无法使用键盘访问工具提示内容 [英] Tool tip content is not accessible using keyboard
问题描述
使用键盘将其聚焦时，我看不到图像工具提示的内容.下面是一个代码示例:
I am unable to see the contents of the image tool tip when focussed on it using keyboard. Below is a code example:
<img id= "id1" title ="title1" tabindex ="0" src="/images/home.gif" alt="title1" />
使用鼠标悬停时，我可以看到工具提示的内容.
I am able to see the tool tip contents when hovered using mouse.
推荐答案
简短回答
不要使用title属性，它没有任何目的不适合用作图像下的标题或<input>上的<label>的标题(请不要使用在输入上输入title ....即使对于搜索框，即使是占位符"文本也是可取的，因为至少某些屏幕阅读器会读取该文本，而您的触摸屏用户仍将能够读取该输入的含义.
Short Answer
Don't use the title attribute, it doesn't serve any purpose that wouldn't be better suited as a caption under an image or a <label> on an <input> (please don't use a title on an input....even for a search box, even 'placeholder' text is preferable as at least some screen readers will read that and your touch screen users will still be able to read what the input is for).
title属性的支持率较低，在现代触摸屏时代为人们提供的东西很少(只有不使用放大镜或其他辅助技术的有视力的鼠标用户才能从title属性中获得任何收益)，通常对于大多数用例而言，并不是一个好主意.
The title attribute has low support, offers very little to people in the modern age of touch screens (it is only sighted mouse users who don't use magnifiers or other assistive tech who gain anything from a title attribute) and in general is not a good idea for most use cases.
作为一般规则，如果您确实要使用它(以便鼠标用户可以看到图像的内容)，请确保它与alt属性相同，以便您向屏幕阅读器用户提供与非屏幕阅读器用户相同的信息/体验.
As a general rule if you do want to use it (so mouse users can see what an image is about) then make sure it is the same as the alt attribute so that you are providing the same information / experience to screen reader users as non screen reader users.
我们玩了一段时间，在某些情况下title属性(或者至少是显示有关图像的额外信息的效果)会很有用.最后，我们滚动"了自己的title属性版本，该属性使我们能够获得有关图片的其他信息，而不会使用caption中断文档的流动.
We played with this for a while, there are some circumstances where the title attribute (or at least the effect of revealing extra information about an image) can be useful. In the end we 'rolled our own' version of the title attribute that allowed us to have additional information about a picture, without interrupting the flow of a document with a caption.
在下面的示例(我们使用的简化版本)中，我们有:-
In the example below (a stripped back version of what we use) we have:-
- 使它可以通过键盘和悬停进行访问.
- 为需要的人提供了有用的信息，它具有易于访问的附加好处(因为标题工具提示在某些浏览器中不遵循最小尺寸指导，并且即使您在浏览器中更改了字体大小设置也无法缩放) ).
- 使它可以在触摸设备上工作.
- 旨在像插件一样工作，因为您可以生成标准标记，其余的则由JavaScript和CSS魔术完成.
它仍然不如简单地在图像下提供标题那么好，但我相信它抓住了图像的标题"属性旨在用于的目的，同时考虑了可访问性和技术从其发布之日起的变化.介绍.
It still isn't as good as simply providing a caption under the image but I believe it captures the spirit of what the 'title' attribute on an image is designed for, while accounting for accessibility and technology changes from when it was introduced.
请注意-前80行左右的JavaScript只是一个允许jQuery样式语法的小型帮助程序库，相关部分从$("img").each(function(){开始.
Please Note - the first 80 or so lines of JavaScript are just a small helper library that allows jQuery style syntax, the relevant part starts at $("img").each(function(){.
