Losing text sharpness (blur) when scaling div over a fixed position element (on mobile safari / webkit browser)

问题

The repro code is attached. It (basically) contains two div elements: red (fixed) and black (with text). When clicking on the black div, it is up-scaled and the text on it stays sharp. However, in 4 seconds the z-index of the black div changes and the black div becomes to be over the red div. Boom! Here the text becomes blurry (which is a big problem).

The "effect" is especially visible on iPhone 3GS, less noticeable on iPhone 4.

The question is: is there a solution/workaround to tweak every code, but not the red div code, so that the text on the black div will remain sharp?

I am here for any questions / clarification requests.

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html><head><meta http-equiv="Content-Type" content="text/html; charset=windows-1255">

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.2.6/jquery.min.js" type="text/javascript"></script>
<script>
    $(function() {
        $("#main_div").bind("click", function() {
            $("#wrapper").css({"z-index": -1});
            $("#main_div").css({"-webkit-transform": "scale(1.4)"});

            setTimeout(function() {
                $("#wrapper").css({"z-index": 2});
            }, 4000);

            return true;
        });
    });
</script>
<title>Title</title>
</head>
<body>

<div id="wrapper" style="position: absolute; z-index: 2; visibility: visible; height: 598px; top: 150px; width: 972px; left: 20px;">
    <div style="position: absolute; width: 972px; height: 598px; ">
        <div id="main_div" style="position: relative; height: 375px; width: 610px; background-color:rgb(2,2,2); -webkit-transform-origin-x: 0px; -webkit-transform-origin-y: 0px;">
            <div style="position: relative; padding-top: 26px; padding-right: 10px; padding-bottom: 26px; padding-left: 10px; font-size: 10px; ">
                <div style="display: inline; font: normal normal normal 14px/normal arial; color: rgb(150, 150, 150); ">
                    <span>Here is some TEXT</span>
                </div>
            </div>
        </div>
    </div>
</div>

<div style="position: fixed; visibility: visible; height: 598px; top: 150px; width: 972px; left: 20px;">
    <div style="position:fixed; bottom:0; right:0; width:70%; height:30%; background-color: red;"></div>
</div>
</body></html>

回答1:

I was having similar issues with fixed-position elements dipping behind relative-positioned elements when zooming on the relative-positioned content. I was determined to figure out a solution.

When I changed the relative-positioned element back to static, all was well, but then that element was being covered by the fixed position elements. This was the reason I changed that element to relative to begin with... so I could put a z-index on it.

I also tried dynamically assigning the CSS styles of position and z-index, but that didn't seem to change anything either.

Then, I removed the 'left' CSS style from the stylesheet, and I dynamically assigned a style of 'right' via JS, with a value equal to the width of the window, minus the width of that fixed-position element, and this seemed to improve the issue, but not 100%.

Then I found your thread here, and tried your code. I uploaded an HTML file with your code to my server, then loaded that page up in my iPhone, and tried zooming around. I saw no such issues with your text being blurred. Odd enough.

So then I went back to my other page, refreshed, and all was well, even with the fixed-position elements dipping behind the relative-positioned element.

Thus, it seems this is a bug, perhaps caused by low memory or something. I'm not 100% sure, but without being able to reproduce the issue so easily, it may be hard to report such a bug to Apple's iPhone/Safari Mobile development team. :\

来源：https://stackoverflow.com/questions/8298696/losing-text-sharpness-blur-when-scaling-div-over-a-fixed-position-element-on

标签

javascript

iphone

css

webkit

mobile-safari