Re: Drawing images on a JPanel

From:

Knute Johnson <nospam@rabbitbrush.frazmtn.com>

Newsgroups:

comp.lang.java.programmer

Date:

Thu, 07 May 2009 19:03:33 -0700

Message-ID:

<4a0392f5$0$4177$b9f67a60@news.newsdemon.com>

John B. Matthews wrote:

In article <4a037ce1$0$1043$b9f67a60@news.newsdemon.com>,
Knute Johnson <nospam@rabbitbrush.frazmtn.com> wrote:

Knute Johnson wrote:

John B. Matthews wrote:

In article <4a0347a5$0$4183$b9f67a60@news.newsdemon.com>,
Knute Johnson <nospam@rabbitbrush.frazmtn.com> wrote:

[...]

If you change it to a JPanel instead of the JComponent, the
yellow background will be drawn if it is opaque and you call
super.paintComponent(). That is apparently the one real
difference between a JComponent and a JPanel.

I get the same result.

In any of the cases however, I do not see any artifacts. I'm
running 1.6.0_14-ea on Windows XP.

Thanks for looking at this. Interestingly, I get variations on [1]
as I resize the window under Java 1.5, but not 1.6 (Mac OS X
10.5.6).

[1]<http://tinypic.com/r/md32q0/5>

I see those artifacts on the link. I'll have to try this on Linux
and see what happens.

Results are the same on Linux as they are on Windows. Xubuntu 9.04
with Sun JDK 1.6.0_13.

Yes, I got expected results on Fedora Core 10 & Java 1.6.0_07 with a
similar program that does not respect the opaque property [1]. In
contrast I get normal operation of several platforms for a program that
does respect the opaque property [2].

Perhaps it would be fair to say that the API admonition still applies,
even though it may not affect all implementations & versions equally.

I think so or something strange 'could' happen. I just don't understand
how writing non-opaque color to the background solves the problem.
Wouldn't writing an opaque color do the same thing?

--

Knute Johnson
email s/nospam/knute2009/

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