Method DebugRenderViewportThumbnail

tutorials/common/imgui/imgui.cpp:12876–12904

#ifndef IMGUI_DISABLE_DEBUG_TOOLS

void ImGui::DebugRenderViewportThumbnail(ImDrawList* draw_list, ImGuiViewportP* viewport, const ImRect& bb)
{
    ImGuiContext& g = *GImGui;
    ImGuiWindow* window = g.CurrentWindow;

    ImVec2 scale = bb.GetSize() / viewport->Size;
    ImVec2 off = bb.Min - viewport->Pos * scale;
    float alpha_mul = 1.0f;
    window->DrawList->AddRectFilled(bb.Min, bb.Max, GetColorU32(ImGuiCol_Border, alpha_mul * 0.40f));
    for (int i = 0; i != g.Windows.Size; i++)
    {
        ImGuiWindow* thumb_window = g.Windows[i];
        if (!thumb_window->WasActive || (thumb_window->Flags & ImGuiWindowFlags_ChildWindow))
            continue;

        ImRect thumb_r = thumb_window->Rect();
        ImRect title_r = thumb_window->TitleBarRect();
        thumb_r = ImRect(ImFloor(off + thumb_r.Min * scale), ImFloor(off +  thumb_r.Max * scale));
        title_r = ImRect(ImFloor(off + title_r.Min * scale), ImFloor(off +  ImVec2(title_r.Max.x, title_r.Min.y) * scale) + ImVec2(0,5)); // Exaggerate title bar height
        thumb_r.ClipWithFull(bb);
        title_r.ClipWithFull(bb);
        const bool window_is_focused = (g.NavWindow && thumb_window->RootWindowForTitleBarHighlight == g.NavWindow->RootWindowForTitleBarHighlight);
        window->DrawList->AddRectFilled(thumb_r.Min, thumb_r.Max, GetColorU32(ImGuiCol_WindowBg, alpha_mul));
        window->DrawList->AddRectFilled(title_r.Min, title_r.Max, GetColorU32(window_is_focused ? ImGuiCol_TitleBgActive : ImGuiCol_TitleBg, alpha_mul));
        window->DrawList->AddRect(thumb_r.Min, thumb_r.Max, GetColorU32(ImGuiCol_Border, alpha_mul));
        window->DrawList->AddText(g.Font, g.FontSize * 1.0f, title_r.Min, GetColorU32(ImGuiCol_Text, alpha_mul), thumb_window->Name, FindRenderedTextEnd(thumb_window->Name));
    }
    draw_list->AddRect(bb.Min, bb.Max, GetColorU32(ImGuiCol_Border, alpha_mul));
}

static void RenderViewportsThumbnails()
{