test: Add halo

halo uses text_path + stroke + (fill | show_text)  to generate a "halo"
around the string. This is to try to replicate a bug described by Ian
Britten in the PDF backend where the rendering of the show_text looked
distorted compared to the stroke.

test/Makefile.am

@@ -684,6 +684,9 @@ REFERENCE_IMAGES = \
 	group-unaligned.svg.rgb24.xfail.png \
 	group-unaligned.xlib-fallback.ref.png \
 	group-unaligned.xlib.ref.png \
+	halo.ref.png \
+	halo.image16.ref.png \
+	halo.xlib.ref.png \
 	huge-linear.image16.ref.png \
 	huge-linear.pdf.ref.png \
 	huge-linear.ps3.ref.png \

test/Makefile.sources

@@ -118,6 +118,7 @@ test_sources = \
 	group-paint.c					\
 	group-unaligned.c				\
 	half-coverage.c					\
+	halo.c						\
 	huge-linear.c					\
 	huge-radial.c					\
 	image-surface-source.c				\

test/halo.c

@@ -0,0 +1,98 @@
+/*
+ * Copyright 2010 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person
+ * obtaining a copy of this software and associated documentation
+ * files (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy,
+ * modify, merge, publish, distribute, sublicense, and/or sell copies
+ * of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ * Author: Chris Wilson <chris@chris-wilson.co.uk>
+ */
+
+#include "cairo-test.h"
+
+/* Try to replicate the misbehaviour of show_glyphs() versus glyph_path()
+ * in the PDF backend reported by Ian Britten.
+ */
+
+static void
+halo_around_path (cairo_t *cr, const char *str)
+{
+    cairo_text_path (cr, str);
+
+    cairo_set_source_rgba (cr, 0, .5, 1, .5);
+    cairo_stroke_preserve (cr);
+    cairo_set_source_rgb (cr, 1, .5, 0);
+    cairo_fill (cr);
+}
+
+static void
+halo_around_text (cairo_t *cr, const char *str)
+{
+    double x, y;
+
+    cairo_get_current_point (cr, &x, &y);
+    cairo_text_path (cr, str);
+
+    cairo_set_source_rgba (cr, 0, .5, 1, .5);
+    cairo_stroke(cr);
+
+    cairo_set_source_rgb (cr, 1, .5, 0);
+    cairo_move_to (cr, x, y);
+    cairo_show_text  (cr, str);
+}
+
+static cairo_test_status_t
+draw (cairo_t *cr, int width, int height)
+{
+    const char *string = "0123456789";
+    cairo_text_extents_t extents;
+
+    cairo_set_source_rgb (cr, 1, 1, 1);
+    cairo_paint (cr);
+
+    cairo_text_extents (cr, string, &extents);
+
+    cairo_set_line_width (cr, 3);
+    cairo_move_to (cr, 9, 4 + extents.height);
+    halo_around_path (cr, string);
+
+    cairo_move_to (cr, 109, 4 + extents.height);
+    halo_around_path (cr, string);
+
+    cairo_set_font_size (cr, 64);
+    cairo_set_line_width (cr, 10);
+    cairo_move_to (cr, 8, 70);
+    halo_around_path (cr, "6");
+    cairo_move_to (cr, 32, 90);
+    halo_around_path (cr, "7");
+
+    cairo_move_to (cr, 108, 70);
+    halo_around_text (cr, "6");
+    cairo_move_to (cr, 132, 90);
+    halo_around_text (cr, "7");
+
+    return CAIRO_TEST_SUCCESS;
+}
+
+CAIRO_TEST (halo,
+	    "Check the show_glyphs() vs glyph_path()",
+	    "text", /* keywords */
+	    NULL, /* requirements */
+	    200, 100,
+	    NULL, draw)