1 files changed, 144 insertions, 0 deletions
diff --git a/plugins/infra/gmfdiag/org.eclipse.papyrus.infra.gmfdiag.common/src/org/eclipse/papyrus/infra/gmfdiag/common/linklf/DiagramGridSpec.java b/plugins/infra/gmfdiag/org.eclipse.papyrus.infra.gmfdiag.common/src/org/eclipse/papyrus/infra/gmfdiag/common/linklf/DiagramGridSpec.java
new file mode 100644
index 00000000000..885fc7fe7e5
--- /dev/null
+++ b/plugins/infra/gmfdiag/org.eclipse.papyrus.infra.gmfdiag.common/src/org/eclipse/papyrus/infra/gmfdiag/common/linklf/DiagramGridSpec.java
@@ -0,0 +1,144 @@
+package org.eclipse.papyrus.infra.gmfdiag.common.linklf;
+
+import java.beans.PropertyChangeEvent;
+import java.beans.PropertyChangeListener;
+
+import org.eclipse.draw2d.geometry.Dimension;
+import org.eclipse.draw2d.geometry.Point;
+import org.eclipse.draw2d.geometry.PrecisionRectangle;
+import org.eclipse.gef.EditPartViewer;
+import org.eclipse.gef.GraphicalEditPart;
+import org.eclipse.gef.SnapToGrid;
+
+/**
+ * Utility class to compute active grid specification for given edit part viewer.
+ * <p/>
+ * Clients may call static methods to compute grid spec once, or may setup listeners 
+ * that will automatically update the active spec when it changed
+ */
+public class DiagramGridSpec {
+
+	private final EditPartViewer myViewer;
+
+	private PrecisionRectangle myRelativeGridSpec;
+
+	private PrecisionRectangle myAbsoluteGridSpec;
+
+	private final GridSpecListener myGridListener;
+
+	public DiagramGridSpec(EditPartViewer viewer) {
+		myViewer = viewer;
+		myGridListener = new GridSpecListener() {
+
+			@Override
+			public void gridSpecChanged() {
+				myRelativeGridSpec = null;
+				myAbsoluteGridSpec = null;
+			}
+		};
+		myViewer.addPropertyChangeListener(myGridListener);
+	}
+
+	public void dispose() {
+		myViewer.removePropertyChangeListener(myGridListener);
+		myRelativeGridSpec = null;
+		myAbsoluteGridSpec = null;
+	}
+
+	/**
+	 * Always returns the same instance to avoid endless creation
+	 * @return active grid specification in absolute coordinates or <code>null</code> if not enabled
+	 */
+	public PrecisionRectangle getAbsoluteGridSpec() {
+		PrecisionRectangle result = getRelativeGridSpec();
+		if (result == null) {
+			return null;
+		}
+
+		if (myAbsoluteGridSpec == null) {
+			myAbsoluteGridSpec = new PrecisionRectangle();
+		}
+		myAbsoluteGridSpec.setPreciseBounds(result.preciseX(), result.preciseY(), result.preciseWidth(), result.preciseHeight());
+		GraphicalEditPart diagramEP = (GraphicalEditPart) myViewer.getContents();
+		diagramEP.getContentPane().translateToAbsolute(myAbsoluteGridSpec);
+
+		return myAbsoluteGridSpec;
+	}
+
+	private PrecisionRectangle getRelativeGridSpec() {
+		if (myRelativeGridSpec == null) {
+			myRelativeGridSpec = getRelativeGridSpec(myViewer);
+		}
+		return myRelativeGridSpec;
+	}
+
+	public EditPartViewer getViewer() {
+		return myViewer;
+	}
+
+	/**
+	 * Computes actual grid specification (origin + single cell width and height) in the absolute coordinate system. 
+	 * Note, in contrast to {@link #getRelativeGridSpec(EditPartViewer)} this specification depends on the active zoom or scroll 
+	 * and can't be cached by clients.
+	 * @param viewer
+	 * @return absolute grid specification, or <code>null</code> if grid is not enabled 
+	 */
+	public static PrecisionRectangle getAbsoluteGridSpec(EditPartViewer viewer) {
+		PrecisionRectangle spec = getRelativeGridSpec(viewer);
+		if (spec != null) {
+			GraphicalEditPart diagramEP = (GraphicalEditPart) viewer.getContents();
+			diagramEP.getContentPane().translateToAbsolute(spec);
+		}
+		return spec;
+	}
+
+	/**
+	 * Computes actual grid specification (origin + single cell width and height) in the coordinates relative 
+	 * to the diagram content pane. 
+	 * <p/>
+	 * This specification depends only on the grid-relative properties stored in 
+	 * the {@link EditPartViewer}, so client may cache it and rely on {@link EditPartViewer#addPropertyChangeListener(PropertyChangeListener)}
+	 * @param viewer
+	 * @return grid specification in the coordinate system relative to diagram content pane, or <code>null</code> if grid is not enabled
+	 */
+	private static PrecisionRectangle getRelativeGridSpec(EditPartViewer viewer) {
+		Boolean enabled = (Boolean) viewer.getProperty(SnapToGrid.PROPERTY_GRID_ENABLED);
+		if (enabled == null || !enabled) {
+			return null;
+		}
+		double gridX = 0;
+		double gridY = 0;
+		Dimension spacing = (Dimension) viewer.getProperty(SnapToGrid.PROPERTY_GRID_SPACING);
+		if (spacing != null) {
+			gridX = spacing.preciseWidth();
+			gridY = spacing.preciseHeight();
+		}
+		if (gridX <= 0) {
+			gridX = SnapToGrid.DEFAULT_GRID_SIZE;
+		}
+		if (gridY <= 0) {
+			gridY = SnapToGrid.DEFAULT_GRID_SIZE;
+		}
+		Point origin = (Point) viewer.getProperty(SnapToGrid.PROPERTY_GRID_ORIGIN);
+		PrecisionRectangle result = new PrecisionRectangle(//
+				origin == null ? 0 : origin.preciseX(), origin == null ? 0 : origin.preciseY(), gridX, gridY);
+
+		return result;
+	}
+
+	public static abstract class GridSpecListener implements PropertyChangeListener {
+
+		public void propertyChange(PropertyChangeEvent evt) {
+			String propertyName = evt.getPropertyName();
+			if (SnapToGrid.PROPERTY_GRID_ORIGIN.equals(propertyName) || //
+					SnapToGrid.PROPERTY_GRID_ENABLED.equals(propertyName) || //
+					SnapToGrid.PROPERTY_GRID_SPACING.equals(propertyName)) {
+
+				gridSpecChanged();
+			}
+		}
+
+		public abstract void gridSpecChanged();
+	};
+
+}