RGraph: HTML5 canvas graph library - API documentation

Overview
Canvas and context references
Working with events
Working with graph data
RGraph functions
- Arrays
- Strings
- Miscellaneous
- Other

Overview

Working with RGraph objects is purposefully easy, to make them straight forward to integrate into your own scripts if you want to. For any particular graph type there are only two files required - the common library and the graph specific library. Eg:

<script src="RGraph.common.js"></script>
<script src="RGraph.bar.js"></script>

RGraph.common.js is a function library that contains a large set of functions that support the graph classes. Each of the graph libraries (RGraph.*.js) contains that particular graphs class. If you'd like to see a "bare bones" implementation, you can look at the basic example.

Canvas and context references

Each graph object maintains references to the context and canvas as properties. So to get hold of them all you need to do is this:

<script>
    window.onload = function ()
    {
        // 1/2 First draw the chart
        var myBar = new RGraph.Bar('myCanvas', [1,5,8,4,6,3,1,5,7,8,4,6]);
        myBar.Set('chart.labels', ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec']);
        myBar.Draw();
    
        // 2/2 Now get hold of the references
        var context = myBar.context; // Get hold of a reference to the context
        var canvas  = myBar.canvas;  // Get hold of a reference to the canvas
    }
</script>

Working with events

When working with events, you may come across the situation where you have a reference to the canvas, but also need to access the graph object. For this reason the constructor of each object adds a reference to the object to the canvas and you can access them like this:

<script>
    document.getElementById("myCanvas").onclick = function (e)
    {
        var src = (document.all ? event.srcElement : e.target);
    
        // The RGraph object constructors add __object__ to the canvas.
        var myBar = src.__object__;
    }
</script>

Working with graph data

Another variable you may need is the data variable. For most graph types, this is where the data is stored. It is usually untouched, so it is as you supplied to the graph objects constructor. An exception to this is filled line charts. Here the original data is stored in the class variable original_data. The data supplied is modified to produce the stacking effect. If you need to modify a filled line charts data you will need to change this variable instead.

Not all graph types use the data variable. For some the name is slightly different so that it makes a little more sense. An example is the Progress bar, which stores the indicated value in the chart.value property, and the maximum value in chart.max.

RGraph functions

This is a list of some of the functions available to you in RGraph.common.js. It's not every single one that's available, but is a list of the common ones that you're likely to want to use. Arguments in square brackets are optional.

<script src="RGraph.common.js"></script>

<script>
    // Returns 9
    myArray = [3,2,5,4,9,7,8];
    max = RGraph.array_max(myArray);
</script>

Arrays

(number) RGraph.array_max(array)
Returns the maximum value in the array.
(number) RGraph.array_sum(array)
Returns the sum of all values in the array. You can also pass a single integer, in which case it is simply returned as-is.
(array) RGraph.array_clone(array)
Creates a copy/clone of the given array. Only numerically indexed arrays are supported.
(array) RGraph.array_reverse(array)
Returns a reversal of the given array.

Strings

(string) RGraph.rtrim(string)
Strips the right hand white space from the string that you pass it.
(string) RGraph.number_format(number[, prepend[, append]])
This formats the given number (which can be either an integer or a float. The prepend and append variables are strings which are added to the string (eg 5%).

