Element editor: changed the way scaling operations get rounded.

git-svn-id: svn+ssh://svn.tuxfamily.org/svnroot/qet/qet/trunk@2058 bfdf4180-ca20-0410-9c96-a3a8aa849046

sources/editor/customelementpart.cpp

@@ -59,6 +59,17 @@ void CustomElementPart::setDecorator(ElementPrimitiveDecorator *decorator) {
 	Q_UNUSED(decorator)
 }
 
+/**
+	This method is called by the decorator when it needs to determine the best
+	way to interactively scale a primitive. It is typically called when only a
+	single primitive is being scaled.
+	The default implementation systematically returns
+	QET::SnapScalingPointToGrid
+*/
+QET::ScalingMethod CustomElementPart::preferredScalingMethod() const {
+	return(QET::SnapScalingPointToGrid);
+}
+
 /**
 	This method is called by the decorator when it manages only a single
 	primitive and it received a mouse press event.

sources/editor/customelementpart.h

@@ -20,6 +20,7 @@
 #include <QtGui>
 #include <QtXml>
 #include <QImage>
+#include "qet.h"
 class CustomElement;
 class ElementPrimitiveDecorator;
 class ElementScene;
@@ -101,6 +102,7 @@ class CustomElementPart {
 	virtual QGraphicsItem *toItem();
 	
 	virtual void setDecorator(ElementPrimitiveDecorator *);
+	virtual QET::ScalingMethod preferredScalingMethod() const;
 	virtual bool singleItemPressEvent(ElementPrimitiveDecorator *, QGraphicsSceneMouseEvent *);
 	virtual bool singleItemMoveEvent(ElementPrimitiveDecorator *, QGraphicsSceneMouseEvent *);
 	virtual bool singleItemReleaseEvent(ElementPrimitiveDecorator *, QGraphicsSceneMouseEvent *);

sources/editor/elementprimitivedecorator.cpp

@@ -245,15 +245,30 @@ void ElementPrimitiveDecorator::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
 	QPointF scene_pos = event -> scenePos();
 	QPointF movement = scene_pos - latest_pos_;
 	
-	// snap the movement to a non-visible grid when scaling selection
-	if (mustSnapToGrid(event)) {
-		// We now want some point belonging to the selection to be snapped to this rounded position
 	if (current_operation_square_ > QET::NoOperation) {
+		// This is a scaling operation.
+		
+		// For convenience purposes, we may need to adjust mouse movements.
+		QET::ScalingMethod scaling_method = scalingMethod(event);
+		if (scaling_method > QET::FreeScaling) {
 			// real, non-rounded movement from the mouse press event
 			QPointF global_movement = scene_pos - first_pos_;
 			
+			QPointF rounded_global_movement;
+			if (scaling_method == QET::SnapScalingPointToGrid) {
 				// real, rounded movement from the mouse press event
-			QPointF rounded_global_movement = snapConstPointToGrid(global_movement);
+				rounded_global_movement = snapConstPointToGrid(global_movement);
+			}
+			else {
+				QRectF new_bounding_rect = original_bounding_rect_;
+				applyMovementToRect(current_operation_square_, global_movement, new_bounding_rect);
+				
+				const qreal scale_epsilon = 20.0; // rounds to 0.05
+				QPointF delta = deltaForRoundScaling(original_bounding_rect_, new_bounding_rect, scale_epsilon);
+				
+				// real, rounded movement from the mouse press event
+				rounded_global_movement = global_movement + delta;
+			}
 			
 			// rounded position of the current mouse move event
 			QPointF rounded_scene_pos = first_pos_ + rounded_global_movement;
@@ -262,12 +277,17 @@ void ElementPrimitiveDecorator::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
 			QPointF current_position = mapToScene(rects.at(current_operation_square_).center());
 			// determine the final, effective movement
 			movement = rounded_scene_pos - current_position;
-		} else if (current_operation_square_ == QET::MoveArea) {
+		}
-			// when moving the selection, consider the position of the first selected item
+	}
+	else if (current_operation_square_ == QET::MoveArea) {
+		// When moving the selection, consider the position of the first selected item
 		QPointF current_position = scene_pos - mouse_offset_;
 		QPointF rounded_current_position = snapConstPointToGrid(current_position);
 		movement = rounded_current_position - decorated_items_.at(0) -> toItem() -> scenePos();
-		} else {
+	}
+	else {
+		// Neither a movement nor a scaling operation -- perhaps the underlying item
+		// is interested in the mouse event for custom operations?
 		if (CustomElementPart *single_item = singleItem()) {
 			bool event_accepted = single_item -> singleItemMoveEvent(this, event);
 			if (event_accepted) {
@@ -276,7 +296,6 @@ void ElementPrimitiveDecorator::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
 			}
 		}
 	}
-	}
 	
 	QRectF bounding_rect = modified_bounding_rect_;
 	applyMovementToRect(current_operation_square_, movement, modified_bounding_rect_);
@@ -627,6 +646,30 @@ int ElementPrimitiveDecorator::resizingSquareAtPos(const QPointF &position) {
 	return(current_square);
 }
 
