<divclass="platform-hinted "data-platform-hinted="data-platform-hinted"><divclass="content sourceset-dependent-content"data-active=""data-togglable=":tgbotapi.webapps:dokkaHtmlPartial/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><spanclass="parameters "><spanclass="parameter ">eventHandler<spanclass="token operator">: </span><ahref="index.html#698381110%2FClasslikes%2F155593271">ViewportChangedEventHandler</a></span></span><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></div><spanclass="kdoc-tag"><h4class="">Return</h4><pclass="paragraph">The callback which should be used in case you want to turn off events handling</p></span></div></div>