HTML canvas textBaseline-attribut
Definition och användning
textBaseline-attributet sätter eller returnerar den aktuella textbaslinjen vid ritning av text.
Följande illustration visar de olika baslinjer som textBaseline-attributet stöder:
Note:fillText() eller strokeText() När text placeras på canvas används den specifika textBaseline-värdet.
Exempel
Definiera en rektangel med blå färg:
JavaScript:
var c=document.getElementById("myCanvas");
var ctx=c.getContext("2d");
//rita blå linje i position y=100
ctx.strokeStyle="blue";
ctx.moveTo(5,100);
ctx.lineTo(395,100);
ctx.stroke();
ctx.font="20px Arial"
//i position y=200 med olika textBaseline-värden
ctx.textBaseline="top";
ctx.fillText("Top",5,100);
ctx.textBaseline="bottom";
ctx.fillText("Bottom",50,100);
ctx.textBaseline="middle";
ctx.fillText("Middle",120,100);
ctx.textBaseline="alphabetic";
ctx.fillText("Alphabetic",190,100);
ctx.textBaseline="hanging";
ctx.fillText("Hanging",290,100);
语法
context.textBaseline="alphabetic|top|hanging|middle|ideographic|bottom";
Attribute value
| Value | Description |
|---|---|
| alphabetic | Default. The text baseline is the standard letter baseline. |
| top | The text baseline is the top of the em box. |
| hanging | The text baseline is the hanging baseline. |
| middle | The text baseline is the center of the em box. |
| ideographic | The text baseline is the ideographic baseline. |
| bottom | The text baseline is the bottom of the em box. |
Technical details
| Default value: | alphabetic |
|---|
Browser support
The numbers in the table indicate the first browser version that fully supports this property.
| Chrome | Edge | Firefox | Safari | Opera |
|---|---|---|---|---|
| Chrome | Edge | Firefox | Safari | Opera |
| 4.0 | 9.0 | 3.6 | 4.0 | 10.1 |
Note:Internet Explorer 8 and earlier versions do not support the <canvas> element.
