Add advance property to QQuickText

This is a step on the way to certain optimization possibilities
for text in Qt Quick. Basically, to allow users the ability to
split text into separate items (so that you can distinguish
dynamic from static, and unshaped from shaped text), we also
need a way to string those items together visually later. The
advance property is required for this.

[ChangeLog][QtQuick][Text] Added "advance" property to Text element.

Task-number: QTBUG-56728
Change-Id: I8e7bf9bac410fa9c5553b48db90956431a2873f6
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

1 files changed, 47 insertions, 0 deletions

diff --git a/src/quick/items/qquicktext.cpp b/src/quick/items/qquicktext.cpp
index 09371db66d..080cc9412e 100644
--- a/src/quick/items/qquicktext.cpp
+++ b/src/quick/items/qquicktext.cpp
@@ -384,6 +384,7 @@ void QQuickTextPrivate::updateSize()
         updateBaseline(fm.ascent(), q->height() - fontHeight - vPadding);
         q->setImplicitSize(hPadding, fontHeight + vPadding);
         layedOutTextRect = QRectF(0, 0, 0, fontHeight);
+        advance = QSizeF();
         emit q->contentSizeChanged();
         updateType = UpdatePaintNode;
         q->update();
@@ -457,8 +458,26 @@ void QQuickTextPrivate::updateSize()
 
         if (iWidth == -1)
             q->setImplicitHeight(size.height() + vPadding);
+
+        QTextBlock firstBlock = extra->doc->firstBlock();
+        while (firstBlock.layout()->lineCount() == 0)
+            firstBlock = firstBlock.next();
+
+        QTextBlock lastBlock = extra->doc->lastBlock();
+        while (lastBlock.layout()->lineCount() == 0)
+            lastBlock = lastBlock.previous();
+
+        if (firstBlock.lineCount() > 0 && lastBlock.lineCount() > 0) {
+            QTextLine firstLine = firstBlock.layout()->lineAt(0);
+            QTextLine lastLine = lastBlock.layout()->lineAt(lastBlock.layout()->lineCount() - 1);
+            advance = QSizeF(lastLine.horizontalAdvance(),
+                             (lastLine.y() + lastBlock.layout()->position().y()) - (firstLine.y() + firstBlock.layout()->position().y()));
+        } else {
+            advance = QSizeF();
+        }
     }
 
+
     if (layedOutTextRect.size() != previousSize)
         emit q->contentSizeChanged();
     updateType = UpdatePaintNode;
@@ -968,6 +987,16 @@ QRectF QQuickTextPrivate::setupTextLayout(qreal *const baseline)
 
         br.moveTop(0);
 
+        // Find the advance of the text layout
+        if (layout.lineCount() > 0) {
+            QTextLine firstLine = layout.lineAt(0);
+            QTextLine lastLine = layout.lineAt(layout.lineCount() - 1);
+            advance = QSizeF(lastLine.horizontalAdvance(),
+                             lastLine.y() - firstLine.y());
+        } else {
+            advance = QSizeF();
+        }
+
         if (!horizontalFit && !verticalFit)
             break;
 
@@ -3055,6 +3084,24 @@ QJSValue QQuickText::fontInfo() const
     return value;
 }
 
+/*!
+    \qmlproperty size QtQuick::Text::advance
+    \since 5.10
+
+    The distance, in pixels, from the baseline origin of the first
+    character of the text item, to the baseline origin of the first
+    character in a text item occurring directly after this one
+    in a text flow.
+
+    Note that the advance can be negative if the text flows from
+    the right to the left.
+*/
+QSizeF QQuickText::advance() const
+{
+    Q_D(const QQuickText);
+    return d->advance;
+}
+
 QT_END_NAMESPACE
 
 #include "moc_qquicktext_p.cpp"