Bookmark and share:
Bookmark with delicious tweet this site Post to Google Buzz! Post to Facebook Share on FriendFeed Stumble! this site

RGraph: HTML5 canvas graph library - Annotating your graphs

[No canvas support]

The annotations feature brings presentation style functionality to RGraph graphs. You can use this feature for highlighting your graphs if you need to.

How do annotations work?

Enabling annotations is a very simple affair, and consists of doing the following:

myGraph.Set('chart.annotatable', true);

Browser support

Annotations are supported in all browsers that RGraph works with - Firefox 3.5+, Chrome 2+, Safari 4+, Opera 10.5+ and MSIE/Google Chrome Frame. They DO NOT however work with MSIE 8/ExCanvas.

What can I use annotations for?

As mentioned you can use it for presentations, highlighting things to yourself or others or just to have fun drawing (!).

Are annotations persistent?

That depends on which browser you're using. The annotation data is stored in the users web browser (not on the web server), meaning currently (21st March 2010) browser support is limited to Firefox 3.5+, Safari 4+, Chrome 4+ and Opera 10.5+. MSIE 8 also has the required storage capabilities, but since it doesn't yet support canvas, the point is moot. The user does not have to confirm anything for storage to be allowed - try it out on this page by drawing on the graph and then refreshing the page.

How do I show the mini-palette?

You can show the palette by using the RGraph.Showpalette function shown below as a context menu item:

myObj.Set('chart.contextmenu', [
                                ['Show palette', RGraph.Showpalette],
                                ['Clear', function () {RGraph.Clear(myObj.canvas); myObj.Draw();}]

This code will result in the same context menu as the graph above.

How can I clear the annotations?

You can simply clear the graph and redraw it:
RGraph.Clear(myGraph.canvas); // Clear the graph
myGraph.Draw();               // Redraw it

In the graph above, there is a context menu that allows you to both clear the graph and also demonstrates the mini-palette feature available to you.

Replaying annotations when they're off

When annotations are not enabled, any prior annotations that may have been made are not displayed. To show them you need to use the API function RGraph.ReplayAnnotations(object) after the call to .Draw().