Merge branch 'baseline-handling' into 'main'

Handle baselines

See merge request GNOME/pango!589

2 files changed, 181 insertions, 3 deletions

diff --git a/pango/pango-layout.c b/pango/pango-layout.c
index 9167883c..6e4bb357 100644
--- a/pango/pango-layout.c
+++ b/pango/pango-layout.c
@@ -85,6 +85,7 @@
 #include <locale.h>
 
 #include <hb-ot.h>
+#include <hb-glib.h>
 
 #include "pango-layout-private.h"
 #include "pango-attributes-private.h"
@@ -6694,6 +6695,12 @@ apply_baseline_shift (PangoLayoutLine *line,
 {
   int y_offset = 0;
   PangoItem *prev = NULL;
+  hb_position_t baseline_adjustment = 0;
+#if HB_VERSION_ATLEAST(4,0,0)
+  hb_ot_layout_baseline_tag_t baseline_tag = 0;
+  hb_position_t baseline;
+  hb_position_t run_baseline;
+#endif
 
   for (GSList *l = line->runs; l; l = l->next)
     {
@@ -6701,16 +6708,71 @@ apply_baseline_shift (PangoLayoutLine *line,
       PangoItem *item = run->item;
       int start_x_offset, end_x_offset;
       int start_y_offset, end_y_offset;
+#if HB_VERSION_ATLEAST(4,0,0)
+      hb_font_t *hb_font;
+      hb_script_t script;
+      hb_language_t language;
+      hb_direction_t direction;
+      hb_tag_t script_tags[HB_OT_MAX_TAGS_PER_SCRIPT];
+      hb_tag_t lang_tags[HB_OT_MAX_TAGS_PER_LANGUAGE];
+      unsigned int script_count = HB_OT_MAX_TAGS_PER_SCRIPT;
+      unsigned int lang_count = HB_OT_MAX_TAGS_PER_LANGUAGE;
+
+      hb_font = pango_font_get_hb_font (item->analysis.font);
+
+      script = hb_glib_script_to_script (item->analysis.script);
+      language = hb_language_from_string (pango_language_to_string (item->analysis.language), -1);
+      hb_ot_tags_from_script_and_language (script, language,
+                                           &script_count, script_tags,
+                                           &lang_count, lang_tags);
+
+      if (item->analysis.flags & PANGO_ANALYSIS_FLAG_CENTERED_BASELINE)
+        direction = HB_DIRECTION_TTB;
+      else
+        direction = HB_DIRECTION_LTR;
+
+      if (baseline_tag == 0)
+        {
+          if (item->analysis.flags & PANGO_ANALYSIS_FLAG_CENTERED_BASELINE)
+            baseline_tag = HB_OT_LAYOUT_BASELINE_TAG_IDEO_EMBOX_CENTRAL;
+          else
+            baseline_tag = hb_ot_layout_get_horizontal_baseline_tag_for_script (script);
+          hb_ot_layout_get_baseline_with_fallback (hb_font,
+                                                   baseline_tag,
+                                                   direction,
+                                                   script_tags[script_count - 1],
+                                                   lang_count ? lang_tags[lang_count - 1] : HB_TAG_NONE,
+                                                   &run_baseline);
+          baseline = run_baseline;
+        }
+      else
+        {
+          hb_ot_layout_get_baseline_with_fallback (hb_font,
+                                                   baseline_tag,
+                                                   direction,
+                                                   script_tags[script_count - 1],
+                                                   lang_count ? lang_tags[lang_count - 1] : HB_TAG_NONE,
+                                                   &run_baseline);
+        }
+
+      /* Don't do baseline adjustment in vertical, since the renderer
+       * is still doing its own baseline shifting there
+       */
+      if (item->analysis.flags & PANGO_ANALYSIS_FLAG_CENTERED_BASELINE)
+        baseline_adjustment = 0;
+      else
+        baseline_adjustment = baseline - run_baseline;
+#endif
 
       collect_baseline_shift (state, item, prev, &start_x_offset, &start_y_offset, &end_x_offset, &end_y_offset);
 
-      y_offset += start_y_offset;
+      y_offset += start_y_offset + baseline_adjustment;
 
       run->y_offset = y_offset;
       run->start_x_offset = start_x_offset;
       run->end_x_offset = end_x_offset;
 
-      y_offset += end_y_offset;
+      y_offset += end_y_offset - baseline_adjustment;
 
       prev = item;
     }
diff --git a/utils/viewer-pangocairo.c b/utils/viewer-pangocairo.c
index 8fe9db59..2cfe2cee 100644
--- a/utils/viewer-pangocairo.c
+++ b/utils/viewer-pangocairo.c
@@ -26,6 +26,9 @@
 
 #include <pango/pangocairo.h>
 
+#include <hb-ot.h>
+#include <hb-glib.h>
+
 static int opt_annotate = 0;
 
 typedef struct
@@ -158,7 +161,8 @@ enum {
   ANNOTATE_GLYPH_EXTENTS     =  256,
   ANNOTATE_CARET_POSITIONS   =  512,
   ANNOTATE_CARET_SLOPE       = 1024,
-  ANNOTATE_LAST              = 2048,
+  ANNOTATE_RUN_BASELINES     = 2048,
+  ANNOTATE_LAST              = 4096,
 };
 
 static struct {
@@ -169,6 +173,7 @@ static struct {
   { ANNOTATE_GRAVITY_ROOF,      "gravity-roof",      "gravity" },
   { ANNOTATE_BLOCK_PROGRESSION, "block-progression", "progression" },
   { ANNOTATE_BASELINES,         "baselines",         "baselines" },
+  { ANNOTATE_RUN_BASELINES,     "run-baselines",     "run-baselines" },
   { ANNOTATE_LAYOUT_EXTENTS,    "layout-extents",    "layout" },
   { ANNOTATE_LINE_EXTENTS,      "line-extents",      "line" },
   { ANNOTATE_RUN_EXTENTS,       "run-extents",       "run" },
@@ -308,6 +313,117 @@ render_callback (PangoLayout *layout,
           cairo_restore (cr);
         }
 
