<divclass="content sourceset-depenent-content"data-active=""data-togglable=":docs:dokkaHtml/jsMain"><divclass="symbol monospace"><spanclass="token keyword"></span><spanclass="token keyword">fun </span><ahref="-web-app/index.html">WebApp</a><spanclass="token punctuation">.</span><ahref="on-viewport-changed.html"><spanclass="token function">onViewportChanged</span></a><spanclass="token punctuation">(</span>eventHandler<spanclass="token operator">: </span><ahref="index.html#698381110%2FClasslikes%2F-1203563889">ViewportChangedEventHandler</a><spanclass="token punctuation">)</span><spanclass="token operator">: </span><spanclass="token punctuation">(</span><spanclass="token keyword"></span><ahref="-viewport-changed-data/index.html">ViewportChangedData</a><spanclass="token punctuation">)</span><spanclass="token operator"> -></span><spanclass="token keyword"></span><ahref="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html">Unit</a><spanclass="top-right-position"><spanclass="copy-icon"></span><divclass="copy-popup-wrapper popup-to-left"><spanclass="copy-popup-icon"></span><span>Content copied to clipboard</span></div></span></div><h4class="">Return</h4><pclass="paragraph">The callback which should be used in case you want to turn off events handling</p></div></div>