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kovidgoyalkovidgoyal
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Improve rendering of rounded rectangles
Uses the standard distance to curve via sampling method of antialiasing instead of super sampled antialiasing. Need to investigate behavior very thin lines <= 3 pixels. Also need to check if we should migrate the other call sites of draw_parametrized_curve_with_derivate() Fixes #9000
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-33
lines changed

2 files changed

+111
-33
lines changed

‎docs/changelog.rst‎

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -176,6 +176,8 @@ Detailed list of changes
176176
- Fix updating panel configuration on visibility toggle and via remote control
177177
not working (:iss:`8984`)
178178

179+
- Improve rendering of rounded rectangles (:pull:`9000`)
180+
179181
- Wayland: Update bundled copy of libwayland to 1.24 from 1.23.1 because the
180182
just released mesa 25.2.0 breaks with libwayland < 1.24 (:iss:`8884`)
181183

‎kitty/decorations.c‎

Lines changed: 109 additions & 33 deletions
Original file line numberDiff line numberDiff line change
@@ -412,6 +412,12 @@ half_vline(Canvas *self, uint level, bool bottom_half, uint extend_by) {
412412
draw_vline(self, y1, y2, half_width(self), level);
413413
}
414414

415+
static void
416+
fractional_vline(Canvas *self, uint level, uint y1, uint y2) {
417+
draw_vline(self, y1, y2, half_width(self), level);
418+
}
419+
420+
415421
static void
416422
hline(Canvas *self, uint level) {
417423
half_hline(self, level, false, 0);
@@ -726,6 +732,71 @@ static bool cmpr_point(Point a, Point b) { return a.val == b.val; }
726732
vt_cleanup(&seen); \
727733
}
728734

