[pango/redo-attrs: 5/13] Add a userfont example

[Matthias Clasen <matthiasc src gnome org>]

commit 0f2ccba533ab01e955e6e9becbb2a687f6206909
Author: Matthias Clasen <mclasen redhat com>
Date:   Thu Jan 27 20:44:14 2022 -0500

    Add a userfont example
    
    This is a more-or-less direct adaptation of
    the user-font test in cairo.

 examples/meson.build |   1 +
 examples/userfont.c  | 357 +++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 358 insertions(+)
---
diff --git a/examples/meson.build b/examples/meson.build
index 0ec3860e..f8e416f8 100644
--- a/examples/meson.build
+++ b/examples/meson.build
@@ -5,6 +5,7 @@ if pango_cairo_backends.contains('png')
     'cairoshape',
     'cairosimple',
     'cairotwisted',
+    'userfont',
   ]
 endif
 
diff --git a/examples/userfont.c b/examples/userfont.c
new file mode 100644
index 00000000..3196e03e
--- /dev/null
+++ b/examples/userfont.c
@@ -0,0 +1,357 @@
+/* Example code to show how to use user fonts with Pango
+ *
+ * Written by Matthias Clasen, 2022
+ *
+ * Permission to use, copy, modify, distribute, and sell this example
+ * for any purpose is hereby granted without fee.
+ * It is provided "as is" without express or implied warranty.
+ *
+ * Font data taken from the cairo user-font test, written by
+ *   Kristian Høgsberg <krh redhat com>
+ *   Behdad Esfahbod <behdad behdad org>
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+
+#include <pango/pangocairo.h>
+#include <pango/pangofc-hbfontmap.h>
+
+static PangoFontMap *fontmap;
+
+#define END_GLYPH 0
+#define STROKE 126
+#define CLOSE 127
+
+/* Simple glyph definition: 1 - 15 means lineto (or moveto for first
+ * point) for one of the points on this grid:
+ *
+ *      1  2  3
+ *      4  5  6
+ *      7  8  9
+ * ----10 11 12----(baseline)
+ *     13 14 15
+ */
+typedef struct
+{
+  gunichar ucs4;
+  int width;
+  char data[16];
+} test_scaled_font_glyph_t;
+
+/* Simple glyph definition: 1 - 15 means lineto (or moveto for first
+ * point) for one of the points on this grid:
+ *
+ *      1  2  3
+ *      4  5  6
+ *      7  8  9
+ * ----10 11 12----(baseline)
+ *     13 14 15
+ */
+static const test_scaled_font_glyph_t glyphs [] = {
+  { 'a',  3, { 4, 6, 12, 10, 7, 9, STROKE, END_GLYPH } },
+  { 'c',  3, { 6, 4, 10, 12, STROKE, END_GLYPH } },
+  { 'e',  3, { 12, 10, 4, 6, 9, 7, STROKE, END_GLYPH } },
+  { 'f',  3, { 3, 2, 11, STROKE, 4, 6, STROKE, END_GLYPH } },
+  { 'g',  3, { 12, 10, 4, 6, 15, 13, STROKE, END_GLYPH } },
+  { 'h',  3, { 1, 10, STROKE, 7, 5, 6, 12, STROKE, END_GLYPH } },
+  { 'i',  1, { 1, 1, STROKE, 4, 10, STROKE, END_GLYPH } },
+  { 'l',  1, { 1, 10, STROKE, END_GLYPH } },
+  { 'n',  3, { 10, 4, STROKE, 7, 5, 6, 12, STROKE, END_GLYPH } },
+  { 'o',  3, { 4, 10, 12, 6, CLOSE, END_GLYPH } },
+  { 'p',  3, { 4, 10, 12, 6, CLOSE, 4, 13, STROKE, END_GLYPH } },
+  { 'r',  3, { 4, 10, STROKE, 7, 5, 6, STROKE, END_GLYPH } },
+  { 's',  3, { 6, 4, 7, 9, 12, 10, STROKE, END_GLYPH } },
+  { 't',  3, { 2, 11, 12, STROKE, 4, 6, STROKE, END_GLYPH } },
+  { 'u',  3, { 4, 10, 12, 6, STROKE, END_GLYPH } },
+  { 'y',  3, { 4, 10, 12, 6, STROKE, 12, 15, 13, STROKE, END_GLYPH } },
+  { 'z',  3, { 4, 6, 10, 12, STROKE, END_GLYPH } },
+  { ' ',  1, { END_GLYPH } },
+  { '-',  2, { 7, 8, STROKE, END_GLYPH } },
+  { '.',  1, { 10, 10, STROKE, END_GLYPH } },
+  { 0xe000, 3, { 3, 2, 11, STROKE, 4, 6, STROKE, 3, 3, STROKE, 6, 12, STROKE, END_GLYPH } }, /* fi */
+  { -1,  0, { END_GLYPH } },
+};
+
+const char text[] = "finally... pango user-font";
+
+static PangoLayout *
