Re: [hackers] [dmenu|libsl][PATCH] optimize drw_text() for large strings

From: NRK <nrk_AT_disroot.org>
Date: Tue, 22 Mar 2022 01:15:25 +0600

On Mon, Mar 21, 2022 at 07:00:32PM +0600, NRK wrote:
> The only "issue" is that it doesn't render the ellipsis in case font
> changes, but current upstream dmenu doesn't seem to do it either.

OK, I think I have a solution to this. The problem here, as far as I
understand, is this:

Let's say we have a maxwidth of 100, and printing the ellipsis takes 20.
In this case as long as our string is below 80, we're fine; and if it's
above 100 then we should print up to 80 and then print the ellipsis.

The problem case is when we're between 80-100, and we need to change
font. The current code always renders whatever is available when we
change font, so if the text turns out to be bigger than 100 we've
already rendered some of the text into the problem area where the
ellipsis should've been.

The solution I came up with is to simply not render anything if we're at
the problem case, and instead put the problem cases into a queue and
keep going forwards until either:

1) The text overflows, in which case we discard the queue and just print
   the ellipsis instead.
2) Encounter the end of text, which means the text barely fit into our
   maxwidth (this would happen with the prompt); in which case we just
   render the queue and don't print any ellipsis.

I already have a patch that *roughly* does what I described above and
with it applied I don't see any truncation problems anymore.

However the patch is quite messy atm, and in order to do things cleanly
and avoid special casing, I think a good portion of drw_text() will need
to be overhauled to use a queue like this:

        struct { const char *str; int len; Fnt *fnt; } q[32] = {0};

I'm not sure if such overhaul is going to be welcome or not, but if all
of this sounds acceptable then I can proceed with cleaning things up and
supplying the patch.

- NRK
Received on Mon Mar 21 2022 - 20:15:25 CET