diff --git a/docs/CHANGELOG.txt b/docs/CHANGELOG.txt
index a753438e7..bc326affc 100644
--- a/docs/CHANGELOG.txt
+++ b/docs/CHANGELOG.txt
@@ -34,6 +34,8 @@ HOW TO UPDATE?
 -----------------------------------------------------------------------
 
 Breaking Changes:
+- ImDrawList: Fixed rectangles with thick lines (>1.0f) not being as thick as requested. (#2518)
+  If you have custom rendering using thick lines, they will appear thicker now.
 - Examples: Vulkan: Added MinImageCount/ImageCount fields in ImGui_ImplVulkan_InitInfo, required
   during initialization to specify the number of in-flight image requested by swap chains.
   (was previously a hard #define IMGUI_VK_QUEUED_FRAMES 2). (#2071, #1677) [@nathanvoglsam]
@@ -73,6 +75,8 @@ Other Changes:
 - Separator: Declare its thickness (1.0f) to the layout, making items around separator more symmetrical.
 - Combo, Slider, Scrollbar: Improve rendering in situation when there's only a few pixels available (<3 pixels).
 - Nav: Fixed Drag/Slider functions going into text input mode when keyboard CTRL is held while pressing NavActivate.
+- ImDrawList: Improved algorithm for mitre joints on thick lines, preserving correct thickness up to 90 degrees
+  angles, also faster to output. (#2518) [@rmitton]
 - Misc: Added IM_MALLOC/IM_FREE macros mimicking IM_NEW/IM_DELETE so user doesn't need to revert
   to using the ImGui::MemAlloc()/MemFree() calls directly.
 - Metrics: Added "Show windows rectangles" tool to visualize the different rectangles.
diff --git a/imgui.cpp b/imgui.cpp
index 5a584c900..61f410a7c 100644
--- a/imgui.cpp
+++ b/imgui.cpp
@@ -369,6 +369,7 @@ CODE
  When you are not sure about a old symbol or function name, try using the Search/Find function of your IDE to look for comments or references in all imgui files.
  You can read releases logs https://github.com/ocornut/imgui/releases for more details.
 
+ - 2019/04/29 (1.70) - fixed ImDrawList rectangles with thick lines (>1.0f) not being as thick as requested. If you have custom rendering using rectangles with thick lines, they will appear thicker now.
  - 2019/03/04 (1.69) - renamed GetOverlayDrawList() to GetForegroundDrawList(). Kept redirection function (will obsolete).
  - 2019/02/26 (1.69) - renamed ImGuiColorEditFlags_RGB/ImGuiColorEditFlags_HSV/ImGuiColorEditFlags_HEX to ImGuiColorEditFlags_DisplayRGB/ImGuiColorEditFlags_DisplayHSV/ImGuiColorEditFlags_DisplayHex. Kept redirection enums (will obsolete).
  - 2019/02/14 (1.68) - made it illegal/assert when io.DisplayTime == 0.0f (with an exception for the first frame). If for some reason your time step calculation gives you a zero value, replace it with a dummy small value!