735+
static void
736+
draw_parametrized_curve_with_derivative_and_antialiasing(
737+
Canvas *self, void *curve_data, double line_width, curve_func xfunc, curve_func yfunc,
738+
curve_func x_prime, curve_func y_prime, double x_offset, double y_offset
739+
) {
740+
line_width = fmax(1., line_width);
741+
double half_thickness = line_width / 2.0;
742+
uint i=0, larger_dim = MAX(self->height, self->width);
743+
double t = 0;
744+
double step = 1.0 / larger_dim;
745+
uint cap = 2 * larger_dim;
746+
const double min_step = step / 1000., max_step = step;
747+
RAII_ALLOC(double, x_samples, malloc(sizeof(double) * cap));
748+
RAII_ALLOC(double, y_samples, malloc(sizeof(double) * cap));
749+
while (true) {
750+
x_samples[i] = xfunc(curve_data, t) + x_offset;
751+
y_samples[i] = yfunc(curve_data, t) + y_offset;
752+
if (t >= 1.0) break;
753+
// Dynamically adjust step size based on curve's derivative
754+
double dx = x_prime(curve_data, t), dy = y_prime(curve_data, t);
755+
double d = sqrt(dx * dx + dy * dy);
756+
step = 1.0 / fmax(1e-6, d);
757+
step = fmax(min_step, fmin(step, max_step));
758+
t = fmin(t + step, 1.0);
759+
i++;
760+
if (i >= cap) {
761+
cap *= 2;
762+
x_samples = realloc(x_samples, sizeof(x_samples[0]) * cap);
763+
y_samples = realloc(y_samples, sizeof(x_samples[0]) * cap);
764+
}
765+
}
766+
const uint num_samples = i;
767+
for (uint py = 0; py < self->height; py++) {
768+
uint ypos = self->width * py;
769+
for (uint px = 0; px < self->width; px++) {
770+
// Center of the current pixel
771+
double pixel_center_x = (double)px + 0.5;
772+
double pixel_center_y = (double)py + 0.5;
773+
774+
double min_dist_sq = -1.0;
775+
776+
// Find the closest point on the curve to the pixel center by sampling the curve.
777+
for (uint i = 0; i < num_samples; ++i) {
778+
double dx = x_samples[i] - pixel_center_x;
779+
double dy = y_samples[i] - pixel_center_y;
780+
double dist_sq = dx * dx + dy * dy;
781+
if (min_dist_sq < 0 || dist_sq < min_dist_sq) min_dist_sq = dist_sq;
782+
}
783+
784+
double distance = sqrt(min_dist_sq);
785+
786+
// Calculate alpha based on the distance from the curve.
787+
// This creates the anti-aliased edge. The distance from the center
788+
// of the pixel to the edge of the stroke is used.
789+
// We assume a pixel has a width of 1.0 for this calculation.
790+
double alpha_unclamped = half_thickness - distance + 0.5;
791+
792+
uint offset = ypos + px;
793+
uint8_t old_alpha = self->mask[offset];
794+
double alpha = MAX(0.0, MIN(alpha_unclamped, 1.0));
795+
self->mask[offset] = (uint8_t)(alpha * 255 + (1 - alpha) * old_alpha); // alpha blend
796+
}
797+
}
798+
}
799+
729800
static void
730801
draw_parametrized_curve_with_derivative(
731802
Canvas *self, void *curve_data, double line_width, curve_func xfunc, curve_func yfunc, curve_func x_prime, curve_func y_prime,
@@ -1333,12 +1404,16 @@ rectcircle(Canvas *self, Corner which) {
13331404
static void
13341405
rounded_corner(Canvas *self, uint level, Corner which) {
13351406
Rectircle r = rectcircle(self, which);
1407+
double line_width = thickness_as_float(self, level, true);
13361408
uint cell_width_is_odd = (self->width / self->supersample_factor) & 1;
13371409
uint cell_height_is_odd = (self->height / self->supersample_factor) & 1;
13381410
// adjust for odd cell dimensions to line up with box drawing lines
1339-
int x_offset = -(cell_width_is_odd & 1), y_offset = -(cell_height_is_odd & 1);
1340-
double line_width = thickness_as_float(self, level, true);
1341-
draw_parametrized_curve_with_derivative(self, &r, line_width, rectircle_x, rectircle_y, rectircle_x_prime, rectircle_y_prime, x_offset, y_offset, 0.1);
1411+
double x_offset = cell_width_is_odd ? 0 : 0.5, y_offset = cell_height_is_odd ? 0 : 0.5;
1412+
draw_parametrized_curve_with_derivative_and_antialiasing(
1413+
self, &r, line_width, rectircle_x, rectircle_y, rectircle_x_prime, rectircle_y_prime, x_offset, y_offset);
1414+
// make the vertical stems be same brightness as straightline segments
1415+
if (which & TOP_EDGE) fractional_vline(self, level, self->height - self->width / 2, self->height);
1416+
else fractional_vline(self, level, 0, self->width / 2);
13421417
}
13431418

13441419
static void
@@ -1509,7 +1584,8 @@ sextant(Canvas *self, uint which) {
15091584
void
15101585
render_box_char(char_type ch, uint8_t *buf, unsigned width, unsigned height, double dpi_x, double dpi_y, double scale) {
15111586
Canvas canvas = {.mask=buf, .width = width, .height = height, .dpi={.x=dpi_x, .y=dpi_y}, .supersample_factor=1u, .scale=scale}, ss = canvas;
1512-
ss.mask = buf + width*height; ss.supersample_factor = SUPERSAMPLE_FACTOR; ss.width *= SUPERSAMPLE_FACTOR; ss.height *= SUPERSAMPLE_FACTOR;
1587+
ss.mask = buf + width*height; ss.supersample_factor = SUPERSAMPLE_FACTOR;
1588+
ss.width *= SUPERSAMPLE_FACTOR; ss.height *= SUPERSAMPLE_FACTOR;
15131589
fill_canvas(&canvas, 0);
15141590
Canvas *c = &canvas;
15151591

