diff --git a/conductor.cpp b/conductor.cpp
index d67a0e2ae..5f6dc27a2 100644
--- a/conductor.cpp
+++ b/conductor.cpp
@@ -499,7 +499,7 @@ void Conductor::mousePressEvent(QGraphicsSceneMouseEvent *e) {
 	// clic gauche
 	if (e -> buttons() & Qt::LeftButton) {
 		// recupere les coordonnees du clic
-		press_point = mapFromScene(e -> pos());
+		press_point = e -> pos();
 		
 		/*
 			parcourt les segments pour determiner si le clic a eu lieu
@@ -541,6 +541,11 @@ void Conductor::mouseMoveEvent(QGraphicsSceneMouseEvent *e) {
 		qreal mouse_x = e -> pos().x();
 		qreal mouse_y = e -> pos().y();
 		
+		bool snap_conductors_to_grid = e -> modifiers() ^ Qt::ShiftModifier;
+		if (snap_conductors_to_grid) {
+			mouse_x = qRound(mouse_x / (Diagram::xGrid * 1.0)) * Diagram::xGrid;
+			mouse_y = qRound(mouse_y / (Diagram::yGrid * 1.0)) * Diagram::yGrid;
+		}
 		if (moving_point) {
 			// la modification par points revient bientot
 			/*
diff --git a/diagram.cpp b/diagram.cpp
index 50f45facb..252cdabf2 100644
--- a/diagram.cpp
+++ b/diagram.cpp
@@ -6,6 +6,10 @@
 #include "exportdialog.h"
 #include "diagramcommands.h"
 
+const int   Diagram::xGrid  = 10;
+const int   Diagram::yGrid  = 10;
+const qreal Diagram::margin = 5.0;
+
 /**
 	Constructeur
 	@param parent Le QObject parent du schema
@@ -58,18 +62,18 @@ void Diagram::drawBackground(QPainter *p, const QRectF &r) {
 		qreal limite_y = r.y() + r.height();
 		
 		int g_x = (int)ceil(r.x());
-		while (g_x % GRILLE_X) ++ g_x;
+		while (g_x % xGrid) ++ g_x;
 		int g_y = (int)ceil(r.y());
-		while (g_y % GRILLE_Y) ++ g_y;
+		while (g_y % yGrid) ++ g_y;
 		
-		for (int gx = g_x ; gx < limite_x ; gx += GRILLE_X) {
-			for (int gy = g_y ; gy < limite_y ; gy += GRILLE_Y) {
+		for (int gx = g_x ; gx < limite_x ; gx += xGrid) {
+			for (int gy = g_y ; gy < limite_y ; gy += yGrid) {
 				p -> drawPoint(gx, gy);
 			}
 		}
 	}
 	
-	if (use_border) border_and_inset.draw(p, MARGIN, MARGIN);
+	if (use_border) border_and_inset.draw(p, margin, margin);
 	p -> restore();
 }
 
@@ -80,10 +84,10 @@ void Diagram::drawBackground(QPainter *p, const QRectF &r) {
 void Diagram::keyPressEvent(QKeyEvent *e) {
 	QPointF movement;
 	switch(e -> key()) {
-		case Qt::Key_Left:  movement = QPointF(-GRILLE_X, 0.0); break;
-		case Qt::Key_Right: movement = QPointF(+GRILLE_X, 0.0); break;
-		case Qt::Key_Up:    movement = QPointF(0.0, -GRILLE_Y); break;
-		case Qt::Key_Down:  movement = QPointF(0.0, +GRILLE_Y); break;
+		case Qt::Key_Left:  movement = QPointF(-xGrid, 0.0); break;
+		case Qt::Key_Right: movement = QPointF(+xGrid, 0.0); break;
+		case Qt::Key_Up:    movement = QPointF(0.0, -yGrid); break;
+		case Qt::Key_Down:  movement = QPointF(0.0, +yGrid); break;
 	}
 	if (!movement.isNull()) {
 		QSet<Element *> moved_elements = elementsToMove();
@@ -136,15 +140,15 @@ bool Diagram::toPaintDevice(QPaintDevice &pix, int width, int height, Qt::Aspect
 	QRectF source_area;
 	if (!use_border) {
 		source_area = itemsBoundingRect();
-		source_area.translate(-MARGIN, -MARGIN);
-		source_area.setWidth (source_area.width () + 2.0 * MARGIN);
-		source_area.setHeight(source_area.height() + 2.0 * MARGIN);
+		source_area.translate(-margin, -margin);
+		source_area.setWidth (source_area.width () + 2.0 * margin);
+		source_area.setHeight(source_area.height() + 2.0 * margin);
 	} else {
 		source_area = QRectF(
 			0.0,
 			0.0,
-			border_and_inset.borderWidth () + 2.0 * MARGIN,
-			border_and_inset.borderHeight() + 2.0 * MARGIN
+			border_and_inset.borderWidth () + 2.0 * margin,
+			border_and_inset.borderHeight() + 2.0 * margin
 		);
 	}
 	
