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Visual Basic Reference

Visual Studio 6.0

MouseMove Event

See Also    Example    Applies To

Occurs when the user moves the mouse.

Syntax

Private Sub Form_MouseMove(button As Integer, shift As Integer, x As Single, y As Single)

Private Sub MDIForm_MouseMove(button As Integer, shift As Integer, x As Single, y As Single)

Private Sub object_MouseMove([index As Integer,] button As Integer, shift As Integer, x As Single, y As Single)

The MouseMove event syntax has these parts:

Part Description
object An object expression that evaluates to an object in the Applies To list.
index An integer that uniquely identifies a control if it's in a control array.
button An integer that corresponds to the state of the mouse buttons in which a bit is set if the button is down. The button argument is a bit field with bits corresponding to the left button (bit 0), right button (bit 1), and middle button (bit 2). These bits correspond to the values 1, 2, and 4, respectively. It indicates the complete state of the mouse buttons; some, all, or none of these three bits can be set, indicating that some, all, or none of the buttons are pressed.
shift An integer that corresponds to the state of the SHIFT, CTRL, and ALT keys. A bit is set if the key is down. The shift argument is a bit field with the least-significant bits corresponding to the SHIFT key (bit 0), the CTRL key (bit 1), and the ALT key (bit 2 ). These bits correspond to the values 1, 2, and 4, respectively. The shift argument indicates the state of these keys. Some, all, or none of the bits can be set, indicating that some, all, or none of the keys are pressed. For example, if both CTRL and ALT were pressed, the value of shift would be 6.
x, y A number that specifies the current location of the mouse pointer. The x and y values are always expressed in terms of the coordinate system set by the ScaleHeight, ScaleWidth, ScaleLeft, and ScaleTop properties of the object.

Remarks

The MouseMove event is generated continually as the mouse pointer moves across objects. Unless another object has captured the mouse, an object recognizes a MouseMove event whenever the mouse position is within its borders.

If you need to test for the button or shift arguments, you can use constants listed in the Visual Basic (VB) object library in the Object Browser to define the bits within the argument:

Constant (Button) Value Description
vbLeftButton 1 Left button is pressed.
vbRightButton 2 Right button is pressed.
vbMiddleButton 4 Middle button is pressed.

Constant (Shift) Value Description
vbShiftMask 1 SHIFT key is pressed.
vbCtrlMask 2 CTRL key is pressed.
vbAltMask 4 ALT key is pressed.

The constants then act as bit masks you can use to test for any combination of buttons without having to figure out the unique bit field value for each combination.

You test for a condition by first assigning each result to a temporary integer variable and then comparing the button or shift arguments to a bit mask. Use the And operator with each argument to test if the condition is greater than zero, indicating the key or button is pressed, as in this example:

LeftDown = (Button And vbLeftButton) > 0
CtrlDown = (Shift And vbCtrlMask) > 0

Then, in a procedure, you can test for any combination of conditions, as in this example:

If LeftDown And CtrlDown Then

Note   You can use MouseDown and MouseUp event procedures to respond to events caused by pressing and releasing mouse buttons.

The button argument for MouseMove differs from the button argument for MouseDown and MouseUp. For MouseMove, the button argument indicates the current state of all buttons; a single MouseMove event can indicate that some, all, or no buttons are pressed. For MouseDown and MouseUp, the button argument indicates exactly one button per event.

Any time you move a window inside a MouseMove event, it can cause a cascading event. MouseMove events are generated when the window moves underneath the pointer. A MouseMove event can be generated even if the mouse is perfectly stationary.

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