Merge branch 'ligature-caret-rtl-fixes' into 'main'

Some fixes for ligature caret positioning in rtl

See merge request GNOME/pango!445

4 files changed, 114 insertions, 28 deletions

diff --git a/pango/glyphstring.c b/pango/glyphstring.c
index 8d4aa604..30d68220 100644
--- a/pango/glyphstring.c
+++ b/pango/glyphstring.c
@@ -520,25 +520,60 @@ pango_glyph_string_index_to_x (PangoGlyphString *glyphs,
    * with an m-n situation, where LigatureCaretList is
    * not going to help. Just give up and do the simple thing.
    */
-  if (cluster_offset > 0 && cluster_offset < cluster_chars &&
-      start_glyph_pos == end_glyph_pos)
+  if (cluster_offset > 0 && cluster_offset < cluster_chars)
     {
       hb_font_t *hb_font;
       hb_position_t caret;
       unsigned int caret_count = 1;
+      int glyph_pos;
 
       hb_font = pango_font_get_hb_font (analysis->font);
+
+      if (start_glyph_pos == end_glyph_pos)
+        glyph_pos = start_glyph_pos;
+      else
+        {
+          hb_face_t *hb_face;
+
+          hb_face = hb_font_get_face (hb_font);
+
+          glyph_pos = -1;
+          for (i = start_glyph_pos; i <= end_glyph_pos; i++)
+            {
+              if (hb_ot_layout_get_glyph_class (hb_face, glyphs->glyphs[i].glyph) != HB_OT_LAYOUT_GLYPH_CLASS_MARK)
+                {
+                  if (glyph_pos != -1)
+                    {
+                      /* multiple non-mark glyphs in cluster, giving up */
+                      goto fallback;
+                    }
+                  glyph_pos = i;
+                }
+            }
+          if (glyph_pos == -1)
+            {
+              /* no non-mark glyph in a multi-glyph cluster, giving up */
+              goto fallback;
+            }
+        }
+
       hb_ot_layout_get_ligature_carets (hb_font,
                                         (analysis->level % 2) ? HB_DIRECTION_RTL : HB_DIRECTION_LTR,
-                                        glyphs->glyphs[start_glyph_pos].glyph,
+                                        glyphs->glyphs[glyph_pos].glyph,
                                         cluster_offset - 1, &caret_count, &caret);
       if (caret_count > 0)
         {
-          *x_pos = start_xpos + caret;
+          if (analysis->level % 2) /* Right to left */
+            *x_pos = end_xpos + caret;
+          else
+            *x_pos = start_xpos + caret;
+          *x_pos += glyphs->glyphs[glyph_pos].geometry.x_offset;
           return;
         }
     }
 
+fallback:
+
   *x_pos = ((cluster_chars - cluster_offset) * start_xpos +
             cluster_offset * end_xpos) / cluster_chars;
 }
diff --git a/pango/pango-glyph.h b/pango/pango-glyph.h
index 4dc77fd1..2094fa53 100644
--- a/pango/pango-glyph.h
+++ b/pango/pango-glyph.h
@@ -58,6 +58,19 @@ typedef gint32 PangoGlyphUnit;
  *
  * The `PangoGlyphGeometry` structure contains width and positioning
  * information for a single glyph.
+ *
+ * Note that @width is not guaranteed to be the same as the glyph
+ * extents. Kerning and other positioning applied during shaping will
+ * affect both the @width and the @x_offset for the glyphs in the
+ * glyph string that results from shaping.
+ *
+ * The information in this struct is intended for rendering the glyphs,
+ * as follows:
+ *
+ * 1. Render the current glyph at (x + x_offset, y + y_offset),
+ *    where (x, y) is the current point
+ * 2. Advance the current point to (x + xoffset, y)
+ * 3. Render the next glyph...
  */
 struct _PangoGlyphGeometry
 {
diff --git a/tests/test-shape.c b/tests/test-shape.c
index 2b78e96a..674c6cc9 100644
--- a/tests/test-shape.c
+++ b/tests/test-shape.c
@@ -34,6 +34,8 @@
 
 static PangoContext *context;
 
+gboolean opt_hex_chars;
+
 static void
 append_text (GString    *s,
              const char *text,
@@ -46,7 +48,9 @@ append_text (GString    *s,
       gunichar ch = g_utf8_get_char (p);
       if (ch == ' ')
         g_string_append (s, "[ ]");
-      if (ch == 0x0A || ch == 0x2028 || !g_unichar_isprint (ch))
+      else if (opt_hex_chars)
+        g_string_append_printf (s, "[%#04x]", ch);
+      else if (ch == 0x0A || ch == 0x2028 || !g_unichar_isprint (ch))
         g_string_append_printf (s, "[%#04x]", ch);
       else
         g_string_append_unichar (s, ch);
@@ -214,6 +218,18 @@ test_file (const gchar *filename, GString *string)
           int len;
           PangoGlyphInfo *gi = &glyphs->glyphs[i];
 
