| 1 | Dojo Charting Engine
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| 2 | =========================================================================
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| 3 | The Dojo Charting Engine is a (fairly) complex object structure, designed
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| 4 | to provide as much flexibility as possible in terms of chart construction.
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| 5 | To this end, the engine details the following structure:
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| 6 |
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| 7 | Chart
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| 8 | ---PlotArea[]
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| 9 | ------Plot[]
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| 10 | ---------Axis (axisX)
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| 11 | ---------Axis (axisY)
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| 12 | ---------Series[]
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| 13 |
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| 14 |
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| 15 | A Chart object is the main entity; it is the entire graphic. A Chart may
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| 16 | have any number of PlotArea objects, which are the basic canvas against
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| 17 | which data is plotted. A PlotArea may have any number of Plot objects,
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| 18 | which is a container representing up to 2 axes and any number of series
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| 19 | to be plotted against those axes; a Series represents a binding against
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| 20 | two fields from a data source (initial rev, this data source is always of
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| 21 | type dojo.collections.Store but this will probably change once dojo.data
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| 22 | is in production).
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| 23 |
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| 24 | The point of this structure is to allow for as much flexibility as possible
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| 25 | in terms of what kinds of charts can be represented by the engine. The
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| 26 | current plan is to accomodate up to analytical financial charts, which tend
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| 27 | to have 3 plot areas and any number of different types of axes on each one.
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| 28 |
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| 29 | The main exception to this is the pie chart, which will have it's own
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| 30 | custom codebase. Also, 3D charts are not accounted for at this time,
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| 31 | although the only thing that will probably need to be altered to make
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| 32 | that work would be Plot and Series (to accomodate the additional Z axis).
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| 33 |
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| 34 | Finally, a Plot will render its series[] through the use of Plotters, which
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| 35 | are custom methods to render specific types of charts.
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| 36 | -------------------------------------------------------------------------
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| 37 | In terms of widgets, the basic concept is that there is a central, super-
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| 38 | flexible Chart widget (Chart, oddly enough), and then any number of preset
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| 39 | chart type widgets, that are basically built to serve a simple, easy
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| 40 | purpose. For instance, if someone just needs to plot a series of lines,
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| 41 | they would be better off using the LineChart widget; but if someone needed
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| 42 | to plot a combo chart, that has 2 Y Axes (one linear, one log) against the
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| 43 | same X Axis, using lines and areas, then they will want to use a Chart widget.
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| 44 | Note also that unlike other widgets, the Charting engine *can* be called
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| 45 | directly from script *without* the need for the actual widget engine to be
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| 46 | loaded; the Chart widgets are thin wrappers around the charting engine. |
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