@@ -1790,31 +1866,31 @@ START_ALLOW_CASE_RANGE
17901866
C(L'', fading_vline, 1, 5, BOTTOM_EDGE);
17911867
C(L'', fading_vline, 1, 5, TOP_EDGE);
17921868

1793-
S(L'', rounded_corner, 1, TOP_LEFT);
1794-
S(L'', rounded_corner, 1, TOP_RIGHT);
1795-
S(L'', rounded_corner, 1, BOTTOM_LEFT);
1796-
S(L'', rounded_corner, 1, BOTTOM_RIGHT);
1797-
1798-
SS(L'', vline(c, 1); rounded_corner(c, 1, BOTTOM_LEFT));
1799-
SS(L'', vline(c, 1); rounded_corner(c, 1, TOP_LEFT));
1800-
SS(L'', rounded_corner(c, 1, BOTTOM_LEFT), rounded_corner(c, 1, TOP_LEFT));
1801-
SS(L'', vline(c, 1); rounded_corner(c, 1, BOTTOM_RIGHT));
1802-
SS(L'', vline(c, 1); rounded_corner(c, 1, TOP_RIGHT));
1803-
SS(L'', rounded_corner(c, 1, TOP_RIGHT), rounded_corner(c, 1, BOTTOM_RIGHT));
1804-
SS(L'', hline(c, 1); rounded_corner(c, 1, TOP_RIGHT));
1805-
SS(L'', hline(c, 1); rounded_corner(c, 1, TOP_LEFT));
1806-
SS(L'', rounded_corner(c, 1, TOP_LEFT), rounded_corner(c, 1, TOP_RIGHT));
1807-
SS(L'', hline(c, 1); rounded_corner(c, 1, BOTTOM_RIGHT));
1808-
SS(L'', hline(c, 1); rounded_corner(c, 1, BOTTOM_LEFT));
1809-
SS(L'', rounded_corner(c, 1, BOTTOM_LEFT), rounded_corner(c, 1, BOTTOM_RIGHT));
1810-
SS(L'', vline(c, 1); rounded_corner(c, 1, BOTTOM_LEFT), rounded_corner(c, 1, BOTTOM_RIGHT));
1811-
SS(L'', vline(c, 1); rounded_corner(c, 1, TOP_LEFT), rounded_corner(c, 1, TOP_RIGHT));
1812-
SS(L'', hline(c, 1); rounded_corner(c, 1, TOP_RIGHT), rounded_corner(c, 1, BOTTOM_RIGHT));
1813-
SS(L'', hline(c, 1); rounded_corner(c, 1, BOTTOM_LEFT), rounded_corner(c, 1, TOP_LEFT));
1814-
SS(L'', vline(c, 1); rounded_corner(c, 1, TOP_LEFT), rounded_corner(c, 1, BOTTOM_RIGHT));
1815-
SS(L'', vline(c, 1); rounded_corner(c, 1, TOP_RIGHT), rounded_corner(c, 1, BOTTOM_LEFT));
1816-
SS(L'', hline(c, 1); rounded_corner(c, 1, TOP_LEFT), rounded_corner(c, 1, BOTTOM_RIGHT));
1817-
SS(L'', hline(c, 1); rounded_corner(c, 1, TOP_RIGHT), rounded_corner(c, 1, BOTTOM_LEFT));
1869+
C(L'', rounded_corner, 1, TOP_LEFT);
1870+
C(L'', rounded_corner, 1, TOP_RIGHT);
1871+
C(L'', rounded_corner, 1, BOTTOM_LEFT);
1872+
C(L'', rounded_corner, 1, BOTTOM_RIGHT);
1873+
1874+
CC(L'', vline(c, 1); rounded_corner(c, 1, BOTTOM_LEFT));
1875+
CC(L'', vline(c, 1); rounded_corner(c, 1, TOP_LEFT));
1876+
CC(L'', rounded_corner(c, 1, BOTTOM_LEFT), rounded_corner(c, 1, TOP_LEFT));
1877+
CC(L'', vline(c, 1); rounded_corner(c, 1, BOTTOM_RIGHT));
1878+
CC(L'', vline(c, 1); rounded_corner(c, 1, TOP_RIGHT));
1879+
CC(L'', rounded_corner(c, 1, TOP_RIGHT), rounded_corner(c, 1, BOTTOM_RIGHT));
1880+
CC(L'', hline(c, 1); rounded_corner(c, 1, TOP_RIGHT));
1881+
CC(L'', hline(c, 1); rounded_corner(c, 1, TOP_LEFT));
1882+
CC(L'', rounded_corner(c, 1, TOP_LEFT), rounded_corner(c, 1, TOP_RIGHT));
1883+
CC(L'', hline(c, 1); rounded_corner(c, 1, BOTTOM_RIGHT));
1884+
CC(L'', hline(c, 1); rounded_corner(c, 1, BOTTOM_LEFT));
1885+
CC(L'', rounded_corner(c, 1, BOTTOM_LEFT), rounded_corner(c, 1, BOTTOM_RIGHT));
1886+
CC(L'', vline(c, 1); rounded_corner(c, 1, BOTTOM_LEFT), rounded_corner(c, 1, BOTTOM_RIGHT));
1887+
CC(L'', vline(c, 1); rounded_corner(c, 1, TOP_LEFT), rounded_corner(c, 1, TOP_RIGHT));
1888+
CC(L'', hline(c, 1); rounded_corner(c, 1, TOP_RIGHT), rounded_corner(c, 1, BOTTOM_RIGHT));
1889+
CC(L'', hline(c, 1); rounded_corner(c, 1, BOTTOM_LEFT), rounded_corner(c, 1, TOP_LEFT));
1890+
CC(L'', vline(c, 1); rounded_corner(c, 1, TOP_LEFT), rounded_corner(c, 1, BOTTOM_RIGHT));
1891+
CC(L'', vline(c, 1); rounded_corner(c, 1, TOP_RIGHT), rounded_corner(c, 1, BOTTOM_LEFT));
1892+
CC(L'', hline(c, 1); rounded_corner(c, 1, TOP_LEFT), rounded_corner(c, 1, BOTTOM_RIGHT));
1893+
CC(L'', hline(c, 1); rounded_corner(c, 1, TOP_RIGHT), rounded_corner(c, 1, BOTTOM_LEFT));
18181894

