The-Render-Package.md

Oak's render subpackage handles all operations related to drawing elements to window. This includes primitive types that can be drawn, loading of files and sprite sheets, and providing handlers to organize draw order. render provides subpackages of its own for specific operations on drawable elements and specific subtypes of drawable elements.

The Renderable Interface

// A Renderable is anything which can
// be drawn at a given draw layer, undrawn,
// and set in a particular position.
//
// Basic Implementing struct: Sprite
type Renderable interface {
    Draw(buff draw.Image)
    DrawOffset(buff draw.Image, xOff, yOff float64)
    GetDims() (int, int)

    Positional
    Layered
    physics.Attachable
}

The Renderable interface defines all types that can be drawn in oak's draw stack. Oak provides several implementations of this interface that should satisfy all basic use cases, and when creating your own implementation of the interface you can almost always rely on composing one of the built in types to satisfy most of these functions.

The lesser interfaces making up a Renderable provide the ability to set and manipulate 2D position and manipulate an element's draw layer. physics.Attachable allows different 2D elements to be attached to one another so that when one moves, so does the other.

The Modifiable Interface

// A Modifiable is a Renderable that has functions to change its
// underlying image.
type Modifiable interface {
    Renderable
    GetRGBA() *image.RGBA
    Modify(...mod.Mod) Modifiable
    Filter(...mod.Filter)
    Copy() Modifiable
}

Most Implementations of Renderable that Oak provides also implement Modifiable. This interface catches each sort of image manipulation function into the Modify and Filter functions, the former to change an image and create a new image, and the latter to change an image in place.

Renderable Implementations

• Sprite: Sprite is the most basic implementation of a Renderable, combining a 2D position, a draw layer, and a color buffer. When this is drawn to the window it's color buffer will be set at it's 2D position in the world. As with all Renderables, for draw stack items that respect layers a Sprite at a higher layer will be visible on top of a Sprite at a lower layer.
• Composite: A Composite is equivalent to a list for Renderables. There are two types of Composite, the Composite, and CompositeR, where the former is made up of the Modifiable interface and the latter of the Renderable interface. Most implementations of Renderable also satisfy Modifiable but if you are working with Text types or using this as a draw stack element you will need to use CompositeR.
• Switch: A Switch is a Renderable type that stores multiple Modifiables but at one time will only draw one of them, keyed by strings. This is ideal for something like an animating character that changes animation based on input.
• Sequence: A Sequence is a series of Modifiables that will be drawn in order. Sequences have a frames per second rate for how fast they change Modifiables, and each keeps track of whether they are allowed to be interrupted by other animations. When a Sequence reaches its last frame it will trigger the AnimationEnd event on its associated CID if it was assigned one.
• Reverting: A Reverting type is a Modifiable extension that can revert sets of modifications and restore old renderable elements.
• ScrollBox: A ScrollBox type holds a set of Renderables and a scroll rate in the X and Y axes. It's manipulable to define at what positions the drawn Renderables should be looped back around. This can build things like news tickers or scrolling backgrounds.
• Polygon: A Polygon is a extension of a Sprite which stores point locations and a bounding rectangle so it can be filled with color to create a shape.
• Text: Text is created through the render.Font type and stores any fmt.Stringer. This means that a basic Text type can store actively changing text like score or a timer. Because of this, Text is not a Modifiable, but can be converted to one through ToSprite.

Fonts

in progress

The Draw Stack

in progress

Stackable Implementations

in progress

Draw Polygons

in progress

Loading and Batch Loading

in progress

Other Constructors

in progress

Paint Functions

in progress

Subpackages

in progress