add a test to exercise tor22 spans allocation code path

test/Makefile.sources

@@ -26,6 +26,7 @@ test_sources = \
 	bilevel-image.c					\
 	bug-40410.c					\
 	bug-51910.c					\
+	bug-75705.c					\
 	bug-84115.c					\
 	bug-bo-rectangular.c				\
 	bug-bo-collins.c				\

test/bug-75705.c

@@ -0,0 +1,32 @@
+#include "cairo-test.h"
+
+static cairo_test_status_t
+draw (cairo_t *cr, int width, int height)
+{
+    double dsh[2] = {1,3};
+
+    cairo_set_source_rgba (cr, 0, 0, 0, 1);
+    cairo_paint (cr);
+
+    cairo_set_line_cap (cr, CAIRO_LINE_CAP_ROUND);
+
+    cairo_move_to (cr, 3, 3);
+    /* struct glitter_scan_converter spans_embedded array size is 64 */
+    cairo_line_to (cr, 65+3, 3);
+
+    cairo_set_antialias (cr, CAIRO_ANTIALIAS_FAST);
+    cairo_set_tolerance (cr, 1);
+
+    cairo_set_dash (cr, dsh, 2, 0);
+    cairo_set_line_width (cr, 2);
+
+    cairo_stroke (cr);
+    return CAIRO_TEST_SUCCESS;
+}
+
+CAIRO_TEST (bug_75705,
+	    "Bug 75705 (exercise tor22-scan-converter)",
+	    "dash, stroke, antialias", /* keywords */
+	    NULL, /* requirements */
+	    72, 8,
+	    NULL, draw)