18191895
#define P(ch, lines) S(ch, commit, lines, true); S(ch+1, commit, lines, false);
18201896
P(L'', 0);
@@ -1837,10 +1913,10 @@ START_ALLOW_CASE_RANGE
18371913
#define Q(ch, which) C(ch, corner, t, t, which); C(ch + 1, corner, f, t, which); C(ch + 2, corner, t, f, which); C(ch + 3, corner, f, f, which);
18381914
Q(L'┌', BOTTOM_RIGHT); Q(L'┐', BOTTOM_LEFT); Q(L'└', TOP_RIGHT); Q(L'┘', TOP_LEFT);
18391915
#undef Q
1840-
S(L'╭', rounded_corner, 1, TOP_LEFT);
1841-
S(L'╮', rounded_corner, 1, TOP_RIGHT);
1842-
S(L'╰', rounded_corner, 1, BOTTOM_LEFT);
1843-
S(L'╯', rounded_corner, 1, BOTTOM_RIGHT);
1916+
C(L'╭', rounded_corner, 1, TOP_LEFT);
1917+
C(L'╮', rounded_corner, 1, TOP_RIGHT);
1918+
C(L'╰', rounded_corner, 1, BOTTOM_LEFT);
1919+
C(L'╯', rounded_corner, 1, BOTTOM_RIGHT);
18441920

18451921
case L'┼' ... L'┼' + 15: cross(c, ch - L'┼'); break;
18461922
#define T(q, func) case q ... q + 7: func(c, q, ch - q); break;

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