| <?php |
| header("ACCEPT-CH: DPR, Width, Viewport-Width"); |
| ?> |
| <!DOCTYPE html> |
| <body> |
| <script> |
| var fail = function(num) { |
| opener.postMessage("fail "+ num, "*"); |
| }; |
| |
| var success = function() { |
| opener.postMessage("success", "*"); |
| }; |
| |
| var resize = function() { |
| opener.postMessage("resize", "*"); |
| }; |
| |
| var counter = 1; |
| var error = function() { |
| fail(counter); |
| } |
| var load = function() { |
| if (counter == 1) { |
| ++counter; |
| resize(); |
| return; |
| } |
| success(); |
| } |
| </script> |
| <picture> |
| <source sizes="50vw" media="(min-width: 800px)" srcset="image-checks-for-width.php?rw=400"> |
| <source sizes="50vw" srcset="image-checks-for-width.php?rw=300"> |
| <img onerror="error()" onload="load()"> |
| </picture> |
