如何使用javascript给SVG文本元素提供固定的高度和宽度？

Question

I have multiple rect of different height and width, I need to show a text on the top left corner of the rect and no matter how much the width of the text is ,it should get adjusted in 50% of rect width.

Here is the code I have tried.

 rectBbox = rectElem.getBBox();
 textBbox = textElem.getBBox();
 scale = rectBbox.width / textBbox.width;
 X = parseFloat(rectBbox.x) 
 Y = parseFloat(rectBbox.y) 
 textElem.setAttribute("transform", "translate(" + X + "," + Y + ") scale(" + scale + ")");

my svg looks like

<svg>
<g id="maingroup">
<g id="firstchild">
<rect></rect>
<text></text>
</g>
<g id="nthchild">
<rect></rect>
<text></text>
</g>
<g>
</svg>

How can i scale it so that no matter what is the size of the rect or text is,text will get properly adjusted within 50% of rect's width

Answer 1

In this example, we are positioning the <text> elements at the default 0,0 . Then we calculate the difference between the top left of the rect and the top left of the text.

The scale part is similar: 0.5 * the ratio of the text width and the rect width.

 function adjustText(boxElem) { var rectElem = boxElem.querySelector("rect"); var textElem = boxElem.querySelector("text"); var rectBbox = rectElem.getBBox(); var textBbox = textElem.getBBox(); var scale = 0.5 * rectBbox.width / textBbox.width; var translateX = rectBbox.x - textBbox.x; var translateY = rectBbox.y - textBbox.y; textElem.setAttribute("transform", "translate(" + translateX + "," + translateY + ") scale(" + scale + ")"); } adjustText(document.getElementById("firstchild")); adjustText(document.getElementById("nthchild")); 

 <svg width="500" height="500"> <g id="maingroup"> <g id="firstchild"> <rect x="20" y="30" width="250" height="100" fill="lightgrey" stroke="black"/> <text>Very Very Very Very Very Long Text</text> </g> <g id="nthchild"> <rect x="200" y="200" width="200" height="100" fill="lightgrey" stroke="black"/> <text>Smaller Text</text> </g> </g> </svg> 

Answer 2

First I need to calculate the width of the text ( txtlength ) and the width of the box ( w ). I want to scale the text so I'm calculating the scale let thescale = w / (2*txtlength); . // this will scale the text at 50% of the rect width. Next, using setAttributeNS I'm setting the value for the transform attribute. Please observe that the text has no x and no y attributes being centered around the origin of the SVG canvas.

 let txtlength = txt.getComputedTextLength() let w = theRect.getBBox().width; let c = {x:50,y:25}// the center of the rect let thescale = w / (2 * txtlength);// 50% of rect's width //scale the text and translate in the center txt.setAttributeNS(null, "transform", `scale(${thescale},${thescale}) translate(${cx/thescale},${cy/thescale})`) 

 svg{border:1px solid; width:120vh} text{font-size:10; dominant-baseline: middle; text-anchor: middle} 

 <svg viewBox="0 0 100 50"> <rect id="theRect" x="10" y="10" width="80" height ="30" stroke="black" fill="none" /> <text id="txt" dominant-baseline="middle" text-anchor="middle">A very long text, sooo long </text> </svg>