QTextDocument/QGraphicsTextItem: skip layout in setTextWidth(0)

In a QGraphicsTextItem without a width yet, there's no need to do any
layouting. The use case is obviously items with an app-defined size,
not the default where text items adapt to their contents.

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

QTextEdit was abusing the width 0 to mean "no wrap, width comes from
contents", but since the value -1 means that already in QTextDocument,
QTextEdit now uses a width of -1 for that meaning.

Change-Id: I67ad59c305e5dd34830886e4e6c56dde03c93668
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

1 files changed, 3 insertions, 2 deletions

diff --git a/tests/auto/widgets/widgets/qtextedit/tst_qtextedit.cpp b/tests/auto/widgets/widgets/qtextedit/tst_qtextedit.cpp
index bc533df48a..72d2cc7aa7 100644
--- a/tests/auto/widgets/widgets/qtextedit/tst_qtextedit.cpp
+++ b/tests/auto/widgets/widgets/qtextedit/tst_qtextedit.cpp
@@ -1194,8 +1194,9 @@ void tst_QTextEdit::undoRedoShouldRepositionTextEditCursor()
 void tst_QTextEdit::lineWrapModes()
 {
     ed->setLineWrapMode(QTextEdit::NoWrap);
-    // NoWrap at the same time as having all lines that are all left aligned means we optimize to only layout once. The effect is that the width is always 0
-    QCOMPARE(ed->document()->pageSize().width(), qreal(0));
+    // NoWrap at the same time as having all lines that are all left aligned means we optimize to
+    // only layout once. The effect is that the width is always -1
+    QCOMPARE(ed->document()->pageSize().width(), qreal(-1));
 
     QTextCursor cursor = QTextCursor(ed->document());
     cursor.insertText(QString("A simple line"));