nc-mouse-left-down

Arguments: window buttons cursor-position frame-section

This generic function is called when the user presses the left mouse button while the mouse cursor is in the frame (border) area of a window. An application may add methods to this generic function to respond to mouse events in its windows, though frame-area events are usually left to the operating system.

window is the window in which the event occurred.

buttons is an integer indicating which mouse buttons and shift keys were down when the event occurred. The value is the result of applying logior to the values of the following bit-flag variables:

• left-mouse-button
• middle-mouse-button
• right-mouse-button
• first-x-button (see *ignore-mouse-x-buttons*)
• second-x-button (see *ignore-mouse-x-buttons*),
• shift-key
• control-key
• alt-key

Other bits might be turned on as well, so functions such as logtest should be used to determine whether a particular mouse button or shift key was down; for example,

(logtest left-mouse-button buttons) 

will return true if and only if the left mouse button was down. For "down" events, the value includes the button or key being pressed now; for "up" events, the value does not include the button or key being released.

cursor-position is a position object indicating the location of the mouse cursor when the event occurred. It is in pixel coordinates relative to the upper-left corner of the screen.

frame-section is a keyword indicating the general area of the frame in which the event occurred. The value will be one of the following symbols:

• :left
• :top-left
• :top
• :top-right
• :right
• :bottom-right
• :bottom
• :bottom-left
• :caption
• :client
• :error
• :nowhere
• :grow-box
• :horizontal-scrollbar
• :vertical-scrollbar
• :menu
• :system-menu
• :minimize
• :maximize
• :transparent
• :object
• :close
• :help

Thus, :top-left, for example, denotes the area at the upper left where the window's left and top edges can be stretched, while :maximize refers to the gadget that maximizes the window.

See cg-events.htm for information about event handling in Common Graphics.

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This page was not revised from the 8.1 page.
Created 2010.1.21.