{"action":"created","issue":{"url":"https://api.github.com/repos/servo/servo/issues/10020","repository_url":"https://api.github.com/repos/servo/servo","labels_url":"https://api.github.com/repos/servo/servo/issues/10020/labels{/name}","comments_url":"https://api.github.com/repos/servo/servo/issues/10020/comments","events_url":"https://api.github.com/repos/servo/servo/issues/10020/events","html_url":"https://github.com/servo/servo/issues/10020","id":141117000,"number":10020,"title":"webrender: rendered glyphs corruption (possibly `text-shadow`-related)","user":{"login":"pygy","id":54515,"avatar_url":"https://avatars.githubusercontent.com/u/54515?v=3","gravatar_id":"","url":"https://api.github.com/users/pygy","html_url":"https://github.com/pygy","followers_url":"https://api.github.com/users/pygy/followers","following_url":"https://api.github.com/users/pygy/following{/other_user}","gists_url":"https://api.github.com/users/pygy/gists{/gist_id}","starred_url":"https://api.github.com/users/pygy/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/pygy/subscriptions","organizations_url":"https://api.github.com/users/pygy/orgs","repos_url":"https://api.github.com/users/pygy/repos","events_url":"https://api.github.com/users/pygy/events{/privacy}","received_events_url":"https://api.github.com/users/pygy/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":1,"created_at":"2016-03-15T22:27:35Z","updated_at":"2016-03-15T22:32:59Z","closed_at":null,"body":"Here's a first reduced text case for #9849. Specs: Mac OS X 10.10.5, Intel HD Graphics 4000. Servo last updated seconds ago (thus pulled ~30 min earlier).\r\n\r\nThis is webrender-only.\r\n\r\nCapture:\r\n\r\n![screen shot 2016-03-15 at 21 43 41](https://cloud.githubusercontent.com/assets/54515/13794097/80fbf7e6-eafa-11e5-9cdb-60ba41a7ff61.png)\r\n\r\nLive: http://pygy.github.io/servo-rendering-bugs/j2c/j2c/glyphs.html\r\nSource: https://github.com/pygy/servo-rendering-bugs/blob/gh-pages/j2c/j2c/glyphs.html\r\n\r\nThe oddest thing is that The affected glyphs change from one run to the next. I don't know how you implemented this, but I'll take a guess based on how these things are often done: it looks like the glyph cache is poisoned. The glitch disappears if you remove the `h6`, its `text-shadow` or even its `font-size`. \r\n\r\nAs you can see the same characters are mangled identically. It isn't visible in the screenshot, but if you scroll further down, you'll see that text whose only difference is a larger `font-size` is rendered correctly. This leads me to believe that the corruption occurs at the rendered glyph level, rather than at the vector coordinates level.\r\n\r\nThe glitch isn't always visible. With the example as is, corruption occurs most of the time in the normal-sized `<code>` elements, and rarley in the `<h6>` text. Modifying the CSS and/or markup may move the corruption elsewhere.\r\n\r\nPlease note that webrender also doesn't show the `text-shadow`.\r\n\r\nIf memory is corrupted beyond the glyph cache, this may well explain other parts of #9849... I guess the nice thing when you use Rust is that you know where to look when memory is corrupted.\r\n\r\n---\r\n\r\n"},"comment":{"url":"https://api.github.com/repos/servo/servo/issues/comments/197054142","html_url":"https://github.com/servo/servo/issues/10020#issuecomment-197054142","issue_url":"https://api.github.com/repos/servo/servo/issues/10020","id":197054142,"user":{"login":"jdm","id":27658,"avatar_url":"https://avatars.githubusercontent.com/u/27658?v=3","gravatar_id":"","url":"https://api.github.com/users/jdm","html_url":"https://github.com/jdm","followers_url":"https://api.github.com/users/jdm/followers","following_url":"https://api.github.com/users/jdm/following{/other_user}","gists_url":"https://api.github.com/users/jdm/gists{/gist_id}","starred_url":"https://api.github.com/users/jdm/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/jdm/subscriptions","organizations_url":"https://api.github.com/users/jdm/orgs","repos_url":"https://api.github.com/users/jdm/repos","events_url":"https://api.github.com/users/jdm/events{/privacy}","received_events_url":"https://api.github.com/users/jdm/received_events","type":"User","site_admin":false},"created_at":"2016-03-15T22:32:59Z","updated_at":"2016-03-15T22:32:59Z","body":"cc @glennw @pcwalton "}}