Hi guys,
I know that this is a naive question, but plz bear with me.

I'm trying to develop a device for my proposal.
The first device that i developed was based on atxmega32 that satisfied all the functional requirement. But know there is a non-functional requirement that must be implemented and that is "Display Device Must Be A Full Color TFT LCD".

So, to implement this req, I had to use an AT91SAM9260 micro (why? be cause of lake of other chips in our country marked).

Now the question is what IDE is good enough to do this job and if I want to use linux or windows ce, is there a step-by-step tut?

BTW, in Atmel web site for SAM9260 parameters tab, there is stated:
Segment LCD: 0
Graphic LCD: No

Is it means that AT91SAM9260 can't support an LCD display device?
I've a TM056KDH01 LCD.
Any suggestion?

Pick a different micro capable of driving a dumb LCD panel directly. Try a 9263, still that and the 9260 are getting quite old, and I'd worry about long term availability. Whatever the current availability/marketing, in your unspecified country.

Pick a different LCD panel, ideally one capable of digital drive, not analogue. That way you can DMA directly from a frame buffer. If your micro can't handle a dumb panel, use a smarter one.

How big does the screen need to be? physical/pixels, 5.6" 320x234?

Windows CE has a development environment, with a Visual Studio type IDE, Platform Builder.

For Linux, try looking at the Linux4Sam resources.

Does your unspecified application need a Linux/WinCE type OS, or can you use something more lightweight?

If at this juncture of the project you need a step-by-step to pick an OS, you have a real problem, both the aforementioned OS are complex and difficult beasts. Suggest you actually get an 9263-EK development board, with board support package to test/develop your code from a viable, pre-built platform, which has workable software and directions, to start from.

At the very least download some of the materials for the 9263 and look at the schematics, and bill of materials.

Depending on the interface and available GPIO, LCD panels will need to be smart/dumb to be accommodated. To use dumb panels, you'll need a controller capable of driving them.