From c29b6a615260d140c2dc04a05fa47c43e66d6f35 Mon Sep 17 00:00:00 2001
From: Robin Watts <robin.watts@artifex.com>
Date: Mon, 23 Jan 2012 20:23:50 +0000
Subject: Do XPS mitering properly.

Modified version of Sumatras patch. Thanks for this.
---
 draw/draw_path.c | 66 ++++++++++++++++++++++++++++++++------------------------
 1 file changed, 38 insertions(+), 28 deletions(-)

(limited to 'draw')

diff --git a/draw/draw_path.c b/draw/draw_path.c
index 29614ec5..de616ef7 100644
--- a/draw/draw_path.c
+++ b/draw/draw_path.c
@@ -225,6 +225,7 @@ fz_add_line_join(struct sctx *s, fz_point a, fz_point b, fz_point c)
 	float dmr2;
 	float scale;
 	float cross;
+	float len0, len1;
 
 	dx0 = b.x - a.x;
 	dy0 = b.y - a.y;
@@ -242,16 +243,18 @@ fz_add_line_join(struct sctx *s, fz_point a, fz_point b, fz_point c)
 		cross = -cross;
 	}
 
-	if (dx0 * dx0 + dy0 * dy0 < FLT_EPSILON)
+	len0 = dx0 * dx0 + dy0 * dy0;
+	if (len0 < FLT_EPSILON)
 		linejoin = FZ_LINEJOIN_BEVEL;
-	if (dx1 * dx1 + dy1 * dy1 < FLT_EPSILON)
+	len1 = dx1 * dx1 + dy1 * dy1;
+	if (len1 < FLT_EPSILON)
 		linejoin = FZ_LINEJOIN_BEVEL;
 
-	scale = linewidth / sqrtf(dx0 * dx0 + dy0 * dy0);
+	scale = linewidth / sqrtf(len0);
 	dlx0 = dy0 * scale;
 	dly0 = -dx0 * scale;
 
-	scale = linewidth / sqrtf(dx1 * dx1 + dy1 * dy1);
+	scale = linewidth / sqrtf(len1);
 	dlx1 = dy1 * scale;
 	dly1 = -dx1 * scale;
 
@@ -262,15 +265,35 @@ fz_add_line_join(struct sctx *s, fz_point a, fz_point b, fz_point c)
 	if (cross * cross < FLT_EPSILON && dx0 * dx1 + dy0 * dy1 >= 0)
 		linejoin = FZ_LINEJOIN_BEVEL;
 
-	if (linejoin == FZ_LINEJOIN_MITER)
-		if (dmr2 * miterlimit * miterlimit < linewidth * linewidth)
+	/* XPS miter joins are clipped at miterlength, rather than simply
+	 * being converted to bevelled joins. */
+	if (linejoin == FZ_LINEJOIN_MITER_XPS)
+	{
+		if (cross == 0)
 			linejoin = FZ_LINEJOIN_BEVEL;
+		else if (dmr2 * miterlimit * miterlimit >= linewidth * linewidth)
+			linejoin = FZ_LINEJOIN_MITER;
+		else
+		{
+			float k, t0x, t0y, t1x, t1y;
+			scale = linewidth * linewidth / dmr2;
+			dmx *= scale;
+			dmy *= scale;
+			k = (scale - linewidth * miterlimit / sqrtf(dmr2)) / (scale - 1);
+			t0x = b.x - dmx + k * (dmx - dlx0);
+			t0y = b.y - dmy + k * (dmy - dly0);
+			t1x = b.x - dmx + k * (dmx - dlx1);
+			t1y = b.y - dmy + k * (dmy - dly1);
 
-	if (linejoin == FZ_LINEJOIN_BEVEL)
-	{
-		fz_add_line(s, b.x - dlx0, b.y - dly0, b.x - dlx1, b.y - dly1);
-		fz_add_line(s, b.x + dlx1, b.y + dly1, b.x + dlx0, b.y + dly0);
+			fz_add_line(s, b.x + dlx1, b.y + dly1, b.x + dlx0, b.y + dly0);
+			fz_add_line(s, b.x - dlx0, b.y - dly0, t0x, t0y);
+			fz_add_line(s, t0x, t0y, t1x, t1y);
+			fz_add_line(s, t1x, t1y, b.x - dlx1, b.y - dly1);
+		}
 	}
+	else if (linejoin == FZ_LINEJOIN_MITER)
+		if (dmr2 * miterlimit * miterlimit < linewidth * linewidth)
+			linejoin = FZ_LINEJOIN_BEVEL;
 
 	if (linejoin == FZ_LINEJOIN_MITER)
 	{
@@ -283,27 +306,14 @@ fz_add_line_join(struct sctx *s, fz_point a, fz_point b, fz_point c)
 		fz_add_line(s, b.x - dmx, b.y - dmy, b.x - dlx1, b.y - dly1);
 	}
 
-	/* XPS miter joins are clipped at miterlength, rather than simply
-	 * being converted to bevelled joins. */
-	if (linejoin == FZ_LINEJOIN_MITER_XPS)
-	{
-		scale = linewidth * linewidth / dmr2;
-		dmx *= scale;
-		dmy *= scale;
 
-		if (cross == 0)
-		{
-			fz_add_line(s, b.x + dlx1, b.y + dly1, b.x + dlx0, b.y + dly0);
-			fz_add_line(s, b.x - dlx0, b.y - dly0, b.x - dlx1, b.y - dly1);
-		}
-		else
-		{
-			fz_add_line(s, b.x + dlx1, b.y + dly1, b.x + dlx0, b.y + dly0);
-			fz_add_line(s, b.x - dlx0, b.y - dly0, b.x - dmx, b.y - dmy);
-			fz_add_line(s, b.x - dmx, b.y - dmy, b.x - dlx1, b.y - dly1);
-		}
+	if (linejoin == FZ_LINEJOIN_BEVEL)
+	{
+		fz_add_line(s, b.x - dlx0, b.y - dly0, b.x - dlx1, b.y - dly1);
+		fz_add_line(s, b.x + dlx1, b.y + dly1, b.x + dlx0, b.y + dly0);
 	}
 
+
 	if (linejoin == FZ_LINEJOIN_ROUND)
 	{
 		fz_add_line(s, b.x + dlx1, b.y + dly1, b.x + dlx0, b.y + dly0);
-- 
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