Graphics

Package qml offers graphical QML application support for the Go language. This package is in an alpha stage, and still in heavy development. APIs may change, and things may break. At this time contributors and developers that are interested in tracking the development closely are encouraged to use it. If you'd prefer a more stable release, please hold on a bit and subscribe to the mailing list for news. It's in a pretty good state, so it shall not take too long. See http://github.com/go-qml/qml for details. The qml package enables Go programs to display and manipulate graphical content using Qt's QML framework. QML uses a declarative language to express structure and style, and supports JavaScript for in-place manipulation of the described content. When using the Go qml package, such QML content can also interact with Go values, making use of its exported fields and methods, and even explicitly creating new instances of registered Go types. A simple Go application that integrates with QML may perform the following steps for offering a graphical interface: Some of these topics are covered below, and may also be observed in practice in the following examples: The following logic demonstrates loading a QML file into a window: Any QML object may be manipulated by Go via the Object interface. That interface is implemented both by dynamic QML values obtained from a running engine, and by Go types in the qml package that represent QML values, such as Window, Context, and Engine. For example, the following logic creates a window and prints its width whenever it's made visible: Information about the methods, properties, and signals that are available for QML objects may be obtained in the Qt documentation. As a reference, the "visibleChanged" signal and the "width" property used in the example above are described at: When in doubt about what type is being manipulated, the Object.TypeName method provides the type name of the underlying value. The simplest way of making a Go value available to QML code is setting it as a variable of the engine's root context, as in: This logic would enable the following QML code to successfully run: While registering an individual Go value as described above is a quick way to get started, it is also fairly limited. For more flexibility, a Go type may be registered so that QML code can natively create new instances in an arbitrary position of the structure. This may be achieved via the RegisterType function, as the following example demonstrates: With this logic in place, QML code can create new instances of Person by itself: Independently from the mechanism used to publish a Go value to QML code, its methods and fields are available to QML logic as methods and properties of the respective QML object representing it. As required by QML, though, the Go method and field names are lowercased according to the following scheme when being accesed from QML: While QML code can directly read and write exported fields of Go values, as described above, a Go type can also intercept writes to specific fields by declaring a setter method according to common Go conventions. This is often useful for updating the internal state or the visible content of a Go-defined type. For example: In the example above, whenever QML code attempts to update the Person.Name field via any means (direct assignment, object declarations, etc) the SetName method is invoked with the provided value instead. A setter method may also be used in conjunction with a getter method rather than a real type field. A method is only considered a getter in the presence of the respective setter, and according to common Go conventions it must not have the Get prefix. Inside QML logic, the getter and setter pair is seen as a single object property. Custom types implemented in Go may have displayable content by defining a Paint method such as: A simple example is available at: Resource files (qml code, images, etc) may be packed into the Go qml application binary to simplify its handling and distribution. This is done with the genqrc tool: The following blog post provides more details:

Package graphics provides functions to draw 2D graphics based on OpenGL 3.0.

Package go3d is a performance oriented vector and matrix math package for 2D and 3D graphics. Every type has its own sub-package and is named T. So vec3.T is the 3D vector type. For every vector and matrix type there is a String() method and a Parse() function. Besides methods of T there are also functions in the packages, like vec3.Dot(a, b). Packages under the float64 directory are using float64 values instead of float32. Matrices are organized as arrays of columns which is also the way OpenGL expects matrices. DirectX expects "arrays of rows" matrices, use the Transpose() to convert. Methods that don't return a specific value, return a pointer to the struct to allow method call chaining. Example: Method names in the past tense return a copy of the struct instead of a pointer to it. Example: Documentation: http://godoc.org/github.com/ungerik/go3d

Package merkletree is an implementation of a Merkle tree (https://en.wikipedia.org/wiki/Merkle_tree). It provides methods to create a tree and generate and verify proofs. The hashing algorithm for the tree is selectable between BLAKE2b and Keccak256, or you can supply your own. Creating a Merkle tree requires a list of values that are each byte arrays. Once a tree has been created proofs can be generated using the tree's GenerateProof() function. The package includes a function to verify a generated proof given only the data to prove, proof and the root hash of the relevant Merkle tree. This allows for efficient verification of proofs without requiring the entire Merkle tree to be stored or recreated. The tree pads its values to the next highest power of 2; values not supplied are treated as 0. This can be seen graphically by generating a DOT representation of the graph with DOT().

Package imgui contains all the functions to create an immediate mode graphical user interface based on Dear ImGui. For integration, please refer to the dedicated repository https://github.com/inkyblackness/imgui-go-examples , which contains ported examples of the C++ version, available to Go. The exported functions and constants are named closely to that of the wrapped library. If a function has optional parameters, it will be available in two versions: A verbose one, which has all optional parameters listed, and a terse one, with only the mandatory parameters in its signature. The verbose variant will have the suffix V in its name. For example, there are and The terse variant will list the default parameters it uses to call the verbose variant. There are several types which are based on uintptr. These are references to the wrapped instances in C++. You will always get to such a reference via some function - you never "instantiate" such an instance on your own.

Package openvg is a wrapper to a C library of high-level 2D graphics operations built on OpenVG 1.1 The typical "hello world" program looks like this: The Init function provides the necessary graphics subsystem initialization and the dimensions of the whole canvas. The Init() call must be paired with a corresponding Finish() call, which performs an orderly shutdown. Typically a "drawing" begins with the Start() call, and ends with End(). A program can have an arbitrary set of Start()/End() pairs. The coordinate system uses float64 coordinates, with the origin at the lower left, with x increasing to the right, and y increasing upwards. Currently, the library provides no mouse or keyboard events, other than those provided by the base operating system. It is typical to pause for user input between drawings by reading standard input. The library's functionally includes shapes, attributes, transformations, text, images, and convenince functions. Shape functions include Polygon, Polyline, Cbezier, Qbezier, Rect, Roundrect, Line, Elipse, Circle, and Arc. Transformation functions are: Translate, Rotate, Shear, and Scale. For displaying and measuring text: Text, TextMid, TextEnd, and TextWidth. The attribute functions are StrokeColor, StrokeRGB, StrokeWidth, and FillRGB, FillColor, FillLinearGradient, and FillRadialGradient. Colors are specfied with RGB triples (0-255) with alpha values (0.0-1.0), or named colors as specified by the SVG standard. Convenience functions are used to set the Background color, start the drawing with a background color, and save the raster to a file. The input terminal may be set/restored to/from raw and cooked mode. Package openvg is a high-level 2D vector graphics library built on OpenVG

Package gg provides a simple API for rendering 2D graphics in pure Go.