Add an internal font face

The font data and rendering is adapted from Keith Packard's Twin
window system.  The hinting stuff is not ported yet, but hey, it renders!

The implementation uses user fonts, and the user font backend is modified
to use this font face (which we call "twin" font face internally) when
a toy font is needed.

The font face layer is then modified to use this font if:

  - The toy font face "cairo" is asked for, or

  - No native font backend is available, or

  - The preferred native font backend fails to return a font with
    STATUS_UNSUPPORTED.  No font backend does this right now but
    the idea is to change FreeType to return it if no fonts found
    on the system.

We also allow building with no font backends now!

The new doc/tutorial/src/twin.c file tests the twin face at various
sizes.

1 files changed, 199 insertions, 0 deletions

diff --git a/src/cairo-font-face-twin.c b/src/cairo-font-face-twin.c
new file mode 100644
index 000000000..86e083df0
--- /dev/null
+++ b/src/cairo-font-face-twin.c
@@ -0,0 +1,199 @@
+/*
+ * Copyright © 2004 Keith Packard
+ * Copyright © 2008 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it either under the terms of the GNU Lesser General Public
+ * License version 2.1 as published by the Free Software Foundation
+ * (the "LGPL") or, at your option, under the terms of the Mozilla
+ * Public License Version 1.1 (the "MPL"). If you do not alter this
+ * notice, a recipient may use your version of this file under either
+ * the MPL or the LGPL.
+ *
+ * You should have received a copy of the LGPL along with this library
+ * in the file COPYING-LGPL-2.1; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ * You should have received a copy of the MPL along with this library
+ * in the file COPYING-MPL-1.1
+ *
+ * The contents of this file are subject to the Mozilla Public License
+ * Version 1.1 (the "License"); you may not use this file except in
+ * compliance with the License. You may obtain a copy of the License at
+ * http://www.mozilla.org/MPL/
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
+ * OF ANY KIND, either express or implied. See the LGPL or the MPL for
+ * the specific language governing rights and limitations.
+ *
+ * The Original Code is the cairo graphics library.
+ *
+ * The Initial Developer of the Original Code is Keith Packard
+ *
+ * Contributor(s):
+ *      Keith Packard <keithp@keithp.com>
+ *      Behdad Esfahbod <behdad@behdad.org>
+ */
+
+#include "cairoint.h"
+
+/*
+ * This file implements a user-font rendering the decendant of the Hershey
+ * font coded by Keith Packard for use in the Twin window system.
+ * The actual font data is in cairo-font-face-twin-data.c
+ *
+ * Ported to cairo user font by Behdad Esfahbod.
+ */
+
+
+#define twin_glyph_left(g)      ((g)[0])
+#define twin_glyph_right(g)     ((g)[1])
+#define twin_glyph_ascent(g)    ((g)[2])
+#define twin_glyph_descent(g)   ((g)[3])
+
+#define twin_glyph_n_snap_x(g)  ((g)[4])
+#define twin_glyph_n_snap_y(g)  ((g)[5])
+#define twin_glyph_snap_x(g)    (&g[6])
+#define twin_glyph_snap_y(g)    (twin_glyph_snap_x(g) + twin_glyph_n_snap_x(g))
+#define twin_glyph_draw(g)      (twin_glyph_snap_y(g) + twin_glyph_n_snap_y(g))
+
+#define SNAPI(p)	(p)
+#define SNAPH(p)	(p)
+
+#define FX(g)		((g) / 64.)
+#define FY(g)		((g) / 64.)
+
+
