[pango/line-breaking-fixes: 8/12] Improve the BREAK_ALL_FIT case

[Matthias Clasen <matthiasc src gnome org>]

commit 5de5c03385d2c4d3445c268e416ac6cd760a2015
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri Nov 12 21:00:37 2021 -0500

    Improve the BREAK_ALL_FIT case
    
    We always need to check if we still fit, after shaping.
    The width we use before is just an estimate.

 pango/pango-layout.c | 39 ++++++++++++++++++++++++++++++---------
 1 file changed, 30 insertions(+), 9 deletions(-)
---
diff --git a/pango/pango-layout.c b/pango/pango-layout.c
index 5cdaa531..13e974d2 100644
--- a/pango/pango-layout.c
+++ b/pango/pango-layout.c
@@ -3872,13 +3872,24 @@ process_item (PangoLayout     *layout,
   if ((width <= state->remaining_width || (item->num_chars == 1 && !line->runs)) &&
       !no_break_at_end)
     {
-      state->remaining_width -= width;
-      state->remaining_width = MAX (state->remaining_width, 0);
-      insert_run (line, state, item, TRUE);
+      insert_run (line, state, item, FALSE);
+      width = pango_glyph_string_get_width (((PangoGlyphItem *)(line->runs->data))->glyphs);
 
-      return BREAK_ALL_FIT;
+      if (width <= state->remaining_width || (item->num_chars == 1 && !line->runs))
+        {
+          state->remaining_width -= width;
+          state->remaining_width = MAX (state->remaining_width, 0);
+
+          pango_glyph_string_free (state->glyphs);
+          state->glyphs = NULL;
+
+          return BREAK_ALL_FIT;
+        }
+
+      /* if it doesn't fit after shaping, revert and proceed to break the item */
+      uninsert_run (line);
     }
-  else
+
     {
       int num_chars = item->num_chars;
       int break_num_chars = num_chars;
@@ -3918,11 +3929,21 @@ process_item (PangoLayout     *layout,
           /* check one more time if the whole item fits after removing the space */
           if (width + break_extra_width <= state->remaining_width && !no_break_at_end)
             {
-              state->remaining_width -= width + break_extra_width;
-              state->remaining_width = MAX (state->remaining_width, 0);
-              insert_run (line, state, item, TRUE);
+              insert_run (line, state, item, FALSE);
+              width = pango_glyph_string_get_width (((PangoGlyphItem *)(line->runs->data))->glyphs);
 
-              return BREAK_ALL_FIT;
+              if (width + break_extra_width <= state->remaining_width)
+                {
+                  state->remaining_width -= width + break_extra_width;
+                  state->remaining_width = MAX (state->remaining_width, 0);
+
+                  pango_glyph_string_free (state->glyphs);
+                  state->glyphs = NULL;
+
+                  return BREAK_ALL_FIT;
+                }
+
+              uninsert_run (line);
             }
         }