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/*
* Copyright (C) 2010 The Android Open Source Project
*
* Licensed under the Eclipse Public License, Version 1.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.eclipse.org/org/documents/epl-v10.php
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.android.ide.eclipse.adt.internal.editors.layout.gle2;
import com.android.annotations.NonNull;
import com.android.annotations.Nullable;
import com.android.ide.common.api.IViewRule;
import com.android.ide.common.api.Rect;
/**
* This singleton is used to keep track of drag'n'drops initiated within this
* session of Eclipse. A drag can be initiated from a palette or from a canvas
* and its content is an Android View fully-qualified class name.
* <p/>
* Overall this is a workaround: the issue is that the drag'n'drop SWT API does not
* allow us to know the transfered data during the initial drag -- only when the
* data is dropped do we know what it is about (and to be more exact there is a workaround
* to do just that which works on Windows but not on Linux/Mac SWT).
* <p/>
* In the GLE we'd like to adjust drag feedback to the data being actually dropped.
* The singleton instance of this class will be used to track the data currently dragged
* off a canvas or its palette and then set back to null when the drag'n'drop is finished.
* <p/>
* Note that when a drag starts in one instance of Eclipse and the dragOver/drop is done
* in a <em>separate</em> instance of Eclipse, the dragged FQCN won't be registered here
* and will be null.
*/
final class GlobalCanvasDragInfo {
private static final GlobalCanvasDragInfo sInstance = new GlobalCanvasDragInfo();
private SimpleElement[] mCurrentElements = null;
private SelectionItem[] mCurrentSelection;
private Object mSourceCanvas = null;
private Runnable mRemoveSourceHandler;
private Rect mDragBounds;
private int mDragBaseline = -1;
/** Private constructor. Use {@link #getInstance()} to retrieve the singleton. */
private GlobalCanvasDragInfo() {
// pass
}
/** Returns the singleton instance. */
public static GlobalCanvasDragInfo getInstance() {
return sInstance;
}
/**
* Registers the XML elements being dragged.
*
* @param elements The elements being dragged
* @param primary the "primary" element among the elements; when there is a
* single item dragged this will be the same, but in
* multi-selection it will be the element under the mouse as the
* selection was initiated
* @param selection The selection (which can be null, for example when the
* user drags from the palette)
* @param sourceCanvas An object representing the source we are dragging
* from (used for identity comparisons only)
* @param removeSourceHandler A runnable (or null) which can clean up the
* source. It should only be invoked if the drag operation is a
* move, not a copy.
*/
public void startDrag(
@NonNull SimpleElement[] elements,
@Nullable SelectionItem[] selection,
@Nullable Object sourceCanvas,
@Nullable Runnable removeSourceHandler) {
mCurrentElements = elements;
mCurrentSelection = selection;
mSourceCanvas = sourceCanvas;
mRemoveSourceHandler = removeSourceHandler;
}
/** Unregisters elements being dragged. */
public void stopDrag() {
mCurrentElements = null;
mCurrentSelection = null;
mSourceCanvas = null;
mRemoveSourceHandler = null;
mDragBounds = null;
}
public boolean isDragging() {
return mCurrentElements != null;
}
/** Returns the elements being dragged. */
@NonNull
public SimpleElement[] getCurrentElements() {
return mCurrentElements;
}
/** Returns the selection originally dragged.
* Can be null if the drag did not start in a canvas.
*/
public SelectionItem[] getCurrentSelection() {
return mCurrentSelection;
}
/**
* Returns the object that call {@link #startDrag(SimpleElement[], SelectionItem[], Object)}.
* Can be null.
* This is not meant to access the object indirectly, it is just meant to compare if the
* source and the destination of the drag'n'drop are the same, so object identity
* is all what matters.
*/
public Object getSourceCanvas() {
return mSourceCanvas;
}
/**
* Removes source of the drag. This should only be called when the drag and
* drop operation is a move (not a copy).
*/
public void removeSource() {
if (mRemoveSourceHandler != null) {
mRemoveSourceHandler.run();
mRemoveSourceHandler = null;
}
}
/**
* Get the bounds of the drag, relative to the starting mouse position. For example,
* if you have a rectangular view of size 100x80, and you start dragging at position
* (15,20) from the top left corner of this rectangle, then the drag bounds would be
* (-15,-20, 100x80).
* <p>
* NOTE: The coordinate units will be in SWT/control pixels, not Android view pixels.
* In other words, they are affected by the canvas zoom: If you zoom the view and the
* bounds of a view grow, the drag bounds will be larger.
*
* @return the drag bounds, or null if there are no bounds for the current drag
*/
public Rect getDragBounds() {
return mDragBounds;
}
/**
* Set the bounds of the drag, relative to the starting mouse position. See
* {@link #getDragBounds()} for details on the semantics of the drag bounds.
*
* @param dragBounds the new drag bounds, or null if there are no drag bounds
*/
public void setDragBounds(Rect dragBounds) {
mDragBounds = dragBounds;
}
/**
* Returns the baseline of the drag, or -1 if not applicable
*
* @return the current SWT modifier key mask as an {@link IViewRule} modifier mask
*/
public int getDragBaseline() {
return mDragBaseline;
}
/**
* Sets the baseline of the drag
*
* @param baseline the new baseline
*/
public void setDragBaseline(int baseline) {
mDragBaseline = baseline;
}
}
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