@@ -190,8 +194,8 @@ QSize Diagram::imageSize() const {
 		image_height = border_and_inset.borderHeight();
 	}
 	
-	image_width  += 2.0 * MARGIN;
-	image_height += 2.0 * MARGIN;
+	image_width  += 2.0 * margin;
+	image_height += 2.0 * margin;
 	
 	// renvoie la taille de la zone source
 	return(QSizeF(image_width, image_height).toSize());
@@ -448,8 +452,8 @@ void Diagram::slot_checkSelectionEmptinessChange() {
 QRectF Diagram::border() const {
 	return(
 		QRectF(
-			MARGIN,
-			MARGIN,
+			margin,
+			margin,
 			border_and_inset.borderWidth(),
 			border_and_inset.borderHeight()
 		)
diff --git a/diagram.h b/diagram.h
index b37cb5535..9191b353f 100644
--- a/diagram.h
+++ b/diagram.h
@@ -1,8 +1,5 @@
 #ifndef SCHEMA_H
 #define SCHEMA_H
-#define GRILLE_X 10
-#define GRILLE_Y 10
-#define MARGIN   5.0
 #include <QtGui>
 #include <QtXml>
 #include "qetdiagrameditor.h"
@@ -32,6 +29,12 @@ class Diagram : public QGraphicsScene {
 	enum BorderOptions { EmptyBorder, Inset, Columns };
 	BorderInset border_and_inset;
 	QPointF current_movement;
+	/// taille de la grille en abscisse
+	static const int xGrid;
+	/// taille de la grille en ordonnee
+	static const int yGrid;
+	/// marge autour du schema
+	static const qreal margin;
 	
 	private:
 	QGraphicsLineItem *conductor_setter;
diff --git a/diagramview.cpp b/diagramview.cpp
index 747f1db20..4337a0d9d 100644
--- a/diagramview.cpp
+++ b/diagramview.cpp
@@ -47,7 +47,9 @@ DiagramView::~DiagramView() {
 */
 void DiagramView::selectAll() {
 	if (scene -> items().isEmpty()) return;
-	foreach (QGraphicsItem *item, scene -> items()) item -> setSelected(true);
+	QPainterPath path;
+	path.addRect(scene -> itemsBoundingRect());
+	scene -> setSelectionArea(path);
 }
 
 /**
@@ -55,7 +57,7 @@ void DiagramView::selectAll() {
 */
 void DiagramView::selectNothing() {
 	if (scene -> items().isEmpty()) return;
-	foreach (QGraphicsItem *item, scene -> items()) item -> setSelected(false);
+	scene -> clearSelection();
 }
 
 /**
@@ -595,7 +597,7 @@ void DiagramView::adjustSceneRect() {
 	QRectF elements_bounding_rect = scene -> itemsBoundingRect();
 	
 	// rectangle contenant le cadre = colonnes + cartouche
-	QRectF border_bounding_rect = scene -> border().adjusted(-MARGIN, -MARGIN, MARGIN, MARGIN);
+	QRectF border_bounding_rect = scene -> border().adjusted(-Diagram::margin, -Diagram::margin, Diagram::margin, Diagram::margin);
 	
 	// ajuste la sceneRect
 	QRectF new_scene_rect = elements_bounding_rect.united(border_bounding_rect);
diff --git a/editor/elementscene.cpp b/editor/elementscene.cpp
index 60b66e6ce..120c8c222 100644
--- a/editor/elementscene.cpp
+++ b/editor/elementscene.cpp
@@ -11,8 +11,9 @@
 #include "partarc.h"
 #include "hotspoteditor.h"
 #include "editorcommands.h"
-#define GRILLE_X 10
-#define GRILLE_Y 10
+
+const int ElementScene::xGrid = 10;
+const int ElementScene::yGrid = 10;
 
 ElementScene::ElementScene(QETElementEditor *editor, QObject *parent) :
 	QGraphicsScene(parent),
@@ -248,12 +249,12 @@ void ElementScene::drawBackground(QPainter *p, const QRectF &r) {
 		qreal limite_y = r.y() + r.height();
 		
 		int g_x = (int)ceil(r.x());
-		while (g_x % GRILLE_X) ++ g_x;
+		while (g_x % xGrid) ++ g_x;
 		int g_y = (int)ceil(r.y());
-		while (g_y % GRILLE_Y) ++ g_y;
+		while (g_y % yGrid) ++ g_y;
 		
-		for (int gx = g_x ; gx < limite_x ; gx += GRILLE_X) {
-			for (int gy = g_y ; gy < limite_y ; gy += GRILLE_Y) {
+		for (int gx = g_x ; gx < limite_x ; gx += xGrid) {
+			for (int gy = g_y ; gy < limite_y ; gy += yGrid) {
 				p -> drawPoint(gx, gy);
 			}
 		}
diff --git a/editor/elementscene.h b/editor/elementscene.h
index 8a7eb55d0..be4737144 100644
--- a/editor/elementscene.h
+++ b/editor/elementscene.h
@@ -26,6 +26,10 @@ class ElementScene : public QGraphicsScene {
 	ElementScene(const ElementScene &);
 	