diff --git a/imgui_demo.cpp b/imgui_demo.cpp
index 05311c525..33f33af88 100644
--- a/imgui_demo.cpp
+++ b/imgui_demo.cpp
@@ -4077,44 +4077,48 @@ static void ShowExampleAppCustomRendering(bool* p_open)
         if (ImGui::BeginTabItem("Primitives"))
         {
             static float sz = 36.0f;
-            static float thickness = 4.0f;
-            static ImVec4 col = ImVec4(1.0f, 1.0f, 0.4f, 1.0f);
+            static float thickness = 3.0f;
+            static ImVec4 colf = ImVec4(1.0f, 1.0f, 0.4f, 1.0f);
             ImGui::DragFloat("Size", &sz, 0.2f, 2.0f, 72.0f, "%.0f");
             ImGui::DragFloat("Thickness", &thickness, 0.05f, 1.0f, 8.0f, "%.02f");
-            ImGui::ColorEdit4("Color", &col.x);
+            ImGui::ColorEdit4("Color", &colf.x);
             const ImVec2 p = ImGui::GetCursorScreenPos();
-            const ImU32 col32 = ImColor(col);
-            float x = p.x + 4.0f, y = p.y + 4.0f, spacing = 8.0f;
+            const ImU32 col = ImColor(colf);
+            float x = p.x + 4.0f, y = p.y + 4.0f;
+            float spacing = 10.0f;
+            ImDrawCornerFlags corners_none = 0;
+            ImDrawCornerFlags corners_all = ImDrawCornerFlags_All;
+            ImDrawCornerFlags corners_tl_br = ImDrawCornerFlags_TopLeft | ImDrawCornerFlags_BotRight;
             for (int n = 0; n < 2; n++)
             {
-                // First line uses a thickness of 1.0, second line uses the configurable thickness
+                // First line uses a thickness of 1.0f, second line uses the configurable thickness
                 float th = (n == 0) ? 1.0f : thickness;
-                draw_list->AddCircle(ImVec2(x + sz*0.5f, y + sz*0.5f), sz*0.5f, col32, 6, th); x += sz + spacing;   // Hexagon
-                draw_list->AddCircle(ImVec2(x + sz*0.5f, y + sz*0.5f), sz*0.5f, col32, 20, th); x += sz + spacing;  // Circle
-                draw_list->AddRect(ImVec2(x, y), ImVec2(x + sz, y + sz), col32, 0.0f,  ImDrawCornerFlags_All, th); x += sz + spacing;
-                draw_list->AddRect(ImVec2(x, y), ImVec2(x + sz, y + sz), col32, 10.0f, ImDrawCornerFlags_All, th); x += sz + spacing;
-                draw_list->AddRect(ImVec2(x, y), ImVec2(x + sz, y + sz), col32, 10.0f, ImDrawCornerFlags_TopLeft | ImDrawCornerFlags_BotRight, th); x += sz + spacing;
-                draw_list->AddTriangle(ImVec2(x + sz*0.5f, y), ImVec2(x + sz, y + sz - 0.5f), ImVec2(x, y + sz - 0.5f), col32, th); x += sz + spacing;
-                draw_list->AddTriangle(ImVec2(x + sz*0.5f, y), ImVec2(x + sz*0.6f, y + sz - 0.5f), ImVec2(x + sz*0.4f, y + sz - 0.5f), col32, th); x += sz + spacing;
-                draw_list->AddLine(ImVec2(x, y), ImVec2(x + sz, y), col32, th); x += sz + spacing;                  // Horizontal line (note: drawing a filled rectangle will be faster!)
-                draw_list->AddLine(ImVec2(x, y), ImVec2(x, y + sz), col32, th); x += spacing;                       // Vertical line (note: drawing a filled rectangle will be faster!)
