

@@ -1813,11 +1813,8 @@ void QTextEdit::wheelEvent(QWheelEvent *e)
     Q_D(QTextEdit);
     if (!(d->control->textInteractionFlags() & Qt::TextEditable)) {
         if (e->modifiers() & Qt::ControlModifier) {
-            const int delta = e->delta();
-            if (delta < 0)
-                zoomOut();
-            else if (delta > 0)
-                zoomIn();
+            float delta = e->angleDelta().y() / 120.f;
+            zoomInF(delta);
             return;
         }
     }
@@ -2276,12 +2273,7 @@ void QTextEdit::scrollToAnchor(const QString &name)
 */
 void QTextEdit::zoomIn(int range)
 {
-    QFont f = font();
-    const int newSize = f.pointSize() + range;
-    if (newSize <= 0)
-        return;
-    f.setPointSize(newSize);
-    setFont(f);
+    zoomInF(range);
 }
 
 /*!
@@ -2297,7 +2289,22 @@ void QTextEdit::zoomIn(int range)
 */
 void QTextEdit::zoomOut(int range)
 {
-    zoomIn(-range);
+    zoomInF(-range);
+}
+
+/*!
+    \internal
+*/
+void QTextEdit::zoomInF(float range)
+{
+    if (range == 0.f)
+        return;
+    QFont f = font();
+    const float newSize = f.pointSizeF() + range;
+    if (newSize <= 0)
+        return;
+    f.setPointSizeF(newSize);
+    setFont(f);
 }
 
 /*!

src/widgets/widgets/qtextedit.h

@@ -304,6 +304,8 @@ protected:
     virtual void scrollContentsBy(int dx, int dy);
     virtual void doSetTextCursor(const QTextCursor &cursor);
 
+    void zoomInF(float range);
+
 private:
     Q_DISABLE_COPY(QTextEdit)
     Q_PRIVATE_SLOT(d_func(), void _q_repaintContents(const QRectF &r))

tests/auto/widgets/widgets/qtextedit/tst_qtextedit.cpp

@@ -211,6 +211,10 @@ private slots:
     void findWithRegExpReturnsFalseIfNoMoreResults();
 #endif
 
+#ifndef QT_NO_WHEELEVENT
+    void wheelEvent();
+#endif
+
 private:
     void createSelection();
     int blockCount() const;
@@ -2564,5 +2568,39 @@ void tst_QTextEdit::findWithRegExpReturnsFalseIfNoMoreResults()
 }
 #endif
 
+#ifndef QT_NO_WHEELEVENT
+
+class TextEdit : public QTextEdit
+{
+public:
+    TextEdit(QWidget *parent = 0)
+        : QTextEdit(parent)
+    {}
+    void wheelEvent(QWheelEvent *event)
+    {
+        QTextEdit::wheelEvent(event);
+    }
+};
+
+void tst_QTextEdit::wheelEvent()
+{
+    TextEdit ed(0);
+    ed.setPlainText(QStringLiteral("Line\nLine\nLine\n"));
+    ed.setReadOnly(true);
+
+    float defaultFontSize = ed.font().pointSizeF();
+    QWheelEvent wheelUp(QPointF(), QPointF(), QPoint(), QPoint(0, 120), 120, Qt::Vertical, Qt::NoButton, Qt::ControlModifier);
+    ed.wheelEvent(&wheelUp);
+
+    QCOMPARE(defaultFontSize + 1, ed.font().pointSizeF());
+
+    QWheelEvent wheelHalfDown(QPointF(), QPointF(), QPoint(), QPoint(0, -60), -60, Qt::Vertical, Qt::NoButton, Qt::ControlModifier);
+    ed.wheelEvent(&wheelHalfDown);
+
+    QCOMPARE(defaultFontSize + 0.5, ed.font().pointSizeF());
+}
+
+#endif
+
 QTEST_MAIN(tst_QTextEdit)
 #include "tst_qtextedit.moc"