Miscellaneous

(object) RGraph.FixEventObject(event)
Pass this function an event object and it will attempt to "fill in" the missing properties (depending on the browser). It tries to add:
- pageX (MSIE)
- pageY (MSIE)
- target (MSIE)
- offsetX (FF)
- offsetY (FF)
(null) RGraph.OldBrowserCompat(context)
This function "fills in" any required functions that some browsers don't have. At the moment this consists of adding the measureText() and fillText() functions to the context when they're missing (usually this means Opera).
(number) RGraph.GetDays(date)
This returns the number of days in the given month. The argument should be a Date object.
(null) RGraph.pr(mixed)
Emulates the PHP function print_r() by recursively printing the structure of whatever you pass to it. It handles numbers, strings, arrays, booleans, functions and objects.
(null) pd(mixed)
An alias of the above albeit far shorter to type.
(null) RGraph.Clear(canvas[, color])
Clears the canvas by drawing a white (or the optional color you give) rectangle over it.
(null) RGraph.ClearAnnotations(id)
This function clears the annotation data associated with the given canvas ID (but DOES NOT redraw the graph). If you want to clear the visible annotations too, you will need to redraw the canvas. You could do this using the following code:
```
function ClearAndRedraw (obj)
{
    RGraph.Clear(obj.canvas); // This function also calls the RGraph.ClearAnnotations() function
    obj.Draw();
}
```
(array) RGraph.getMouseXY(event)
When passed your event object, it returns the X and Y coordinates (in relation to the canvas) of the mouse pointer.
(array) RGraph.getCanvasXY(event)
Similar to the above function but returns the X/Y coordinates of the canvas.
(number) RGraph.degrees2Radians(number)
Converts and returns the given number of degrees to radians. 1 radian = 57.3 degrees.
(array) RGraph.getScale(max)
Given the maximum value this will return an appropriate scale.
(mixed) RGraph.Registry.Get(name)
In conjunction with the next function, this is an implementation of the Registry pattern which can be used for storing settings.
(mixed) RGraph.Registry.Set(name, value)
In conjunction with the previous function, this is an implementation of the Registry pattern which can be used for storing settings.
(null) RGraph.Register(object)
This function is used in conjunction with the next to register a canvas for redrawing. Canvases are redrawn (for example) when tooltips or crosshairs are being used.
(null) RGraph.Redraw()
This function is used in conjunction with the previous to redraw a canvas. Canvases are redrawn (for example) when tooltips or crosshairs are being used.
(null) RGraph.NoShadow(object)
This function is a shortcut function used to "turn off" the shadow. The argument is your graph object.
(array) RGraph.getSegment(event)
This function can be used with the Donut, Pie and Radar charts to get segment information when the canvas is clicked on. It returns an array consisting of: The center X coordinate, the center Y coordinate, the radius, the start angle (in degrees)and the end angle (in degrees).
(number) RGraph.Async(mixed[, delay])
This is a simple function but has significant implications on your pages performance. You can pass this either a function pointer, or a string containing the code to run and it will run the code asynchronously (ie in parallel to the page loading). In doing so it can mean that your page is displayed faster, as the graph is created seperate to the page loading. As such, the placement of your canvas tag becomes more important. What you can do is define the canvas tag and then the code to produce the graph immediately after it. This is how the front page is coded. There's an example of it here. The optional delay argument is measured in milliseconds (1 second = 1000 milliseconds) and defaults to 1. What you can do is specify something like 1000 to make the effect more pronounced to ensure it's working as expected.
(null) RGraph.filledCurvyRect(context, x, y, width, height[, radius[, curvy top left[, curvy top right[, curvy bottom right[, curvy bottom left]]]]])
This draws a rectangle with curvy corners. Similar to the built in rectangle functions, and you can control individual corners. The radius controls the severity of the corner curvature and defaults to 3. By default all the corners are curvy.
(null) RGraph.strokedCurvyRect(context, x, y, width, height[, radius[, curvy top left[, curvy top right[, curvy bottom right[, curvy bottom left]]]]])
This draws a rectangle with curvy corners. Similar to the built in rectangle functions, and you can control individual corners. The radius controls the severity of the corner curvature and defaults to 3. By default all the corners are curvy.

Other

These are functions which are less generic, and used to build the graphs. You may still wish to use them however.

(null) RGraph.lineByAngle(context, x, y, angle, length)
This function draws a line from the given X and Y coordinates at the specified angle.
(null) RGraph.Text(context, font, size, x, y, text[[[[[[, valign], halign], border], angle], background], bold])
This function acts as a wrapper around the canvas text functionality.
(null) RGraph.DrawTitle(canvas, text, gutter[, centerx[, size]])
This function draws the title. The centerx argument is the center point to use. If not given the center of the canvas is used.
(null) RGraph.Tooltip(canvas, text, x, y)
This function shows a tooltip.
(null) RGraph.DrawKey(object, key, colors)
This function draws the key. The first argument is the graph object, the second is an array of key information and the last is an array of the colors to use.
(null) RGraph.DrawBars(object)
This draws the horizontal background bars. The argument is the graph object.
(null) RGraph.DrawInGraphLabels(object)
This draws the in-graph labels. The argument is the graph object.
(null) RGraph.DrawCrosshairs(object)
This function draws the crosshairs. The argument is the graph object.
(null) RGraph.HideContext()
This function clears the context menu. RGraph uses it to hide the context menu, but only AFTER your function/callback is run. You may wish to hide the context menu before your own function, in which case you can call this function.

Questions

If you have a question regarding the API, please ask on the mailing list