This sample demonstrates the ability to build an updateable pie chart with selectable slices. The Geometry for each slice is built using a PathFigure with a SegmentType.Arc. Slices use a custom click function, which sets a stroke and offsets slices as they are selected. Functionality for "selection" and deletion of these slices is similar to the Selectable Fields sample, using some overridden CommandHandler functions. Each slice also has a tooltip showing the text and percentage of votes.

Poll results can be adjusted and the pie chart will automatically update to reflect any changes. This includes deleting selected slices, updating the count using a TextBlock, or using the +/- buttons.

### GoJS Features in this sample

#### Table Panels

The "Table" Panel, Panel.Table, arranges objects in rows and columns. Each object in a Table Panel is put into the cell indexed by the value of GraphObject.row and GraphObject.column. The panel will look at the rows and columns for all of the objects in the panel to determine how many rows and columns the table should have. More information can be found in the GoJS Intro.

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#### Item Arrays

It is sometimes useful to display a variable number of elements in a node by data binding to a JavaScript Array. In GoJS, this is simply achieved by binding (or setting) Panel.itemArray. The Panel will create an element in the panel for each value in the Array. More information can be found in the GoJS Intro.

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#### Collections

GoJS provides its own collection classes: List, Set, and Map. You can iterate over a collection by using an Iterator. More information can be found in the GoJS Intro.

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#### ToolTips

A tooltip is an Adornment that is shown when the mouse hovers over an object that has its GraphObject.toolTip set. The tooltip part is bound to the same data as the part itself.

It is typical to implement a tooltip as a "ToolTip" Panel holding a TextBlock or a Panel of TextBlocks and other objects. Each "ToolTip" is just an "Auto" Panel Adornment that is shadowed, and where the border is a rectangular Shape with a light gray fill. However you can implement the tooltip as any arbitrarily complicated Adornment.

More information can be found in the GoJS Intro.

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#### Buttons

GoJS defines several Panels for common uses. These include "Button", "TreeExpanderButton", "SubGraphExpanderButton", "PanelExpanderButton", "ContextMenuButton", and "CheckBoxButton". "ContextMenuButton"s are typically used inside of "ContextMenu" Panels; "CheckBoxButton"s are used in the implementation of "CheckBox" Panels.

These predefined panels can be used as if they were Panel-derived classes in calls to GraphObject.make. They are implemented as simple visual trees of GraphObjects in Panels, with pre-set properties and event handlers.

More information can be found in the GoJS Intro.

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#### Geometry Path Strings

The GoJS Geometry class controls the "shape" of a Shape, whereas the Shape.fill and Shape.stroke and other shape properties control the colors and appearance of the shape. For common shape figures, there are predefined geometries that can be used by setting Shape.figure. However one can also define custom geometries.

One can construct any Geometry by allocating and initializing a Geometry of at least one PathFigure holding some PathSegments. But you may find that using the string representation of a Geometry is easier to write and save in a database. Use the static method Geometry.parse or the Shape.geometryString property to transform a geometry path string into a Geometry object.

More information can be found in the GoJS Intro.

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