ImDrawList: added PathEllipticalArcTo(), AddEllipse(), AddEllipseFilled(). (#2743)

Rebased with mods by ocornut: defaults to num_segments==0, supports for auto-tesselation, tweak demo.

docs/CHANGELOG.txt

@@ -50,6 +50,7 @@ Other changes:
 - MenuBar: Fixed an issue where layouting an item in the menu-bar would erroneously
   register contents size in a way that would affect the scrolling layer.
   Was most often noticable when using an horizontal scrollbar. (#6789)
+- ImDrawList: Added AddEllipse(), AddEllipseFilled(), PathEllipticalArcTo(). (#2743) [@Doohl]
 - Backends: GLFW: Clear emscripten's MouseWheel callback before shutdown. (#6790, #6096, #4019) [@halx99]
 
 

imgui.h

@@ -2675,6 +2675,8 @@ struct ImDrawList
     IMGUI_API void  AddCircleFilled(const ImVec2& center, float radius, ImU32 col, int num_segments = 0);
     IMGUI_API void  AddNgon(const ImVec2& center, float radius, ImU32 col, int num_segments, float thickness = 1.0f);
     IMGUI_API void  AddNgonFilled(const ImVec2& center, float radius, ImU32 col, int num_segments);
+    IMGUI_API void  AddEllipse(const ImVec2& center, float radius_x, float radius_y, ImU32 col, float rot = 0.0f, int num_segments = 0, float thickness = 1.0f);
+    IMGUI_API void  AddEllipseFilled(const ImVec2& center, float radius_x, float radius_y, ImU32 col, float rot = 0.0f, int num_segments = 0);
     IMGUI_API void  AddText(const ImVec2& pos, ImU32 col, const char* text_begin, const char* text_end = NULL);
     IMGUI_API void  AddText(const ImFont* font, float font_size, const ImVec2& pos, ImU32 col, const char* text_begin, const char* text_end = NULL, float wrap_width = 0.0f, const ImVec4* cpu_fine_clip_rect = NULL);
     IMGUI_API void  AddPolyline(const ImVec2* points, int num_points, ImU32 col, ImDrawFlags flags, float thickness);
@@ -2699,6 +2701,7 @@ struct ImDrawList
     inline    void  PathStroke(ImU32 col, ImDrawFlags flags = 0, float thickness = 1.0f) { AddPolyline(_Path.Data, _Path.Size, col, flags, thickness); _Path.Size = 0; }
     IMGUI_API void  PathArcTo(const ImVec2& center, float radius, float a_min, float a_max, int num_segments = 0);
     IMGUI_API void  PathArcToFast(const ImVec2& center, float radius, int a_min_of_12, int a_max_of_12);                // Use precomputed angles for a 12 steps circle
+    IMGUI_API void  PathEllipticalArcTo(const ImVec2& center, float radius_x, float radius_y, float rot, float a_min, float a_max, int num_segments = 0); // Ellipse
     IMGUI_API void  PathBezierCubicCurveTo(const ImVec2& p2, const ImVec2& p3, const ImVec2& p4, int num_segments = 0); // Cubic Bezier (4 control points)
     IMGUI_API void  PathBezierQuadraticCurveTo(const ImVec2& p2, const ImVec2& p3, int num_segments = 0);               // Quadratic Bezier (3 control points)
     IMGUI_API void  PathRect(const ImVec2& rect_min, const ImVec2& rect_max, float rounding = 0.0f, ImDrawFlags flags = 0);

imgui_demo.cpp

@@ -7772,6 +7772,7 @@ static void ShowExampleAppCustomRendering(bool* p_open)
                 float th = (n == 0) ? 1.0f : thickness;
                 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->AddEllipse(ImVec2(x + sz*0.5f, y + sz*0.5f), sz*0.5f, sz*0.3f, col, -0.3f, circle_segments, th); x += sz + spacing;	// Ellipse
                 draw_list->AddRect(ImVec2(x, y), ImVec2(x + sz, y + sz), col, 0.0f, ImDrawFlags_None, th);          x += sz + spacing;  // Square
                 draw_list->AddRect(ImVec2(x, y), ImVec2(x + sz, y + sz), col, rounding, ImDrawFlags_None, th);      x += sz + spacing;  // Square with all 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
@@ -7792,8 +7793,9 @@ static void ShowExampleAppCustomRendering(bool* p_open)
                 x = p.x + 4;
                 y += sz + spacing;
             }
-            draw_list->AddNgonFilled(ImVec2(x + sz * 0.5f, y + sz * 0.5f), sz*0.5f, col, ngon_sides);               x += sz + spacing;  // N-gon
+            draw_list->AddNgonFilled(ImVec2(x + sz * 0.5f, y + sz * 0.5f), sz * 0.5f, col, ngon_sides);             x += sz + spacing;  // N-gon
-            draw_list->AddCircleFilled(ImVec2(x + sz*0.5f, y + sz*0.5f), sz*0.5f, col, circle_segments);            x += sz + spacing;  // Circle
+            draw_list->AddCircleFilled(ImVec2(x + sz * 0.5f, y + sz * 0.5f), sz * 0.5f, col, circle_segments);      x += sz + spacing;  // Circle
+            draw_list->AddEllipseFilled(ImVec2(x + sz * 0.5f, y + sz * 0.5f), sz * 0.5f, sz * 0.3f, col, -0.3f, circle_segments); x += sz + spacing;// Ellipse
             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
@@ -7804,7 +7806,7 @@ static void ShowExampleAppCustomRendering(bool* p_open)
             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) * 10.2f, (sz + spacing) * 3.0f));
+            ImGui::Dummy(ImVec2((sz + spacing) * 11.2f, (sz + spacing) * 3.0f));
             ImGui::PopItemWidth();
             ImGui::EndTabItem();
         }

