Improved miter and bevel line joins

src/nanovg.c

@@ -1084,13 +1084,13 @@ static int nvg__curveDivs(float r, float arc, float tol)
 }
 
 static void nvg__chooseBevel(int bevel, struct NVGpoint* p0, struct NVGpoint* p1, float w,
-							float* x0, float* y0, float* x1, float* y1, float fringe)
+							float* x0, float* y0, float* x1, float* y1)
 {
 	if (bevel) {
-		*x0 = p1->x + p0->dy * w + p0->dx * fringe;
-		*y0 = p1->y - p0->dx * w + p0->dy * fringe;
-		*x1 = p1->x + p1->dy * w - p1->dx * fringe;
-		*y1 = p1->y - p1->dx * w - p1->dy * fringe;
+		*x0 = p1->x + p0->dy * w;
+		*y0 = p1->y - p0->dx * w;
+		*x1 = p1->x + p1->dy * w;
+		*y1 = p1->y - p1->dx * w;
 	} else {
 		*x0 = p1->x + p1->dmx * w;
 		*y0 = p1->y + p1->dmy * w;
@@ -1110,7 +1110,7 @@ static struct NVGvertex* nvg__roundJoin(struct NVGvertex* dst, struct NVGpoint*
 
 	if (p1->flags & NVG_PT_LEFT) {
 		float lx0,ly0,lx1,ly1,a0,a1;
-		nvg__chooseBevel(p1->flags & NVG_PR_INNERBEVEL, p0, p1, lw, &lx0,&ly0, &lx1,&ly1, -fringe);
+		nvg__chooseBevel(p1->flags & NVG_PR_INNERBEVEL, p0, p1, lw, &lx0,&ly0, &lx1,&ly1);
 		a0 = atan2f(-dly0, -dlx0);
 		a1 = atan2f(-dly1, -dlx1);
 		if (a1 > a0) a1 -= NVG_PI*2;
@@ -1133,7 +1133,7 @@ static struct NVGvertex* nvg__roundJoin(struct NVGvertex* dst, struct NVGpoint*
 
 	} else {
 		float rx0,ry0,rx1,ry1,a0,a1;
-		nvg__chooseBevel(p1->flags & NVG_PR_INNERBEVEL, p0, p1, -rw, &rx0,&ry0, &rx1,&ry1, -fringe);
+		nvg__chooseBevel(p1->flags & NVG_PR_INNERBEVEL, p0, p1, -rw, &rx0,&ry0, &rx1,&ry1);
 		a0 = atan2f(dly0, dlx0);
 		a1 = atan2f(dly1, dlx1);
 		if (a1 < a0) a1 += NVG_PI*2;
@@ -1161,48 +1161,85 @@ static struct NVGvertex* nvg__roundJoin(struct NVGvertex* dst, struct NVGpoint*
 static struct NVGvertex* nvg__bevelJoin(struct NVGvertex* dst, struct NVGpoint* p0, struct NVGpoint* p1,
 										float lw, float rw, float lu, float ru, float fringe)
 {
-	int left = 0, right = 0;
-	float dot, rf, lf;
 	float rx0,ry0,rx1,ry1;
 	float lx0,ly0,lx1,ly1;
+	float mx,my,len,mu;
+	int i, n;
+	float dlx0 = p0->dy;
+	float dly0 = -p0->dx;
+	float dlx1 = p1->dy;
+	float dly1 = -p1->dx;
 
 	if (p1->flags & NVG_PT_LEFT) {
-		left = p1->flags & NVG_PR_INNERBEVEL;
-		right = p1->flags & NVG_PT_BEVEL;
-		lf = 0;
-		rf = fringe;
-	} else {		
-		left = p1->flags & NVG_PT_BEVEL;
-		right = p1->flags & NVG_PR_INNERBEVEL;
-		lf = fringe;
-		rf = 0;
-	}
+		nvg__chooseBevel(p1->flags & NVG_PR_INNERBEVEL, p0, p1, lw, &lx0,&ly0, &lx1,&ly1);
 
-	nvg__chooseBevel(left, p0, p1, lw, &lx0,&ly0, &lx1,&ly1, lf);
-	nvg__chooseBevel(right, p0, p1, -rw, &rx0,&ry0, &rx1,&ry1, rf);
+		nvg__vset(dst, lx0, ly0, lu,1); dst++;
+		nvg__vset(dst, p1->x - dlx0*rw, p1->y - dly0*rw, ru,1); dst++;
 
-	dot = p0->dx*p1->dx + p0->dy*p1->dy;
-	dot = (1.0f - dot) * 0.5f;
+		if (p1->flags & NVG_PT_BEVEL) {
+			// TODO: this needs more work.
+			mx = (dlx0 + dlx1) * 0.5f;
+			my = (dly0 + dly1) * 0.5f;
+			len = sqrtf(mx*mx + my*my);
+			mu = ru + len*(lu-ru)*0.5f;
 
