SurfaceView.java

/* Copyright (c) 2009 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
 *
 * 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.google.appengine.demos.sticky.client;

import com.google.appengine.demos.sticky.client.model.Model;
import com.google.appengine.demos.sticky.client.model.Note;
import com.google.appengine.demos.sticky.client.model.Surface;
import com.google.gwt.dom.client.DivElement;
import com.google.gwt.dom.client.Document;
import com.google.gwt.dom.client.EventTarget;
import com.google.gwt.dom.client.Style;
import com.google.gwt.event.dom.client.MouseDownEvent;
import com.google.gwt.event.dom.client.MouseDownHandler;
import com.google.gwt.event.dom.client.MouseMoveEvent;
import com.google.gwt.event.dom.client.MouseMoveHandler;
import com.google.gwt.event.dom.client.MouseUpEvent;
import com.google.gwt.event.dom.client.MouseUpHandler;
import com.google.gwt.event.logical.shared.ValueChangeEvent;
import com.google.gwt.event.logical.shared.ValueChangeHandler;
import com.google.gwt.user.client.DOM;
import com.google.gwt.user.client.Element;
import com.google.gwt.user.client.ui.FlowPanel;
import com.google.gwt.user.client.ui.SimplePanel;
import com.google.gwt.user.client.ui.TextArea;
import com.google.gwt.user.client.ui.WidgetCollection;

/**
 * A widget to display the collection of notes that are on a particular
 * {@link Surface}.
 * 
 * @author knorton@google.com (Kelly Norton)
 */
public class SurfaceView extends FlowPanel implements Model.DataObserver {

  /**
   * A widget for displaying a single {@link Note}.
   */
  private class NoteView extends SimplePanel implements Note.Observer,
      MouseUpHandler, MouseDownHandler, MouseMoveHandler,
      ValueChangeHandler<String> {
    private final Note note;

    private final DivElement titleElement;

    private final TextArea content = new TextArea();

    // Dragging state.
    private boolean dragging;

    private int dragOffsetX, dragOffsetY;

    /**
     * @param note
     *          the note to render
     */
    public NoteView(Note note) {
      this.note = note;
      setStyleName("note");
      note.setObserver(this);

      // Build simple DOM Structure.
      final Element elem = getElement();
      elem.getStyle().setProperty("position", "absolute");
      titleElement = elem.appendChild(Document.get().createDivElement());
      titleElement.setClassName("note-title");

      content.setStyleName("note-content");
      content.addValueChangeHandler(this);
      setWidget(content);

      render();

      addDomHandler(this, MouseDownEvent.getType());
      addDomHandler(this, MouseMoveEvent.getType());
      addDomHandler(this, MouseUpEvent.getType());
    }

    public void onMouseDown(MouseDownEvent event) {
      SurfaceView.this.select(this);
      if (!note.isOwnedByCurrentUser()) {
        return;
      }

      final EventTarget target = event.getNativeEvent().getEventTarget();
      assert Element.is(target);
      if (!Element.is(target)) {
        return;
      }

      if (titleElement.isOrHasChild(Element.as(target))) {
        dragging = true;
        final Element elem = getElement().cast();
        dragOffsetX = event.getX();
        dragOffsetY = event.getY();
        DOM.setCapture(elem);
        event.preventDefault();
      }
    }

    public void onMouseMove(MouseMoveEvent event) {
      if (dragging) {
        setPixelPosition(event.getX() + getAbsoluteLeft() - dragOffsetX,
            event.getY() + getAbsoluteTop() - dragOffsetY);
        event.preventDefault();
      }
    }

    public void onMouseUp(MouseUpEvent event) {
      if (dragging) {
        dragging = false;
        DOM.releaseCapture(getElement());
        event.preventDefault();
        model.updateNotePosition(note, getAbsoluteLeft(), getAbsoluteTop(),
            note.getWidth(), note.getHeight());
      }
    }

    public void onUpdate(Note note) {
      render();
    }

    public void onValueChange(ValueChangeEvent<String> event) {
      model.updateNoteContent(note, event.getValue());
    }

    public void setPixelPosition(int x, int y) {
      final Style style = getElement().getStyle();
      style.setPropertyPx("left", x);
      style.setPropertyPx("top", y);
    }

    public void setPixelSize(int width, int height) {
      content.setPixelSize(width, height);
    }

    private void render() {
      setPixelPosition(note.getX(), note.getY());

      setPixelSize(note.getWidth(), note.getHeight());

      titleElement.setInnerHTML(note.getAuthorName());

      final String noteContent = note.getContent();
      content.setText((noteContent == null) ? "" : noteContent);

      content.setReadOnly(!note.isOwnedByCurrentUser());
    }

    private void select() {
      getElement().getStyle().setProperty("zIndex", "" + nextZIndex());
    }
  }

  private final Model model;

  private NoteView selectedNoteView;

  private int zIndex = 1;

  /**
   * @param model
   *          the model to which the Ui will bind itself
   */
  public SurfaceView(Model model) {
    this.model = model;
    final Element elem = getElement();
    elem.setId("surface");
    elem.getStyle().setProperty("position", "absolute");
    model.addDataObserver(this);
  }

  public void onNoteCreated(Note note) {
    final NoteView view = new NoteView(note);
    add(view);
    select(view);
  }

  public void onSurfaceCreated(Surface group) {
  }

  public void onSurfaceNotesReceived(Note[] notes) {
    removeAllNotes();
    for (int i = 0, n = notes.length; i < n; ++i) {
      add(new NoteView(notes[i]));
    }
  }

  public void onSurfaceSelected(Surface nowSelected, Surface wasSelected) {
  }

  public void onSurfacesReceived(Surface[] surfaces) {
  }

  private int nextZIndex() {
    return zIndex++;
  }

  private void removeAllNotes() {
    final WidgetCollection kids = getChildren();
    while (kids.size() > 0) {
      remove(kids.size() - 1);
    }
  }

  private void select(NoteView noteView) {
    assert noteView != null;
    if (selectedNoteView != noteView) {
      noteView.select();
      selectedNoteView = noteView;
    }
  }
}