Add a simple dialog box that automatically centers itself

Blatantly stolen from Gerrit Code Review, this is a simple dialog
that registers a window listener to recenter itself whenever the
main browser window resizes.

Signed-off-by: Shawn O. Pearce <sop@google.com>

1 files changed, 72 insertions, 0 deletions

diff --git a/src/main/java/com/google/gwtexpui/user/client/AutoCenterDialogBox.java b/src/main/java/com/google/gwtexpui/user/client/AutoCenterDialogBox.java
new file mode 100644
index 0000000..ad28d3a
--- /dev/null
+++ b/src/main/java/com/google/gwtexpui/user/client/AutoCenterDialogBox.java
@@ -0,0 +1,72 @@
+// Copyright 2008 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.gwtexpui.user.client;
+
+import com.google.gwt.user.client.Window;
+import com.google.gwt.user.client.WindowResizeListener;
+import com.google.gwt.user.client.ui.DialogBox;
+
+/** A DialogBox that automatically re-centers itself if the window changes */
+public class AutoCenterDialogBox extends DialogBox {
+  private WindowResizeListener recenter;
+
+  public AutoCenterDialogBox() {
+  }
+
+  public AutoCenterDialogBox(final boolean autoHide) {
+    super(autoHide);
+  }
+
+  public AutoCenterDialogBox(final boolean autoHide, final boolean modal) {
+    super(autoHide, modal);
+  }
+
+  @Override
+  public void show() {
+    if (recenter == null) {
+      recenter = new WindowResizeListener() {
+        public void onWindowResized(final int width, final int height) {
+          onResize(width, height);
+        }
+      };
+      Window.addWindowResizeListener(recenter);
+    }
+    super.show();
+  }
+
+  @Override
+  protected void onUnload() {
+    if (recenter != null) {
+      Window.removeWindowResizeListener(recenter);
+      recenter = null;
+    }
+    super.onUnload();
+  }
+
+  /**
+   * Invoked when the outer browser window resizes.
+   * <p>
+   * Subclasses may override (but should ensure they still call super.onResize)
+   * to implement custom logic when a window resize occurs.
+   * 
+   * @param width new browser window width
+   * @param height new browser window height
+   */
+  protected void onResize(final int width, final int height) {
+    if (isAttached()) {
+      center();
+    }
+  }
+}