Method RenderWindowDecorations

tutorials/common/imgui/imgui.cpp:6080–6161

Draw background and borders Draw and handle scrollbars

// Draw background and borders
// Draw and handle scrollbars
void ImGui::RenderWindowDecorations(ImGuiWindow* window, const ImRect& title_bar_rect, bool title_bar_is_highlight, int resize_grip_count, const ImU32 resize_grip_col[4], float resize_grip_draw_size)
{
    ImGuiContext& g = *GImGui;
    ImGuiStyle& style = g.Style;
    ImGuiWindowFlags flags = window->Flags;

    // Ensure that ScrollBar doesn't read last frame's SkipItems
    IM_ASSERT(window->BeginCount == 0);
    window->SkipItems = false;

    // Draw window + handle manual resize
    // As we highlight the title bar when want_focus is set, multiple reappearing windows will have their title bar highlighted on their reappearing frame.
    const float window_rounding = window->WindowRounding;
    const float window_border_size = window->WindowBorderSize;
    if (window->Collapsed)
    {
        // Title bar only
        float backup_border_size = style.FrameBorderSize;
        g.Style.FrameBorderSize = window->WindowBorderSize;
        ImU32 title_bar_col = GetColorU32((title_bar_is_highlight && !g.NavDisableHighlight) ? ImGuiCol_TitleBgActive : ImGuiCol_TitleBgCollapsed);
        RenderFrame(title_bar_rect.Min, title_bar_rect.Max, title_bar_col, true, window_rounding);
        g.Style.FrameBorderSize = backup_border_size;
    }
    else
    {
        // Window background
        if (!(flags & ImGuiWindowFlags_NoBackground))
        {
            ImU32 bg_col = GetColorU32(GetWindowBgColorIdx(window));
            bool override_alpha = false;
            float alpha = 1.0f;
            if (g.NextWindowData.Flags & ImGuiNextWindowDataFlags_HasBgAlpha)
            {
                alpha = g.NextWindowData.BgAlphaVal;
                override_alpha = true;
            }
            if (override_alpha)
                bg_col = (bg_col & ~IM_COL32_A_MASK) | (IM_F32_TO_INT8_SAT(alpha) << IM_COL32_A_SHIFT);
            window->DrawList->AddRectFilled(window->Pos + ImVec2(0, window->TitleBarHeight()), window->Pos + window->Size, bg_col, window_rounding, (flags & ImGuiWindowFlags_NoTitleBar) ? 0 : ImDrawFlags_RoundCornersBottom);
        }

        // Title bar
        if (!(flags & ImGuiWindowFlags_NoTitleBar))
        {
            ImU32 title_bar_col = GetColorU32(title_bar_is_highlight ? ImGuiCol_TitleBgActive : ImGuiCol_TitleBg);
            window->DrawList->AddRectFilled(title_bar_rect.Min, title_bar_rect.Max, title_bar_col, window_rounding, ImDrawFlags_RoundCornersTop);
        }

        // Menu bar
        if (flags & ImGuiWindowFlags_MenuBar)
        {
            ImRect menu_bar_rect = window->MenuBarRect();
            menu_bar_rect.ClipWith(window->Rect());  // Soft clipping, in particular child window don't have minimum size covering the menu bar so this is useful for them.
            window->DrawList->AddRectFilled(menu_bar_rect.Min + ImVec2(window_border_size, 0), menu_bar_rect.Max - ImVec2(window_border_size, 0), GetColorU32(ImGuiCol_MenuBarBg), (flags & ImGuiWindowFlags_NoTitleBar) ? window_rounding : 0.0f, ImDrawFlags_RoundCornersTop);
            if (style.FrameBorderSize > 0.0f && menu_bar_rect.Max.y < window->Pos.y + window->Size.y)
                window->DrawList->AddLine(menu_bar_rect.GetBL(), menu_bar_rect.GetBR(), GetColorU32(ImGuiCol_Border), style.FrameBorderSize);
        }