-                draw_list->AddLine(ImVec2(x, y), ImVec2(x + sz, y + sz), col32, th); x += sz + spacing;             // Diagonal line
-                draw_list->AddBezierCurve(ImVec2(x, y), ImVec2(x + sz*1.3f, y + sz*0.3f), ImVec2(x + sz - sz*1.3f, y + sz - sz*0.3f), ImVec2(x + sz, y + sz), col32, th);
+                draw_list->AddCircle(ImVec2(x + sz*0.5f, y + sz*0.5f), sz*0.5f, col, 6, th);                x += sz + spacing;  // Hexagon
+                draw_list->AddCircle(ImVec2(x + sz*0.5f, y + sz*0.5f), sz*0.5f, col, 20, th);               x += sz + spacing;  // Circle
+                draw_list->AddRect(ImVec2(x, y), ImVec2(x + sz, y + sz), col, 0.0f,  corners_none, th);     x += sz + spacing;  // Square
+                draw_list->AddRect(ImVec2(x, y), ImVec2(x + sz, y + sz), col, 10.0f, corners_all, th);      x += sz + spacing;  // Square with all rounded corners
+                draw_list->AddRect(ImVec2(x, y), ImVec2(x + sz, y + sz), col, 10.0f, corners_tl_br, th);    x += sz + spacing;  // Square with two rounded corners
+                draw_list->AddTriangle(ImVec2(x+sz*0.5f,y), ImVec2(x+sz, y+sz-0.5f), ImVec2(x, y+sz-0.5f), col, th);      x += sz + spacing;      // Triangle
+                draw_list->AddTriangle(ImVec2(x+sz*0.2f,y), ImVec2(x, y+sz-0.5f), ImVec2(x+sz*0.4f, y+sz-0.5f), col, th); x += sz*0.4f + spacing; // Thin triangle
+                draw_list->AddLine(ImVec2(x, y), ImVec2(x + sz, y), col, th);                               x += sz + spacing;  // Horizontal line (note: drawing a filled rectangle will be faster!)
+                draw_list->AddLine(ImVec2(x, y), ImVec2(x, y + sz), col, th);                               x += spacing;       // Vertical line (note: drawing a filled rectangle will be faster!)
+                draw_list->AddLine(ImVec2(x, y), ImVec2(x + sz, y + sz), col, th);                          x += sz + spacing;  // Diagonal line
+                draw_list->AddBezierCurve(ImVec2(x, y), ImVec2(x + sz*1.3f, y + sz*0.3f), ImVec2(x + sz - sz*1.3f, y + sz - sz*0.3f), ImVec2(x + sz, y + sz), col, th);
                 x = p.x + 4;
                 y += sz + spacing;
             }
-            draw_list->AddCircleFilled(ImVec2(x + sz*0.5f, y + sz*0.5f), sz*0.5f, col32, 6); x += sz + spacing;     // Hexagon
-            draw_list->AddCircleFilled(ImVec2(x + sz*0.5f, y + sz*0.5f), sz*0.5f, col32, 32); x += sz + spacing;    // Circle
-            draw_list->AddRectFilled(ImVec2(x, y), ImVec2(x + sz, y + sz), col32); x += sz + spacing;
-            draw_list->AddRectFilled(ImVec2(x, y), ImVec2(x + sz, y + sz), col32, 10.0f); x += sz + spacing;
-            draw_list->AddRectFilled(ImVec2(x, y), ImVec2(x + sz, y + sz), col32, 10.0f, ImDrawCornerFlags_TopLeft | ImDrawCornerFlags_BotRight); x += sz + spacing;
-            draw_list->AddTriangleFilled(ImVec2(x + sz*0.5f, y), ImVec2(x + sz, y + sz - 0.5f), ImVec2(x, y + sz - 0.5f), col32); x += sz + spacing;
-            draw_list->AddTriangleFilled(ImVec2(x + sz*0.5f, y), ImVec2(x + sz*0.6f, y + sz - 0.5f), ImVec2(x + sz*0.4f, y + sz - 0.5f), col32); x += sz + spacing;
-            draw_list->AddRectFilled(ImVec2(x, y), ImVec2(x + sz, y + thickness), col32); x += sz + spacing;        // Horizontal line (faster than AddLine, but only handle integer thickness)
-            draw_list->AddRectFilled(ImVec2(x, y), ImVec2(x + thickness, y + sz), col32); x += spacing + spacing;   // Vertical line (faster than AddLine, but only handle integer thickness)
