This replaces the use of painting in RenderImage to display an image's alt text with an implementation in shadow DOM. This initial implementation is close in appearance to the legacy display of alt-text but will ultimately move closer to the one seen in Firefox and described in http://hixie.ch/specs/alttext. The alt-text and broken-image icon is now rendered as: <style> #alttext-container { overflow: hidden; border: 1px solid silver; padding: 1px; display: inline-block; } #alttext { display: none; overflow: hidden;} </style> <div id="alttext-container"> <img src="data:png, [broken-image-icon]" width="16" height="16" align="left" style="margin: 0px"> <div id="alt-text">Alt text in here</div> </div> Some notes on the way the fallback content is now rendered: - The fallback content is rendered inside an inline-block so it does not calculate its dimensions the way a replaced element (i.e. an image) would (as defined by http://www.w3.org/TR/CSS2/visudet.html#inline-replaced-width). So where one of width or height is auto but the other is not, the fallback content will not exactly match the dimensions calculated by RenderImage in error mode currently. We do a modest imitation of the logic in quirks mode, but in strict mode it will behave exactly like an inline-block. - Where the image has no src attribute and no alt attribute RenderImage.cpp still looks after the painting of the element - no fallback content is generated and no broken image is displayed. This is consistent with existing behaviour. - The only image resource requests that still use the synchronous load path are those where the item is cached (and didn't error out), where its the fallback image for an object element, or where it's the image for a main resource load. All other image loads are now asynchronous so that fallback content can be loaded outside the style recalc phase. - Instead of aborting an image resource request when the src element is empty (i.e. src='') we now allow the request to go through so that it can fail and invoke the fallback content in HTMLImageLoader.cpp. - As you can see in the new result for fast/borders/rtl-border-05.html, since the alt-text is displayed as an inline-block it no longer artificially shrinks any border on the element to the broken-image icon. Some notes on the rebaselined test results: - I've modified inspector/network/network-image-404.html to output the state of both the resource requests, i.e. the failed one and the resource request for the data:png to display the broken image icon. - I've added a missing support file for fast/css/counters/complex-before.html - its absence meant that the result was polluted by the behaviour of broken image rendering. - Likewise for fast/images/imagemap-polygon* tests - our new rendering of failed image loads was interfering with an assumption in the tests that a broken image still painted a RenderImage. So I've removed the src attribute to allow the assumption hold (img elements without a src attribute are painted by RenderImage). - I have altered fast/forms/state-restore-to-non-edited-controls.html to wait 100ms before submitting the form as the image load in the input element is now asynchronous. Likewise for fast/forms/basic-buttons.html. - I did the same to svg/canvas/canvas-draw-image-globalalpha.html and fast/canvas/canvas-drawImage-out-of-bounds-src.html. Since all image loads that might need alt content are performed asynchronously canvas.drawImage() now needs to ensure the content has loaded before drawing. - http/tests/security/local-image-from-remote-whitelisted.html has been masking a bug - blink does not load the image even though it is whitelisted. I am rebaselining the test to reflect the failure revealed by this CL and tracking a fix under crbug.com/410949. - As the alt text is now always exposed if the image doesn't load, any input elements that use an image will show the default alt title 'Submit'. This shows up in the accessibility unit tests in content_browsertests. I plan to rebaseline these in a separate CL. Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=185847 Review URL: https://codereview.chromium.org/481753002 git-svn-id: svn://svn.chromium.org/blink/trunk@186800 bbb929c8-8fbe-4397-9dbb-9b2b20218538