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

[Aaron Jensen]

On Sat, Jan 9, 2021 at 11:07 AM martin rudalics <rudalics@gmx.at> wrote:
> 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.

It doesn't skip enough. I believe this fixes both the leading and
trailing space problems:

diff --git a/src/xdisp.c b/src/xdisp.c
index 6a4304d194..20e7ca3a1e 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -10652,7 +10652,10 @@ DEFUN ("window-text-pixel-size",
Fwindow_text_pixel_size, Swindow_text_pixel_siz
  {
    c = fetch_char_advance (&start, &bpos);
    if (!(c == ' ' || c == '\t' || c == '\n' || c == '\r'))
-     break;
+            {
+              dec_both (&start, &bpos);
+       break;
+            }
  }
       while (bpos > BEGV_BYTE)
  {
@@ -10680,12 +10683,17 @@ DEFUN ("window-text-pixel-size",
Fwindow_text_pixel_size, Swindow_text_pixel_siz
  {
    dec_both (&end, &bpos);
    c = FETCH_BYTE (bpos);
    if (!(c == ' ' || c == '\t' || c == '\n' || c == '\r'))
-     break;
+            {
+              inc_both (&end, &bpos);
+       break;
+            }
  }
       while (bpos < ZV_BYTE)
  {
    c = fetch_char_advance (&end, &bpos);
    if (!(c == ' ' || c == '\t'))
      break;
  }

The problem is that the first loop leaves the pointer pointing to the
next character and it's only back tracked once.