 	// attributs
+	public:
+	static const int xGrid;
+	static const int yGrid;
+	
 	private:
 	/// longueur de l'element en dizaines de pixels
 	uint _width;
diff --git a/editor/parttext.h b/editor/parttext.h
index aefe56366..6de0adf7b 100644
--- a/editor/parttext.h
+++ b/editor/parttext.h
@@ -1,5 +1,5 @@
-#ifndef PART_TEXT
-#define PART_TEXT
+#ifndef PART_TEXT_H
+#define PART_TEXT_H
 #include <QtGui>
 #include "customelementpart.h"
 class TextEditor;
diff --git a/editor/parttextfield.h b/editor/parttextfield.h
index 7194fdf24..8ef8ced66 100644
--- a/editor/parttextfield.h
+++ b/editor/parttextfield.h
@@ -1,5 +1,5 @@
-#ifndef PART_TEXTFIELD
-#define PART_TEXTFIELD
+#ifndef PART_TEXTFIELD_H
+#define PART_TEXTFIELD_H
 #include <QtGui>
 #include "customelementpart.h"
 class TextFieldEditor;
diff --git a/element.cpp b/element.cpp
index 0e1c7a23a..f1dcedb63 100644
--- a/element.cpp
+++ b/element.cpp
@@ -206,9 +206,9 @@ void Element::setPos(const QPointF &p) {
 	// pas la peine de positionner sur la grille si l'element n'est pas sur un Diagram
 	if (scene()) {
 		// arrondit l'abscisse a 10 px pres
-		int p_x = qRound(p.x() / 10.0) * 10;
+		int p_x = qRound(p.x() / (Diagram::xGrid * 1.0)) * Diagram::xGrid;
 		// arrondit l'ordonnee a 10 px pres
-		int p_y = qRound(p.y() / 10.0) * 10;
+		int p_y = qRound(p.y() / (Diagram::yGrid * 1.0)) * Diagram::yGrid;
 		QGraphicsItem::setPos(p_x, p_y);
 	} else QGraphicsItem::setPos(p);
 }
diff --git a/hotspoteditor.cpp b/hotspoteditor.cpp
index de8edf680..1d36d26b9 100644
--- a/hotspoteditor.cpp
+++ b/hotspoteditor.cpp
@@ -33,7 +33,7 @@ HotspotEditor::HotspotEditor(QWidget *parent) :
 	
 	diagram_view = new QGraphicsView(diagram_scene);
 	diagram_view -> setMaximumSize(
-		static_cast<int>((5 * diagram_scene -> border_and_inset.columnsWidth()) + (3 * MARGIN)),
+		static_cast<int>((5 * diagram_scene -> border_and_inset.columnsWidth()) + (3 * Diagram::margin)),
 		300
 	);
 	diagram_view -> setTransformationAnchor(QGraphicsView::AnchorUnderMouse);
diff --git a/terminal.cpp b/terminal.cpp
index bb11fe016..f87fb085d 100644
--- a/terminal.cpp
+++ b/terminal.cpp
@@ -8,6 +8,7 @@ QColor Terminal::couleur_neutre   = QColor(Qt::blue);
 QColor Terminal::couleur_autorise = QColor(Qt::darkGreen);
 QColor Terminal::couleur_prudence = QColor("#ff8000");
 QColor Terminal::couleur_interdit = QColor(Qt::red);
+const qreal Terminal::terminalSize = 4.0;
 
 /**
 	Fonction privee pour initialiser la borne.
@@ -25,11 +26,11 @@ void Terminal::initialise(QPointF pf, QET::Orientation o) {
 	// calcul de la position du point d'amarrage a l'element
 	amarrage_elmt = amarrage_conductor;
 	switch(sens) {
-		case QET::North: amarrage_elmt += QPointF(0, TAILLE_BORNE);  break;
-		case QET::East : amarrage_elmt += QPointF(-TAILLE_BORNE, 0); break;
-		case QET::West : amarrage_elmt += QPointF(TAILLE_BORNE, 0);  break;
+		case QET::North: amarrage_elmt += QPointF(0, Terminal::terminalSize);  break;
+		case QET::East : amarrage_elmt += QPointF(-Terminal::terminalSize, 0); break;
+		case QET::West : amarrage_elmt += QPointF(Terminal::terminalSize, 0);  break;
 		case QET::South:
-		default        : amarrage_elmt += QPointF(0, -TAILLE_BORNE);
+		default        : amarrage_elmt += QPointF(0, -Terminal::terminalSize);
 	}
 	
 	// par defaut : pas de conducteur
diff --git a/terminal.h b/terminal.h
index 432810a43..6f6516396 100644
--- a/terminal.h
+++ b/terminal.h
@@ -61,6 +61,7 @@ class Terminal : public QGraphicsItem {
 	// attributs
 	public:
 	enum { Type = UserType + 1002 };
+	static const qreal terminalSize;
 	
 	// differentes couleurs statiques utilisables pour l'effet "hover"
 	static QColor couleur_neutre;