CanvasRenderingContext2D: textBaseline property
Baseline
Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
The
CanvasRenderingContext2D.textBaseline
property of the Canvas 2D API specifies the current text baseline used when drawing
text.
Value
Possible values:
"top"-
The text baseline is the top of the em square.
"hanging"-
The text baseline is the hanging baseline. (Used by Tibetan and other Indic scripts.)
"middle"-
The text baseline is the middle of the em square.
"alphabetic"-
The text baseline is the normal alphabetic baseline. Default value.
"ideographic"-
The text baseline is the ideographic baseline; this is the bottom of the body of the characters, if the main body of characters protrudes beneath the alphabetic baseline. (Used by Chinese, Japanese, and Korean scripts.)
"bottom"-
The text baseline is the bottom of the bounding box. This differs from the ideographic baseline in that the ideographic baseline doesn't consider descenders.
The default value is "alphabetic".
Examples
Comparison of property values
This example demonstrates the various textBaseline property values.
HTML
<canvas id="canvas" width="550" height="500"></canvas>
JavaScript
const canvas = document.getElementById("canvas");
const ctx = canvas.getContext("2d");
const baselines = [
"top",
"hanging",
"middle",
"alphabetic",
"ideographic",
"bottom",
];
ctx.font = "36px serif";
ctx.strokeStyle = "red";
baselines.forEach((baseline, index) => {
ctx.textBaseline = baseline;
const y = 75 + index * 75;
ctx.beginPath();
ctx.moveTo(0, y + 0.5);
ctx.lineTo(550, y + 0.5);
ctx.stroke();
ctx.fillText(`Abcdefghijklmnop (${baseline})`, 0, y);
});
Result
Comparison of property values on the same line
As with the previous example, this example demonstrates the various textBaseline property values, but in this case with all of them lined up horizontally along the same line — to make it easier to see how they differ from each other.
HTML
<canvas id="canvas" width="724" height="160"></canvas>
JavaScript
const canvas = document.getElementById("canvas");
const ctx = canvas.getContext("2d");
const baselines = [
"top",
"hanging",
"middle",
"alphabetic",
"ideographic",
"bottom",
];
ctx.font = "20px serif";
ctx.strokeStyle = "red";
ctx.beginPath();
ctx.moveTo(0, 100);
ctx.lineTo(840, 100);
ctx.moveTo(0, 55);
ctx.stroke();
baselines.forEach((baseline, index) => {
ctx.save();
ctx.textBaseline = baseline;
let x = index * 120 + 10;
ctx.fillText("Abcdefghijk", x, 100);
ctx.restore();
ctx.fillText(baseline, x + 5, 50);
});
Result
Specifications
| Specification |
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| HTML # dom-context-2d-textbaseline-dev |
Browser compatibility
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textBaseline
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Legend
Tip: you can click/tap on a cell for more information.
- Full support
- Full support
See also
- The interface defining this property:
CanvasRenderingContext2D