[pango/visible-things: 83/87] Apply show space, invisible and LS attributes

[Matthias Clasen <matthiasc src gnome org>]

commit 852e307c2b8f5a5d2e59e112b90fb77cc3d42fd6
Author: Matthias Clasen <mclasen redhat com>
Date:   Sun Jul 7 14:00:36 2019 -0400

    Apply show space, invisible and LS attributes
    
    For this, we need to pull the attributes out
    and pass them on to the harfbuzz font funcs,
    so we can select different glyphs.

 pango/pangofc-shape.c | 273 +++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 270 insertions(+), 3 deletions(-)
---
diff --git a/pango/pangofc-shape.c b/pango/pangofc-shape.c
index 86b620a2..fce3fcea 100644
--- a/pango/pangofc-shape.c
+++ b/pango/pangofc-shape.c
@@ -113,6 +113,263 @@ apply_extra_attributes (GSList       *attrs,
     }
 }
 
+typedef struct
+{
+  PangoFont *font;
+  hb_font_t *parent;
+  gboolean show_space;
+  gboolean show_ignorables;
+  gboolean show_line_separators;
+} PangoHbShapeContext;
+
+static hb_bool_t
+pango_hb_font_get_nominal_glyph (hb_font_t      *font,
+                                 void           *font_data,
+                                 hb_codepoint_t  unicode,
+                                 hb_codepoint_t *glyph,
+                                 void           *user_data G_GNUC_UNUSED)
+{
+  PangoHbShapeContext *context = (PangoHbShapeContext *) font_data;
+
+  if (context->show_ignorables)
+    {
+      if (pango_get_ignorable (unicode))
+        {
+          *glyph = PANGO_GET_UNKNOWN_GLYPH (unicode);
+          return TRUE;
+        }
+    }
+
+  if (context->show_space)
+    {
+      if (g_unichar_type (unicode) == G_UNICODE_SPACE_SEPARATOR)
+        {
+          /* Replace 0x20 by visible space, since we
+           * don't draw a hex box for 0x20
+           */
+          if (unicode == 0x20)
+            *glyph = PANGO_GET_UNKNOWN_GLYPH (0x2423);
+          else
+            *glyph = PANGO_GET_UNKNOWN_GLYPH (unicode);
+          return TRUE;
+        }
+    }
+
+  if (context->show_line_separators)
+    {
+      if (unicode == 0x2028)
+        {
+          /* Always mark LS as unknown. If it ends up
+           * at the line end, PangoLayout takes care of
+           * hiding them, and if they end up in the middle
+           * of a line, we are in single paragraph mode
+           * and want to show the LS
+           */
+          *glyph = PANGO_GET_UNKNOWN_GLYPH (unicode);
+          return TRUE;
+        }
+    }
+
+  if (hb_font_get_glyph (context->parent, unicode, 0, glyph))
+    return TRUE;
+
+  *glyph = PANGO_GET_UNKNOWN_GLYPH (unicode);
+
+  /* We draw our own invalid-Unicode shape, so prevent HarfBuzz
+   * from using REPLACEMENT CHARACTER. */
+  if (unicode > 0x10FFFF)
+    return TRUE;
+
+  return FALSE;
+}
+
+static hb_bool_t
+pango_hb_font_get_variation_glyph (hb_font_t      *font,
+                                   void           *font_data,
+                                   hb_codepoint_t  unicode,
+                                   hb_codepoint_t  variation_selector,
+                                   hb_codepoint_t *glyph,
+                                   void           *user_data G_GNUC_UNUSED)
+{
+  PangoHbShapeContext *context = (PangoHbShapeContext *) font_data;
+
+  if (hb_font_get_glyph (context->parent,
+                         unicode, variation_selector, glyph))
+    return TRUE;
+
+  return FALSE;
+}
+
+static hb_bool_t
+pango_hb_font_get_glyph_contour_point (hb_font_t      *font,
+                                       void           *font_data,
+                                       hb_codepoint_t  glyph,
+                                       unsigned int    point_index,
+                                       hb_position_t  *x,
+                                       hb_position_t  *y,
+                                       void           *user_data G_GNUC_UNUSED)
+{
+  PangoHbShapeContext *context = (PangoHbShapeContext *) font_data;
+
+  return hb_font_get_glyph_contour_point (context->parent, glyph, point_index, x, y);
+}
+
+static hb_position_t
+pango_hb_font_get_glyph_advance (hb_font_t      *font,
+                                 void           *font_data,
+                                 hb_codepoint_t  glyph,
+                                 void           *user_data G_GNUC_UNUSED)
+{
+  PangoHbShapeContext *context = (PangoHbShapeContext *) font_data;
+
+  if (glyph & PANGO_GLYPH_UNKNOWN_FLAG)
+    {
+      PangoRectangle logical;
+
+      pango_font_get_glyph_extents (context->font, glyph, NULL, &logical);
+      return logical.width;
+    }
+
+  return hb_font_get_glyph_h_advance (context->parent, glyph);
+}
+
+static hb_bool_t
+pango_hb_font_get_glyph_extents (hb_font_t          *font,
+                                 void               *font_data,
+                                 hb_codepoint_t      glyph,
+                                 hb_glyph_extents_t *extents,
+                                 void               *user_data G_GNUC_UNUSED)
+{
+  PangoHbShapeContext *context = (PangoHbShapeContext *) font_data;
+
+  if (glyph & PANGO_GLYPH_UNKNOWN_FLAG)
+    {
+      PangoRectangle ink;
+