+get_layout (void)
+{
+  PangoContext *context;
+  PangoLayout *layout;
+  PangoFontDescription *desc;
+
+  /* Create a PangoLayout, set the font and text */
+  context = pango_font_map_create_context (fontmap);
+  layout = pango_layout_new (context);
+  g_object_unref (context);
+
+  pango_layout_set_text (layout, text, -1);
+
+  desc = pango_font_description_from_string ("Userfont 20");
+  pango_layout_set_font_description (layout, desc);
+  pango_font_description_free (desc);
+
+  pango_layout_write_to_file (layout, PANGO_LAYOUT_SERIALIZE_OUTPUT, "out.layout", NULL);
+
+  return layout;
+}
+
+static gboolean
+glyph_cb (PangoUserFace  *face,
+          hb_codepoint_t  unicode,
+          hb_codepoint_t *glyph,
+          gpointer        user_data)
+{
+  test_scaled_font_glyph_t *glyphs = user_data;
+
+  for (int i = 0; glyphs[i].ucs4 != (gunichar) -1; i++)
+    {
+      if (glyphs[i].ucs4 == unicode)
+        {
+          *glyph = i;
+          return TRUE;
+        }
+    }
+
+  return FALSE;
+}
+
+static gboolean
+glyph_info_cb (PangoUserFace      *face,
+               int                 size,
+               hb_codepoint_t      glyph,
+               hb_glyph_extents_t *extents,
+               hb_position_t      *h_advance,
+               hb_position_t      *v_advance,
+               gboolean           *is_color,
+               gpointer            user_data)
+{
+  test_scaled_font_glyph_t *glyphs = user_data;
+
+  extents->x_bearing = 0;
+  extents->y_bearing = - 0.75 * size;
+  extents->width = glyphs[glyph].width / 4.0 * size;
+  extents->height = size;
+
+  *h_advance = *v_advance = glyphs[glyph].width / 4.0 * size;
+
+  *is_color = FALSE;
+
+  return TRUE;
+}
+
+static gboolean
+shape_cb (PangoUserFace       *face,
+          int                  size,
+          const char          *text,
+          int                  length,
+          const PangoAnalysis *analysis,
+          PangoGlyphString    *glyphs,
+          PangoShapeFlags      flags,
+          gpointer             user_data)
+{
+  int n_chars;
+  const char *p;
+  int cluster = 0;
+  int i, j;
+  int last_cluster;
+  gboolean is_color;
+  hb_glyph_extents_t ext;
+  hb_position_t dummy;
+
+  n_chars = g_utf8_strlen (text, length);
+
+  pango_glyph_string_set_size (glyphs, n_chars);
+
+  last_cluster = -1;
+
+  p = text;
+  j = 0;
+  for (i = 0; i < n_chars; i++)
+    {
+      gunichar wc;
+      PangoGlyph glyph;
+      PangoRectangle logical_rect;
+
+      wc = g_utf8_get_char (p);
+
+      if (g_unichar_type (wc) != G_UNICODE_NON_SPACING_MARK)
+        cluster = p - text;
+
+      /* Handle the fi ligature */
+      if (p[0] == 'f' && p[1] == 'i')
+        {
+          p = g_utf8_next_char (p);
+          i++;
+          glyph_cb (face, 0xe000, &glyph, user_data);
+        }
+      else if (pango_is_zero_width (wc))
+        glyph = PANGO_GLYPH_EMPTY;
+      else if (!glyph_cb (face, wc, &glyph, user_data))
+        glyph = PANGO_GET_UNKNOWN_GLYPH (wc);
+
+      glyph_info_cb (face, size, glyph, &ext, &dummy, &dummy, &is_color, user_data);
+      pango_font_get_glyph_extents (analysis->font, glyph, NULL, &logical_rect);
+
+      glyphs->glyphs[j].glyph = glyph;
+
+      glyphs->glyphs[j].attr.is_cluster_start = cluster != last_cluster;
+      glyphs->glyphs[j].attr.is_color = is_color;
+
+      glyphs->glyphs[j].geometry.x_offset = 0;
+      glyphs->glyphs[j].geometry.y_offset = 0;
+      glyphs->glyphs[j].geometry.width = logical_rect.width;
+
+      glyphs->log_clusters[j] = cluster;
+
+      j++;
+
