# Plot Composition All plots in Androidplot inherit from the abstract base class `Plot` which provides common behaviors for all `Plot` implementations. # Widgets Plots are composed of one or more Widgets. A `Widget` is an abstraction of a visual component that may be positioned and scaled within the visible area of a Plot. For example, an `XYPlot` is typically composed of these 5 `Widgets`: * Title * Graph * Domain Label * Range Label * [Legend](legend.md) All implementations of `Plot` will contain at least one default `Widget` providing the core behavior encapsulated by that `Plot`. In addition to moving and scaling a `Widget`, developers may also extend them and replace the `Plot` instance's default instance with the derived implementation in order to get custom behavior. # The LayoutManager The `LayoutManager` provides the logic for visually positioning and scaling Widgets; all `Plot` implementations contain an instance of `LayoutManager` that can be retrieved via `Plot.getLayoutManager()`. ## Z-Indexing Z-indexing is a 2D drawing concept which associates each drawable entity with a value that determines which elements get drawn onto the screen first, producing the visual effect that certain elements appear on top of others. While Androidplot uses the term "z-index" it's implemented internally as a linked list to prevent the possibility of duplicate index values and therefore ensuring that `Widget` drawing order is always explicit. The [Layerable](../androidplot-core/src/main/java/com/androidplot/util/Layerable.java) interface defines methods used for manipulating the z-index of a `Widget`. ## Adding & Removing Widgets New `Widget` instances can be added either to the front or back of the z-index using these methods: * `LayoutManager.addToTop(Widget)` * `LayoutManager.addToBottom(Widget)` ## Positioning Widgets Once a Widget has been added to the LayoutManager, it's position within the Plot can be adjusted via `Widget.position(...)`. This method takes a layout style and value for the x and y dimension and an optional anchor position from which the layout modes will be applied. ### HorizontalPosition & VerticalPosition These define the part of the Plot from which Widget will be positioned using relative or absolute units. * XPosition - Supports positioning in relation to the Plot's left edge, right edge or horizontal center. * YPosition - Supports positioning in relation to the Plot's top edge, bottom edge or vertical center. #### Absolute Positioning Absolute positioning means that positions are expressed as an absolute pixel offset from the specified edge or center point. #### Relative Positioning Relative positions are expressed as a ratio of the total size of the Plot along the given axis. This ration must fall within the range of -1 to 1. **Example #1: A relative XPosition of 1 and YPosition of 0.5 in a 100Hx200W pixel Plot** x = 1 * 200 = 200 y = 0.5 * 100 = 50 **Example #2: An absolute XPosition of 50 and an absolute YPosition of 25 in a 100Hx200W pixel Plot** x = 50 y = 25 #### Anchors The Anchor param specifies the point on the Widget from which the XPosition and YPosition calculations will be applied. Using example #1 above, an Anchor value of `Anchor.LEFT_TOP` means that the top left corner of the Widget would be positioned at the screen coordinate [200, 50]. #### Examples ```xml ap:graphAnchor="right_bottom" ap:graphHorizontalPositioning="absolute_from_right" ap:graphHorizontalPosition="0dp" ap:graphVerticalPositioning="relative_from_bottom" ap:graphVerticalPosition="0dp" ``` ![alt text](images/positioning/bottom-right-absolute.png "bottom-right-absolute") *** ```xml ap:graphAnchor="right_bottom" ap:graphHorizontalPositioning="absolute_from_right" ap:graphHorizontalPosition="10dp" ap:graphVerticalPositioning="relative_from_bottom" ap:graphVerticalPosition="10dp" ``` ![alt text](images/positioning/bottom-right-absolute-with-offset.png "bottom-right-absolute-with-offset") *** ```xml ap:graphAnchor="right_bottom" ap:graphHorizontalPositioning="absolute_from_left" ap:graphHorizontalPosition="0dp" ap:graphVerticalPositioning="relative_from_top" ap:graphVerticalPosition="0dp" ``` ![alt text](images/positioning/top-left-absolute.png "top-left-absolute") *** ```xml ap:graphAnchor="center" ap:graphHorizontalPositioning="absolute_from_center" ap:graphHorizontalPosition="0dp" ap:graphVerticalPositioning="absolute_from_center" ap:graphVerticalPosition="0dp" ``` ![alt text](images/positioning/center-absolute.png "center-absolute") ## Scaling Widgets TODO ### SizeMetric TODO #### Examples TODO ## Margins and Padding Every widget has a margin, padding and an optional border that can be drawn around it. These params behave very similarly to those defined in the [CSS Box Model](http://www.w3schools.com/css/css_boxmodel.asp). ## Markup Mode. If you're having trouble visualizing the effects of tweaking margins and padding, you can enable markup mode which will highlight these spaces on each widget, as well as draw a green line around it's absolute border. To turn markup mode on for a plot programmatically: ```java plot.setMarkupEnabled(true); ``` Or via XML: ```xml ap:markupEnabled="true" ``` This is what it looks like: ![alt text](images/markup_mode.jpg "markup enabled") # Formatters, Renderers and Series Data Each Plot specifies the type of Series it supports; XYPlots support XYSeries, PieCharts support Segment, etc. In all cases, the Series encapsulates the numeric model of the data being represented by the Plot. ## Formatters The Plot keeps a mapping between Series data and the Formatter instance provided by the user that is to be used to render that data. It is the Formatter that tells Androiplot which Renderer to use to draw the Series along with which colors, line thicknesses, text style, etc. to apply while drawing. ## Renderers The Renderer is what renders Series data onto a Plot. Users can provide their own custom rendering behavior by writing their own Renderer implementation along with a custom Formatter telling Androidplot about the Renderer via the `Formatter.getRendererClass()` method. # XML Styling Androidplot supports an increasing number of XML attributes. The two best resources for learning about these attributes is the [demo app source code](../demoapp) and [attrs.xml](../androidplot-core/src/main/res/values/attrs.xml) file which contains the exhaustive list of available attributes.