From fdda8b8c12c740a141544192f29780ae997df47d Mon Sep 17 00:00:00 2001
From: ocornut <omarcornut@gmail.com>
Date: Mon, 19 Apr 2021 14:03:21 +0200
Subject: [PATCH] ImDrawList: Fixed/improved thickness of thick strokes with
 sharp angles. (#4053, #3366, #2964, #2868, #2518, #2183)

---
 docs/CHANGELOG.txt | 4 ++++
 imgui_draw.cpp     | 3 ++-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/docs/CHANGELOG.txt b/docs/CHANGELOG.txt
index 6e497633..0bd685ab 100644
--- a/docs/CHANGELOG.txt
+++ b/docs/CHANGELOG.txt
@@ -55,6 +55,10 @@ Other Changes:
 - LabelText: Fixed clipping of multi-line value text when label is single-line. (#4004)
 - LabelText: Fixed vertical alignment of single-line value text when label is multi-line. (#4004)
 - Popups: Added 'OpenPopup(ImGuiID id)' overload to facilitate calling from nested stacks. (#3993, #331) [@zlash]
+- ImDrawList: Fixed/improved thickness of thick strokes with sharp angles. (#4053, #3366, #2964, #2868, #2518, #2183)
+  Effectively introduced a regression in 1.67 (Jan 2019), and a fix in 1.70 (Apr 2019) but the fix wasn't actually on
+  par with original version. Now incorporating the correct fix + tweaked threshold to further mitigate the effect of
+  varying thickness, up to a certain degree. Shapes with very sharp angles and thick strokes will extend a little more.
 - ImDrawList: Fixed PathArcTo() regression from 1.82 preventing use of counter-clockwise angles. (#4030, #3491) [@thedmd]
 - Demo: Improved popups demo and comments.
 - Backends: SDL: Rework global mouse pos availability check listing supported platforms explicitly,
diff --git a/imgui_draw.cpp b/imgui_draw.cpp
index 2b0fdb8f..2604ac1a 100644
--- a/imgui_draw.cpp
+++ b/imgui_draw.cpp
@@ -689,7 +689,8 @@ void ImDrawList::PrimQuadUV(const ImVec2& a, const ImVec2& b, const ImVec2& c, c
 // On AddPolyline() and AddConvexPolyFilled() we intentionally avoid using ImVec2 and superfluous function calls to optimize debug/non-inlined builds.
 // Those macros expects l-values.
 #define IM_NORMALIZE2F_OVER_ZERO(VX,VY)     do { float d2 = VX*VX + VY*VY; if (d2 > 0.0f) { float inv_len = 1.0f / ImSqrt(d2); VX *= inv_len; VY *= inv_len; } } while (0)
-#define IM_FIXNORMAL2F(VX,VY)               do { float d2 = VX*VX + VY*VY; if (d2 < 0.5f) d2 = 0.5f; float inv_lensq = 1.0f / d2; VX *= inv_lensq; VY *= inv_lensq; } while (0)
+#define IM_FIXNORMAL2F_MAX_INVLEN2          500.0f
+#define IM_FIXNORMAL2F(VX,VY)               do { float d2 = VX*VX + VY*VY; if (d2 > 0.000001f) { float inv_len2 = 1.0f / d2; if (inv_len2 > IM_FIXNORMAL2F_MAX_INVLEN2) inv_len2 = IM_FIXNORMAL2F_MAX_INVLEN2; VX *= inv_len2; VY *= inv_len2; } } while (0)
 
 // TODO: Thickness anti-aliased lines cap are missing their AA fringe.
 // We avoid using the ImVec2 math operators here to reduce cost to a minimum for debug/non-inlined builds.