QQuickText: don't clear the text formats on every layout

In order to fix QTBUG-21919, 6ff9ba0 added a QTextLayout::clearFormats()
call to QQuickTextPrivate::updateLayout(). This patch moves that logic
to clearFormats(), called from setText() and setTextFormat() in order to
avoid clearing the formats on every text layout update.

This allows Qt Quick Controls 2 to extend QQuickText with support for
mnenonics by adding a text format range to underline the appropriate
piece of text in the internal QTextLayout.

Task-number: QTBUG-61422
Change-Id: I646d53f0feeeaa3c106db94f187c7accabdc6a61
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>

2 files changed, 12 insertions, 4 deletions

diff --git a/src/quick/items/qquicktext.cpp b/src/quick/items/qquicktext.cpp
index 1bcfbd41f7..2e66367e85 100644
--- a/src/quick/items/qquicktext.cpp
+++ b/src/quick/items/qquicktext.cpp
@@ -269,9 +269,6 @@ void QQuickTextPrivate::updateLayout()
                 formatModifiesFontSize = fontSizeModified;
                 multilengthEos = -1;
             } else {
-                layout.clearFormats();
-                if (elideLayout)
-                    elideLayout->clearFormats();
                 QString tmp = text;
                 multilengthEos = tmp.indexOf(QLatin1Char('\x9c'));
                 if (multilengthEos != -1)
@@ -632,6 +629,13 @@ QString QQuickTextPrivate::elidedText(qreal lineWidth, const QTextLine &line, QT
     }
 }
 
+void QQuickTextPrivate::clearFormats()
+{
+    layout.clearFormats();
+    if (elideLayout)
+        elideLayout->clearFormats();
+}
+
 /*!
     Lays out the QQuickTextPrivate::layout QTextLayout in the constraints of the QQuickText.
 
@@ -1060,7 +1064,8 @@ QRectF QQuickTextPrivate::setupTextLayout(qreal *const baseline)
             elideLayout = new QTextLayout;
             elideLayout->setCacheEnabled(true);
         }
-        if (styledText) {
+        QTextEngine *engine = layout.engine();
+        if (engine && engine->hasFormats()) {
             QVector<QTextLayout::FormatRange> formats;
             switch (elideMode) {
             case QQuickText::ElideRight:
@@ -1612,6 +1617,7 @@ void QQuickText::setText(const QString &n)
             d->extra->doc->setText(n);
             d->rightToLeftText = d->extra->doc->toPlainText().isRightToLeft();
         } else {
+            d->clearFormats();
             d->rightToLeftText = d->text.isRightToLeft();
         }
         d->determineHorizontalAlignment();
@@ -2102,6 +2108,7 @@ void QQuickText::setTextFormat(TextFormat format)
             d->extra->doc->setText(d->text);
             d->rightToLeftText = d->extra->doc->toPlainText().isRightToLeft();
         } else {
+            d->clearFormats();
             d->rightToLeftText = d->text.isRightToLeft();
             d->textHasChanged = true;
         }
diff --git a/src/quick/items/qquicktext_p_p.h b/src/quick/items/qquicktext_p_p.h
index fde07eaf2e..957641ec0a 100644
--- a/src/quick/items/qquicktext_p_p.h
+++ b/src/quick/items/qquicktext_p_p.h
@@ -85,6 +85,7 @@ public:
     int lineHeightOffset() const;
     QString elidedText(qreal lineWidth, const QTextLine &line, QTextLine *nextLine = 0) const;
     void elideFormats(int start, int length, int offset, QVector<QTextLayout::FormatRange> *elidedFormats);
+    void clearFormats();
 
     void processHoverEvent(QHoverEvent *event);