<Swing Dev> <AWT Dev> Inefficiencies with custom TableCellRenderer and Applets

[Artem Ananiev]

Shannon Hickey wrote:
> Clemens Eisserer wrote:
>> Hi,
>>
>> I've created a library which has to use custom TableCellRenderers for
>> its tables.
>> I experienced a large performance difference between running my
>> application as Application inside an JFrame and as an JApplet.
>> Parented inside of the JFrame scrolling the table was smooth, however
>> scrolling inside the applet was slow, especially if the mouse is over
>> the table while scrolling.
>>
>> I did some profiling with netbeans-profiler and found the root-cause:
>> BasicTableUI.paintCell->CellRendererPane.paintComponent->Container.validate->Component.updateCursorImmediatly->GlobalCursorManager.updateCursorImmediatly()->_updateCursor.... 
>>
>>
>> The updateCursorImmediatly was called both times about 16.000 times,
>> with JFrame it consumed 22% of the cycles which is already
>> inefficient.
>> As JApplet it calls into getLocationOnScreen() which calls down till
>> XBaseWindow.toOtherWindow even slower which is about as slow as
>> updating the Cursor itself, so as applet it consumes 48% of all EDT
>> cycles.

What a sad story... I will file a bug against AWT about this problem.

>> The DefaultTableCellRenderer simply overrides validate with an empty
>> method, therefor no such calls are done.
>> But why does CellRendererPane.paintComponent() call validate at all?
> 
> CellRendererPain takes an argument that dictates whether or not it 
> validates. In most cases it's told to validate by the caller since the 
> renderer may need to do layout on its children.
> 
> I suggest you override validate() on your custom renderer to do nothing, 
> the same way the DefaultTableCellRenderer does.
> 
>> If it cannot be avoided, is there no way to cache stuff in
>> XBaseWindow.toOtherWindow at all?

We have some kind of caching for this call, however in the case of 
applets (embedded frames) it doesn't work very well...

Artem

> You'll have to ask the AWT team about this. I've CC'd them.
> 
> Shannon
> 
>>
>> Thanks, lg Clemens
>>
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>> Very simple TableCellRenderer which triggers the slowness:
>>       JLabel renderer = new JLabel();
>>       public Component getTableCellRendererComponent(JTable table, 
>> Object value,
>>           boolean isSelected, boolean hasFocus, int row, int column) {
>>          renderer.setText((String)value);
>>          renderer.setOpaque(true);
>>         return renderer;
>>       }
>