A RedrawGrid message is added to the message queue when all or part of a grid is exposed or otherwise becomes visible.

XgrRedrawWindow ( window, action, xWin, yWin, width, height ) queues or sends a RedrawGrid message to every grid in window that is partially or wholly within the specified rectangle, or all grids in window if width <= 0 and/or height <= 0 . 

(x,y,width,height) are the local coordinates of the smallest rectangle in grid that includes all of the exposed area.

If width<=0 and/or height<=0 the entire grid must be redrawn because the entire grid needs redrawing. Most programs have no provision to partially redraw grids and ignore x,y,width,height .

A TimeOut message is added to the message queue when a timer created by XgrStartGridTimer() times out. Grid timers are destroyed when they time out, so grids that want periodic TimeOut messages must call XgrStartGridTimer() every time they receive a TimeOut message.

A WindowDeselected message is added to the message queue when a window is deselected. Windows usually stay selected until another is selected. A window is selected when a user points at it with the mouse cursor and presses a mouse button, and when programs call XgrDisplayWindow() or XgrSetSelectedWindow() .

Selecting a window deselects the currently selected window, because only one window can be selected at a time. Selected windows are recognizable on the display because their title-bar and frame are emphasized, usually by a colorful background color. The title-bar and frame of deselected windows are deemphasized.

Selecting a window means giving it keyboard focus. Whenever GraphicsDesigner detects a keyboard event, it prepares a keyboard message for the selected window.

A WindowDestroyed message is added to the message queue when a window is destroyed, whether by user action or as a result of XgrDestroyWindow() .