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(gpm.info)Concepts

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Concepts
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   The high-level library is completely independent of the low-level
one, so it uses `gpm_handler' and `gpm_data' as connection point with
`Gpm_Getc()'.

   All the functionality is based on the concept of RoI's. each RoI is
described by a `Gpm_Roi' structure, which is made up by the following
fields:

`short xMin, xMax'
     These numbers identify the upper-left corner of the region.  When
     events are reported to the region, the event coordinate will be
     relative to this position (zero-based).

`short yMin, yMax'
     These numbers identify the lower-right corner of the region.

`unsigned short minMod, maxMod'
     These modifier masks have the same role within the application as
     the same fields have in inter-application multiplexing.

`unsigned short eventMask'
     It is the mask of events which are to be reported to the current
     region.

`unsigned short owned'
     This is a bit, used to know if the region is owned by the library
     or the application, in order to issue `free(0' when needed.

`Gpm_Handler *handler'
     The function to be called when events are to be reported to the
     current region.

`void *clientdata'
     The clientdata to be passed to the handler

`Gpm_Roi *next, *prev'
     Links to the RoI chain.