imgui_draw.cpp

@@ -1217,6 +1217,27 @@ void ImDrawList::PathArcTo(const ImVec2& center, float radius, float a_min, floa
     }
 }
 
+void ImDrawList::PathEllipticalArcTo(const ImVec2& center, float radius_x, float radius_y, float rot, float a_min, float a_max, int num_segments)
+{
+    if (num_segments <= 0)
+        num_segments = _CalcCircleAutoSegmentCount(ImMax(radius_x, radius_y)); // A bit pessimistic, maybe there's a better computation to do here.
+
+    _Path.reserve(_Path.Size + (num_segments + 1));
+
+    const float cos_rot = ImCos(rot);
+    const float sin_rot = ImSin(rot);
+    for (int i = 0; i <= num_segments; i++)
+    {
+        const float a = a_min + ((float)i / (float)num_segments) * (a_max - a_min);
+        ImVec2 point(ImCos(a) * radius_x, ImSin(a) * radius_y);
+        const float rel_x = (point.x * cos_rot) - (point.y * sin_rot);
+        const float rel_y = (point.x * sin_rot) + (point.y * cos_rot);
+        point.x = rel_x + center.x;
+        point.y = rel_y + center.y;
+        _Path.push_back(point);
+    }
+}
+
 ImVec2 ImBezierCubicCalc(const ImVec2& p1, const ImVec2& p2, const ImVec2& p3, const ImVec2& p4, float t)
 {
     float u = 1.0f - t;
@@ -1547,6 +1568,35 @@ void ImDrawList::AddNgonFilled(const ImVec2& center, float radius, ImU32 col, in
     PathFillConvex(col);
 }
 
+// Ellipse
+void ImDrawList::AddEllipse(const ImVec2& center, float radius_x, float radius_y, ImU32 col, float rot, int num_segments, float thickness)
+{
+    if ((col & IM_COL32_A_MASK) == 0)
+        return;
+
+    if (num_segments <= 0)
+        num_segments = _CalcCircleAutoSegmentCount(ImMax(radius_x, radius_y)); // A bit pessimistic, maybe there's a better computation to do here.
+
+    // Because we are filling a closed shape we remove 1 from the count of segments/points
+    const float a_max = IM_PI * 2.0f * ((float)num_segments - 1.0f) / (float)num_segments;
+    PathEllipticalArcTo(center, radius_x, radius_y, rot, 0.0f, a_max, num_segments - 1);
+    PathStroke(col, true, thickness);
+}
+
+void ImDrawList::AddEllipseFilled(const ImVec2& center, float radius_x, float radius_y, ImU32 col, float rot, int num_segments)
+{
+    if ((col & IM_COL32_A_MASK) == 0)
+        return;
+
+    if (num_segments <= 0)
+        num_segments = _CalcCircleAutoSegmentCount(ImMax(radius_x, radius_y)); // A bit pessimistic, maybe there's a better computation to do here.
+
+    // Because we are filling a closed shape we remove 1 from the count of segments/points
+    const float a_max = IM_PI * 2.0f * ((float)num_segments - 1.0f) / (float)num_segments;
+    PathEllipticalArcTo(center, radius_x, radius_y, rot, 0.0f, a_max, num_segments - 1);
+    PathFillConvex(col);
+}
+
 // Cubic Bezier takes 4 controls points
 void ImDrawList::AddBezierCubic(const ImVec2& p1, const ImVec2& p2, const ImVec2& p3, const ImVec2& p4, ImU32 col, float thickness, int num_segments)
 {