在HTML画布上格式化文本 [英] Formatting text on HTML canvas
问题描述
我使用HTML Canvas和vanilla javascript制作游戏。我是新的javascript,所以这可能比我想更容易。我有两个数组的对象代表卡,每个对象有一个40-100个字符的'文本'属性,在屏幕上动态绘制到130 x 70像素的卡上。
I'm making a game using HTML Canvas and vanilla javascript. I'm new to javascript so this may be easier than I think. I have two array's of objects that represent cards, each object has a 'text' property of between 40-100 characters that's drawn onto the screen dynamically onto a card that is 130 x 70px.
我需要格式化文本以适应卡的宽度限制(130像素),并在需要时创建一个新行。
I need to format the text to fit the width restriction of the card (130px) and create a new line whenever necessary.
任何帮助
编辑为更清楚
Edited to make clearer
推荐答案
可以使用 measureText()
方法。
正如 Ken Fyrstenberg 这个真棒答案,
canvas'
measureText
目前不支援量测高度(上升+下降)。
canvas'
measureText
doesn't currently support measuring height (ascent + descent).
下面的尝试使用一个硬编码的 Ken的回答确实提供了一种以编程方式找到它的方法。 lineHeight
值,您必须在渲染文本之前找到它。
Below attempt uses an hardcoded Ken's answer does provide a way to programmatically find it. lineHeight
value that you'd have to find before rendering text.
[编辑:由于下面的markE的评论,它现在使用1.286 *的字体大小的近似。 ]
[ Edit: thanks to markE's comment below, it now uses an approximation of 1.286*the font-size. ]
所以这里是脏的,必须有更好的方法,但无论如何...
So here it is, dirty and there must be better ways to do so but anyway...
var input = document.querySelector('input');
input.addEventListener('keyup', write, false);
var c = document.createElement('canvas'),ctx = c.getContext('2d');
c.width = 400, c.height = 150; document.body.appendChild(c);
// simple box object for the card
var card = {x: 25, y: 25, w: 130, h: 70};
ctx.fillStyle = "#CCCCCC";
ctx.fillRect(card.x, card.y, card.w, card.h);
var fontSize = 12;
ctx.font=fontSize+'px arial';
// Margins multipliers are chosen arbitrarly here, just because they fit well to my eyes
var margins = {t: 1.25*fontSize, l: .7*fontSize, b: 2*fontSize, r: .7*fontSize},
marginsX = margins.l+margins.r,
marginsY = margins.t+margins.b;
// As suggested by markE, lineHeight is set to 1.286* the fontSize,
// for a calculated way, see Ken's answer here : http://stackoverflow.com/a/17631567/3702797
var lineHeight = 1.286*fontSize;
// just a shortcut
var lineWidth = function(text) {
return ctx.measureText(text).width;
};
function write() {
var txt = this.value;
// Redraw our card
ctx.fillStyle = "#CCCCCC";
ctx.fillRect(card.x, card.y, card.w, card.h);
// Split the input at any white space, you might want to change it
var txtLines = txt.split(/\s/);
var i = 0, maxWidth = card.w - marginsX;
if(lineWidth(txt[0])>card.w || lineHeight>card.h-(margins.t/4) ){
console.warn('TOO BIG FONT!!');
return;
}
while(txtLines[i]) {
// If our current line merged with the next line width isn't greater than the card one
if (txtLines[i+1] && lineWidth(txtLines[i] + ' ' + txtLines[i+1]) < maxWidth) {
// Merge them
txtLines[i] += ' ' + txtLines.splice(i + 1, 1);
}
else {
// Is the one word too big? --> Dirtyphenation !
if (lineWidth(txtLines[i]) > maxWidth) {
// Add a new index with the two last chars since we'll add a dash
txtLines.splice(i+1, 0, "");
// If it's still too big
while (lineWidth(txtLines[i]) > maxWidth) {
var lastChars = txtLines[i].length - 2;
// Append those two last chars to our new array index
txtLines[i+1] = txtLines[i].substring(lastChars) + txtLines[i+1];
// Remove them from our current index
txtLines[i] = txtLines[i].substring(0, lastChars);
}
// Add the final dash
txtLines[i] += "-";
}
// Is our text taller than the card height?
if (lineHeight*i > card.h-marginsY){
// If there is more text coming after...
if (txtLines[i+1]){
// ...and it fits in the line
if(lineWidth(txtLines[i]+' '+txtLines[i+1])<maxWidth){
continue;
}
// ...and it doesn't fit in the line
else{
// Does a single char fit with the ellipsis ?
if(lineWidth(txtLines[i][0]+'...')<maxWidth){
// remove a char until we can put our ellipsis
while (lineWidth(txtLines[i]+'...') > maxWidth){
txtLines[i] = txtLines[i].substring(0,txtLines[i].length-1)
}
}else{
return;
}
txtLines[i] += '...';
// remove the surplus from the array
txtLines = txtLines.slice(0,i+1);
}
}
// stop looping here since we don't have space anymore
break;
}
// Go to next line
i++;
}
}
ctx.fillStyle = "#000";
// Where to draw
var x = card.x + (margins.l);
var y = card.y + (margins.t);
// Iterate through our lines
for (var i = 0; i < txtLines.length; i++) {
ctx.fillText(txtLines[i], x, y + (i * lineHeight));
}
}
canvas {border: 1px solid}
<input type="text" />
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