From 7c0f7ef46fc224daf21ba060e925fa113f3424b4 Mon Sep 17 00:00:00 2001
From: John Alanbrook <john@pockle.world>
Date: Thu, 16 Feb 2023 07:56:22 +0000
Subject: [PATCH] line thicknesses

---
 source/engine/debug/debugdraw.c | 77 +++++++++++++++++++++++++++++++++
 1 file changed, 77 insertions(+)

diff --git a/source/engine/debug/debugdraw.c b/source/engine/debug/debugdraw.c
index 0938389..6d40d02 100644
--- a/source/engine/debug/debugdraw.c
+++ b/source/engine/debug/debugdraw.c
@@ -91,13 +91,62 @@ cpVect inflateline(cpVect a, cpVect b, float d)
   return c;
 }
 
+cpVect inflatepoint(cpVect a, cpVect b, cpVect c, float d)
+{
+  cpVect ba = cpvnormalize(cpvsub(a,b));
+  cpVect bc = cpvnormalize(cpvsub(c,b));
+  cpVect avg = cpvadd(ba, bc);
+  avg = cpvmult(avg, 0.5);
+  float dot = cpvdot(ba, bc);
+  dot /= cpvlength(ba);
+  dot /= cpvlength(bc);
+  float mid = acos(dot)/2;
+  avg = cpvnormalize(avg);
+  return cpvadd(b, cpvmult(avg, d/sin(mid)));
+}
+
+void inflatepoints(cpVect *r, cpVect *p, float d, int n)
+{    if (d == 0) {
+       for (int i = 0; i < n; i++)
+         r[i] = p[i];
+
+       return;
+     }
+     
+     if (cpveql(p[0], p[n-1])) {
+        r[0] = inflatepoint(p[n-2],p[0],p[1],d);
+	r[n-1] = r[0];
+      } else {
+        cpVect outdir = cpvmult(cpvnormalize(cpvsub(p[0],p[1])),fabs(d));
+	cpVect perp;
+	if (d > 0)
+          perp = cpvperp(outdir);
+	else
+	  perp = cpvrperp(outdir);
+        r[0] = cpvadd(p[0],cpvadd(outdir,perp));
+	
+	outdir = cpvmult(cpvnormalize(cpvsub(p[n-1],p[n-2])),fabs(d));
+	if (d > 0)
+          perp = cpvrperp(outdir);
+	else
+	  perp = cpvperp(outdir);
+        r[n-1] = cpvadd(p[n-1],cpvadd(outdir,perp));
+      }
+
+      for (int i = 0; i < n-2; i++)
+        r[i+1] = inflatepoint(p[i],p[i+1],p[i+2], d);
+
+}
+
 void draw_edge(cpVect  *points, int n, float *color, int thickness)
 {
     static_assert(sizeof(cpVect) == 2*sizeof(float));
 
     shader_use(rectShader);
     shader_setvec3(rectShader, "linecolor", color);
+
     if (thickness <= 1) {
+      shader_setfloat(rectShader, "alpha", 1.f);
       glBindBuffer(GL_ARRAY_BUFFER, rectVBO);
       glBufferData(GL_ARRAY_BUFFER, sizeof(float) * n * 2, points, GL_DYNAMIC_DRAW);
       glBindVertexArray(rectVAO);
@@ -107,6 +156,34 @@ void draw_edge(cpVect  *points, int n, float *color, int thickness)
       shader_setfloat(rectShader, "alpha", 1.f);
       glDrawArrays(GL_LINE_STRIP, 0, n);
     } else {
+      shader_setfloat(rectShader, "alpha", 0.1f);
+      thickness /= 2;
+      glBindBuffer(GL_ARRAY_BUFFER, rectVBO);
+      glBindVertexArray(rectVAO);
+      glEnableVertexAttribArray(0);
+      glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, NULL);
+
+      cpVect inflate_out[n];
+      cpVect inflate_in[n];
+
+      inflatepoints(inflate_out, points, thickness, n);
+      inflatepoints(inflate_in, points, -thickness, n);
+      cpVect interleaved[n*2];
+      for (int i = 0; i < n; i++) {
+        interleaved[i*2] = inflate_in[i];
+	interleaved[i*2+1] = inflate_out[i];
+      }
+      glBufferData(GL_ARRAY_BUFFER, sizeof(interleaved), interleaved, GL_DYNAMIC_DRAW);
+      glDrawArrays(GL_TRIANGLE_STRIP, 0, n*2);
+
+      shader_setfloat(rectShader, "alpha", 1.f);
+
+      cpVect inlined[n*2];
+      for (int i = 0; i < n; i++)
+        inlined[i] = inflate_out[n-1-i];
+      memcpy(inlined+n,inflate_in,sizeof(inflate_in));
+      glBufferData(GL_ARRAY_BUFFER,sizeof(inlined),inlined,GL_DYNAMIC_DRAW);
+      glDrawArrays(GL_LINE_LOOP,0,n*2);
       
     }
 }