+      pango_font_get_glyph_extents (context->font, glyph, &ink, NULL);
+
+      extents->x_bearing = ink.x;
+      extents->y_bearing = ink.y;
+      extents->width     = ink.width;
+      extents->height    = ink.height;
+
+      return TRUE;
+    }
+
+  return hb_font_get_glyph_extents (context->parent, glyph, extents);
+}
+
+static hb_bool_t
+pango_hb_font_get_glyph_h_origin (hb_font_t      *font,
+                                  void           *font_data,
+                                  hb_codepoint_t  glyph,
+                                  hb_position_t  *x,
+                                  hb_position_t  *y,
+                                  void           *user_data G_GNUC_UNUSED)
+{
+  PangoHbShapeContext *context = (PangoHbShapeContext *) font_data;
+
+  return hb_font_get_glyph_h_origin (context->parent, glyph, x, y);
+}
+
+static hb_bool_t
+pango_hb_font_get_glyph_v_origin (hb_font_t      *font,
+                                  void           *font_data,
+                                  hb_codepoint_t  glyph,
+                                  hb_position_t  *x,
+                                  hb_position_t  *y,
+void *user_data G_GNUC_UNUSED)
+{
+  PangoHbShapeContext *context = (PangoHbShapeContext *) font_data;
+
+  return hb_font_get_glyph_v_origin (context->parent, glyph, x, y);
+}
+
+static hb_position_t
+pango_hb_font_get_h_kerning (hb_font_t      *font,
+                             void           *font_data,
+                             hb_codepoint_t  left_glyph,
+                             hb_codepoint_t  right_glyph,
+                             void           *user_data G_GNUC_UNUSED)
+{
+  PangoHbShapeContext *context = (PangoHbShapeContext *) font_data;
+
+  return hb_font_get_glyph_h_kerning (context->parent, left_glyph, right_glyph);
+}
+
+static hb_font_t *
+pango_font_get_hb_font_for_context (PangoFont           *font,
+                                    PangoHbShapeContext *context)
+{
+  hb_font_t *hb_font;
+  static hb_font_funcs_t *funcs;
+
+  hb_font = pango_font_get_hb_font (font);
+  if (!context->show_ignorables &&
+      !context->show_space &&
+      !context->show_line_separators)
+    return hb_font_reference (hb_font);
+
+  if (G_UNLIKELY (!funcs))
+    {
+      funcs = hb_font_funcs_create ();
+      hb_font_funcs_set_nominal_glyph_func (funcs, pango_hb_font_get_nominal_glyph, NULL, NULL);
+      hb_font_funcs_set_variation_glyph_func (funcs, pango_hb_font_get_variation_glyph, NULL, NULL);
+      hb_font_funcs_set_glyph_h_advance_func (funcs, pango_hb_font_get_glyph_advance, NULL, NULL);
+      hb_font_funcs_set_glyph_v_advance_func (funcs, pango_hb_font_get_glyph_advance, NULL, NULL);
+      hb_font_funcs_set_glyph_h_origin_func (funcs, pango_hb_font_get_glyph_h_origin, NULL, NULL);
+      hb_font_funcs_set_glyph_v_origin_func (funcs, pango_hb_font_get_glyph_v_origin, NULL, NULL);
+      hb_font_funcs_set_glyph_h_kerning_func (funcs, pango_hb_font_get_h_kerning, NULL, NULL);
+      hb_font_funcs_set_glyph_extents_func (funcs, pango_hb_font_get_glyph_extents, NULL, NULL);
+      hb_font_funcs_set_glyph_contour_point_func (funcs, pango_hb_font_get_glyph_contour_point, NULL, NULL);
+  }
+
+  context->font = font;
+  context->parent = hb_font;
+
+  hb_font = hb_font_create_sub_font (hb_font);
+  hb_font_set_funcs (hb_font, funcs, context, NULL);
+
+  return hb_font;
+}
+
+static void
+find_shape_flags (const PangoAnalysis *analysis,
+                  PangoHbShapeContext *context)
+{
+  GSList *l;
+  gboolean seen_space = FALSE;
+  gboolean seen_ignorables = FALSE;
+  gboolean seen_line_separators = FALSE;
+
+  context->show_space = FALSE;
+  context->show_ignorables = FALSE;
+  context->show_line_separators = FALSE;
+
+  for (l = analysis->extra_attrs; l; l = l->next)
+    {
+      PangoAttribute *attr = l->data;
+
+      if (attr->klass->type == PANGO_ATTR_SHOW_SPACE)
+        {
+          context->show_space = ((PangoAttrInt*)attr)->value != 0;
+          seen_space = TRUE;
+        }
+      else if (attr->klass->type == PANGO_ATTR_SHOW_IGNORABLES)
+        {
+          context->show_ignorables = ((PangoAttrInt*)attr)->value != 0;
+          seen_ignorables = TRUE;
+        }
+      else if (attr->klass->type == PANGO_ATTR_SHOW_LINE_SEPARATORS)
+        {
+          context->show_line_separators = ((PangoAttrInt*)attr)->value != 0;
+          seen_line_separators = TRUE;
+        }
+      if (seen_space && seen_ignorables && seen_line_separators)
+        break;
+    }
+}
+
 void
 pango_hb_shape (PangoFont           *font,
                 const char          *item_text,
@@ -122,8 +379,10 @@ pango_hb_shape (PangoFont           *font,
                 const char          *paragraph_text,
                 unsigned int         paragraph_length)
 {
+  PangoHbShapeContext context;
   hb_font_t *hb_font;
   hb_buffer_t *hb_buffer;
+  hb_buffer_flags_t hb_buffer_flags;
   hb_direction_t hb_direction;
   gboolean free_buffer;
   hb_glyph_info_t *hb_glyph;
@@ -138,8 +397,8 @@ pango_hb_shape (PangoFont           *font,
   g_return_if_fail (font != NULL);
   g_return_if_fail (analysis != NULL);
 
