Method UpdateMouseMovingWindowEndFrame

src/third-party/imgui/imgui.cpp:3853–3903

Initiate moving window when clicking on empty space or title bar. Handle left-click and right-click focus.

// Initiate moving window when clicking on empty space or title bar.
// Handle left-click and right-click focus.
void ImGui::UpdateMouseMovingWindowEndFrame()
{
    ImGuiContext& g = *GImGui;
    if (g.ActiveId != 0 || g.HoveredId != 0)
        return;

    // Unless we just made a window/popup appear
    if (g.NavWindow && g.NavWindow->Appearing)
        return;

    // Click on empty space to focus window and start moving
    // (after we're done with all our widgets)
    if (g.IO.MouseClicked[0])
    {
        // Handle the edge case of a popup being closed while clicking in its empty space.
        // If we try to focus it, FocusWindow() > ClosePopupsOverWindow() will accidentally close any parent popups because they are not linked together any more.
        ImGuiWindow* root_window = g.HoveredWindow ? g.HoveredWindow->RootWindow : NULL;
        const bool is_closed_popup = root_window && (root_window->Flags & ImGuiWindowFlags_Popup) && !IsPopupOpen(root_window->PopupId, ImGuiPopupFlags_AnyPopupLevel);

        if (root_window != NULL && !is_closed_popup)
        {
            StartMouseMovingWindow(g.HoveredWindow); //-V595

            // Cancel moving if clicked outside of title bar
            if (g.IO.ConfigWindowsMoveFromTitleBarOnly && !(root_window->Flags & ImGuiWindowFlags_NoTitleBar))
                if (!root_window->TitleBarRect().Contains(g.IO.MouseClickedPos[0]))
                    g.MovingWindow = NULL;

            // Cancel moving if clicked over an item which was disabled or inhibited by popups (note that we know HoveredId == 0 already)
            if (g.HoveredIdDisabled)
                g.MovingWindow = NULL;
        }
        else if (root_window == NULL && g.NavWindow != NULL && GetTopMostPopupModal() == NULL)
        {
            // Clicking on void disable focus
            FocusWindow(NULL);
        }
    }

    // With right mouse button we close popups without changing focus based on where the mouse is aimed
    // Instead, focus will be restored to the window under the bottom-most closed popup.
    // (The left mouse button path calls FocusWindow on the hovered window, which will lead NewFrame->ClosePopupsOverWindow to trigger)
    if (g.IO.MouseClicked[1])
    {
        // Find the top-most window between HoveredWindow and the top-most Modal Window.
        // This is where we can trim the popup stack.
        ImGuiWindow* modal = GetTopMostPopupModal();
        bool hovered_window_above_modal = g.HoveredWindow && (modal == NULL || IsWindowAbove(g.HoveredWindow, modal));
        ClosePopupsOverWindow(hovered_window_above_modal ? g.HoveredWindow : modal, true);
    }
}

static bool IsWindowActiveAndVisible(ImGuiWindow* window)
{