gerrit-gwtui/src/main/java/com/google/gerrit/client/ui/TextBoxChangeListener.java

// Copyright (C) 2012 The Android Open Source Project
//
// 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.gerrit.client.ui;

import com.google.gwt.core.client.Scheduler;
import com.google.gwt.core.client.Scheduler.ScheduledCommand;
import com.google.gwt.event.dom.client.FocusEvent;
import com.google.gwt.event.dom.client.FocusHandler;
import com.google.gwt.event.dom.client.KeyDownEvent;
import com.google.gwt.event.dom.client.KeyDownHandler;
import com.google.gwt.event.dom.client.KeyPressEvent;
import com.google.gwt.event.dom.client.KeyPressHandler;
import com.google.gwt.event.dom.client.MouseUpEvent;
import com.google.gwt.event.dom.client.MouseUpHandler;
import com.google.gwt.event.shared.GwtEvent;
import com.google.gwt.user.client.ui.TextBoxBase;

public abstract class TextBoxChangeListener implements KeyPressHandler, KeyDownHandler, MouseUpHandler {

  private String oldText;

  public TextBoxChangeListener(final TextBoxBase tb) {
    oldText = tb.getText();

    tb.addKeyPressHandler(this);

    // Is there another way to capture middle button X11 pastes in browsers
    // which do not yet support ONPASTE events (Firefox)?
    tb.addMouseUpHandler(this);

    // Resetting the "original text" on focus ensures that we are
    // up to date with non-user updates of the text (calls to
    // setText()...) and also up to date with user changes which
    // occurred after enabling "widget".
    tb.addFocusHandler(new FocusHandler() {
        @Override
        public void onFocus(FocusEvent event) {
          oldText = tb.getText();
        }
      });

    // CTRL-V Pastes in Chrome seem only detectable via BrowserEvents or
    // KeyDownEvents, the latter is better.
    tb.addKeyDownHandler(this);
  }


  @Override
  public void onKeyPress(final KeyPressEvent e) {
    on(e);
  }

  @Override
  public void onKeyDown(final KeyDownEvent e) {
    on(e);
  }

  @Override
  public void onMouseUp(final MouseUpEvent e) {
    on(e);
  }

  private void on(final GwtEvent<?> e) {
    final TextBoxBase tb = (TextBoxBase) e.getSource();

    if (!tb.getText().equals(oldText)) {
      onTextChanged(tb.getText());
      oldText = tb.getText();
    } else {
      // The text appears to not always get updated until the handlers complete.
      Scheduler.get().scheduleDeferred(new ScheduledCommand() {
        @Override
        public void execute() {
          if (!tb.getText().equals(oldText)) {
            onTextChanged(tb.getText());
            oldText = tb.getText();
          }
        }
      });
    }
  }

  public abstract void onTextChanged(String newText);
}