+/**
+	Receive two rects, assuming they share a common corner and current is a \a
+	scaled version of \a original.
+	Calculate the scale ratios implied by this assumption, round them to the
+	nearest multiple of \a epsilon, then return the horizontal and vertical
+	offsets to be applied in order to pass from \a current to \a original scaled
+	by the rounded factors.
+	This method can be used to adjust a mouse movement so that it inputs a
+	round scaling operation.
+*/
+QPointF ElementPrimitiveDecorator::deltaForRoundScaling(const QRectF &original, const QRectF &current, qreal epsilon) {
+	qreal sx = current.width()  / original.width();
+	qreal sy = current.height() / original.height();
+	
+	qreal sx_rounded = QET::round(sx, epsilon);
+	qreal sy_rounded = QET::round(sy, epsilon);
+	
+	QPointF delta(
+		original.width()  * (sx_rounded - sx),
+		original.height() * (sy_rounded - sy)
+	);
+	return(delta);
+}
+
 /**
 	Round the coordinates of \a point so it is snapped to the grid defined by the
 	grid_step_x_ and grid_step_y_ attributes.
@@ -656,3 +699,19 @@ void ElementPrimitiveDecorator::snapPointToGrid(QPointF &point) const {
 bool ElementPrimitiveDecorator::mustSnapToGrid(QGraphicsSceneMouseEvent *event) {
 	return(!(event -> modifiers() & Qt::ControlModifier));
 }
+
+/**
+	@param event Mouse event during the scale operations -- simply passed to mustSnapToGrid()
+	@return the scaling method to be used for the currently decorated items.
+	@see QET::ScalingMethod
+	@see mustSnapToGrid()
+*/
+QET::ScalingMethod ElementPrimitiveDecorator::scalingMethod(QGraphicsSceneMouseEvent *event) {
+	if (event && !mustSnapToGrid(event)) {
+		return(QET::FreeScaling);
+	}
+	if (CustomElementPart *single_item = singleItem()) {
+		return single_item -> preferredScalingMethod();
+	}
+	return QET::RoundScaleRatios;
+}

sources/editor/elementprimitivedecorator.h

@@ -1,6 +1,7 @@
 #ifndef ELEMENTPRIMITIVEDECORATOR_H
 #define ELEMENTPRIMITIVEDECORATOR_H
 #include <QGraphicsObject>
+#include "qet.h"
 class ElementEditionCommand;
 class ElementScene;
 class CustomElementPart;
@@ -49,9 +50,11 @@ class ElementPrimitiveDecorator : public QGraphicsObject {
 	void mouseReleaseEvent(QGraphicsSceneMouseEvent *);
 	void keyPressEvent(QKeyEvent *);
 	void keyReleaseEvent(QKeyEvent *);
+	QPointF deltaForRoundScaling(const QRectF &, const QRectF &, qreal);
 	QPointF snapConstPointToGrid(const QPointF &) const;
 	void snapPointToGrid(QPointF &) const;
 	bool mustSnapToGrid(QGraphicsSceneMouseEvent *);
+	QET::ScalingMethod scalingMethod(QGraphicsSceneMouseEvent *);
 	
 	private:
 	void init();

sources/editor/partpolygon.cpp

@@ -190,6 +190,17 @@ void PartPolygon::handleUserTransformation(const QRectF &initial_selection_rect,
 	setPolygon(mapFromScene(QPolygonF(mapped_points.toVector())));
 }
 
+/**
+	@reimp CustomElementPart::preferredScalingMethod
+	This method is called by the decorator when it needs to determine the best
+	way to interactively scale a primitive. It is typically called when only a
+	single primitive is being scaled.
+	This reimplementation systematically returns QET::RoundScaleRatios.
+*/
+QET::ScalingMethod PartPolygon::preferredScalingMethod() const {
+	return(QET::RoundScaleRatios);
+}
+
 /**
 	@return le rectangle delimitant cette partie.
 */

sources/editor/partpolygon.h

@@ -59,6 +59,7 @@ class PartPolygon : public QGraphicsPolygonItem, public CustomElementGraphicPart
 	virtual QRectF sceneGeometricRect() const;
 	virtual void startUserTransformation(const QRectF &);
 	virtual void handleUserTransformation(const QRectF &, const QRectF &);
+	virtual QET::ScalingMethod preferredScalingMethod() const;
 	
 	protected:
 	QVariant itemChange(GraphicsItemChange, const QVariant &);

sources/qet.h

@@ -59,6 +59,13 @@ namespace QET {
 		ResizeFromBottomRightCorner = 7
 	};
 	
+	/// Supported types of interactive scaling, typically for a single element primitive
+	enum ScalingMethod {
+		FreeScaling,              ///< do not interfer with the default scaling process
+		SnapScalingPointToGrid,   ///< snap the point used to define the new bounding rectangle to the grid
+		RoundScaleRatios          ///< adjust the scaling movement so that the induced scaling ratios are rounded
+	};
+	
 	/// Known kinds of conductor segments
 	enum ConductorSegmentType {
 		Horizontal = 1, ///< Horizontal segment