Can a canvas within a canvas easily be cleared from the main canvas?

I'm currently working on an interface where I have a primary canvas that is 800x800 in size. At the top I've generated a bunch of icons. When a user mouses over the icons at the top, it matches his mouse's x and y coordinates to determine if he is currently hovering over any of the icons. If he is, I want to have a hover effect where a label appears next to the mouse with the name of the icon. As he moves, the label follows the mouse. If he leaves the icon or moves to a different one, the last one is cleared, and either there is no label displayed (if the user moved off all icons), or another label is displayed next to the mouse in the last one's place (if he hovers over another icon, the width of the label is a variable length depending upon the width of the text).

The proce开发者_开发问答ss of ordering and displaying these icons all occurs within a separate object from the rest of the canvas renderings, thus I wouldn't exactly want to re-render that entire object to display the icons every time a mousemove event triggers, so I'm wondering if there's a way to draw to another "temporary" canvas' context and whether or not that could be easily cleared. as the mouse moves so there isn't any trails left behind on the primary canvas? Can anyone point me in the direction of an example like this or advise me on how I should go about accomplishing this sort of task?

Yes you can certainly draw it onto a temporary (in-memory) canvas. This is done a lot of various reasons, and yours may be valid (especially if you don't have any background that changes). But it may not be the easiest to implement, its hard to say without knowing more about your app.

There's a decent alternative you should consider: you could have two canvases that are 800x800 in size overlaid atop each-other. This can be useful for some applications (like games) where there is a background, foreground, and middle-ground that all have different moving parts (but the background parts move rarely, and foreground isn't always present, etc)

In the same way, you could "layer" your canvas app, with the icons being on one canvas, and the background and other parts of the app being on the other canvas.