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