-  hb_font = pango_font_get_hb_font (font);
-
+  find_shape_flags (analysis, &context);
+  hb_font = pango_font_get_hb_font_for_context (font, &context);
   hb_buffer = acquire_buffer (&free_buffer);
 
   hb_direction = PANGO_GRAVITY_IS_VERTICAL (analysis->gravity) ? HB_DIRECTION_TTB : HB_DIRECTION_LTR;
@@ -148,6 +407,11 @@ pango_hb_shape (PangoFont           *font,
   if (PANGO_GRAVITY_IS_IMPROPER (analysis->gravity))
     hb_direction = HB_DIRECTION_REVERSE (hb_direction);
 
+  hb_buffer_flags = HB_BUFFER_FLAG_BOT | HB_BUFFER_FLAG_EOT;
+
+  if (context.show_ignorables)
+    hb_buffer_flags |= HB_BUFFER_FLAG_PRESERVE_DEFAULT_IGNORABLES;
+
   /* setup buffer */
 
   hb_buffer_set_direction (hb_buffer, hb_direction);
@@ -156,7 +420,8 @@ pango_hb_shape (PangoFont           *font,
 #if HB_VERSION_ATLEAST(1,0,3)
   hb_buffer_set_cluster_level (hb_buffer, HB_BUFFER_CLUSTER_LEVEL_MONOTONE_CHARACTERS);
 #endif
-  hb_buffer_set_flags (hb_buffer, HB_BUFFER_FLAG_BOT | HB_BUFFER_FLAG_EOT);
+  hb_buffer_set_flags (hb_buffer, hb_buffer_flags);
+  hb_buffer_set_invisible_glyph (hb_buffer, PANGO_GLYPH_EMPTY);
 
   hb_buffer_add_utf8 (hb_buffer, paragraph_text, paragraph_length, item_offset, item_length);
 
@@ -174,6 +439,7 @@ pango_hb_shape (PangoFont           *font,
   pango_glyph_string_set_size (glyphs, num_glyphs);
   infos = glyphs->glyphs;
   last_cluster = -1;
+
   for (i = 0; i < num_glyphs; i++)
     {
       infos[i].glyph = hb_glyph->codepoint;
@@ -203,4 +469,5 @@ pango_hb_shape (PangoFont           *font,
       }
 
   release_buffer (hb_buffer, free_buffer);
+  hb_font_destroy (hb_font);
 }