values 1, 2, and 4, respectively. Only one of the bits is set, indicating which button caused the event.See Also Example
Apply To
Form (not MDI form), check box, command button, data control, directory list box, file list box, frame, grid, image, label, list box, option button, OLE control, picture box, text box.
Description
Occur when the user presses (MouseDown) or releases (MouseUp) a mouse button.
Syntax
Sub Form_MouseDown (Button As Integer, Shift As Integer, X As Single, Y As Single)
Sub ctlname_MouseDown ([Index As Integer,]Button As Integer, Shift As Integer, X As Single, Y As Single)
Sub Form_MouseUp (Button As Integer, Shift As Integer, X As Single, Y As Single)
Sub ctlname_MouseUp ([Index As Integer,]Button As Integer, Shift As Integer, X As Single, Y As Single)
Remarks
The MouseDown and MouseUp events use these arguments:
Argument Description
Index Uniquely identifies a control if it is in a control array.
Button The button was pressed (MouseDown) or released (MouseUp) to cause the event. 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)values 1, 2, and 4, respectively. Only one of the bits is set, indicating which button caused the event.
Shift The state of the Shift, Ctrl and Alt keys when the button specified in the Button argument was pressed or released. 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. Shift 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 is pressed. For example, if both Ctrl and Alt were pressed, the value of Shift would be 6.
X, Y The current location of the mouse pointer. X and Y are always expressed in terms of the coordinate system set by the ScaleHeight, Scale Width, ScaleLeft, and ScaleTop properties of the object.
Use a MouseDown or MouseUp procedure to specify actions to occur when a given mouse button is pressed or released. Unlike the Click and DblClick events, MouseDown and MouseUp events allow you to distinguish between the left, right, and middle mouse buttons. You can also write code for mouse-keyboard combinations that use the Shift, Ctrl, and Alt keyboard modifiers.
The following applies to both Click and DblClick events:
If a mouse button is pressed while the pointer is over a form or control, that object "captures" the mouse and receives all mouse events up to and including the last MouseUp event. This implies that the X, Y mouse-pointer coordinates given by a mouse event may not always be in the client area of the object that receives them.
If mouse buttons are pressed in succession, the object that captures the mouse after the first press receives all mouse events until all buttons are released.
If you need to test for the Button or Shift arguments, you can declare constants that define the bits within the argument by loading the CONSTANT.TXT file into a module. These mouse button constants have the following values:
Constant Value
LEFT_BUTTON 1
RIGHT_BUTTON 2
MIDDLE_BUTTON 4
SHIFT_MASK 1
CTRL_MASK 2
ALT_MASK 4
These constants are in CONSTANT.TXT. 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.
Note You can use a MouseMove procedure to respond to an event caused by moving the mouse. The Button argument for MouseDown and MouseUp differs from the Button argument used for MouseMove. For MouseDown or MouseUp, the Button argument indicates exactly one button per event; for MouseMove, it indicates the current state of all buttons.
Help:
Click Event
DblClick Event
MouseMove Event
MousePointer Property
Programmer's Guide:
Chapter 12, "Responding to Mouse Events"
MouseDown, MouseUp Events Example
The example demonstrates a simple paint application. The MouseDown procedure works with a related MouseMove procedure to paint when any mouse button is pressed and dragged. The MouseUp procedure turns off the paintbrush. To try this example, paste the code into the Declarations section of a form. Then press F5, click the form and move the mouse while the mouse button is depressed.
Dim PaintNow As Integer
Sub Form_MouseDown (Button As Integer, Shift As Integer, X As Single, Y As Single)
PaintNow = True ' Paintbrush on.
End Sub
Sub Form_MouseUp (Button As Integer, Shift As Integer, X As Single, Y As Single)
PaintNow = False ' Turn off painting.
End Sub
Sub Form_MouseMove (Button As Integer, Shift As Integer, X As Single, Y As Single)
If PaintNow Then
PSet (X, Y) ' Draw a point.
End If
End Sub
Sub Form_Load ()
DrawWidth = 10 ' Use wider paintbrush.
ForeColor = RGB(0, 0, 255) ' Set drawing color.
End Sub