fontBoundingBoxAscent

Summary

The distance from the horizontal line indicated by the textBaseline attribute to the top of the highest bounding rectangle of all the fonts used to render the text, in CSS pixels; positive numbers indicating a distance going up from the given baseline.

Property of apis/canvas/TextMetrics apis/canvas/TextMetrics

Syntax

Note: This property is read-only.

var result = TextMetrics.fontBoundingBoxAscent;

Return Value

Returns an object of type NumberNumber

Examples

<canvas id="myCanvas" width="300" height="150" style="border:1px solid blue;"></canvas>
<p>. . .</p>
<script>
var can = document.getElementById("myCanvas");
var ctxt = can.getContext("2d");
ctxt.font = "24px Arial";
var txt = "Hello world!"
ctxt.fillText(txt, 10, 75);
var mets = ctxt.measureText(txt);
alert("fontBoundingBoxAscent: " + mets.fontBoundingBoxAscent);
//Use with caution: may return "undefined" even in supported browsers
</script>

Related specifications

W3C HTML Canvas 2D Specification: W3C Candidate Recommendation

Attributions

Microsoft Developer Network: Windows Internet Explorer API reference Article