-            draw_list->AddRectFilled(ImVec2(x, y), ImVec2(x + 1, y + 1), col32);          x += sz;                  // Pixel (faster than AddLine)
+            draw_list->AddCircleFilled(ImVec2(x + sz*0.5f, y + sz*0.5f), sz*0.5f, col, 6);              x += sz + spacing;  // Hexagon
+            draw_list->AddCircleFilled(ImVec2(x + sz*0.5f, y + sz*0.5f), sz*0.5f, col, 32);             x += sz + spacing;  // Circle
+            draw_list->AddRectFilled(ImVec2(x, y), ImVec2(x + sz, y + sz), col);                        x += sz + spacing;  // Square
+            draw_list->AddRectFilled(ImVec2(x, y), ImVec2(x + sz, y + sz), col, 10.0f);                 x += sz + spacing;  // Square with all rounded corners
+            draw_list->AddRectFilled(ImVec2(x, y), ImVec2(x + sz, y + sz), col, 10.0f, corners_tl_br);  x += sz + spacing;  // Square with two rounded corners
+            draw_list->AddTriangleFilled(ImVec2(x+sz*0.5f,y), ImVec2(x+sz, y+sz-0.5f), ImVec2(x, y+sz-0.5f), col);      x += sz + spacing;      // Triangle
+            draw_list->AddTriangleFilled(ImVec2(x+sz*0.2f,y), ImVec2(x, y+sz-0.5f), ImVec2(x+sz*0.4f, y+sz-0.5f), col); x += sz*0.4f + spacing; // Thin triangle
+            draw_list->AddRectFilled(ImVec2(x, y), ImVec2(x + sz, y + thickness), col);                 x += sz + spacing;  // Horizontal line (faster than AddLine, but only handle integer thickness)
+            draw_list->AddRectFilled(ImVec2(x, y), ImVec2(x + thickness, y + sz), col);                 x += spacing*2.0f;  // Vertical line (faster than AddLine, but only handle integer thickness)
+            draw_list->AddRectFilled(ImVec2(x, y), ImVec2(x + 1, y + 1), col);                          x += sz;            // Pixel (faster than AddLine)
             draw_list->AddRectFilledMultiColor(ImVec2(x, y), ImVec2(x + sz, y + sz), IM_COL32(0, 0, 0, 255), IM_COL32(255, 0, 0, 255), IM_COL32(255, 255, 0, 255), IM_COL32(0, 255, 0, 255));
-            ImGui::Dummy(ImVec2((sz + spacing) * 9.5f, (sz + spacing) * 3));
+            ImGui::Dummy(ImVec2((sz + spacing) * 9.8f, (sz + spacing) * 3));
             ImGui::EndTabItem();
         }
 
diff --git a/imgui_draw.cpp b/imgui_draw.cpp
index 959036606..5d493600c 100644
--- a/imgui_draw.cpp
+++ b/imgui_draw.cpp
@@ -662,9 +662,8 @@ void ImDrawList::PrimQuadUV(const ImVec2& a, const ImVec2& b, const ImVec2& c, c
 
 // On AddPolyline() and AddConvexPolyFilled() we intentionally avoid using ImVec2 and superflous function calls to optimize debug/non-inlined builds.
 // Those macros expects l-values.
-#define IM_NORMALIZE2F_OVER_ZERO(VX,VY)                         { float d2 = VX*VX + VY*VY; if (d2 > 0.0f) { float inv_len = 1.0f / ImSqrt(d2); VX *= inv_len; VY *= inv_len; } }
-#define IM_NORMALIZE2F_OVER_EPSILON_CLAMP(VX,VY,EPS,INVLENMAX)  { float d2 = VX*VX + VY*VY; if (d2 > EPS)  { float inv_len = 1.0f / ImSqrt(d2); if (inv_len > INVLENMAX) inv_len = INVLENMAX; VX *= inv_len; VY *= inv_len; } }
-#define IM_FIXNORMAL2F(VX,VY)                                   { 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; }
+#define IM_NORMALIZE2F_OVER_ZERO(VX,VY)     { float d2 = VX*VX + VY*VY; if (d2 > 0.0f) { float inv_len = 1.0f / ImSqrt(d2); VX *= inv_len; VY *= inv_len; } }
+#define IM_FIXNORMAL2F(VX,VY)               { 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; }
 
 // 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.