LGTM But lots of formatting errors.
http://gwt-code-reviews.appspot.com/864801/diff/3001/4009 File user/src/com/google/gwt/user/client/ui/AbsolutePanel.java (right): http://gwt-code-reviews.appspot.com/864801/diff/3001/4009#newcode99 user/src/com/google/gwt/user/client/ui/AbsolutePanel.java:99: extra spaces http://gwt-code-reviews.appspot.com/864801/diff/3001/4009#newcode154 user/src/com/google/gwt/user/client/ui/AbsolutePanel.java:154: extra spaces http://gwt-code-reviews.appspot.com/864801/diff/3001/4010 File user/src/com/google/gwt/user/client/ui/ComplexPanel.java (right): http://gwt-code-reviews.appspot.com/864801/diff/3001/4010#newcode46 user/src/com/google/gwt/user/client/ui/ComplexPanel.java:46: extra spaces http://gwt-code-reviews.appspot.com/864801/diff/3001/4012 File user/src/com/google/gwt/user/client/ui/FlowPanel.java (right): http://gwt-code-reviews.appspot.com/864801/diff/3001/4012#newcode41 user/src/com/google/gwt/user/client/ui/FlowPanel.java:41: extra newline http://gwt-code-reviews.appspot.com/864801/diff/3001/4013 File user/src/com/google/gwt/user/client/ui/HasOneWidget.java (right): http://gwt-code-reviews.appspot.com/864801/diff/3001/4013#newcode21 user/src/com/google/gwt/user/client/ui/HasOneWidget.java:21: public interface HasOneWidget { Would HasWidget be a better name? The singularity of Widget implicitly assumes it has one. http://gwt-code-reviews.appspot.com/864801/diff/3001/4015 File user/src/com/google/gwt/user/client/ui/HorizontalPanel.java (right): http://gwt-code-reviews.appspot.com/864801/diff/3001/4015#newcode34 user/src/com/google/gwt/user/client/ui/HorizontalPanel.java:34: extra newline http://gwt-code-reviews.appspot.com/864801/diff/3001/4015#newcode35 user/src/com/google/gwt/user/client/ui/HorizontalPanel.java:35: private VerticalAlignmentConstant vertAlign = ALIGN_TOP; missing newline http://gwt-code-reviews.appspot.com/864801/diff/3001/4015#newcode46 user/src/com/google/gwt/user/client/ui/HorizontalPanel.java:46: public void add(IsWidget w) { missing newline http://gwt-code-reviews.appspot.com/864801/diff/3001/4016 File user/src/com/google/gwt/user/client/ui/IndexedPanel.java (right): http://gwt-code-reviews.appspot.com/864801/diff/3001/4016#newcode30 user/src/com/google/gwt/user/client/ui/IndexedPanel.java:30: * /** Gets the child widget at the specified index. syntax http://gwt-code-reviews.appspot.com/864801/diff/3001/4019 File user/src/com/google/gwt/user/client/ui/Panel.java (right): http://gwt-code-reviews.appspot.com/864801/diff/3001/4019#newcode69 user/src/com/google/gwt/user/client/ui/Panel.java:69: extra spaces http://gwt-code-reviews.appspot.com/864801/diff/3001/4019#newcode110 user/src/com/google/gwt/user/client/ui/Panel.java:110: extra spaces http://gwt-code-reviews.appspot.com/864801/diff/3001/4020 File user/src/com/google/gwt/user/client/ui/PopupPanel.java (right): http://gwt-code-reviews.appspot.com/864801/diff/3001/4020#newcode971 user/src/com/google/gwt/user/client/ui/PopupPanel.java:971: public void setWidget(IsWidget w) { +1 users may override setWidget(Widget) and expect it to be called. I think this method should delegate to setWidget(widget) http://gwt-code-reviews.appspot.com/864801/diff/3001/4021 File user/src/com/google/gwt/user/client/ui/SimplePanel.java (right): http://gwt-code-reviews.appspot.com/864801/diff/3001/4021#newcode47 user/src/com/google/gwt/user/client/ui/SimplePanel.java:47: extra spaces http://gwt-code-reviews.appspot.com/864801/diff/3001/4021#newcode117 user/src/com/google/gwt/user/client/ui/SimplePanel.java:117: extra spaces http://gwt-code-reviews.appspot.com/864801/diff/3001/4023 File user/src/com/google/gwt/user/client/ui/StackPanel.java (right): http://gwt-code-reviews.appspot.com/864801/diff/3001/4023#newcode72 user/src/com/google/gwt/user/client/ui/StackPanel.java:72: } missing newline http://gwt-code-reviews.appspot.com/864801/diff/3001/4024 File user/src/com/google/gwt/user/client/ui/TabLayoutPanel.java (right): http://gwt-code-reviews.appspot.com/864801/diff/3001/4024#newcode264 user/src/com/google/gwt/user/client/ui/TabLayoutPanel.java:264: extra spaces http://gwt-code-reviews.appspot.com/864801/diff/3001/4024#newcode277 user/src/com/google/gwt/user/client/ui/TabLayoutPanel.java:277: extra spaces http://gwt-code-reviews.appspot.com/864801/diff/3001/4025 File user/src/com/google/gwt/user/client/ui/TabPanel.java (right): http://gwt-code-reviews.appspot.com/864801/diff/3001/4025#newcode323 user/src/com/google/gwt/user/client/ui/TabPanel.java:323: extra spaces http://gwt-code-reviews.appspot.com/864801/diff/3001/4025#newcode327 user/src/com/google/gwt/user/client/ui/TabPanel.java:327: extra spaces http://gwt-code-reviews.appspot.com/864801/diff/3001/4026 File user/src/com/google/gwt/user/client/ui/VerticalPanel.java (right): http://gwt-code-reviews.appspot.com/864801/diff/3001/4026#newcode33 user/src/com/google/gwt/user/client/ui/VerticalPanel.java:33: extra newline http://gwt-code-reviews.appspot.com/864801/diff/3001/4026#newcode41 user/src/com/google/gwt/user/client/ui/VerticalPanel.java:41: } missing newline http://gwt-code-reviews.appspot.com/864801/diff/3001/4034 File user/test/com/google/gwt/user/client/ui/SimplePanelTest.java (right): http://gwt-code-reviews.appspot.com/864801/diff/3001/4034#newcode35 user/test/com/google/gwt/user/client/ui/SimplePanelTest.java:35: p.setWidget(null); Is that because Widget extends IsWidget? I assume it uses the IsWidget version then, and in general does a runtime check? http://gwt-code-reviews.appspot.com/864801/diff/3001/4036 File user/test/com/google/gwt/user/client/ui/WidgetTest.java (right): http://gwt-code-reviews.appspot.com/864801/diff/3001/4036#newcode49 user/test/com/google/gwt/user/client/ui/WidgetTest.java:49: final com.google.gwt.event.shared.HandlerManager manager = new com.google.gwt.event.shared.HandlerManager( Why did you inline the path for HandlerManager? http://gwt-code-reviews.appspot.com/864801/show -- http://groups.google.com/group/Google-Web-Toolkit-Contributors
