test: Add new round-join-bug-520 tests

https://gitlab.freedesktop.org/cairo/cairo/-/issues/520

.gitlab-ci/ignore-quartz-argb32.txt

@@ -39,6 +39,8 @@ record-replay-extend-reflect
 record-replay-extend-repeat
 record-select-font-face
 record-text-transform
+round-join-bug-520-round
+round-join-bug-520-bevel
 simple-edge
 subsurface
 subsurface-outside-target

.gitlab-ci/ignore-quartz-rgb24.txt

@@ -67,6 +67,8 @@ record-replay-extend-repeat
 record-select-font-face
 record-text-transform
 rel-path
+round-join-bug-520-round
+round-join-bug-520-bevel
 scale-source-surface-paint
 set-source
 shifted-operator

test/Makefile.sources

@@ -304,6 +304,7 @@ test_sources = \
 	rotated-clip.c					\
 	rounded-rectangle-fill.c			\
 	rounded-rectangle-stroke.c			\
+	round-join-bug-520.c                \
 	sample.c					\
 	scale-down-source-surface-paint.c		\
 	scale-offset-image.c				\

test/meson.build

@@ -304,6 +304,7 @@ test_sources = [
   'rotated-clip.c',
   'rounded-rectangle-fill.c',
   'rounded-rectangle-stroke.c',
+  'round-join-bug-520.c',
   'sample.c',
   'scale-down-source-surface-paint.c',
   'scale-offset-image.c',

test/round-join-bug-520.c

@@ -0,0 +1,109 @@
+/*
+ * Author: Christian Rohlfs, 2022
+ *
+ * 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.
+ */
+
+#include "cairo-test.h"
+
+#define WIDTH   100
+#define HEIGHT  WIDTH
+
+static cairo_test_status_t
+draw_round(cairo_t *cr, int width, int height)
+{
+    /* Fail condition:
+            0  >=  2 * ( 1 - tolerance / (line_width / 2) )^2 - 1,
+       with the default tolerance of 0.1, `failing_line_width` is in
+            [0.117157287525381; 0.682842712474619]
+       range.
+    */
+
+    double failing_line_width = 0.3;
+
+    cairo_set_tolerance(cr, 0.1);
+    cairo_scale(cr, width, height);
+
+    cairo_set_source_rgb(cr, 1, 1, 1);
+    cairo_paint(cr);
+
+    cairo_move_to(cr, 0.2, 0.2);
+    cairo_line_to(cr, 0.8, 0.2);
+    cairo_line_to(cr, 0.8, 0.8);
+    cairo_line_to(cr, 0.2, 0.8);
+    cairo_close_path(cr);
+
+    cairo_set_line_join(cr, CAIRO_LINE_JOIN_ROUND);
+    cairo_set_source_rgb(cr, 0, 0, 0);
+    cairo_set_line_width(cr, failing_line_width);
+    cairo_stroke(cr);
+
+    return CAIRO_TEST_SUCCESS;
+}
+
+static cairo_test_status_t
+draw_bevel(cairo_t *cr, int width, int height)
+{
+    /* Fail condition:
+            arc_height < tolerance
+       For 90° join `arc_height` is equal to
+            line_width / 2 * (1 - sqrt(1/2))
+       which is 0.1464466094067262 of a `line_width`.
+    */
+
+    double line_width = 0.3;
+    double failing_tolerance = 0.3 * line_width;
+
+    cairo_set_tolerance(cr, width * failing_tolerance);
+    cairo_scale(cr, width, height);
+
+    cairo_set_source_rgb(cr, 1, 1, 1);
+    cairo_paint(cr);
+
+    cairo_move_to(cr, 0.2, 0.2);
+    cairo_line_to(cr, 0.8, 0.2);
+    cairo_line_to(cr, 0.8, 0.8);
+    cairo_line_to(cr, 0.2, 0.8);
+    cairo_close_path(cr);
+
+    cairo_set_line_join(cr, CAIRO_LINE_JOIN_ROUND);
+    cairo_set_source_rgb(cr, 0, 0, 0);
+    cairo_set_line_width(cr, line_width);
+    cairo_stroke(cr);
+
+    return CAIRO_TEST_SUCCESS;
+}
+
+
+CAIRO_TEST (round_join_bug_520_round,
+    "Tests round joins within tolerance",
+    "stroke, cap, join", /* keywords */
+    NULL, /* requirements */
+    WIDTH, HEIGHT,
+    NULL, draw_round)
+
+CAIRO_TEST (round_join_bug_520_bevel,
+    "Tests round joins omission when `arc_height < tolerance`",
+    "stroke, cap, join", /* keywords */
+    NULL, /* requirements */
+    WIDTH, HEIGHT,
+    NULL, draw_bevel)
+