QQuickTextInputPrivate: refactor getImplicitWidth() to calculateImplicitWidth()

This patch moves the implicit width calculation in getImplicitWidth()
into calculateImplicitWidth(const QString &text).

This allows QQuickComboBox in qtquickcontrols2 to get the implicit
width of a TextInput (TextField) item, as QQuickTextInput does some
extra layouting and accounting for padding that QFontMetrics does not.

Change-Id: I81e6c2627e21ca4d89ea9502abbb6aec79068793
Reviewed-by: Jan Arve Sæther <jan-arve.saether@qt.io>

1 files changed, 27 insertions, 23 deletions

diff --git a/src/quick/items/qquicktextinput.cpp b/src/quick/items/qquicktextinput.cpp
index 163df3522f..2f022e6c08 100644
--- a/src/quick/items/qquicktextinput.cpp
+++ b/src/quick/items/qquicktextinput.cpp
@@ -2907,36 +2907,40 @@ void QQuickTextInputPrivate::updateDisplayText(bool forceUpdate)
     }
 }
 
-qreal QQuickTextInputPrivate::getImplicitWidth() const
+qreal QQuickTextInputPrivate::calculateImplicitWidthForText(const QString &text) const
 {
     Q_Q(const QQuickTextInput);
-    if (!requireImplicitWidth) {
-        QQuickTextInputPrivate *d = const_cast<QQuickTextInputPrivate *>(this);
-        d->requireImplicitWidth = true;
+    QTextLayout layout(text);
 
-        if (q->isComponentComplete()) {
-            // One time cost, only incurred if implicitWidth is first requested after
-            // componentComplete.
-            QTextLayout layout(m_text);
-
-            QTextOption option = m_textLayout.textOption();
-            option.setTextDirection(m_layoutDirection);
-            option.setFlags(QTextOption::IncludeTrailingSpaces);
-            option.setWrapMode(QTextOption::WrapMode(wrapMode));
-            option.setAlignment(Qt::Alignment(q->effectiveHAlign()));
-            layout.setTextOption(option);
-            layout.setFont(font);
+    QTextOption option = m_textLayout.textOption();
+    option.setTextDirection(m_layoutDirection);
+    option.setFlags(QTextOption::IncludeTrailingSpaces);
+    option.setWrapMode(QTextOption::WrapMode(wrapMode));
+    option.setAlignment(Qt::Alignment(q->effectiveHAlign()));
+    layout.setTextOption(option);
+    layout.setFont(font);
 #if QT_CONFIG(im)
-            layout.setPreeditArea(m_textLayout.preeditAreaPosition(), m_textLayout.preeditAreaText());
+    layout.setPreeditArea(m_textLayout.preeditAreaPosition(), m_textLayout.preeditAreaText());
 #endif
-            layout.beginLayout();
+    layout.beginLayout();
 
-            QTextLine line = layout.createLine();
-            line.setLineWidth(INT_MAX);
-            d->implicitWidth = qCeil(line.naturalTextWidth()) + q->leftPadding() + q->rightPadding();
+    QTextLine line = layout.createLine();
+    line.setLineWidth(INT_MAX);
+    const qreal theImplicitWidth = qCeil(line.naturalTextWidth()) + q->leftPadding() + q->rightPadding();
 
-            layout.endLayout();
-        }
+    layout.endLayout();
+    return theImplicitWidth;
+}
+
+qreal QQuickTextInputPrivate::getImplicitWidth() const
+{
+    Q_Q(const QQuickTextInput);
+    if (!requireImplicitWidth) {
+        QQuickTextInputPrivate *d = const_cast<QQuickTextInputPrivate *>(this);
+        d->requireImplicitWidth = true;
+
+        if (q->isComponentComplete())
+            d->implicitWidth = calculateImplicitWidthForText(m_text);
     }
     return implicitWidth;
 }