Multi-tasking in desktop applications is a commonly performed activity in which a user may open several child windows to view and operate different objects in the main window of the same program. For a regular computing device, a screen size is commonly above 12 inches in diagonal, and user-inputs are performed through a mouse and a keyboard, while for mobile devices, the screen size is commonly about 5 inches or less diagonally, and user-input may be facilitated by a touch screen.
These discrepancies may bring about a problem in a user interface (UI) design for mobile devices, i.e., the size of the UI elements is configured to be large enough for both good visual effects and accurate touch operations. For example, the computing device screen, even if the resolution is limited to 1024*768, may hold far more UI elements (buttons, menus, text fields, etc.) than the screen size of the mobile device screen with a full high-definition (HD) resolution. On the other hand, if the mobile device utilizes such limited resolution to display a UI element (e.g., a button, menu, or a text field), the UI element may be barely visible and touched accurately by touch-operation input.