What are some good API's to consider when starting development on a stand alone GUI applications?

[SleepyMushroom]

For most of my career I've implemented client / server console applications, shell, server-side web applications and tons of Javascript. I know this is pretty generic but some of the things that are important to me<br />
<br />
- Cross platform compatibility<br />
- Ease of end user installation<br />
- Robust high level OO API<br />
- Ability to prototype but not critical<br />
- HTTP network interfaces /w cookies / sessions and ssl capable<br />
- Good community support<br />
<br />
I've looked at a few different GTK solutions like PHPGTK, pyGTK, Java and C#.<br />
<br />
My core competencies are C, Python, PHP, Perl and Javascript on mostly Linux and Solaris platforms so it would be nice to not have to brain up on something completely foreign. <br />
<br />
Could anyone recommend a good open source solution and briefly explain their advice?<br />
<br />
Thanks!<br />

 

[mapighimagsik_so]

if your goal demands cross-platform, java is a good answer, though GTK is good as well. Both have a pretty good cross platform history.