Is a unicode code point can be displayed normally? - google-chrome

Question

I want to know whether a unicode code point can be displayed in chrome, and check it in golang, so I can escape some parts of a string before i send it to chrome.
I have found that there is three types of unicode code point can not be displayed normally in chrome :
Space . like code point 0x20(32). ' '
Font not exist. There is a question mark in the square box. (occupy two English letters width) like code point 0x378(888) "͸"
Invaild code point value. A diamond-shaped black box with a question mark inside (occupy one English letter width) like code point 0xd800(55296) "�"

Answer 1

I found that I can use js and OffscreenCanvas to render all of the unicode code point and check if them looks like above three types.
Then I got a function that can tell you whether a rune/character can be displayed normally by the operating system. https://github.com/fastslothlab/fslRune
js code:
(function(){
var start = 0;
var end = 1114111;
const imageSize = 20;
var tufoCiList = [32,888,55296];
var num = end-start+1;
var startTime = performance.now()
var hasDataCiList = [];
var c = new OffscreenCanvas(imageSize,imageSize);
var ctx = c.getContext("2d");
function getImageDataByCi(ci){
var s = String.fromCodePoint(ci);
ctx.clearRect(0,0,imageSize,imageSize);
ctx.fillText(s, 5, 15);
var imgD = ctx.getImageData(0,0,imageSize,imageSize);
var hasNoneZero = false;
var buf = imgD.data;
return buf;
}
var tofuBufList = [];
for (var i in tufoCiList){
tofuBufList.push(getImageDataByCi(tufoCiList[i]));
}
function debugImage(){
c.convertToBlob({
type: "image/png",
}).then(function(blob) {
var url = URL.createObjectURL(blob);
var imgObj = document.createElement("img");
imgObj.src = url;
document.body.appendChild(imgObj);
console.log(url);
});
}
function bufEqual(buf1, buf2){
if (buf1.byteLength != buf2.byteLength) return false;
for (var i = 0 ; i != buf1.byteLength ; i++){
if (buf1[i] != buf2[i]) return false;
}
return true;
}
for (var ci =start;ci<=end;ci++){
var buf = getImageDataByCi(ci);
var hasFound = false;
for (var i in tofuBufList){
if (bufEqual(buf,tofuBufList[i])){
hasFound = true;
break;
}
}
if (hasFound){
continue;
}
hasDataCiList.push(ci);
}
console.log((performance.now()-startTime)/num);
console.log(JSON.stringify(hasDataCiList));
})();