From fcd52f6db3dc9092dbd7a502e3e561ad16bf0743 Mon Sep 17 00:00:00 2001
From: Federico Angelilli <code@fedang.net>
Date: Wed, 20 Nov 2024 23:11:10 +0100
Subject: Fix capsule edge case

---
 src/util.c | 30 +++++++++++++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

(limited to 'src/util.c')

diff --git a/src/util.c b/src/util.c
index f9e00f2..b06fbae 100644
--- a/src/util.c
+++ b/src/util.c
@@ -214,9 +214,10 @@ bool iszero(const void *ptr, size_t size)
     return true;
 }
 
-void render_capsule(cairo_t *cr, int x, int y, int w, int r1, int r2)
+void render_capsule_fast(cairo_t *cr, int x, int y, int w, int r1, int r2)
 {
     const double degree = M_PI / 180.0;
+    assert(w >= r1 * 2);
 
     cairo_new_sub_path(cr);
     cairo_arc(cr, x + r1, y + r1, r2, 90 * degree, 270 * degree);
@@ -224,6 +225,33 @@ void render_capsule(cairo_t *cr, int x, int y, int w, int r1, int r2)
     cairo_close_path(cr);
 }
 
+void render_capsule(cairo_t *cr, int x, int y, int w, int r1, int r2)
+{
+    // Fast path
+    if (w >= r1 * 2) {
+        render_capsule_fast(cr, x, y, w, r1, r2);
+        return;
+    }
+
+    if (w == 0) return;
+
+    const double degree = M_PI / 180.0;
+    int x_off = -(r1 - w);
+
+    double angle1 = acos(1.0 - (w / 2.0) / (double)r1);
+    double angle2 = acos(1.0 - (w / 2.0) / (double)r1);
+
+    double left1  = 180 * degree - angle2,
+           left2  = 180 * degree + angle1,
+           right1 = 360 * degree - angle2,
+           right2 = angle2;
+
+    cairo_new_sub_path(cr);
+    cairo_arc(cr, x + r1, y + r1, r2, left1, left2);
+    cairo_arc(cr, x + x_off, y + r1, r2, right1, right2);
+    cairo_close_path(cr);
+}
+
 int snprintf_units(char *buffer, size_t max, uint64_t bytes, unit_t unit)
 {
     int base = unit & UNIT_SI ? 1000 : 1024;
-- 
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