+
+          if (gi->attr.is_cluster_start && i > 0)
+            {
+              g_string_append (s1, " ");
+              g_string_append (s2, "|");
+              g_string_append (s3, "|");
+              g_string_append (s4, "|");
+              g_string_append (s5, " ");
+              g_string_append (s6, " ");
+              g_string_append (s7, "|");
+            }
+
           char *p;
           p = text + item->offset + glyphs->log_clusters[i];
           if (rtl)
@@ -254,17 +270,6 @@ test_file (const gchar *filename, GString *string)
           g_string_append_printf (s5, "%*s", len - (int)g_utf8_strlen (s5->str, s5->len), "");
           g_string_append_printf (s6, "%*s", len - (int)g_utf8_strlen (s6->str, s6->len), "");
           g_string_append_printf (s7, "%*s", len - (int)g_utf8_strlen (s7->str, s7->len), "");
-
-          if (gi->attr.is_cluster_start && i + 1 < glyphs->num_glyphs)
-            {
-              g_string_append (s1, " ");
-              g_string_append (s2, "|");
-              g_string_append (s3, "|");
-              g_string_append (s4, "|");
-              g_string_append (s5, " ");
-              g_string_append (s6, " ");
-              g_string_append (s7, "|");
-            }
         }
 
       pango_glyph_string_free (glyphs);
@@ -347,6 +352,21 @@ main (int argc, char *argv[])
   GError *error = NULL;
   const gchar *name;
   gchar *path;
+  GOptionContext *option_context;
+  GOptionEntry entries[] = {
+    { "hex-chars", '0', 0, G_OPTION_ARG_NONE, &opt_hex_chars, "Print all chars in hex", NULL },
+    { NULL, 0 },
+  };
+
+  option_context = g_option_context_new ("");
+  g_option_context_add_main_entries (option_context, entries, NULL);
+  g_option_context_set_ignore_unknown_options (option_context, TRUE);
+  if (!g_option_context_parse (option_context, &argc, &argv, &error))
+    {
+      g_error ("failed to parse options: %s", error->message);
+      return 1;
+    }
+  g_option_context_free (option_context);
 
   setlocale (LC_ALL, "");
 
diff --git a/utils/viewer-pangocairo.c b/utils/viewer-pangocairo.c
index af4925e3..4b27c7e5 100644
--- a/utils/viewer-pangocairo.c
+++ b/utils/viewer-pangocairo.c
@@ -409,10 +409,16 @@ render_callback (PangoLayout *layout,
 
       if (annotate & ANNOTATE_CARET_POSITIONS)
         {
+          const PangoLogAttr *attrs;
+          int n_attrs;
+          int offset;
+
           /* draw the caret positions in purple */
           cairo_save (cr);
           cairo_set_source_rgba (cr, 1.0, 0.0, 1.0, 0.5);
 
+          attrs = pango_layout_get_log_attrs_readonly (layout, &n_attrs);
+
           iter = pango_layout_get_iter (layout);
           do
             {
@@ -431,24 +437,36 @@ render_callback (PangoLayout *layout,
               text = pango_layout_get_text (layout);
               start = text + run->item->offset;
 
+              offset = g_utf8_strlen (text, start - text);
+
               y = pango_layout_iter_get_baseline (iter);
 
               trailing = FALSE;
               p = start;
               for (int i = 0; i <= run->item->num_chars; i++)
                 {
-                  pango_glyph_string_index_to_x (run->glyphs,
-                                                 text + run->item->offset,
-                                                 run->item->length,
-                                                 &run->item->analysis,
-                                                 p - start,
-                                                 trailing,
-                                                 &x);
-                  x += rect.x;
-
-                  cairo_arc (cr, x / PANGO_SCALE, y / PANGO_SCALE, 3.0, 0, 2*G_PI);
-                  cairo_close_path (cr);
-                  cairo_fill (cr);
+                  if (attrs[offset + i].is_cursor_position)
+                    {
+                      pango_glyph_string_index_to_x (run->glyphs,
+                                                     text + run->item->offset,
+                                                     run->item->length,
+                                                     &run->item->analysis,
+                                                     p - start,
+                                                     trailing,
+                                                     &x);
+                      x += rect.x;
+
+                      cairo_set_source_rgba (cr, 1.0, 0.0, 1.0, 0.5);
+                      cairo_arc (cr, x / PANGO_SCALE, y / PANGO_SCALE, 3.0, 0, 2*G_PI);
+                      cairo_close_path (cr);
+                      cairo_fill (cr);
+
+                      char *s = g_strdup_printf ("%d", i + trailing);
+                      cairo_set_source_rgb (cr, 0, 0, 0);
+                      cairo_move_to (cr, x / PANGO_SCALE - 5, y / PANGO_SCALE + 15);
+                      cairo_show_text (cr, s);
+                      g_free (s);
+                   }
 
                   if (i < run->item->num_chars)
                     p = g_utf8_next_char (p);