+static cairo_status_t
+twin_scaled_font_init (cairo_scaled_font_t  *scaled_font,
+		       cairo_t              *cr,
+		       cairo_font_extents_t *metrics)
+{
+  metrics->ascent  = .67;
+  metrics->descent = .33;
+  return CAIRO_STATUS_SUCCESS;
+}
+
+static cairo_status_t
+twin_scaled_font_unicode_to_glyph (cairo_scaled_font_t *scaled_font,
+				   unsigned long        unicode,
+				   unsigned long       *glyph)
+{
+    /* We use an indentity charmap.  Which means we could live
+     * with no unicode_to_glyph method too.  But we define this
+     * to map all unknown chars to a single unknown glyph to
+     * reduce pressure on cache. */
+
+    if (unicode < ARRAY_LENGTH (_cairo_twin_charmap))
+	*glyph = unicode;
+    else
+	*glyph = 0;
+
+    return CAIRO_STATUS_SUCCESS;
+}
+
+#define SNAPX(p)	_twin_snap (p, info.snap_x, info.n_snap_x)
+#define SNAPY(p)	_twin_snap (p, info.snap_y, info.n_snap_y)
+
+static double
+_twin_snap (double v, int a, int b)
+{
+    return v; /* XXX */
+}
+
+static cairo_status_t
+twin_scaled_font_render_glyph (cairo_scaled_font_t  *scaled_font,
+			       unsigned long         glyph,
+			       cairo_t              *cr,
+			       cairo_text_extents_t *metrics)
+{
+    double x1, y1, x2, y2, x3, y3;
+    const int8_t *b = _cairo_twin_outlines +
+		      _cairo_twin_charmap[glyph >= ARRAY_LENGTH (_cairo_twin_charmap) ? 0 : glyph];
+    const int8_t *g = twin_glyph_draw(b);
+
+    struct {
+      cairo_bool_t snap;
+      int snap_x;
+      int snap_y;
+      int n_snap_x;
+      int n_snap_y;
+    } info = {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);
+
+    for (;;) {
+	switch (*g++) {
+	case 'm':
+	    x1 = FX(*g++);
+	    y1 = FY(*g++);
+	    if (info.snap)
+	    {
+		x1 = SNAPX (x1);
+		y1 = SNAPY (y1);
+	    }
+	    cairo_move_to (cr, x1, y1);
+	    continue;
+	case 'l':
+	    x1 = FX(*g++);
+	    y1 = FY(*g++);
+	    if (info.snap)
+	    {
+		x1 = SNAPX (x1);
+		y1 = SNAPY (y1);
+	    }
+	    cairo_line_to (cr, x1, y1);
+	    continue;
+	case 'c':
+	    x1 = FX(*g++);
+	    y1 = FY(*g++);
+	    x2 = FX(*g++);
+	    y2 = FY(*g++);
+	    x3 = FX(*g++);
+	    y3 = FY(*g++);
+	    if (info.snap)
+	    {
+		x1 = SNAPX (x1);
+		y1 = SNAPY (y1);
+		x2 = SNAPX (x2);
+		y2 = SNAPY (y2);
+		x3 = SNAPX (x3);
+		y3 = SNAPY (y3);
+	    }
+	    cairo_curve_to (cr, x1, y1, x2, y2, x3, y3);
+	    continue;
+	case 'o':
+	    cairo_close_path (cr);
+	    break;
+	case 'e':
+	    cairo_stroke (cr);
+	    break;
+	}
+	break;
+    }
+
+    cairo_stroke (cr);
+
+    metrics->x_advance = FX(twin_glyph_right(b)) + cairo_get_line_width (cr);
+    metrics->x_advance +=  cairo_get_line_width (cr)/* XXX 2*x.margin */;
+    if (info.snap)
+	metrics->x_advance = SNAPI (SNAPX (metrics->x_advance));
+
+
+    return CAIRO_STATUS_SUCCESS;
+}
+
+cairo_font_face_t *
+_cairo_font_face_twin_create (cairo_font_slant_t slant,
+			      cairo_font_weight_t weight)
+{
+    cairo_font_face_t *twin_font_face;
+
+    twin_font_face = cairo_user_font_face_create ();
+    cairo_user_font_face_set_init_func             (twin_font_face, twin_scaled_font_init);
+    cairo_user_font_face_set_render_glyph_func     (twin_font_face, twin_scaled_font_render_glyph);
+    cairo_user_font_face_set_unicode_to_glyph_func (twin_font_face, twin_scaled_font_unicode_to_glyph);
+
+    return twin_font_face;
+}