ImDrawList: Clarified PathArcTo() need for a_min <= a_max with an assert. Fixed PathArcToFast() handling of a_min > a_max.

docs/CHANGELOG.txt

@@ -78,6 +78,8 @@ Other Changes:
 - Log/Capture: Improved the ascii look of various widgets, making large dumps more easily human readable.
 - ImDrawList: Fixed AddCircle()/AddCircleFilled() with (rad > 0.0f && rad < 1.0f && num_segments == 0). (#3738)
   Would lead to a buffer read overflow.
+- ImDrawList: Clarified PathArcTo() need for a_min <= a_max with an assert.
+- ImDrawList: Fixed PathArcToFast() handling of a_min > a_max.
 - Demo: Added 'Examples->Fullscreen Window' demo. (#3789)
 - Backends: Win32: Dynamically loading XInput DLL instead of linking with it, facilite compiling with
   old WindowSDK versions or running on Windows 7. (#3646, #3645, #3248, #2716) [@Demonese]

imgui_demo.cpp

@@ -7130,7 +7130,7 @@ static void ShowExampleAppCustomRendering(bool* p_open)
             static bool curve_segments_override = false;
             static int curve_segments_override_v = 8;
             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("Size", &sz, 0.2f, 2.0f, 100.0f, "%.0f");
             ImGui::DragFloat("Thickness", &thickness, 0.05f, 1.0f, 8.0f, "%.02f");
             ImGui::SliderInt("N-gon sides", &ngon_sides, 3, 12);
             ImGui::Checkbox("##circlesegmentoverride", &circle_segments_override);
@@ -7147,6 +7147,7 @@ static void ShowExampleAppCustomRendering(bool* p_open)
             const ImDrawCornerFlags corners_none = 0;
             const ImDrawCornerFlags corners_all = ImDrawCornerFlags_All;
             const ImDrawCornerFlags corners_tl_br = ImDrawCornerFlags_TopLeft | ImDrawCornerFlags_BotRight;
+            const float rounding = sz / 5.0f;
             const int circle_segments = circle_segments_override ? circle_segments_override_v : 0;
             const int curve_segments = curve_segments_override ? curve_segments_override_v : 0;
             float x = p.x + 4.0f;
@@ -7158,8 +7159,8 @@ static void ShowExampleAppCustomRendering(bool* p_open)
                 draw_list->AddNgon(ImVec2(x + sz*0.5f, y + sz*0.5f), sz*0.5f, col, ngon_sides, th);                 x += sz + spacing;  // N-gon
                 draw_list->AddCircle(ImVec2(x + sz*0.5f, y + sz*0.5f), sz*0.5f, col, circle_segments, 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, rounding, 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->AddRect(ImVec2(x, y), ImVec2(x + sz, y + sz), col, rounding, 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!)

imgui_draw.cpp

@@ -1018,11 +1018,12 @@ void ImDrawList::AddConvexPolyFilled(const ImVec2* points, const int points_coun
 
 void ImDrawList::PathArcToFast(const ImVec2& center, float radius, int a_min_of_12, int a_max_of_12)
 {
-    if (radius == 0.0f || a_min_of_12 > a_max_of_12)
+    if (radius == 0.0f)
     {
         _Path.push_back(center);
         return;
     }
+    IM_ASSERT(a_min_of_12 <= a_max_of_12);
 
     // For legacy reason the PathArcToFast() always takes angles where 2*PI is represented by 12,
     // but it is possible to set IM_DRAWLIST_ARCFAST_TESSELATION_MULTIPLIER to a higher value. This should compile to a no-op otherwise.
@@ -1046,6 +1047,7 @@ void ImDrawList::PathArcTo(const ImVec2& center, float radius, float a_min, floa
         _Path.push_back(center);
         return;
     }
+    IM_ASSERT(a_min <= a_max);
 
     // Note that we are adding a point at both a_min and a_max.
     // If you are trying to draw a full closed circle you don't want the overlapping points!