//tiny replacement for jQuery - adapted version of ki.js
!function (b, c, d, e, f) {
f = b['add' + e]
function i(a, d, i) {
for(d = (a && a.nodeType ? [a] : '' + a === a ? b.querySelectorAll(a) : c), i = d.length; i--; c.unshift.call(this, d[i]));
}
$ = function (a) {
return /^f/.test(typeof a) ? /in/.test(b.readyState) ? setTimeout(function() { $(a); }, 9) : a() : new i(a);
};
$[d] = i[d] = {
on: function (a, b) {
return this.each(function (c) {
f ? c['add' + e](a, b, false) : c.attachEvent('on' + a, b)
})
},
off: function (a, b) {
return this.each(function (c) {
f ? c['remove' + e](a, b) : c.detachEvent('on' + a, b)
})
},
each: function (a, b) {
for (var c = this, d = 0, e = c.length; d < e; ++d) {
a.call(b || c[d], c[d], d, c)
}
return c
},
splice: c.splice
}
}(document, [], 'prototype', 'EventListener');
$.each = function(arr, callback) {
if(toString.call(arr) === '[object Array]'){
var i = 0, l = arr.length;
for(; i < l; ++i) {
callback.call(arr[i], i, arr[i]);
}
} else {
for (i in arr)
callback.call(arr[i], i, arr[i]);
}
return arr;
};
//extended to include "attr"
$.prototype.attr = function(a, b) {
return b === []._ ? this[0].getAttribute(a) : this.each(function(c) {
c.setAttribute(a, b);
});
};
//extended to include "removeAttr"
$.prototype.removeAttr = function(a) {
return this.each(function(b) {
b.removeAttribute(a);
});
};
//extend to include "parent"
$.prototype.parent = function() {
return (this.length < 2) ? $(this[0].parentNode): [];
};
//custom function to wrap an element in another
$.prototype.wrap = function(a) {
return this.each(function(b) {
var c = document.createElement(a)
b.parentNode.insertBefore(c, b);
c.appendChild(b);
});
};
//quick way of exposing everything like 'addClass', 'removeClass' etc. without having to define each one indivdually
var props = ['add', 'remove', 'toggle', 'has'],
maps = ['add', 'remove', 'toggle', 'contains'];
props.forEach(function(prop, index) {
$.prototype[prop + 'Class'] = function(a) {
return this.each(function(b) {
if(a){
b.classList[maps[index]](a);
}
});
};
});
//extend to include "after"
$.prototype.after = function(a) {
return this.each(function(b) {
b.insertAdjacentHTML('afterend', a);
});
};
//Below is the actual function, all of the above is just a simple replacement for jQuery.
//Should work with just jQuery but you would have to check.
$("img").each(function(){
$(this).wrap("div"); //create a div around an image
var title = $(this).attr("title"); //grab the title
var wrapper = $(this).parent(); //grab the div we just created
wrapper.attr("data-title", title); //set the data-title that we use in the CSS on the wrapper
wrapper.addClass("image"); //add the class that we use for CSS
wrapper.attr("tabindex", "0"); //make the div focusable with tabindex="0"
$(this).after('<span class="visually-hidden">, Title ' + title + '</span>'); //add a span with the title in that is accessible to screen readers - note the use of a comma before the 'Title' part as this makes it more natural (as we are 'hacking' an experience similar to that of a screen reader reading an actual title.)
$(this).removeAttr('title'); //remove the actual title, otherwise some screen readers will announce the title twice.
});
.image{
display:block;
overflow:hidden;
}
/*need relative position in order to absolutely position the overlay*/
.image {
position:relative;
width:200px;
height:200px;
margin: 10px;
}
.image img {
width:100%;
vertical-align:top;
}
/*add a transition*/
.image:after,
.image:before {
position:absolute;
opacity:0;
transition: all 0.5s;
}
/*remove the transition for people who have reduced motion as a preference*/
@media (prefers-reduced-motion: reduce) {
.image:after,
.image:before {
transition: none;
}
}
/*create an overlay*/
.image:after {
content:'';
width:100%;
height:100%;
top:0;
left:0;
background:rgba(0,0,0,0.4);
}
/*create a box at the bottom that contains the 'data-title' text that was added to the div we created*/
.image:before {
content: attr(data-title);
font-size: 1.25rem;
line-height: 1.9rem;
width:100%;
color:#fff;
z-index:1;
bottom:0;
padding:4px 10px;
text-align:left;
background:black;
box-sizing:border-box;
-moz-box-sizing:border-box;
}
/*make the overlay visible on hover and focus*/
.image:hover::after,
.image:hover::before,
.image:focus::after,
.image:focus::before{
opacity:1;
}
/*put a border around on focus*/
.image:focus{
outline: 2px solid #333;
outline-offset: 4px;
}
/*visually hidden class used to make text screen reader accessible but not visible*/
.visually-hidden {
position: absolute !important;
height: 1px;
width: 1px;
overflow: hidden;
clip: rect(1px 1px 1px 1px); /* IE6, IE7 */
clip: rect(1px, 1px, 1px, 1px);
white-space: nowrap; /* added line */
}
<img src="https://via.placeholder.com/150" title="First Image" alt="First Image"/>
<img src="https://via.placeholder.com/150" title="Second Image, A Longer Text Test for a more complex title, adjust to your needs" alt="Second Image"/>
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