emacs-31 b365ef37b9b: Fix pixels-vs-columns confusion in margin face fill (bug#81109)

branch: emacs-31
commit b365ef37b9b4b6810a1b13f0f8aebe7908e00b63
Author: Andrea Alberti <[email protected]>
Commit: Eli Zaretskii <[email protected]>

    Fix pixels-vs-columns confusion in margin face fill (bug#81109)
    
    * src/xdisp.c (extend_face_to_end_of_line): WINDOW_LEFT/RIGHT_MARGIN_WIDTH
    is a pixel value (columns times the frame column width).  Compare the
    margin glyph count against WINDOW_LEFT/RIGHT_MARGIN_COLS instead, and use
    the *_WIDTH value directly for remaining_pixels rather than multiplying it
    by FRAME_COLUMN_WIDTH a second time.  The old code worked on text
    terminals, where the column width is one pixel, but computed wrong widths
    on GUI frames.
---
 src/xdisp.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/src/xdisp.c b/src/xdisp.c
index 2f02d9faa76..a88f7ce830a 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -24463,11 +24463,10 @@ extend_face_to_end_of_line (struct it *it)
 	     to fill the rest.  */
 	  if (WINDOW_LEFT_MARGIN_WIDTH (it->w) > 0
 	      && (it->glyph_row->used[LEFT_MARGIN_AREA]
-		  < WINDOW_LEFT_MARGIN_WIDTH (it->w)))
+		  < WINDOW_LEFT_MARGIN_COLS (it->w)))
 	    {
 	      int used = it->glyph_row->used[LEFT_MARGIN_AREA];
-	      int remaining_pixels = (WINDOW_LEFT_MARGIN_WIDTH (it->w)
-				      * FRAME_COLUMN_WIDTH (f));
+	      int remaining_pixels = WINDOW_LEFT_MARGIN_WIDTH (it->w);
 
 	      /* Subtract width of existing glyphs.  */
 	      struct glyph *g = it->glyph_row->glyphs[LEFT_MARGIN_AREA];
@@ -24502,11 +24501,10 @@ extend_face_to_end_of_line (struct it *it)
 	     to fill the rest.  */
 	  if (WINDOW_RIGHT_MARGIN_WIDTH (it->w) > 0
 	      && (it->glyph_row->used[RIGHT_MARGIN_AREA]
-		  < WINDOW_RIGHT_MARGIN_WIDTH (it->w)))
+		  < WINDOW_RIGHT_MARGIN_COLS (it->w)))
 	    {
 	      int used = it->glyph_row->used[RIGHT_MARGIN_AREA];
-	      int remaining_pixels = (WINDOW_RIGHT_MARGIN_WIDTH (it->w)
-				      * FRAME_COLUMN_WIDTH (f));
+	      int remaining_pixels = WINDOW_RIGHT_MARGIN_WIDTH (it->w);
 
 	      /* Subtract width of existing glyphs.  */
 	      struct glyph *g = it->glyph_row->glyphs[RIGHT_MARGIN_AREA];