Method FocusWindow

imgui_tiny_app/imgui/imgui.cpp:13643–13710

Moving window to front of display and set focus (which happens to be back of our sorted list)

// Moving window to front of display and set focus (which happens to be back of our sorted list)
void ImGui::FocusWindow(ImGuiWindow* window, ImGuiFocusRequestFlags flags)
{
    ImGuiContext& g = *GImGui;

    // Modal check?
    if ((flags & ImGuiFocusRequestFlags_UnlessBelowModal) && (g.NavWindow != window)) // Early out in common case.
        if (ImGuiWindow* blocking_modal = FindBlockingModal(window))
        {
            // This block would typically be reached in two situations:
            // - API call to FocusWindow() with a window under a modal and ImGuiFocusRequestFlags_UnlessBelowModal flag.
            // - User clicking on void or anything behind a modal while a modal is open (window == NULL)
            IMGUI_DEBUG_LOG_FOCUS("[focus] FocusWindow(\"%s\", UnlessBelowModal): prevented by \"%s\".\n", window ? window->Name : "<NULL>", blocking_modal->Name);
            if (window && window == window->RootWindow && (window->Flags & ImGuiWindowFlags_NoBringToFrontOnFocus) == 0)
                BringWindowToDisplayBehind(window, blocking_modal); // Still bring right under modal. (FIXME: Could move in focus list too?)
            ClosePopupsOverWindow(GetTopMostPopupModal(), false); // Note how we need to use GetTopMostPopupModal() aad NOT blocking_modal, to handle nested modals
            return;
        }

    // Find last focused child (if any) and focus it instead.
    if ((flags & ImGuiFocusRequestFlags_RestoreFocusedChild) && window != NULL)
        window = NavRestoreLastChildNavWindow(window);

    // Apply focus
    if (g.NavWindow != window)
    {
        SetNavWindow(window);
        if (window && g.NavHighlightItemUnderNav)
            g.NavMousePosDirty = true;
        g.NavId = window ? window->NavLastIds[0] : 0; // Restore NavId
        g.NavLayer = ImGuiNavLayer_Main;
        SetNavFocusScope(window ? window->NavRootFocusScopeId : 0);
        g.NavIdIsAlive = false;
        g.NavLastValidSelectionUserData = ImGuiSelectionUserData_Invalid;

        // Close popups if any
        ClosePopupsOverWindow(window, false);
    }

    // Move the root window to the top of the pile
    IM_ASSERT(window == NULL || window->RootWindowDockTree != NULL);
    ImGuiWindow* focus_front_window = window ? window->RootWindow : NULL;
    ImGuiWindow* display_front_window = window ? window->RootWindowDockTree : NULL;
    ImGuiDockNode* dock_node = window ? window->DockNode : NULL;
    bool active_id_window_is_dock_node_host = (g.ActiveIdWindow && dock_node && dock_node->HostWindow == g.ActiveIdWindow);

    // Steal active widgets. Some of the cases it triggers includes:
    // - Focus a window while an InputText in another window is active, if focus happens before the old InputText can run.
    // - When using Nav to activate menu items (due to timing of activating on press->new window appears->losing ActiveId)
    // - Using dock host items (tab, collapse button) can trigger this before we redirect the ActiveIdWindow toward the child window.
    if (g.ActiveId != 0 && g.ActiveIdWindow && g.ActiveIdWindow->RootWindow != focus_front_window)
        if (!g.ActiveIdNoClearOnFocusLoss && !active_id_window_is_dock_node_host)
            ClearActiveID();

    // Passing NULL allow to disable keyboard focus
    if (!window)
        return;
    window->LastFrameJustFocused = g.FrameCount;