Add custom autoexpose helper for viewer drag autoscroll

Add custom autoexpose helper for viewer drag autoscroll with larger
default threshold and acceleration depending on distance from the edges.

plugins/org.eclipse.fordiac.ide.application/src/org/eclipse/fordiac/ide/application/editparts/FBNetworkRootEditPart.java

@@ -25,11 +25,13 @@
 import org.eclipse.fordiac.ide.application.editors.NewInstanceDirectEditManager;
 import org.eclipse.fordiac.ide.gef.editparts.ZoomScalableFreeformRootEditPart;
 import org.eclipse.fordiac.ide.gef.tools.AdvancedMarqueeDragTracker;
+import org.eclipse.fordiac.ide.gef.tools.FordiacViewportAutoexposeHelper;
 import org.eclipse.fordiac.ide.model.commands.create.AbstractCreateFBNetworkElementCommand;
 import org.eclipse.fordiac.ide.model.libraryElement.FBNetwork;
 import org.eclipse.fordiac.ide.model.libraryElement.FBNetworkElement;
 import org.eclipse.fordiac.ide.model.typelibrary.TypeEntry;
 import org.eclipse.fordiac.ide.model.typelibrary.TypeLibrary;
+import org.eclipse.gef.AutoexposeHelper;
 import org.eclipse.gef.DragTracker;
 import org.eclipse.gef.EditPartViewer;
 import org.eclipse.gef.GraphicalEditPart;
@@ -137,6 +139,9 @@ public static Point getInsertPos(final LocationRequest request, final EditPartVi
 
 	@Override
 	public <T> T getAdapter(final Class<T> adapter) {
+		if (adapter == AutoexposeHelper.class) {
+			return adapter.cast(new FordiacViewportAutoexposeHelper(this));
+		}
 		if (adapter == FBNetwork.class) {
 			return adapter.cast(fbNetwork);
 		}

plugins/org.eclipse.fordiac.ide.gef/src/org/eclipse/fordiac/ide/gef/tools/FordiacViewportAutoexposeHelper.java

@@ -0,0 +1,88 @@
+/*******************************************************************************
+ * Copyright (c) 2024 Martin Erich Jobst
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0.
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ *   Martin Jobst - initial API and implementation and/or initial documentation
+ *******************************************************************************/
+package org.eclipse.fordiac.ide.gef.tools;
+
+import org.eclipse.draw2d.PositionConstants;
+import org.eclipse.draw2d.Viewport;
+import org.eclipse.draw2d.geometry.Insets;
+import org.eclipse.draw2d.geometry.Point;
+import org.eclipse.draw2d.geometry.Rectangle;
+import org.eclipse.gef.GraphicalEditPart;
+import org.eclipse.gef.editparts.ViewportAutoexposeHelper;
+
+public class FordiacViewportAutoexposeHelper extends ViewportAutoexposeHelper {
+
+	private static final Insets DEFAULT_EXPOSE_THRESHOLD = new Insets(100);
+
+	private long lastStepTime = 0;
+
+	private final Insets threshold;
+
+	public FordiacViewportAutoexposeHelper(final GraphicalEditPart owner) {
+		this(owner, DEFAULT_EXPOSE_THRESHOLD);
+	}
+
+	public FordiacViewportAutoexposeHelper(final GraphicalEditPart owner, final Insets threshold) {
+		super(owner, threshold);
+		this.threshold = threshold;
+	}
+
+	@Override
+	public boolean step(final Point where) {
+		final Viewport port = findViewport(owner);
+
+		final Rectangle rect = Rectangle.SINGLETON;
+		port.getClientArea(rect);
+		port.translateToParent(rect);
+		port.translateToAbsolute(rect);
+		if (!rect.contains(where)) {
+			return false;
+		}
+
+		rect.shrink(threshold);
+
+		if (rect.contains(where)) {
+			return false;
+		}
+
+		if (lastStepTime == 0) {
+			lastStepTime = System.currentTimeMillis();
+		}
+
+		final long difference = System.currentTimeMillis() - lastStepTime;
+
+		if (difference < 0) {
+			return true;
+		}
+
+		lastStepTime = System.currentTimeMillis();
+
+		final int region = rect.getPosition(where);
+		final Point loc = port.getViewLocation();
+
+		if ((region & PositionConstants.SOUTH) != 0) {
+			loc.y += (int) difference * (where.y() - rect.bottom()) / threshold.bottom;
+		} else if ((region & PositionConstants.NORTH) != 0) {
+			loc.y += (int) difference * (where.y() - rect.top()) / threshold.top;
+		}
+
+		if ((region & PositionConstants.EAST) != 0) {
+			loc.x += (int) difference * (where.x() - rect.right()) / threshold.right;
+		} else if ((region & PositionConstants.WEST) != 0) {
+			loc.x += (int) difference * (where.x() - rect.left()) / threshold.left;
+		}
+
+		port.setViewLocation(loc);
+		return true;
+	}
+}