[cairo-commit] 3 commits - .gitlab-ci/ignore-quartz-argb32.txt .gitlab-ci/ignore-quartz-rgb24.txt src/cairo-path-stroke-polygon.c src/cairo-path-stroke-traps.c test/Makefile.sources test/meson.build test/reference test/round-join-bug-520.c
GitLab Mirror
gitlab-mirror at kemper.freedesktop.org
Wed Dec 28 09:58:37 UTC 2022
.gitlab-ci/ignore-quartz-argb32.txt | 2
.gitlab-ci/ignore-quartz-rgb24.txt | 2
src/cairo-path-stroke-polygon.c | 95 ++++++++--
src/cairo-path-stroke-traps.c | 32 ++-
test/Makefile.sources | 1
test/meson.build | 1
test/reference/round-join-bug-520-bevel.pdf.ref.png |binary
test/reference/round-join-bug-520-bevel.ref.png |binary
test/reference/round-join-bug-520-bevel.svg.ref.png |binary
test/reference/round-join-bug-520-round.ref.png |binary
test/reference/round-join-bug-520-round.xlib-window.ref.png |binary
test/reference/round-join-bug-520-round.xlib.ref.png |binary
test/round-join-bug-520.c | 109 ++++++++++++
13 files changed, 214 insertions(+), 28 deletions(-)
New commits:
commit 0e56ea9d5cce1a53294ccb06f56c68e581d2a62d
Merge: 394256abb e83776572
Author: Uli Schlachter <psychon at znc.in>
Date: Wed Dec 28 09:58:35 2022 +0000
Merge branch 'round-join' into 'master'
Fix for round joins
See merge request cairo/cairo!372
commit e83776572cac2ceaa392e6ba976eec5ac925bdd7
Author: Christian Rohlfs <anonymous8 at protonmail.com>
Date: Wed Dec 28 07:25:30 2022 +0500
Round joins fix (spline_cusp_tolerance)
https://gitlab.freedesktop.org/cairo/cairo/-/issues/520
diff --git a/src/cairo-path-stroke-polygon.c b/src/cairo-path-stroke-polygon.c
index 3f7c49802..44b6675e8 100644
--- a/src/cairo-path-stroke-polygon.c
+++ b/src/cairo-path-stroke-polygon.c
@@ -399,16 +399,16 @@ outer_close (struct stroker *stroker,
switch (stroker->style.line_join) {
case CAIRO_LINE_JOIN_ROUND:
- /* construct a fan around the common midpoint */
if ((in->dev_slope.x * out->dev_slope.x +
in->dev_slope.y * out->dev_slope.y) < stroker->spline_cusp_tolerance)
{
+ /* construct a fan around the common midpoint */
add_fan (stroker,
&in->dev_vector, &out->dev_vector, &in->point,
clockwise, outer);
- break;
- }
- /* else fall through */
+ } /* else: bevel join */
+ break;
+
case CAIRO_LINE_JOIN_MITER:
default: {
/* dot product of incoming slope vector with outgoing slope vector */
@@ -587,10 +587,14 @@ outer_join (struct stroker *stroker,
switch (stroker->style.line_join) {
case CAIRO_LINE_JOIN_ROUND:
- /* construct a fan around the common midpoint */
- add_fan (stroker,
- &in->dev_vector, &out->dev_vector, &in->point,
- clockwise, outer);
+ if ((in->dev_slope.x * out->dev_slope.x +
+ in->dev_slope.y * out->dev_slope.y) < stroker->spline_cusp_tolerance)
+ {
+ /* construct a fan around the common midpoint */
+ add_fan (stroker,
+ &in->dev_vector, &out->dev_vector, &in->point,
+ clockwise, outer);
+ } /* else: bevel join */
break;
case CAIRO_LINE_JOIN_MITER:
@@ -1291,17 +1295,72 @@ _cairo_path_fixed_stroke_to_polygon (const cairo_path_fixed_t *path,
stroker.ctm_inverse = ctm_inverse;
stroker.tolerance = tolerance;
stroker.half_line_width = style->line_width / 2.;
- /* To test whether we need to join two segments of a spline using
- * a round-join or a bevel-join, we can inspect the angle between the
- * two segments. If the difference between the chord distance
- * (half-line-width times the cosine of the bisection angle) and the
- * half-line-width itself is greater than tolerance then we need to
- * inject a point.
+
+ /* If `CAIRO_LINE_JOIN_ROUND` is selected and a joint's `arc height`
+ * is greater than `tolerance` then two segments are joined with
+ * round-join, otherwise bevel-join is used.
