ui: drag and drop selected source code from code view into other appl…

…ications (#817) (issue #707)

src/lib_gui/qt/element/code/QtCodeArea.cpp

@@ -3,14 +3,17 @@
 #include <algorithm>
 
 #include <QApplication>
+#include <QDrag>
 #include <QFont>
 #include <QHBoxLayout>
 #include <QMenu>
+#include <QMimeData>
 #include <QPainter>
 #include <QPropertyAnimation>
 #include <QPushButton>
 #include <QScrollBar>
 #include <QTextBlock>
+#include <QTextDocumentFragment>
 #include <QToolTip>
 
 #include "ApplicationSettings.h"
@@ -80,6 +83,7 @@ QtCodeArea::QtCodeArea(
 	, m_digits(0)
 	, m_isSelecting(false)
 	, m_isPanning(false)
+	, m_isDragging(false)
 	, m_setIDECursorPositionAction(nullptr)
 	, m_eventPosition(0, 0)
 	, m_isActiveFile(false)
@@ -581,70 +585,89 @@ void QtCodeArea::mousePressEvent(QMouseEvent* event)
 {
 	if (event->button() == Qt::LeftButton)
 	{
-		clearSelection();
-
-		m_oldMousePosition = event->pos();
-		m_panningDistance = 0;
-
-		if (Qt::KeyboardModifier::ShiftModifier & QApplication::keyboardModifiers())
+		const QPoint clickPosition(event->pos());
+		m_oldMousePosition = clickPosition;
+		if (isSelectionPosition(clickPosition))
 		{
-			m_isPanning = true;
-			viewport()->setCursor(Qt::ClosedHandCursor);
+			m_isDragging = true;
 		}
 		else
 		{
-			m_isSelecting = true;
-			QTextCursor cursor = this->cursorForPosition(event->pos());
-			setNewTextCursor(cursor);
+			clearSelection();
+
+			m_panningDistance = 0;
+
+			if (Qt::KeyboardModifier::ShiftModifier & QApplication::keyboardModifiers())
+			{
+				m_isPanning = true;
+				viewport()->setCursor(Qt::ClosedHandCursor);
+			}
+			else
+			{
+				m_isSelecting = true;
+				QTextCursor cursor = this->cursorForPosition(event->pos());
+				setNewTextCursor(cursor);
 
-			viewport()->setCursor(Qt::IBeamCursor);
+				viewport()->setCursor(Qt::IBeamCursor);
+			}
 		}
 	}
 }
 
 void QtCodeArea::mouseReleaseEvent(QMouseEvent* event)
 {
-	const int panningThreshold = 5;
+	if (event->button() != Qt::LeftButton)
+	{
+		QtCodeField::mouseReleaseEvent(event);
+		return;
+	}
 
-	if (event->button() == Qt::LeftButton)
+	m_isSelecting = false;
+	m_isPanning = false;
+
+	if (m_isDragging)
 	{
-		m_isSelecting = false;
-		m_isPanning = false;
+		const int distance = (event->pos() - m_oldMousePosition).manhattanLength();
+		if (distance < QApplication::startDragDistance())
+		{
+			clearSelection();
+		}
 
-		viewport()->setCursor(Qt::ArrowCursor);
+		m_isDragging = false;
+		return;
+	}
+
+	viewport()->setCursor(Qt::ArrowCursor);
 
