Why does a CSS border look different on Android?
Question
I have a box with a border.
border: 1px solid #000;
I am using the following viewport setup:
<meta name="viewport" content="width=device-width, initial-scale=1, user-scalable=no" />
The border seems to be 2 pixels on the top and right side. What is the reason for this?
Additional: there are no other CSS rules other than a width and height.
3 answers
solution1
13 2018-03-14 06:38:19
The meta tag that targeted pixel-density specifically has been depreciated and now both Android and iPhone seem to be just using the one metatag:
<meta name="viewport" content="width=device-width, initial-scale=1.0">
But, if you try to make a 1px border, it will be thicker and thinner on different sides depending on the mobile device's pixel density.
How some devices render '1px' with multiple pixels and it is not always pretty because they are using different pixel ratios (dpr) such as 1.5, 2 and 3. Sometimes, all 4 sides of a 1px border will not match.
This is some CSS to make 1px display properly on 2dpr iPhone by dividing 1px by half:
@media only screen and (-webkit-min-device-pixel-ratio: 2) {
div {
border-width: 0.5px;
}
And similar techniques are shown here: http://n12v.com/css-retina-and-physical-pixels/ https://developer.android.com/guide/webapps/targeting.html
solution2
0 2018-03-19 17:37:35
Unless you have a very good reason for it (doubtful), disabling user-zoom is a very bad idea. See user-scalable=no … Evil or Slightly Not Evil? for examples of why this is bad. It also gives some examples where user-scalable=no is perfectly acceptable.
for a 1.5 pixel-ratio, try
@media only screen and (-webkit-min-device-pixel-ratio: 1.5) {
div {
border-width: 0.75px;
}
}
solution3
0 2018-03-20 10:58:01
"Could you modify your answer to make it working for all devices, regardless the DPI? Would be super useful! – Basj"
i dont know how much this helpfull here i added a custom function to get border size on almost all dpr
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>Pixel Ratio</title>
<style>
.bord {
width: 300px;
height: 300px;
border: 10px solid #000;
}
</style>
</head>
<body>
<div class="bord"> </div>
<script>
dprof("bord");
function dprof(elmclass){
var z =document.getElementsByClassName(elmclass).length;
var dpr = window.devicePixelRatio;
for(i=0;i<z;i++){
document.getElementsByClassName(elmclass).item(i).classList.add("dpr-"+dpr);
var bw =getComputedStyle(document.getElementsByClassName(elmclass).item(i),null).getPropertyValue('border-width');
var nw =bw.replace("px","");
var nbw=nw/dpr;
console.log(nbw);
if(nbw!=0){
document.getElementsByClassName(elmclass).item(i).style.borderWidth=nbw+"px";
}
}
}
</script>
</body>
</html>
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