You can't set the letter spacing property, but you you can accomplish wider letter spacing in canvas by inserting one of the various white spaces in between every letter in the string. For instance
ctx.font = "3em sheepsans";
ctx.textBaseline = "middle";
ctx.textAlign = "center";
ctx.fillStyle = "rgb(255, 255, 255)";
var ctext = "Blah blah text".split("").join(String.fromCharCode(8202))
ctx.fillText(ctext, 1024 / 2, 768 / 2);
This will insert a hair space between every letter.
Using 8201 (instead of 8202) will insert the slightly wider thin space
For more white space options, see this list of Unicode Spaces
This method will help you to preserve the font's kerning much more easily than manually positioning each letter, however you wont be able to tighten your letter spacing this way.
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