Cannot draw inside a very small child window about imgui HOT 1 CLOSED

ImGui::BeginChild("Child Window4", ImVec2(15, 15), ImGuiChildFlags_Border, ImGuiWindowFlags_NoScrollbar);
Window_internal_p = ImGui::GetCurrentWindow();
ImDrawList* draw_list4 = ImGui::GetWindowDrawList();
draw_list4->AddRect(ImVec2(Window_internal_p->Pos.x + 1, Window_internal_p->Pos.y + 1), ImVec2(Window_internal_p->Pos.x + Window_internal_p->Size.x - 1, Window_internal_p->Pos.y + Window_internal_p->Size.y - 1), IM_COL32(255, 0, 0, 255));
ImGui::EndChild();

#define IMGUI_DEFINE_MATH_OPERATORS
#include "imgui.h"

ImGui::BeginChild("Child Window1", ImVec2(20, 20), ImGuiChildFlags_Border);
ImGui::GetWindowDrawList()->AddRect(ImGui::GetWindowPos() + ImVec2(1,1), ImGui::GetWindowPos() +ImGui::GetWindowSize() - ImVec2(1,1), IM_COL32(255, 0, 0, 255));
ImGui::EndChild();