<Swing Dev> [9] Crash tabbing to a checkbox with custom model (see e.g. 8074883)

[Luke]

Hi Sergey,

Assuming CR is crash report, I've filed a bug report - assigned internal 
review ID : 9049636.

I included some minimal code to repo the issue there.

Kind regards,
Luke

On 19/06/2017 6:47 PM, Sergey Bylokhov wrote:
> Hi,
> Can you please create a new CR using http://bugs.java.com ?
> It is too late to fix it in jdk9, but I think it will be possible to 
> fix it in 10 and then backport to some update of jdk9.
>
>>
>> Good day,
>>
>> I believe I've hit my first bug in occasional testingof the JDK-9 drops.
>> I hope this is an appropriate way to send feedback?
>>
>> We use a customised "tri-state" checkbox, which triggers a crash when the
>> keyboard focus moves to it by pressing the TAB key. The issue seems 
>> related
>> to some focus logic changes with button-groups introduced in JDK-9.
>> (For example: 8074883?)
>>
>> The top of the stack trace is:
>>
>> java.lang.ClassCastException: 
>> com.example.TristateCheckBox$TristateDecorator cannot be cast to 
>> java.desktop/javax.swing.JToggleButton$ToggleButtonModel
>>    at 
>> java.desktop/javax.swing.LayoutFocusTraversalPolicy.accept(LayoutFocusTraversalPolicy.java:243)
>>    at 
>> java.desktop/javax.swing.SortingFocusTraversalPolicy.getComponentBefore(SortingFocusTraversalPolicy.java:435)
>>    at 
>> java.desktop/javax.swing.LayoutFocusTraversalPolicy.getComponentBefore(LayoutFocusTraversalPolicy.java:143)
>>    at 
>> java.desktop/java.awt.Component.transferFocusBackward(Component.java:8201)
>>    at 
>> java.desktop/java.awt.Component.transferFocusBackward(Component.java:8186)
>>    at 
>> java.desktop/java.awt.DefaultKeyboardFocusManager.focusPreviousComponent(DefaultKeyboardFocusManager.java:1388)
>>    at 
>> java.desktop/java.awt.DefaultKeyboardFocusManager.processKeyEvent(DefaultKeyboardFocusManager.java:1183)
>>    at 
>> java.desktop/java.awt.Component.dispatchEventImpl(Component.java:4877)
>>    at 
>> java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2317)
>>    at java.desktop/java.awt.Component.dispatchEvent(Component.java:4793)
>> ...
>>
>> The relevant code in LayoutFocusTraversalPolicy.accept is:
>>
>>    } else if (aComponent instanceof JComponent) {
>>        if (SunToolkit.isInstanceOf(aComponent,
>> "javax.swing.JToggleButton")) {
>>            JToggleButton.ToggleButtonModel model =
>>                    (JToggleButton.ToggleButtonModel) ((JToggleButton)
>>                            aComponent).getModel();   // <- Line 243
>>            if (model != null) {
>>                ButtonGroup group = model.getGroup(); // <- Only use 
>> of 'model'
>>
>> For whatever reason (probably to do with the 3 states) the button model
>> is not a ToggleButtonModel, but derived from a DefaultButtonModel.
>>
>> I think a simple solution is to (check? and) cast less specifically, to a
>> DefaultButtonModel instead. That looks to be sufficient here, and is also
>> what we find similar code in JToggleButton doing. For example in
>> JToggeleButton.getGroupSelection we see:
>>
>>    if (model instanceof DefaultButtonModel) {
>>        ButtonGroup group = ((DefaultButtonModel) model).getGroup();
>>        //...
>>
>> I note while JToggleButton creates a ToggleButtonModel by default, it
>> does not enforce it via setModel().
>>
>>
>> More background: I think we found this code (over a decade ago) from here
>>
>> http://www.javaspecialists.eu/archive/Issue082.html
>>
>> (There are better solutions implementing this GUI control these days, but
>> I thought you might like to hear about it.)
>>
>> Kind regards,
>> Luke Usherwood
>>
>>
>