QTextDocument: add setLayoutEnabled()

This allows to set up everything first - without paying for the layout
calculation at every step - and only then trigger the layout once.

Results:
 0.065 msecs to create a QGraphicsTextItem with some text (layouted)
 0.036 msecs to set everything up in a QGraphicsTextItem with 0 width

Change-Id: I138bd1d58941d029bc0a36d2730216778f1fbd97
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

1 files changed, 34 insertions, 0 deletions

diff --git a/src/gui/text/qtextdocument.cpp b/src/gui/text/qtextdocument.cpp
index c01c858cc5..71511257f5 100644
--- a/src/gui/text/qtextdocument.cpp
+++ b/src/gui/text/qtextdocument.cpp
@@ -635,6 +635,40 @@ bool QTextDocument::useDesignMetrics() const
 }
 
 /*!
+    \property QTextDocument::layoutEnabled
+    \since 6.4
+    \brief whether QTextDocument should recalculate the layout after every change
+
+    If this property is set to true, any change to the document triggers a layout,
+    which makes everything work as expected but takes time.
+
+    Temporarily disabling the layout can save time when making multiple changes
+    (not just text content, but also default font, default text option....)
+    so that the document is only laid out once at the end. This can be useful when
+    the text width or page size isn't yet known, for instance.
+
+    By default, this property is \c true.
+
+    \sa setTextWidth
+*/
+
+void QTextDocument::setLayoutEnabled(bool b)
+{
+    Q_D(QTextDocument);
+    if (d->layoutEnabled == b)
+        return;
+    d->layoutEnabled = b;
+    if (b && d->lout)
+        d->lout->documentChanged(0, 0, d->length());
+}
+
+bool QTextDocument::isLayoutEnabled() const
+{
+    Q_D(const QTextDocument);
+    return d->layoutEnabled;
+}
+
+/*!
     \since 4.2
 
     Draws the content of the document with painter \a p, clipped to \a rect.