From 4be8155002b2248335eeac57fb185f2020f8f8bb Mon Sep 17 00:00:00 2001
From: omar <omarcornut@gmail.com>
Date: Thu, 16 Jul 2020 21:51:49 +0200
Subject: [PATCH] Style Editor: Added preview of circle auto-tessellation when
 editing the corresponding value..

---
 docs/CHANGELOG.txt |  3 ++-
 imgui_demo.cpp     | 23 ++++++++++++++++++++++-
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/docs/CHANGELOG.txt b/docs/CHANGELOG.txt
index ebce7da01..4e3a5a1a1 100644
--- a/docs/CHANGELOG.txt
+++ b/docs/CHANGELOG.txt
@@ -54,6 +54,7 @@ Other Changes:
 - ImDrawList: Fixed minor bug introduced in 1.75 where AddCircle() with 12 segments would generate
   an extra vertex. (This bug was mistakenly marked as fixed in earlier 1.77 release). [@ShironekoBen]
 - Demo: Tweak "Child Windows" section.
+- Style Editor: Added preview of circle auto-tessellation when editing the corresponding value.
 - Backends: OpenGL3: Added support for glad2 loader. (#3330) [@moritz-h]
 
 
@@ -129,7 +130,7 @@ Other Changes:
   Updated various links/wiki accordingly. Added FAQ entry about DPI. (#2861) [@ButternCream, @ocornut]
 - CI: Added CI test to verify we're never accidentally dragging libstdc++ (on some compiler setups,
   static constructors for non-pod data seems to drag in libstdc++ due to thread-safety concerns).
-  Fixed a static constructor which led to this dependency on some compiler setups.
+  Fixed a static constructor which led to this dependency on some compiler setups. [@rokups]
 - Backends: Win32: Support for #define NOGDI, won't try to call GetDeviceCaps(). (#3137, #2327)
 - Backends: Win32: Fix _WIN32_WINNT < 0x0600 (MinGW defaults to 0x502 == Windows 2003). (#3183)
 - Backends: SDL: Report a zero display-size when window is minimized, consistent with other backends,
diff --git a/imgui_demo.cpp b/imgui_demo.cpp
index 97e2951d3..49ac4180e 100644
--- a/imgui_demo.cpp
+++ b/imgui_demo.cpp
@@ -3829,7 +3829,28 @@ void ImGui::ShowStyleEditor(ImGuiStyle* ref)
             ImGui::PushItemWidth(100);
             ImGui::DragFloat("Curve Tessellation Tolerance", &style.CurveTessellationTol, 0.02f, 0.10f, 10.0f, "%.2f");
             if (style.CurveTessellationTol < 0.10f) style.CurveTessellationTol = 0.10f;
-            ImGui::DragFloat("Circle segment Max Error", &style.CircleSegmentMaxError, 0.01f, 0.10f, 10.0f, "%.2f");
+
+            // When editing the "Circle Segment Max Error" value, draw a preview of its effect on auto-tessellated circles.
+            ImGui::DragFloat("Circle Segment Max Error", &style.CircleSegmentMaxError, 0.01f, 0.10f, 10.0f, "%.2f");
+            if (ImGui::IsItemActive())
+            {
+                ImGui::SetNextWindowPos(ImGui::GetCursorScreenPos());
+                ImGui::BeginTooltip();
+                ImVec2 p = ImGui::GetCursorScreenPos();
+                float RAD_MIN = 10.0f, RAD_MAX = 80.0f;
+                float off_x = 10.0f;
+                for (int n = 0; n < 7; n++)
+                {
+                    const float rad = RAD_MIN + (RAD_MAX - RAD_MIN) * (float)n / (7.0f - 1.0f);
+                    ImGui::GetWindowDrawList()->AddCircle(ImVec2(p.x + off_x + rad, p.y + RAD_MAX), rad, ImGui::GetColorU32(ImGuiCol_Text), 0);
+                    off_x += 10.0f + rad * 2.0f;
+                }
+                ImGui::Dummy(ImVec2(off_x, RAD_MAX * 2.0f));
+                ImGui::EndTooltip();
+            }
+            ImGui::SameLine();
+            HelpMarker("When drawing circle primitives with \"num_segments == 0\" tesselation will be calculated automatically.");
+
             ImGui::DragFloat("Global Alpha", &style.Alpha, 0.005f, 0.20f, 1.0f, "%.2f"); // Not exposing zero here so user doesn't "lose" the UI (zero alpha clips all widgets). But application code could have a toggle to switch between zero and non-zero.
             ImGui::PopItemWidth();