+      last_cluster = cluster;
+
+      p = g_utf8_next_char (p);
+    }
+
+  glyphs->num_glyphs = j;
+
+#if 0
+  /* FIXME export this */
+  if (analysis->level & 1)
+    pango_glyph_string_reverse_range (glyphs, 0, glyphs->num_glyphs);
+#endif
+
+  return TRUE;
+}
+
+static gboolean
+font_info_cb (PangoUserFace     *face,
+              int                size,
+              hb_font_extents_t *extents,
+              gpointer           user_data)
+{
+  extents->ascender = 0.75 * size;
+  extents->descender = 0.25 * size;
+  extents->line_gap = 0;
+
+  return TRUE;
+}
+
+static gboolean
+render_cb (PangoUserFace  *face,
+           int             size,
+           hb_codepoint_t  glyph,
+           gpointer        user_data,
+           const char     *backend_id,
+           gpointer        backend_data)
+{
+  test_scaled_font_glyph_t *glyphs = user_data;
+  cairo_t *cr = backend_data;
+  const char *data;
+  div_t d;
+  double x, y;
+
+  if (strcmp (backend_id, "cairo") != 0)
+    return FALSE;
+
+  cairo_set_line_width (cr, 0.1);
+  cairo_set_line_join (cr, CAIRO_LINE_JOIN_ROUND);
+  cairo_set_line_cap (cr, CAIRO_LINE_CAP_ROUND);
+
+  data = glyphs[glyph].data;
+  for (int i = 0; data[i] != END_GLYPH; i++)
+    {
+      switch (data[i])
+        {
+        case STROKE:
+          cairo_new_sub_path (cr);
+          break;
+
+        case CLOSE:
+          cairo_close_path (cr);
+          break;
+
+        default:
+          d = div (data[i] - 1, 3);
+          x = d.rem / 4.0 + 0.125;
+          y = d.quot / 5.0 + 0.4 - 1.0;
+          cairo_line_to (cr, x, y);
+        }
+    }
+
+  cairo_stroke (cr);
+
+  return TRUE;
+}
+
+static void
+setup_fontmap (PangoHbFontMap *fontmap)
+{
+  PangoFontDescription *desc;
+  PangoUserFace *face;
+
+  desc = pango_font_description_new ();
+  pango_font_description_set_family (desc, "Userfont");
+  face = pango_user_face_new (font_info_cb,
+                              glyph_cb,
+                              glyph_info_cb,
+                              shape_cb,
+                              render_cb,
+                              (gpointer) glyphs, NULL,
+                              "Black", desc);
+  pango_hb_font_map_add_face (fontmap, PANGO_FONT_FACE (face));
+  pango_font_description_free (desc);
+}
+
+int
+main (int argc, char **argv)
+{
+  cairo_t *cr;
+  char *filename;
+  cairo_status_t status;
+  cairo_surface_t *surface;
+  PangoLayout *layout;
+  int width, height;
+
+  if (argc != 2)
+    {
+      g_printerr ("Usage: userfont OUTPUT_FILENAME\n");
+      return 1;
+    }
+
+  filename = argv[1];
+
+  fontmap = PANGO_FONT_MAP (pango_fc_hb_font_map_new ());
+  setup_fontmap (PANGO_HB_FONT_MAP (fontmap));
+
+  layout = get_layout ();
+
+  pango_layout_get_pixel_size (layout, &width, &height);
+
+  /* Now create the final surface and draw to it. */
+  surface = cairo_image_surface_create (CAIRO_FORMAT_ARGB32, width + 20, height + 20);
+  cr = cairo_create (surface);
+
+  cairo_set_source_rgb (cr, 1.0, 1.0, 1.0);
+  cairo_paint (cr);
+  cairo_set_source_rgb (cr, 0.0, 0.0, 0.5);
+
+  cairo_move_to (cr, 10, 10);
+  pango_cairo_show_layout (cr, layout);
+
+  cairo_destroy (cr);
+
+  g_object_unref (layout);
+
+  /* Write out the surface as PNG */
+  status = cairo_surface_write_to_png (surface, filename);
+  cairo_surface_destroy (surface);
+
+  if (status != CAIRO_STATUS_SUCCESS)
+    {
+      g_printerr ("Could not save png to '%s': %s\n", filename, cairo_status_to_string (status));
+      return 1;
+    }
+
+  return 0;
+}