From 17dba653a9bca435b04f195a42268bac258fd4ca Mon Sep 17 00:00:00 2001
From: SergeyN <nenakhov.sergey@gmail.com>
Date: Thu, 14 May 2020 01:52:47 +0200
Subject: [PATCH] bbox overlap test to avoid disappearing lines when two ends
 end up outside culling area

---
 implot.cpp | 59 +++++++++++++++++++++++++-----------------------------
 1 file changed, 27 insertions(+), 32 deletions(-)

diff --git a/implot.cpp b/implot.cpp
index 45aa640..c8245e1 100644
--- a/implot.cpp
+++ b/implot.cpp
@@ -2090,39 +2090,34 @@ inline void RenderLineStrip(Transformer transformer, ImDrawList& DrawList, Gette
    if (i_start >= count ) i_start -= count;
    int i_end = offset + count;
    if (i_end >= count) i_end -= count;
+   
+   const int    segments  = count - 1;
+   ImVec2 p1 = transformer(getter(offset));    
+   if (HasFlag(gp.CurrentPlot->Flags, ImPlotFlags_AntiAliased)) {
+      for (int i1 = i_start; i1 != i_end; i1 = i1 + 1 < count ? i1 + 1 : i1 + 1 - count) {
+         ImVec2 p2 = transformer(getter(i1));
 
-    const int    segments  = count - 1;
-    ImVec2 p1 = transformer(getter(offset));
-    bool test1 = !cull || gp.BB_Grid.Contains(p1);
-    if (HasFlag(gp.CurrentPlot->Flags, ImPlotFlags_AntiAliased)) {
-        for (int i1 = i_start; i1 != i_end; i1 = i1 + 1 < count ? i1 + 1 : i1 + 1 - count)
-        {
-            ImVec2 p2 = transformer(getter(i1));
-            bool test2 = !cull || gp.BB_Grid.Contains(p2);
-            if (test1 | test2)
-                RenderLineAA(DrawList, p1, p2, line_weight, col_line);
-            p1 = p2;
-            test1 = test2;
-        }
-    }
-    else {
-        const ImVec2 uv = DrawList._Data->TexUvWhitePixel;
-        DrawList.PrimReserve(segments * 6, segments * 4);
-        int segments_culled = 0;
-        for (int i1 = i_start; i1 != i_end; i1 = i1 + 1 < count ? i1 + 1 : i1 + 1 - count)
-        {
-           ImVec2 p2 = transformer(getter(i1));
-           bool test2 = !cull || gp.BB_Grid.Contains(p2);
-           if (test1 | test2)
-               RenderLine(DrawList, p1, p2, line_weight, col_line, uv);
-           else
-               segments_culled++;
-           p1 = p2;
-           test1 = test2;
-        }
-        if (segments_culled > 0)
-            DrawList.PrimUnreserve(segments_culled * 6, segments_culled * 4);
-    }
+         if (!cull || gp.BB_Grid.Overlaps(ImRect(ImMin(p1,p2), ImMax(p1,p2))))
+               RenderLineAA(DrawList, p1, p2, line_weight, col_line);
+         p1 = p2;            
+      }
+   }
+   else {
+      const ImVec2 uv = DrawList._Data->TexUvWhitePixel;
+      DrawList.PrimReserve(segments * 6, segments * 4);
+      int segments_culled = 0;
+      for (int i1 = i_start; i1 != i_end; i1 = i1 + 1 < count ? i1 + 1 : i1 + 1 - count) {
+         ImVec2 p2 = transformer(getter(i1));           
+
+         if (!cull || gp.BB_Grid.Overlaps(ImRect(ImMin(p1, p2), ImMax(p1, p2))))
+            RenderLine(DrawList, p1, p2, line_weight, col_line, uv);
+         else
+            segments_culled++;
+         p1 = p2;
+      }
+      if (segments_culled > 0)
+         DrawList.PrimUnreserve(segments_culled * 6, segments_culled * 4);
+   }
 }
 
 //-----------------------------------------------------------------------------