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Re: Comments on display.texi

From: Kim F. Storm
Subject: Re: Comments on display.texi
Date: Tue, 28 Sep 2004 14:58:41 +0200
User-agent: Gnus/5.1006 (Gnus v5.10.6) Emacs/21.3.50 (gnu/linux)

Richard Stallman <address@hidden> writes:

>     But even faces have a limit of 21^2-1, so emacs is not without
>     arbitrary limits.
>     So there must be some limit -- which ?  2^32-1 ?
> A limit of 2^21 would be ok, if it is painful to overcome.

Actually, the 2^21 limit on faces is because we want to reduce
memory usage for glyphs.

Each glyph struct contains a face id as well as a number of 1-bit
boolean fields.  There are 11 such 1-bit fields, so to keep these
together with the face id in 32 bits, the face id is 32-11 = 21 bits

Re. number of bitmaps:

I still have problems envisioning anybody using more than a few
bitmaps in any mode (ok, a mode which shows line numbers in 
the fringe would probably use a couple of 100s).

Currently, the only package using bitmaps is gdb-ui -- and it uses
just ONE.

IMO, for 21.4 a limit of 4095 would be more than adequate.

define-fringe-bitmap should signal an error if there are no free
bitmap slots.

There are several places in the code which uses a static allocation
based on the max number of bitmaps.  Of course they can be made
dynamic, but that would be unnecessary, we could agree on a limit of
4095 for 21.4.  WDYT?

Kim F. Storm <address@hidden> http://www.cua.dk

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