MouseDown Event

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Defined By: ButtonGadget

Description:

Occurs when the user presses any mouse button. Often used with the corresponding MouseUp event to define what occurs when a mouse button is pressed and released.

Usage:

Sub MouseDown(button As Integer, shift As Integer, x As Single, y As Single)

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Syntax Description

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button The button was pressed to trigger the event. The button argument sets bits that correspond to the following values: 1 for the left button, 2 for the right button, and 4 for the middle button. Only one bit is set at a time.

shift The status of the SHIFT, CTRL, and ALT keys when the specified button was pressed. Each of these keys has a corresponding bit-flag value. SHIFT has a value of 1, CTRL is 2, and ALT is 4. To indicate which key or keys were pressed, the key values are summed in the Shift argument. For example, if both CTRL and ALT are pressed, the value of Shift is 6.

x, y The x and y coordinates defining the current location of the mouse pointer. x and y are single-precision variables that use the coordinate system established by the object's ScaleHeight, ScaleWidth, ScaleLeft, and ScaleTop properties.

Details:

The arguments included in the MouseDown event allow you to indicate the status of the mouse at the time the event is called. In addition to using a MouseDown procedure to determine that a mouse button has simply been pressed, you can also determine which mouse button was pressed, and what combination of the SHIFT, ALT, or CTRL keys were being pressed, if any. You can also specify different actions that you would like to occur based on which mouse button is pressed.

MouseDown events allow you to distinguish between the left, right, and middle mouse buttons; the Click and DblClick events do not. When a mouse button is pressed while the pointer is over a form or control, that object essentially owns the mouse and receives all mouse events until the MouseUp event is processed. If the mouse pointer leaves the area of the form or object before the MouseUp event is processed, the x, y mouse-pointer coordinates received could be from outside of the receiving form or control.

If a series of mouse buttons are pressed, the object that receives the second mouse action (the action after the first mouse click) will own all subsequent mouse events until all buttons are released.

To test for the button or shift arguments you can use logical operators. The virtual constants you can use to test for various combinations of buttons are listed as follows:

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Constant Value

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LEFT_BUTTON 1

RIGHT_BUTTON 2

MIDDLE_BUTTON 4

SHIFT_MASK 1

CTRL_MASK 2

ALT_MAST 4

When using a MouseMove procedure, please note that the button argument indicates the current state of all buttons; whereas, the button argument for MouseDown indicates only one button for each event. MouseMove procedures are often used to react to events generated by moving the mouse.

See Also:

Click event, MouseMove event, MouseUp event