From f4c2d116d965bcce6baadedc7ec87563a3a377c3 Mon Sep 17 00:00:00 2001
From: Mira Grudzinska <mira@lottiefiles.com>
Date: Thu, 13 Feb 2025 18:24:49 +0100
Subject: [PATCH] wg_engine: fix dash offset behavior

For an odd number of dash/gap segments, the offset was
handled incorrectly because the non-doubled count of
dashes and gaps was used.
Additionally, in ddcbbf7, an error was introduced by
overlooking the fact that the offset can shift the dash
pattern in such a way that the first segment of the dashed
line becomes a gap.
---
 src/renderer/wg_engine/tvgWgGeometry.h | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/renderer/wg_engine/tvgWgGeometry.h b/src/renderer/wg_engine/tvgWgGeometry.h
index ce6156f4..70a8e12a 100755
--- a/src/renderer/wg_engine/tvgWgGeometry.h
+++ b/src/renderer/wg_engine/tvgWgGeometry.h
@@ -295,21 +295,22 @@ struct WgVertexBufferInd
         float len_total = dashPattern[index_dash];
         // get dashes length
         float dashes_lenth{};
-        for (uint32_t i = 0; i < dashCnt; i++) 
-            dashes_lenth += dashPattern[i];
+        for (uint32_t i = 0; i < dashCnt * (dashCnt % 2 + 1); i++)
+            dashes_lenth += dashPattern[i % dashCnt];
         if (dashes_lenth == 0) return;
         // normalize dash offset
         float dashOffset = rstroke->dashOffset;
         while(dashOffset < 0) dashOffset += dashes_lenth;
         while(dashOffset > dashes_lenth) dashOffset -= dashes_lenth;
+        auto gap = false;
         // scip dashes by offset
-        while(len_total < dashOffset) { 
+        while(len_total < dashOffset) {
             index_dash = (index_dash + 1) % dashCnt;
             len_total += dashPattern[index_dash];
+            gap = !gap;
         }
         len_total -= dashOffset;
         // iterate by polyline points
-        auto gap = false;
         for (uint32_t i = 0; i < buff.vcount - 1; i++) {
             // append current polyline point
             if (!gap) dashed.append(buff.vbuff[i]);