+ *
+ * (See https://gitlab.freedesktop.org/cairo/cairo/-/merge_requests/372#note_1698225
+ * for an illustration.)
+ *
+ * `Arc height` is the distance from the center of arc's chord to
+ * the center of the arc. It is also the difference of arc's radius
+ * and the "distance from a point where segments are joined to the
+ * chord" (distance to the chord). Arc's radius is the half of a line
+ * width and the "distance to the chord" is equal to "half of a line width"
+ * times `cos(half the angle between segment vectors)`. So
+ *
+ * arc_height = w/2 - w/2 * cos(phi/2),
+ *
+ * where `w/2` is the "half of a line width".
+ *
+ * Using the double angle cosine formula we can express the `cos(phi/2)`
+ * with just `cos(phi)` which is also the dot product of segments'
+ * unit vectors.
+ *
+ * cos(phi/2) = sqrt ( (1 + cos(phi)) / 2 );
+ * cos(phi/2) is in [0; 1] range, cannot be negative;
+ *
+ * cos(phi) = a . b = (ax * bx + ay * by),
+ *
+ * where `a` and `b` are unit vectors of the segments to be joined.
+ *
+ * Since `arc height` should be greater than the `tolerance` to produce
+ * a round-join we can write
+ *
+ * w/2 * (1 - cos(phi/2)) > tolerance;
+ * 1 - tolerance / (w/2) > cos(phi/2); [!]
+ *
+ * which can be rewritten with the above double angle formula to
+ *
+ * cos(phi) < 2 * ( 1 - tolerance / (w/2) )^2 - 1,
+ *
+ * [!] Note that `w/2` is in [tolerance; +inf] range, since `cos(phi/2)`
+ * cannot be negative. The left part of the above inequality is the
+ * dot product and the right part is the `spline_cusp_tolerance`:
+ *
+ * (ax * bx + ay * by) < spline_cusp_tolerance.
+ *
+ * In the code below only the `spline_cusp_tolerance` is calculated.
+ * The dot product is calculated later, in the condition expression
+ * itself. "Half of a line width" must be scaled with CTM for tolerance
+ * condition to be properly met. Also, since `arch height` cannot exceed
+ * the "half of a line width" and since `cos(phi/2)` cannot be negative,
+ * when `tolerance` is greater than the "half of a line width" the
+ * bevel-join should be produced.
*/
- stroker.spline_cusp_tolerance = 1 - tolerance / stroker.half_line_width;
- stroker.spline_cusp_tolerance *= stroker.spline_cusp_tolerance;
- stroker.spline_cusp_tolerance *= 2;
- stroker.spline_cusp_tolerance -= 1;
+ double scaled_hlw = hypot(stroker.half_line_width * ctm->xx,
+ stroker.half_line_width * ctm->yx);
+
+ if (scaled_hlw <= tolerance) {
+ stroker.spline_cusp_tolerance = -1.0;
+ } else {
+ stroker.spline_cusp_tolerance = 1 - tolerance / scaled_hlw;
+ stroker.spline_cusp_tolerance *= stroker.spline_cusp_tolerance;
+ stroker.spline_cusp_tolerance *= 2;
+ stroker.spline_cusp_tolerance -= 1;
+ }
+
stroker.ctm_det_positive =
_cairo_matrix_compute_determinant (ctm) >= 0.0;
diff --git a/src/cairo-path-stroke-traps.c b/src/cairo-path-stroke-traps.c
index eab978235..4eabf6583 100644
--- a/src/cairo-path-stroke-traps.c
+++ b/src/cairo-path-stroke-traps.c
@@ -102,17 +102,29 @@ stroker_init (struct stroker *stroker,
stroker->tolerance = tolerance;
stroker->traps = traps;
- /* To test whether we need to join two segments of a spline using
- * a round-join or a bevel-join, we can inspect the angle between the
- * two segments. If the difference between the chord distance
- * (half-line-width times the cosine of the bisection angle) and the
- * half-line-width itself is greater than tolerance then we need to
- * inject a point.
+ /* If `CAIRO_LINE_JOIN_ROUND` is selected and a joint's `arc height`
+ * is greater than `tolerance` then two segments are joined with
+ * round-join, otherwise bevel-join is used.
+ *
+ * `Arc height` is the difference of the "half of a line width" and
+ * the "half of a line width" times `cos(half the angle between segment vectors)`.
