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Diffstat (limited to 'usage')
-rw-r--r-- | usage | 40 |
1 files changed, 40 insertions, 0 deletions
@@ -0,0 +1,40 @@ +Framebuffer abstraction library +------------------------------- + +This library provides a generic abstraction to a linear section of +memory which coresponds to a visible array of pixel elements on a +display device. The memory starts at a base location and is logically +split into rows, the length of each row in memory is refered to as the +stride length. + +The display device may use differing numbers of bits to represent each +pixel, this represented by the bpp value and may be one of 1, 4, 8, +16, 24 or 32. The library assumes packed pixels and does not support +colour depths which do not correspond to the bpp. The 1bpp mode is a +fixed black and white pallette, the 4 and 8 bpp modes use a 16 and 256 +entry pallette respectively and the 16, and 24 bpp modes are direct +indexed RGB modes in 565 and 888 format. The 32bpp mode is RGB in 888 +format with the top byte unused. + +The library may be coupled to several display devices. The available +devices are controlled by compile time configuration. + +Usage +----- + +The library is initialised by calling nsfb_init() with the frontend +type as a parameter. The nsfb_t pointer returned is used in all calls +to the library. The geometry and physical settings may be altered +using the nsfb_set_geometry() and nsfb_set_physical() functions. The +frontend *must* then be initialised. The nsfb_set_geometry() and +nsfb_set_physical() functions may be called at any time, however they +are likely to fail once the frontend has been initialised. + +The nsfb_finalise() function should be called to shut the library down +when finished. + +When directly acessing the framebuffer memory the nsfb_claim() and +nsfb_release() calls should be used. These allow the frontends to +syncronise access and only update the altered regions of the drawing +area. Note the area claimed and released may not neccisarily be the +same. |