messages
When certain kinds of events take place in graphics windows, GraphicsDesigner creates
messages to describe them.
For example, when a keyboard key is pressed, GraphicsDesigner creates a WindowKeyDown
message. When the mouse moves or a button is depressed, a MouseMove or MouseDown message
is created. When a user clicks on a window, a WindowSelected message is created.
In general, whenever the state of the keyboard, mouse, or a window changes,
GraphicsDesigner creates a message that describes it.
Only events in graphics windows are detected by GraphicsDesigner , so only events in
graphics windows cause the creation of messages.
window messages and grid messages
Any particular message name, like WindowKeyDown or MouseDown , refers to either windows or
grids, never both.
Window messages refer to windows.
Grid messages refer to grids.
Window message names must start with "Window".
Grid message names must not start with "Window".