[英]Detecting canvas text API support (Opera Mini)
Although Opera Mini does not display canvas text, a typical test indicates that it has an implementation of the text API functions. 尽管Opera Mini不显示画布文本,但典型测试表明它具有文本API函数的实现。 Is there an alternative technique to check for support? 是否有替代技术来检查支持?
Current method: 当前方法:
var context = document.createElement("canvas").getContext("2d");
var canvasTextSupport = typeof context.fillText == "function"; // true in Opera Mini
An example you can use to see if text shown: tutorialspoint 您可以用来查看是否显示文本的示例: tutorialspoint
You can use a custom build of the Modernizr library to do that! 您可以使用Modernizr库的自定义版本来做到这一点!
As suggested by @kangax, you can test by drawing text to a canvas and then making sure that pixels have been drawn. 按照@kangax的建议,您可以通过将文本绘制到画布上,然后确保已绘制像素来进行测试。
var canvasTextSupported = function() {
var canvas = document.createElement("canvas");
var context = canvas.getContext("2d");
context.fillText("X", 5, 5);
var imageData = context.getImageData(0, 0, 10, 10);
for(var i = 0, l = imageData.data.length; i < l; i++) {
if(imageData.data[i] !== 0)
return true;
}
return false;
}
As I was using canvas
to detect fonts, with errors thrown, a more compact alternative I found is: 当我使用canvas
检测字体并引发错误时,我发现了一个更紧凑的替代方法是:
var canvasTextSupported = function() {
var cvs = document.createElement("canvas");
var ctx = cvs.getContext("2d");
return 'measureText' in ctx && ctx.measureText("") !== undefined;
}
Firefox 3.0.x doesn't have measureText
. Firefox 3.0.x没有measureText
。 And in Opera Mini measureText() returns undefined
. 在Opera Mini中,measureText()返回undefined
。
您可以使用canisuse.js脚本检测您的浏览器是否支持canvas文本API。
caniuse.canvasTextApi();
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