From 95cd0863eb594bca2c0abaa52ffce70e32bb5b1a Mon Sep 17 00:00:00 2001
From: Mira Grudzinska <mira@lottiefiles.com>
Date: Thu, 13 Feb 2025 23:42:02 +0100
Subject: [PATCH] gl_engine: fix dashing

Incorrect condition for drawing segments in cubics;
missing checks.

@Issue: https://github.com/thorvg/thorvg/issues/2729
@Issue: https://github.com/thorvg/thorvg/issues/3222
---
 src/renderer/gl_engine/tvgGlTessellator.cpp | 41 +++++++++++----------
 1 file changed, 21 insertions(+), 20 deletions(-)

diff --git a/src/renderer/gl_engine/tvgGlTessellator.cpp b/src/renderer/gl_engine/tvgGlTessellator.cpp
index 54b6a572..200671f1 100644
--- a/src/renderer/gl_engine/tvgGlTessellator.cpp
+++ b/src/renderer/gl_engine/tvgGlTessellator.cpp
@@ -1999,7 +1999,7 @@ void DashStroke::doStroke(const PathCommand *cmds, uint32_t cmd_count, const Poi
             case PathCommand::MoveTo: {
                 // reset the dash state
                 mCurrIdx = 0;
-                mCurrLen = 0.f;
+                mCurrLen = mDashPattern[0];
                 mCurOpGap = false;
                 mPtStart = mPtCur = *pts;
                 pts++;
@@ -2036,16 +2036,17 @@ void DashStroke::dashLineTo(const Point& to)
         Line curr = {mPtCur, to};
 
         while (len > mCurrLen) {
-            len -= mCurrLen;
-
-            Line left, right;
-            curr.split(mCurrLen, left, right);
-
+            Line right;
+            if (mCurrLen > 0.0f) {
+                Line left;
+                curr.split(mCurrLen, left, right);
+                len -= mCurrLen;
+                if (!mCurOpGap) {
+                    this->moveTo(left.pt1);
+                    this->lineTo(left.pt2);
+                }
+            } else right = curr;
             mCurrIdx = (mCurrIdx + 1) % mDashCount;
-            if (!mCurOpGap) {
-                this->moveTo(left.pt1);
-                this->lineTo(left.pt2);
-            }
             mCurrLen = mDashPattern[mCurrIdx];
             mCurOpGap = !mCurOpGap;
             curr = right;
@@ -2086,16 +2087,16 @@ void DashStroke::dashCubicTo(const Point& cnt1, const Point& cnt2, const Point&
         }
     } else {
         while (len > mCurrLen) {
-            len -= mCurrLen;
-
-            Bezier left, right;
-            cur.split(mCurrLen, left, right);
-
-            if (mCurrIdx == 0) {
-                this->moveTo(left.start);
-                this->cubicTo(left.ctrl1, left.ctrl2, left.end);
-            }
-
+            Bezier right;
+            if (mCurrLen > 0.0f) {
+                Bezier left;
+                cur.split(mCurrLen, left, right);
+                len -= mCurrLen;
+                if (!mCurOpGap) {
+                    this->moveTo(left.start);
+                    this->cubicTo(left.ctrl1, left.ctrl2, left.end);
+                }
+            } else right = cur;
             mCurrIdx = (mCurrIdx + 1) % mDashCount;
             mCurrLen = mDashPattern[mCurrIdx];
             mCurOpGap = !mCurOpGap;