Fix display:none; bug
#28
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Reviewed. LGTM. |
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Any way to write some unit tests for this? |
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Good call. |
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Also, this PR will solve #27. |
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Nice 👍 |
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This PR fixes a gnarly bug that can lead to unexpected requests for (sometimes massive) image files. This occurs for elements that have been marked as
fluidwhile it or its parents are set todisplay:none;.The root cause here is that the mechanism used to determine an element's dimensions in
imgix.calculateElementSize()(https://github.com/imgix/imgix.js/blob/fix-displaynone/src/core.js#L240-L267) reports{width:0, height: 0}for all hidden elements. When the function detemines that the element being measured has no height or width, it proceeds up the chain until an un-hidden element is found, usually the<body>tag. Once a visible element is found, its dimensions are used to request an image and we end up with requests for images that match the width of the entire page--or, in a worst-case scenario, the height of the entire page.This behavior isn't inherently wrong;
imgix.calculateElementSize()should report zeroes when measuring a hidden element. The correct fix is to avoid making this calculation entirely. This patch adds a check to immediately bail from theimgix.Fluidset.updateSrc()method when we determine that the element we're trying to update is hidden, using the same implementation as jQuery does in its:hiddenselector.The final piece of the puzzle is to cover a the case of an
<img>tag with an emptysrcattribute. While we shouldn't encourage imgix.js users to include emptysrcattributes on their tags, it hasn't been a problem before because we never bothered checking whether the element was visible or not. Now that we are, an element like<img src=""/>will be evaluated as hidden regardless of itsdisplayvalue, and imgix.js won't download or render itsdata-srcvalue as expected. To cope with this, we're setting all images with an emptysrcattribute to an empty image before evaluating, to avoid this false positive.Review: @zacman85