| <!DOCTYPE html> |
| <!-- |
| | This test checks that the previousThresholdIndex and previousIsIntersecting |
| | fields of the IntersectionObserverRegistration objects are getting updated |
| | correctly. |
| | If the fields are not updated properly, then the callback is executed |
| | multiple times. In this test, the target element is initially green, and |
| | turns blue if the callback is executed exactly once (as expected). It will |
| | turn red (signifying an error) if the callback is executed more than once. |
| | https://www.w3.org/TR/intersection-observer/ |
| --> |
| <html> |
| <head> |
| <style> |
| #target { |
| background-color: green; |
| width: 200px; |
| height: 150px; |
| position: absolute; |
| left: -100px; |
| top: -75px; |
| } |
| </style> |
| </head> |
| <body> |
| <div> |
| <div id="target"> |
| </div> |
| </div> |
| |
| <script> |
| if (window.testRunner) { |
| window.testRunner.waitUntilDone(); |
| } |
| |
| window.addEventListener("load", function() { |
| var targetElement = document.querySelector('#target'); |
| var io_callback_count = 0; |
| var timeout_callback_count = 0; |
| |
| function handleIntersect(entries, observer) { |
| // This callback should only be executed once if the intersection |
| // observer registration fields have been updated properly |
| ++io_callback_count; |
| console.log("Number of times previousThresholdIndex or " + |
| "previousIsIntersecting values changed: " + |
| io_callback_count); |
| if (io_callback_count > 1) { |
| entries.forEach(function(entry) { |
| entry.target.style.backgroundColor = "red"; |
| }); |
| } else { |
| entries.forEach(function(entry) { |
| entry.target.style.backgroundColor = "blue"; |
| }); |
| } |
| } |
| |
| function timeoutCallback() { |
| // Do multiple explicit non measured layouts |
| if (++timeout_callback_count < 3) { |
| if (window.testRunner) { |
| window.testRunner.DoNonMeasuredLayout(); |
| } |
| window.setTimeout(function() { timeoutCallback(); } , 0); |
| } else { |
| if (window.testRunner) { |
| window.testRunner.notifyDone(); |
| } |
| } |
| } |
| |
| function createObserver() { |
| var options = { |
| root: null, |
| rootMargin: "0px", |
| threshold: 0.0 |
| }; |
| |
| var observer = new IntersectionObserver(handleIntersect, options); |
| observer.observe(targetElement); |
| } |
| |
| createObserver(); |
| window.setTimeout(function() { timeoutCallback(); }, 0); |
| }); |
| </script> |
| |
| </body> |
| </html> |
