bug#45748: 28.0.50; fit-frame-to-buffer ignores leading spaces

[martin rudalics <rudalics@gmx.at>]

 > The problematic code appears to be here in window-text-pixel-size:
 >
 > else if (EQ (from, Qt))
 >    {
 >      start = BEGV;
 >      bpos = BEGV_BYTE;
 >      while (bpos < ZV_BYTE)
 >        {
 > c = fetch_char_advance (&start, &bpos);
 > if (!(c == ' ' || c == '\t' || c == '\n' || c == '\r'))
 >    break;
 >        }
 >      while (bpos > BEGV_BYTE)
 >        {
 > dec_both (&start, &bpos);
 > c = FETCH_BYTE (bpos);
 > if (!(c == ' ' || c == '\t'))
 >    break;
 >        }
 >    }
 >
 > The second loop looks like it's attempting to backtrack to the
 > beginning of the line, but FETCH_BYTE (bpos) after a dec_both returns
 > the same character that the first loop ended on. In other words, start
 > and bpos are not in sync, or the way that FETCH_BYTE works is
 > different. If I subtract 1 from bpos when calling FETCH_BYTE, it works
 > as expected.

Do you mean the first dec_both skips too much or not enough?  That code
was broken when I wrote it initially, someone fixed the char/byte issue
later and now I'm too silly to understand it.

martin