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Programming Language: Object Pascal ( Delphi ) Use Mouse to get information about the system’s mouse, including which window (if any) has captured the mouse, the position of the mouse, and mouse settings from the Control panel.

Mouse can also be used to specify global aspects of how your application responds to mouse messages, such as how much the user must move the mouse to start a drag operation.

A mouse event occurs when a user moves the mouse in the user interface of an application. The VCL has three mouse events.

Mouse events :

Event Description
a) Vcl.Controls.TControl.OnMouseDown event
Occurs when the user presses a mouse button with the mouse pointer over a control.

b) Vcl.Controls.TControl.OnMouseMove event
Occurs when the user moves the mouse while the mouse pointer is over a control.

c) Vcl.Controls.TControl.OnMouseUp event
Occurs when the user releases a mouse button that was pressed with the mouse pointer over a component.

When an application detects a mouse action, it calls whatever event handler you've defined for the corresponding event, passing five parameters. Use the information in those parameters to customize your responses to the events. The five parameters are as follows:

Mouse-event parameters :

Parameter Meaning Sender
The object that detected the mouse action

Button
Indicates which mouse button was involved: mbLeft, mbMiddle, or mbRight

Shift
Indicates the state of the Alt, Ctrl, and Shift keys at the time of the mouse action

X, Y
The coordinates where the event occurred

Most of the time, you need the coordinates returned in a mouse-event handler, but sometimes you also need to check Button to determine which mouse button caused the event.

Note: Delphi uses the same criteria as Microsoft Windows in determining which mouse button has been pressed. Thus, if you have switched the default "primary" and "secondary" mouse buttons (so that the right mouse button is now the primary button), clicking the primary (right) button will record mbLeft as the value of the Button parameter.