By Opera Software

From Opera 15 onward, Opera 11 & 12’s extension format is no longer supported, and instead, we’ve switched to Chromium’s extension model. Check out our new documentation for developing extensions for Opera 15 and higher and start building your own extensions.


When specified as an item in a BrowserWindowProperties object, the top property specifies the desired top offset of a browser window.

When creating a browser window, if this property is not specified the browser's default top offset is used.

When updating a browser window, if this property is not specified the default behaviour is to leave the top offset unchanged.


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The following example creates a button on the browser toolbar. When the button is clicked, a new window is created with the specified height, width, top offset and left offset.

// The background process (e.g. index.html)

// Specify the properties of the button before creating it.
var UIItemProperties = {
  disabled: false,
  title: "Example extension",
  icon: "images/icon_18.png"

// Create the button and add it to the toolbar.
var button = opera.contexts.toolbar.createItem( UIItemProperties );

button.addEventListener('click', handleClick, false);

function handleClick() {
  // Set the properties for the window
  var windowProps = {
    height: 600,
    width: 400,
    top: 50,
    left: 100

  // Create a new window using the specified properties{}, windowProps);

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