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Re: 3d highlights on dark colors

From: Miles Bader
Subject: Re: 3d highlights on dark colors
Date: Mon, 6 Nov 2000 21:56:34 +0900 (JST)

Eli Zaretskii <address@hidden> writes:
>   - pow is an expensive function; isn't there a way to avoid it?

Good point (although in the most common case, where there's only a
single 3d face in a window [e.g., the mode-line], it caches the GC).

I did some simple timings, and I measured (on a pentium 133):

   pow (1.2, 0.5)       -- 4.1 usec / call
   sqrt (1.2)           -- 1.5 usec / call

Since the best `boost' factor I could find is 0.5 anyway, it would be
acceptable, I think, to hard-wire it in and use sqrt instead, given that
it's 1/3 the cost.

I should also mention that everytime this code gets invoked, a shitload
of other expensive stuff happens too --

  * At least one call to XAllocColor == server round-trip
  * A call to an X GC-frobbing function == slow
  * If the frame has a `screen-gamma' parameter, *3* calls to `pow'

...so a single call to pow/sqrt may be simply noise.


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