Hi everyone,
After reading Benson's post about screen rotation and the HP calculator, I tried to build TiEmu on scratchbox in portrait mode.
I was wrong saying it was the screen resolution which was preventing the skin (and the buttons) to appear.
In fact, since TiEmu was being built in an ARM environment, it used specific ipaq optimisations for the screen (other skin, another way to get the menu...). In Maemo, it was impossible to get the skin because of that changes. Disabling them solved all skin problems.
It is not as slow as the HP emulator, but it is four times slower than my Ti-89 Titanium to draw the sinus function (Xres = 1, Ymin = -1, Ymax = 1, Xscl = YScl = 1, Xmin = -2*Pi, Xmax = 2*Pi ; 15 seconds versus 60 seconds).

Changes from the original version

• Configure.ac modified to disable iPaq-specific code when built on ARM.
• Pressing F4 (menu key on N800/N810) brings the menu
• It uses by default the iPaq skins, they aren't pretty on an high-resolution screen, but they work better than the standarts skins (without "zooming", the keys are too small on each skin, in standart mode, some keys aren't displayed with the standart skin, neither in x2 zoom).
• Pressing F6 toggles full-screen mode

Known problems

• If you press a key with your stylus, don't "release" it on another key. If you do that, you will lose the ability to press another key. In that case, simply click on the key on which you should have released your stylus.
• The TiLP libraries packages are really quick&dirty (no changes, no description...). But they work :-)
• I feel a little dumb because I didn't saw before the TiEmu 3 version without GDB ; it was this debugger which was causing some problems while recompiling...

Video
Modified source code

Install now

EDIT : Works in landscape mode with iPaq skin and x1 zoom. It isn't usable, but it works ;-) Just don't try fullscreen mode in landscape mode, it's really, really slow. You will quit before seeing the menu.

EDIT (2) : (to fms) : I saw your post about Cyclone, but my skills in C are really too low for that, sorry ;-)

EDIT (3) : You can use a Ti-92+ ROM to get a good fullscreen landscape skin (thanks to OSEmuTech :-)).