[gtksourceview] contextengine: fix first-line-only in presense of BOM

[Christian Hergert <chergert src gnome org>]

commit e46d7a6489fffb7131f8a71cba13edba12adb3c2
Author: Christian Hergert <chergert redhat com>
Date:   Tue Dec 1 10:40:10 2020 -0800

    contextengine: fix first-line-only in presense of BOM
    
    This fixes an issue where we don't correctly highlight the first line with
    a shebang if we found a BOM sequence. We need to check against an offset
    of zero or one depending on the presense of a BOM (which is always a single
    character GtkTextIter in the buffer).
    
    I still see some issues with #168 in that the rest of the file is still
    not highlighted until an incremental change comes in, but at least this
    ensures the first line gets correctly highlighted.
    
    Related #168

 gtksourceview/gtksourcecontextengine.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)
---
diff --git a/gtksourceview/gtksourcecontextengine.c b/gtksourceview/gtksourcecontextengine.c
index 3d739ac8..6ce3a5ad 100644
--- a/gtksourceview/gtksourcecontextengine.c
+++ b/gtksourceview/gtksourcecontextengine.c
@@ -4175,7 +4175,7 @@ ancestor_ends_here (Segment   *state,
  * @line: analyzed line.
  * @line_pos: position inside @line, bytes.
  * @new_state: where to store the new state.
- * @hint: child of @state used to optimize tree operations.
+ * @had_bom: if a BOM was found in the buffer
  *
  * Verifies if a context starts or ends in @line at @line_pos of after it.
  * If the contexts starts or ends here @new_state and @line_pos are updated.
@@ -4187,7 +4187,8 @@ next_segment (GtkSourceContextEngine  *ce,
               Segment                 *state,
               LineInfo                *line,
               gint                    *line_pos,
-              Segment                **new_state)
+              Segment                **new_state,
+              gboolean                 had_bom)
 {
        gint pos = *line_pos;
 
@@ -4242,7 +4243,7 @@ next_segment (GtkSourceContextEngine  *ce,
                        if (!HAS_OPTION (child_def->u.definition, EXTEND_PARENT) && context_end_found)
                                try_this = FALSE;
 
-                       if (HAS_OPTION (child_def->u.definition, FIRST_LINE_ONLY) && line->start_at != 0)
+                       if (HAS_OPTION (child_def->u.definition, FIRST_LINE_ONLY) && line->start_at != 
had_bom)
                                try_this = FALSE;
 
                        if (HAS_OPTION (child_def->u.definition, ONCE_ONLY))
@@ -4419,7 +4420,7 @@ delete_zero_length_segments (GtkSourceContextEngine *ce,
  * @ce: #GtkSourceContextEngine.
  * @state: the state at the beginning of line.
  * @line: the line.
- * @hint: a child of @state around start of line, to make it faster.
+ * @had_bom: if the buffer had a BOM
  *
  * Finds contexts at the line and updates the syntax tree on it.
  *
@@ -4428,7 +4429,8 @@ delete_zero_length_segments (GtkSourceContextEngine *ce,
 static Segment *
 analyze_line (GtkSourceContextEngine *ce,
               Segment                *state,
-              LineInfo               *line)
+              LineInfo               *line,
+              gboolean                had_bom)
 {
        gint line_pos = 0;
        GList *end_segments = NULL;
@@ -4447,7 +4449,7 @@ analyze_line (GtkSourceContextEngine *ce,
        {
                Segment *new_state = NULL;
 
-               if (!next_segment (ce, state, line, &line_pos, &new_state))
+               if (!next_segment (ce, state, line, &line_pos, &new_state, had_bom))
                        break;
 
                if (g_timer_elapsed (timer, NULL) * 1000 > MAX_TIME_FOR_ONE_LINE)
@@ -5312,6 +5314,7 @@ update_syntax (GtkSourceContextEngine *ce,
        gint line_start_offset, line_end_offset;
        gint analyzed_end;
        gboolean first_line = FALSE;
+       gboolean had_bom = FALSE;
        GTimer *timer;
 
        buffer = ce->buffer;
@@ -5371,6 +5374,7 @@ update_syntax (GtkSourceContextEngine *ce,
                c = gtk_text_iter_get_char (&start_iter);
                if (IS_BOM (c))
                {
+                       had_bom = TRUE;
                        gtk_text_iter_forward_char (&start_iter);
                        start_offset = gtk_text_iter_get_offset (&start_iter);
                        segment_remove (ce, invalid);
@@ -5442,7 +5446,7 @@ update_syntax (GtkSourceContextEngine *ce,
                if (ce->hint2 != NULL && ce->hint2->parent != state)
                        ce->hint2 = NULL;
 
-               state = analyze_line (ce, state, &line);
+               state = analyze_line (ce, state, &line, had_bom);
 
                /* At this point analyze_line() could have disabled highlighting */
                if (ce->disabled)
@@ -5529,7 +5533,7 @@ update_syntax (GtkSourceContextEngine *ce,
                        line_end_offset = gtk_text_iter_get_offset (&line_end);
                }
 
-               first_line = (0 == line_start_offset);
+               first_line = start_offset == line_start_offset;
        }
 
        if (analyzed_end == gtk_text_buffer_get_char_count (buffer))