+#if HB_VERSION_ATLEAST(4,0,0)
+      if (annotate & ANNOTATE_RUN_BASELINES)
+        {
+          hb_ot_layout_baseline_tag_t baseline_tag = 0;
+          /* draw baselines for runs in blue */
+          cairo_save (cr);
+          cairo_set_source_rgba (cr, 0.0, 0.0, 1.0, 0.5);
+
+          iter = pango_layout_get_iter (layout);
+          do
+            {
+              PangoLayoutRun *run;
+              PangoRectangle rect;
+              hb_font_t *hb_font;
+              hb_ot_layout_baseline_tag_t baselines[] = {
+                HB_OT_LAYOUT_BASELINE_TAG_ROMAN,
+                HB_OT_LAYOUT_BASELINE_TAG_HANGING,
+                HB_OT_LAYOUT_BASELINE_TAG_IDEO_FACE_BOTTOM_OR_LEFT,
+                HB_OT_LAYOUT_BASELINE_TAG_IDEO_FACE_TOP_OR_RIGHT,
+                HB_OT_LAYOUT_BASELINE_TAG_IDEO_EMBOX_BOTTOM_OR_LEFT,
+                HB_OT_LAYOUT_BASELINE_TAG_IDEO_EMBOX_CENTRAL,
+                HB_OT_LAYOUT_BASELINE_TAG_IDEO_EMBOX_TOP_OR_RIGHT,
+                HB_OT_LAYOUT_BASELINE_TAG_MATH
+              };
+              hb_direction_t dir;
+              hb_tag_t script, lang;
+              hb_position_t coord;
+
+              run = pango_layout_iter_get_run (iter);
+              if (!run)
+                {
+                  baseline_tag = 0;
+                  continue;
+                }
+
+              if (baseline_tag == 0)
+                {
+                  hb_script_t script = hb_glib_script_to_script (run->item->analysis.script);
+
+                  if (run->item->analysis.flags & PANGO_ANALYSIS_FLAG_CENTERED_BASELINE)
+                    baseline_tag = HB_OT_LAYOUT_BASELINE_TAG_IDEO_EMBOX_CENTRAL;
+                  else
+                    baseline_tag = hb_ot_layout_get_horizontal_baseline_tag_for_script (script);
+                }
+
+              y = pango_layout_iter_get_run_baseline (iter);
+              pango_layout_iter_get_run_extents (iter, NULL, &rect);
+
+              hb_font = pango_font_get_hb_font (run->item->analysis.font);
+              if (run->item->analysis.flags & PANGO_ANALYSIS_FLAG_CENTERED_BASELINE)
+                dir = HB_DIRECTION_TTB;
+              else
+                dir = HB_DIRECTION_LTR;
+              script = hb_glib_script_to_script (run->item->analysis.script);
+              lang = HB_TAG_NONE;
+
+              for (int i = 0; i < G_N_ELEMENTS (baselines); i++)
+                {
+                  char buf[5] = { 0, };
+
+                  cairo_save (cr);
+
+                  if (baselines[i] == baseline_tag)
+                    cairo_set_source_rgba (cr, 1.0, 0.0, 0.0, 0.5);
+                  else
+                    cairo_set_source_rgba (cr, 0.0, 0.0, 1.0, 0.5);
+
+                  if (hb_ot_layout_get_baseline (hb_font,
+                                                 baselines[i],
+                                                 dir,
+                                                 script,
+                                                 lang,
+                                                 &coord))
+                    cairo_set_dash (cr, NULL, 0, 0);
+                  else
+                    {
+                      double dashes[] = { 4 * lw, 4 * lw };
+
+                      hb_ot_layout_get_baseline_with_fallback (hb_font,
+                                                               baselines[i],
+                                                               dir,
+                                                               script,
+                                                               lang,
+                                                               &coord);
+
+                      cairo_set_dash (cr, dashes, 2, 0);
+                      cairo_set_line_cap (cr, CAIRO_LINE_CAP_SQUARE);
+                    }
+                  cairo_move_to (cr,
+                                 (double)rect.x / PANGO_SCALE,
+                                 (double)(y - coord) / PANGO_SCALE);
+                  cairo_rel_line_to (cr, (double)rect.width / PANGO_SCALE, 0);
+                  cairo_stroke (cr);
+                  cairo_set_source_rgb (cr, 0, 0, 0);
+                  cairo_move_to (cr,
+                                 (double)rect.x / PANGO_SCALE - 5,
+                                 (double)(y - coord) / PANGO_SCALE - 5);
+                  hb_tag_to_string (baselines[i], buf);
+                  if (baselines[i] == baseline_tag)
+                    g_print ("dominant %s\n", buf);
+                  cairo_show_text (cr, buf);
+
+                  cairo_restore (cr);
+                }
+            }
+          while (pango_layout_iter_next_run (iter));
+          pango_layout_iter_free (iter);
+          cairo_restore (cr);
+        }
+#endif
+
       if (annotate & ANNOTATE_LAYOUT_EXTENTS)
         {
           /* draw the logical rect in red */