RFE: Look and Feel classes are poorly designed and hostile to subclassing

Name: jk109818 Date: 02/21/2003


FULL PRODUCT VERSION :
java version "1.4.1_01"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.1_01-b01)
Java HotSpot(TM) Client VM (build 1.4.1_01-b01, mixed mode)


A DESCRIPTION OF THE PROBLEM :
The Pluggable Look and Feel classes are designed in such a
way as to make sensible overriding extremely difficult and
frustrating.

As a simple example, the Windows Look and Feel renders
disabled menuitems incorrectly (which I have submitted in a
separate bug report). I would like to fix that bug now,
rather than wait the expected two or more years for a fix to
be available from Sun.

So, a quick investigation revealed that BasicMenuItemUI is
painting the accelerator text in a massive 6KB method.
There is no paintAccelerator() method that I could override
in order to fix the bug with accelerator display, which
means that I would have to copy the entire 6KB
paintMenuItem() method to alter this behavior.
Unfortunately, paintMenuItem() depends on the 5KB
layoutMenuItem(), which is private, and I would therefore
have to copy the entire code of that method as well.

So, to be able to modify the accelator paint behavior in any
way, I have to copy 11KB of code into a subclass of
WindowsMenuItemUI. I can then make the required *ONE LINE*
change to the painting behavior.

I hope I'm not the only one that finds that to be absurd.

Unfortunately, this is far from an isolated example. Unlike
the rest of Swing, the PLAF classes do not seem to have been
designed with anything approaching sane design principles,
requiring ridiculous amounts of effort and code duplication
to solve simple problems. Many of these giant, monolithic
methods need to be broken up so that they can be overridden
in reasonable ways, and a number of methods and fields that
are marked private should instead be protected.

I have no doubt that this will instantly be hit with the
dreaded "Will Not Fix" club, but I figure it's worth a shot.

REPRODUCIBILITY :
This bug can be reproduced always.
(Review ID: 181547)
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