HOTSPOT
You develop an interactive scalable vector graphics (SVG) application. You write the
following HTML markup that makes a rectangle rotate:

You need to control the speed of the rotating rectangle.
How should you complete the relevant code? (To answer, select the appropriate option from
each drop-down list in the answer area.)

Answer:

Explanation:

Note:
* What is SVG?
SVG stands for Scalable Vector Graphics
SVG is used to define vector-based graphics for the Web
SVG defines the graphics in XML format
SVG graphics do NOT lose any quality if they are zoomed or resized

Every element and every attribute in SVG files can be animated
SVG is a W3C recommendation
* Example:
<script>
/* CONSTANTS */
var initialTheta = 0; // The initial rotation angle, in degrees.
var thetaDelta = 0.3; // The amount to rotate the square every “delay” milliseconds, in
degrees.
var delay = 10; // The delay between animation stills, in milliseconds. Affects animation
smoothness.
var angularLimit = 90; // The maximum number of degrees to rotate the square.
/*
Note that it will take the square (angularLimit/thetaDelta)*delay milliseconds to rotate an
angularLimit
number of degrees. For example, (90/0.3)*10 = 3000 ms (or 3 seconds) to rotate the
square 90 degrees.
*/
/* GLOBALS */
var theSquare; // Will contain a reference to the square element, as well as other things.
var timer; // Contains the setInterval() object, used to stop the animation.
function init()
/*
Assumes that this function is called after the page loads.
*/
{
theSquare = document.getElementById(“mySquare”); // Set this custom property after
the page loads.
theSquare.currentTheta = initialTheta; // The initial rotation angle to use when the
animation starts, stored in
timer = setInterval(doAnim, delay); // Call the doAnim() function every “delay”
milliseconds until “timer” is cleared.
}
function doAnim()
/*
This function is called by setInterval() every “delay” milliseconds.
*/
{
if (theSquare.currentTheta > angularLimit)
{
clearInterval(timer); // The square has rotated enough, instruct the browser to stop
calling the doAnim() function.
return; // No point in continuing; stop now.
}
theSquare.setAttribute(“transform”, “rotate(” + theSquare.currentTheta + “)”); // Rotate
the square by a small amount.

theSquare.currentTheta += thetaDelta; // Increase the angle that the square will be
rotated to, by a small amount.
}
</script>
</head>