+ *
+ * See detailed description in the `_cairo_path_fixed_stroke_to_polygon()`
+ * function in the `cairo-path-stroke-polygon.c` file or follow the
+ * https://gitlab.freedesktop.org/cairo/cairo/-/merge_requests/372#note_1698225
+ * link to see the detailed description with an illustration.
*/
- stroker->spline_cusp_tolerance = 1 - tolerance / stroker->half_line_width;
- stroker->spline_cusp_tolerance *= stroker->spline_cusp_tolerance;
- stroker->spline_cusp_tolerance *= 2;
- stroker->spline_cusp_tolerance -= 1;
+ double scaled_hlw = hypot(stroker->half_line_width * ctm->xx,
+ stroker->half_line_width * ctm->yx);
+
+ if (scaled_hlw <= tolerance) {
+ stroker->spline_cusp_tolerance = -1.0;
+ } else {
+ stroker->spline_cusp_tolerance = 1 - tolerance / scaled_hlw;
+ stroker->spline_cusp_tolerance *= stroker->spline_cusp_tolerance;
+ stroker->spline_cusp_tolerance *= 2;
+ stroker->spline_cusp_tolerance -= 1;
+ }
stroker->ctm_determinant = _cairo_matrix_compute_determinant (stroker->ctm);
stroker->ctm_det_positive = stroker->ctm_determinant >= 0.0;
commit 805897b1f7e2b7928e0dc52de5690367ff684e32
Author: Christian Rohlfs <anonymous8 at protonmail.com>
Date: Wed Dec 28 06:46:18 2022 +0500
test: Add new `round-join-bug-520` tests
https://gitlab.freedesktop.org/cairo/cairo/-/issues/520
diff --git a/.gitlab-ci/ignore-quartz-argb32.txt b/.gitlab-ci/ignore-quartz-argb32.txt
index e00077831..29face153 100644
--- a/.gitlab-ci/ignore-quartz-argb32.txt
+++ b/.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
diff --git a/.gitlab-ci/ignore-quartz-rgb24.txt b/.gitlab-ci/ignore-quartz-rgb24.txt
index 0941d59cd..7bceae075 100644
--- a/.gitlab-ci/ignore-quartz-rgb24.txt
+++ b/.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
diff --git a/test/Makefile.sources b/test/Makefile.sources
index 330aa9da1..27f67efb6 100644
--- a/test/Makefile.sources
+++ b/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 \
diff --git a/test/meson.build b/test/meson.build
index 47d590690..d4d6ab539 100644
--- a/test/meson.build
+++ b/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',
diff --git a/test/reference/round-join-bug-520-bevel.pdf.ref.png b/test/reference/round-join-bug-520-bevel.pdf.ref.png
new file mode 100644
index 000000000..b1a38e12f
Binary files /dev/null and b/test/reference/round-join-bug-520-bevel.pdf.ref.png differ
diff --git a/test/reference/round-join-bug-520-bevel.ref.png b/test/reference/round-join-bug-520-bevel.ref.png
new file mode 100644
index 000000000..b888f9ba9
Binary files /dev/null and b/test/reference/round-join-bug-520-bevel.ref.png differ
diff --git a/test/reference/round-join-bug-520-bevel.svg.ref.png b/test/reference/round-join-bug-520-bevel.svg.ref.png
new file mode 100644
index 000000000..b1a38e12f
Binary files /dev/null and b/test/reference/round-join-bug-520-bevel.svg.ref.png differ
diff --git a/test/reference/round-join-bug-520-round.ref.png b/test/reference/round-join-bug-520-round.ref.png
new file mode 100644
index 000000000..b1a38e12f
Binary files /dev/null and b/test/reference/round-join-bug-520-round.ref.png differ
diff --git a/test/reference/round-join-bug-520-round.xlib-window.ref.png b/test/reference/round-join-bug-520-round.xlib-window.ref.png
new file mode 100644
index 000000000..14ed9cbfe
Binary files /dev/null and b/test/reference/round-join-bug-520-round.xlib-window.ref.png differ
diff --git a/test/reference/round-join-bug-520-round.xlib.ref.png b/test/reference/round-join-bug-520-round.xlib.ref.png
new file mode 100644
index 000000000..14ed9cbfe
Binary files /dev/null and b/test/reference/round-join-bug-520-round.xlib.ref.png differ
diff --git a/test/round-join-bug-520.c b/test/round-join-bug-520.c
new file mode 100644
index 000000000..be2b5aa0d
--- /dev/null
+++ b/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)
+
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