#2197 AppFwk : Add supporft for placeholder text (taken from Qt 4.7)

PlaceholderLineEdit is a temporary class to be removed when Qt is upgraded

Fwk/AppFwk/cafUserInterface/cafPdmUiTreeSelectionEditor.cpp

@@ -46,7 +46,10 @@
 #include <QLabel>
 #include <QLineEdit>
 #include <QMenu>
+#include <QPainter>
+#include <QPalette>
 #include <QSortFilterProxyModel>
+#include <QStyleOption>
 #include <QTreeView>
 
 #include <algorithm>
@@ -120,6 +123,82 @@ protected:
     }
 };
 
+//--------------------------------------------------------------------------------------------------
+/// Ported parts of placeholder text painting from Qt 4.7
+/// setPlaceholderText() was introduced in Qt 4.7, 
+/// and this class is intended to be removed when Qt is upgraded
+//--------------------------------------------------------------------------------------------------
+class PlaceholderLineEdit : public QLineEdit
+{
+public:
+    explicit PlaceholderLineEdit(const QString& placeholderText, QWidget* parent = 0)
+        : QLineEdit(parent), 
+        m_placeholderText(placeholderText)
+    {
+    }
+
+private:
+    //--------------------------------------------------------------------------------------------------
+    /// 
+    //--------------------------------------------------------------------------------------------------
+    virtual void paintEvent(QPaintEvent* paintEvent) override
+    {
+        QPainter p(this);
+
+        QRect r = rect();
+        QPalette pal = palette();
+
+        QStyleOptionFrameV2 panel;
+        initStyleOption(&panel);
+        style()->drawPrimitive(QStyle::PE_PanelLineEdit, &panel, &p, this);
+        r = style()->subElementRect(QStyle::SE_LineEditContents, &panel, this);
+
+        int left = 0;
+        int top = 0;
+        int right = 0;
+        int bottom = 0;
+        getTextMargins(&left, &top, &right, &bottom);
+
+        r.setX(r.x() + left);
+        r.setY(r.y() + top);
+        r.setRight(r.right() - right);
+        r.setBottom(r.bottom() - bottom);
+        p.setClipRect(r);
+
+        QFontMetrics fm = fontMetrics();
+    
+        const int horizontalMargin = 2;
+        const int vscroll = r.y() + (r.height() - fm.height() + 1) / 2;
+
+        QRect lineRect(r.x() + horizontalMargin, vscroll, r.width() - 2*horizontalMargin, fm.height());
+
+        int minLB = qMax(0, -fm.minLeftBearing());
+        int minRB = qMax(0, -fm.minRightBearing());
+
+        if (text().isEmpty())
+        {
+            if (!hasFocus() && !m_placeholderText.isEmpty())
+            {
+                QColor col = pal.text().color();
+                col.setAlpha(128);
+                QPen oldpen = p.pen();
+                p.setPen(col);
+                lineRect.adjust(minLB, 0, 0, 0);
+                QString elidedText = fm.elidedText(m_placeholderText, Qt::ElideRight, lineRect.width());
+                p.drawText(lineRect, Qt::AlignLeft | Qt::TextWordWrap, elidedText);
+                p.setPen(oldpen);
+                
+                return;
+            }
+        }
+
+        return QLineEdit::paintEvent(paintEvent);
+    }
+
+private:
+    QString m_placeholderText;
+
+};
 
 namespace caf
 {
@@ -275,12 +354,10 @@ QWidget* PdmUiTreeSelectionEditor::createEditorWidget(QWidget* parent)
 
         connect(m_toggleAllCheckBox, SIGNAL(clicked(bool)), this, SLOT(slotToggleAll()));
 
-        m_textFilterLineEdit = new QLineEdit();
+        m_textFilterLineEdit = new PlaceholderLineEdit("Click to add filter");
-        
+        // TODO: setPlaceholderText() was introduced in Qt 4.7
-
+        // Use QLineEdit instead of PlaceholderLineEdit when Qt is upgraded
-        // TODO: This feature was introduced in Qt 4.7
+        // m_textFilterLineEdit->setPlaceholderText("Click to add filter");
-        // Consider backporting to 4.6
-        //m_textFilterLineEdit->setPlaceholderText("Click to add filter");
 
         headerLayout->addWidget(m_textFilterLineEdit);