-		if (m_panningDistance < panningThreshold)	 // dont do anything if mouse is release to end
-													 // some real panning action.
+	const int panningThreshold = 5;
+	if (m_panningDistance < panningThreshold)	 // dont do anything if mouse is release to end
+												 // some real panning action.
+	{
+		if (Qt::KeyboardModifier::ControlModifier & QApplication::keyboardModifiers())
 		{
-			if (Qt::KeyboardModifier::ControlModifier & QApplication::keyboardModifiers())
+			m_eventPosition = event->pos();
+			setIDECursorPosition();
+		}
+		else
+		{
+			std::vector<const Annotation*> annotations = getInteractiveAnnotationsForPosition(
+				event->pos());
+			if (annotations.size())
 			{
-				m_eventPosition = event->pos();
-				setIDECursorPosition();
+				activateAnnotationsOrErrors(annotations);
 			}
-			else
+			else if (m_navigator->getActiveLocalTokenIds().size())
 			{
-				std::vector<const Annotation*> annotations = getInteractiveAnnotationsForPosition(
-					event->pos());
-				if (annotations.size())
-				{
-					activateAnnotationsOrErrors(annotations);
-				}
-				else if (m_navigator->getActiveLocalTokenIds().size())
-				{
-					MessageActivateLocalSymbols(std::vector<Id>()).dispatch();
-				}
+				MessageActivateLocalSymbols(std::vector<Id>()).dispatch();
 			}
 		}
 	}
-	else
-	{
-		QtCodeField::mouseReleaseEvent(event);
-	}
 }
 
 void QtCodeArea::mouseMoveEvent(QMouseEvent* event)
 {
 	const QPoint currentMousePosition = event->pos();
+	const int delta = (currentMousePosition - m_oldMousePosition).manhattanLength();
 	const int deltaX = currentMousePosition.x() - m_oldMousePosition.x();
 	const int deltaY = currentMousePosition.y() - m_oldMousePosition.y();
 	m_oldMousePosition = currentMousePosition;
@@ -663,6 +686,14 @@ void QtCodeArea::mouseMoveEvent(QMouseEvent* event)
 		float deltaPosRatio = float(deltaX) / (visibleContentWidth);
 		scrollbar->setValue(scrollbar->value() - std::round(deltaPosRatio * scrollbar->pageStep()));
 	}
+	else if (m_isDragging)
+	{
+		if (delta >= QApplication::startDragDistance())
+		{
+			dragSelectedText();
+			m_isDragging = false;
+		}
+	}
 
 	std::vector<const Annotation*> annotations = getInteractiveAnnotationsForPosition(event->pos());
 
@@ -805,6 +836,27 @@ void QtCodeArea::setNewTextCursor(const QTextCursor& cursor)
 	verticalScrollBar()->setValue(verticalValue);
 }
 
+void QtCodeArea::dragSelectedText()
+{
+	QMimeData* mimeData = new QMimeData;
+	const QString text = textCursor().selection().toPlainText();
+	mimeData->setText(text);
+
+	QDrag* drag = new QDrag(this);
+	drag->setMimeData(mimeData);
+	drag->exec(Qt::CopyAction);
+}
+
+bool QtCodeArea::isSelectionPosition(const QPoint positionPoint) const
+{
+	const QTextCursor textCursor = QtCodeArea::textCursor();
+	const int selectionStart = textCursor.selectionStart();
+	const int selectionEnd = textCursor.selectionEnd();
+	const QTextCursor positionCursor = this->cursorForPosition(positionPoint);
+	const int position = positionCursor.position();
+	return selectionStart != selectionEnd && selectionStart <= position && position <= selectionEnd;
+}
+
 void QtCodeArea::activateAnnotationsOrErrors(const std::vector<const Annotation*>& annotations)
 {
 	if (m_navigator->hasErrors())

src/lib_gui/qt/element/code/QtCodeArea.h

@@ -107,6 +107,8 @@ private slots:
 private:
 	void clearSelection();
 	void setNewTextCursor(const QTextCursor& cursor);
+	void dragSelectedText();
+	bool isSelectionPosition(QPoint positionPoint) const;
 
 	void activateAnnotationsOrErrors(const std::vector<const Annotation*>& annotations);
 
@@ -121,6 +123,7 @@ private slots:
 
 	bool m_isSelecting;
 	bool m_isPanning;
+	bool m_isDragging;
 	QPoint m_oldMousePosition;
 	int m_panningDistance;