setCapture method (Windows)

This topic has not yet been rated - Rate this topic

Sets the mouse capture to the object that belongs to the current document.

Syntax

object.setCapture(containerCapture)

Parameters

containerCapture [in, optional]

Type: Boolean

Specifies one of the following values.

true (true): Default. Events originating in a container are captured by the container.
false (false): Events originating in a container are not captured by the container.

Return value

Type: HRESULT

If this method succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code.

Standards information

There are no standards that apply here.

Remarks

After mouse capture is set to an object, all mouse events for the document are routed to that object. Supported mouse events include onmousedown, onmouseup, onmousemove, onclick, ondblclick, onmouseover, and onmouseout. The srcElement property of the window event object always returns the object that is positioned under the mouse, instead of the object that has mouse capture.

Mouse clicks automatically trigger the onlosecapture event. To retain mouse capture, call setCapture inside the onclick event handler.

When the containerCapture parameter is set to true, a container object, such as a div, captures mouse events for all objects in it. By passing the value false, objects in that container can fire events, and cancel event bubbling.

Drag-and-drop operations, such as the ondragstart event, and text selection through the user interface are disabled when mouse capture is set programmatically. The following key events are unaffected by mouse capture and fire as usual: onkeydown, onkeyup, and onkeypress.

Examples

This example shows how to use mouse capture to animate graphics.


<HEAD>
<SCRIPT>
var iRad = 25;
var iX01 = 165;
var iY01 = 170;
var iX02 = 285;
var iY02 = 170;
/* The doImgMouseMove function contains calculations to 
    reposition black.bmp in response to mouse movement  */
   
function doImgMouseMove()
{
  var iX1 = event.x - iX01;
  var iY1 = event.y - iY01;
  var iX2 = event.x - iX02;
  var iY2 = event.y - iY02;
  var change1 = Math.sqrt(iX1 * iX1 + iY1 * iY1);
  var change2 = Math.sqrt(iX2 * iX2 + iY2 * iY2);
  oPupilLeft.style.left = iX01 + iRad * iX1 / change1;
  oPupilLeft.style.top = iY01 + iRad * iY1 / change1;
  oPupilRight.style.left = iX02 + iRad * iX2 / change2;
  oPupilRight.style.top = iY02 + iRad * iY2 / change2;
}
</SCRIPT>
</HEAD>
<BODY onload="oEye.setCapture(false)" 
    onclick="oEye.releaseCapture()"
    ondragstart="event.returnValue = false;">
<INPUT TYPE=button ID=oToggle VALUE="Switch Mouse Capture On" 
    onclick="doClick()">
<IMG ID=oEye SRC="/workshop/graphics/eye.png" 
    onmousemove="doImgMouseMove()">
<IMG ID=oPupilLeft SRC="/workshop/graphics/black.png">
<IMG ID=oPupilRight SRC="/workshop/graphics/black.png">
<P>The eyeballs track pointer movement. When mouse 
    capture is on, they follow the pointer no matter where it 
    is positioned in the document. When mouse capture is off, they 
    detect and follow mouse position only while the pointer is 
    positioned over the eyeball graphic.</P>
<P>In this example, mouse capture is set when the document is 
    loaded. Click anywhere on the document to remove mouse 
    capture.</P>
</BODY>

setCapture method