Topic       : TOS - The Operating System
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Version     : tos.hyp (December 19, 2008)
Subject     : Programmieren/Atari
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Compiled on : Atari
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View Ref-File13.14.6  Notes for authors of other font-selectors                 TOS

Authors of other font-selectors are invited to have their program join 
the xFSL interface. In principle, every font-selector that uses a TSR 
concept can be furnished with the xFSL interface.

To prevent misunderstandings: The overlay technique and the reentrancy 
as offered by Calvino and HuGo! are not part of the actual interface 
and hence need not be supported by other font-selectors. Indeed the 
interface between the resident part ('shell') and the post-loaded part 
('overlay') is also standardized and therefore can be used by other 
font-selectors as well. A description of this internal interface is 
available on request, see 'Contact addresses'.

Since a number of programs already support the old UFSL interface, it 
seems advisable to make this interface available in new font-selectors 
as well. However a quick look at these programs shows that they call 
the font-selector almost exclusively as a modal dialog. Thus the 
recommendation is to build in minimal UFSL support (as a modal dialog 
only) and instead implement the xFSL interface as widely as possible, 
since one can now expect that just those - now finally standardized - 
extensions will be used by programs rather than the UFSL interface.

A font-selector should offer the following additional features if 
possible:

   . Size changes possible
     In particular this means that not just fixed sizes can be chosen, 
     but with vector fonts inbetween sizes can be set as well.

   . fix31 support
     For some applications the setting of the font size in points is 
     not enough, hence a setting in 1/65536 point should be possible.

   . User-popup
     With an additional popup, the font-selector can be used more 
     flexibly.

   . Drag&Drop support
     Besides the 'traditional' call via the cookie, solutions on the 
     Drag&Drop basis are coming more and more into fashion. If the 
     font-selector already supports Drag&Drop natively, then it can be 
     converted easily with a 'front end' program into a full-blown 
     Drag&Drop selector.

The following conventions were agreed for an xFSL font-selector:

   . If the font-selector has a Closer, then clicking on this will be 
     interpreted as 'Cancel', i.e. xFS_STOP will be returned. If the 
     CC_CLOSER control-flag is set, then the font current at the time 
     will be returned nevertheless (in the PFONTINFO structure in 
     xFSL_PAR).

   . If the extended call (xfsl_init, xfsl_event and xfsl_exit) is not 
     supported, then at least a dummy function for xfsl_init will be 
     installed that always returns -32 (GEMDOS error-message EINVFN, 
     invalid function number).

     But it is urgently requested that the extended call is offered, 
     as this is the one used most frequently.

   . It does not matter if the font-selector only appears as a modal 
     dialog for the extended call. But with a set CC_WINDOW, xfsl_init 
     should then return xFS_NO_WINDOW, so that the caller can adjust 
     himself to this.