ScrollbarEx: clarify use of flags and make them optional. (#8215)

imgui_internal.h

@@ -3398,7 +3398,7 @@ namespace ImGui
     IMGUI_API bool          CloseButton(ImGuiID id, const ImVec2& pos);
     IMGUI_API bool          CollapseButton(ImGuiID id, const ImVec2& pos);
     IMGUI_API void          Scrollbar(ImGuiAxis axis);
-    IMGUI_API bool          ScrollbarEx(const ImRect& bb, ImGuiID id, ImGuiAxis axis, ImS64* p_scroll_v, ImS64 avail_v, ImS64 contents_v, ImDrawFlags flags);
+    IMGUI_API bool          ScrollbarEx(const ImRect& bb, ImGuiID id, ImGuiAxis axis, ImS64* p_scroll_v, ImS64 avail_v, ImS64 contents_v, ImDrawFlags draw_rounding_flags = 0);
     IMGUI_API ImRect        GetWindowScrollbarRect(ImGuiWindow* window, ImGuiAxis axis);
     IMGUI_API ImGuiID       GetWindowScrollbarID(ImGuiWindow* window, ImGuiAxis axis);
     IMGUI_API ImGuiID       GetWindowResizeCornerID(ImGuiWindow* window, int n); // 0..3: corners

imgui_widgets.cpp

@@ -950,7 +950,7 @@ void ImGui::Scrollbar(ImGuiAxis axis)
 // - We store values as normalized ratio and in a form that allows the window content to change while we are holding on a scrollbar
 // - We handle both horizontal and vertical scrollbars, which makes the terminology not ideal.
 // Still, the code should probably be made simpler..
-bool ImGui::ScrollbarEx(const ImRect& bb_frame, ImGuiID id, ImGuiAxis axis, ImS64* p_scroll_v, ImS64 size_visible_v, ImS64 size_contents_v, ImDrawFlags flags)
+bool ImGui::ScrollbarEx(const ImRect& bb_frame, ImGuiID id, ImGuiAxis axis, ImS64* p_scroll_v, ImS64 size_visible_v, ImS64 size_contents_v, ImDrawFlags draw_rounding_flags)
 {
     ImGuiContext& g = *GImGui;
     ImGuiWindow* window = g.CurrentWindow;
@@ -1041,7 +1041,7 @@ bool ImGui::ScrollbarEx(const ImRect& bb_frame, ImGuiID id, ImGuiAxis axis, ImS6
     // Render
     const ImU32 bg_col = GetColorU32(ImGuiCol_ScrollbarBg);
     const ImU32 grab_col = GetColorU32(held ? ImGuiCol_ScrollbarGrabActive : hovered ? ImGuiCol_ScrollbarGrabHovered : ImGuiCol_ScrollbarGrab, alpha);
-    window->DrawList->AddRectFilled(bb_frame.Min, bb_frame.Max, bg_col, window->WindowRounding, flags);
+    window->DrawList->AddRectFilled(bb_frame.Min, bb_frame.Max, bg_col, window->WindowRounding, draw_rounding_flags);
     ImRect grab_rect;
     if (axis == ImGuiAxis_X)
         grab_rect = ImRect(ImLerp(bb.Min.x, bb.Max.x, grab_v_norm), bb.Min.y, ImLerp(bb.Min.x, bb.Max.x, grab_v_norm) + grab_h_pixels, bb.Max.y);