-	nvg__vset(dst, lx0, ly0, lu,1); dst++;
-	nvg__vset(dst, rx0, ry0, ru,1); dst++;
+			nvg__vset(dst, lx0, ly0, lu,1); dst++;
+			nvg__vset(dst, p1->x - dlx0*rw, p1->y - dly0*rw, ru,1); dst++;
+
+			nvg__vset(dst, lx1, ly1, lu,1); dst++;
+			nvg__vset(dst, p1->x - dlx1*rw, p1->y - dly1*rw, ru,1); dst++;
+		} else {
+			rx0 = p1->x - p1->dmx * rw;
+			ry0 = p1->y - p1->dmy * rw;
 
-	if (p1->flags & NVG_PR_INNERBEVEL) {
-		if (p1->flags & NVG_PT_LEFT) {
 			nvg__vset(dst, p1->x, p1->y, 0.5f,1); dst++;
+			nvg__vset(dst, p1->x - dlx0*rw, p1->y - dly0*rw, ru,1); dst++;
+
 			nvg__vset(dst, rx0, ry0, ru,1); dst++;
+			nvg__vset(dst, rx0, ry0, ru,1); dst++;
+
 			nvg__vset(dst, p1->x, p1->y, 0.5f,1); dst++;
+			nvg__vset(dst, p1->x - dlx1*rw, p1->y - dly1*rw, ru,1); dst++;
+		}
+
+		nvg__vset(dst, lx1, ly1, lu,1); dst++;
+		nvg__vset(dst, p1->x - dlx1*rw, p1->y - dly1*rw, ru,1); dst++;
+
+	} else {
+		nvg__chooseBevel(p1->flags & NVG_PR_INNERBEVEL, p0, p1, -rw, &rx0,&ry0, &rx1,&ry1);
+
+		nvg__vset(dst, p1->x + dlx0*lw, p1->y + dly0*lw, lu,1); dst++;
+		nvg__vset(dst, rx0, ry0, ru,1); dst++;
+
+		if (p1->flags & NVG_PT_BEVEL) {
+			// TODO: this needs more work.
+			mx = (dlx0 + dlx1) * 0.5f;
+			my = (dly0 + dly1) * 0.5f;
+			len = sqrtf(mx*mx + my*my);
+			mu = lu + len*(ru-lu)*0.5f;
+
+			nvg__vset(dst, p1->x + dlx0*lw, p1->y + dly0*lw, lu,1); dst++;
+			nvg__vset(dst, rx0, ry0, ru,1); dst++;
+
+			nvg__vset(dst, p1->x + dlx1*lw, p1->y + dly1*lw, lu,1); dst++;
 			nvg__vset(dst, rx1, ry1, ru,1); dst++;
 		} else {
-			nvg__vset(dst, lx0, ly0, lu,1); dst++;
+			lx0 = p1->x + p1->dmx * lw;
+			ly0 = p1->y + p1->dmy * lw;
+
+			nvg__vset(dst, p1->x + dlx0*lw, p1->y + dly0*lw, lu,1); dst++;
 			nvg__vset(dst, p1->x, p1->y, 0.5f,1); dst++;
-			nvg__vset(dst, lx1, ly1, lu,1); dst++;
+
+			nvg__vset(dst, lx0, ly0, lu,1); dst++;
+			nvg__vset(dst, lx0, ly0, lu,1); dst++;
+
+			nvg__vset(dst, p1->x + dlx1*lw, p1->y + dly1*lw, lu,1); dst++;
 			nvg__vset(dst, p1->x, p1->y, 0.5f,1); dst++;
 		}
-	}
 
-	nvg__vset(dst, lx1, ly1, lu,1); dst++;
-	nvg__vset(dst, rx1, ry1, ru,1); dst++;
+		nvg__vset(dst, p1->x + dlx1*rw, p1->y + dly1*rw, lu,1); dst++;
+		nvg__vset(dst, rx1, ry1, ru,1); dst++;
+	}
 
 	return dst;
 }
@@ -1294,7 +1331,7 @@ static int nvg__expandStrokeAndFill(struct NVGcontext* ctx, int feats, float w,
 			if (lineCap == NVG_ROUND)
 				cverts += (path->count + path->nbevel*(ncap+2) + 1) * 2; // plus one for loop
 			else
-				cverts += (path->count + path->nbevel*3 + 1) * 2; // plus one for loop
+				cverts += (path->count + path->nbevel*5 + 1) * 2; // plus one for loop
 			if (loop == 0) {
 				// space for caps
 				if (lineCap == NVG_ROUND) {

src/nanovg_gl3buf.h

@@ -369,7 +369,7 @@ static int glnvg__renderCreate(void* uptr)
 		"#ifdef EDGE_AA\n"
 		"// Stroke - from [0..1] to clipped pyramid, where the slope is 1px.\n"
 		"float strokeMask() {\n"
-		"	return min(1.0, (1.0-abs(ftcoord.x*2.0-1.0))*strokeMult) * ftcoord.y;\n"
+		"	return min(1.0, (1.0-abs(ftcoord.x*2.0-1.0))*strokeMult) * min(1.0, ftcoord.y);\n"
 		"}\n"
 		"#endif\n"
 		"\n"