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vendor/github.com/faiface/glhf/README.md
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# glhf [](http://godoc.org/github.com/faiface/glhf) [](https://goreportcard.com/report/github.com/faiface/glhf)
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open**GL** **H**ave **F**un - A Go package that makes life with OpenGL enjoyable.
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```
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go get github.com/faiface/glhf
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```
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## Main features
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- Garbage collected OpenGL objects
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- Dynamically sized vertex slices (vertex arrays are boring)
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- Textures, Shaders, Frames (reasonably managed framebuffers)
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- Always possible to use standard OpenGL with `glhf`
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## Motivation
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OpenGL is verbose, it's usage patterns are repetitive and it's manual memory management doesn't fit
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Go's design. When making a game development library, it's usually desirable to create some
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higher-level abstractions around OpenGL. This library is a take on that.
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## Contribute!
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The library is young and many features are still missing. If you find a bug, have a proposal or a
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feature request, _do an issue_!. If you know how to implement something that's missing, _do a pull
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request_.
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## Code
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The following are parts of the demo program, which can be found in the [examples](https://github.com/faiface/glhf/tree/master/examples/demo).
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```go
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// ... GLFW window creation and stuff ...
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// vertex shader source
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var vertexShader = `
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#version 330 core
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in vec2 position;
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in vec2 texture;
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out vec2 Texture;
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void main() {
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gl_Position = vec4(position, 0.0, 1.0);
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Texture = texture;
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}
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`
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// fragment shader source
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var fragmentShader = `
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#version 330 core
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in vec2 Texture;
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out vec4 color;
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uniform sampler2D tex;
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void main() {
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color = texture(tex, Texture);
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}
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`
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var (
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// Here we define a vertex format of our vertex slice. It's actually a basic slice
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// literal.
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//
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// The vertex format consists of names and types of the attributes. The name is the
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// name that the attribute is referenced by inside a shader.
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vertexFormat = glhf.AttrFormat{
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{Name: "position", Type: glhf.Vec2},
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{Name: "texture", Type: glhf.Vec2},
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}
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// Here we declare some variables for later use.
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shader *glhf.Shader
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texture *glhf.Texture
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slice *glhf.VertexSlice
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)
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// Here we load an image from a file. The loadImage function is not within the library, it
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// just loads and returns a image.NRGBA.
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gopherImage, err := loadImage("celebrate.png")
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if err != nil {
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panic(err)
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}
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// Every OpenGL call needs to be done inside the main thread.
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mainthread.Call(func() {
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var err error
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// Here we create a shader. The second argument is the format of the uniform
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// attributes. Since our shader has no uniform attributes, the format is empty.
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shader, err = glhf.NewShader(vertexFormat, glhf.AttrFormat{}, vertexShader, fragmentShader)
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// If the shader compilation did not go successfully, an error with a full
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// description is returned.
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if err != nil {
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panic(err)
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}
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// We create a texture from the loaded image.
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texture = glhf.NewTexture(
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gopherImage.Bounds().Dx(),
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gopherImage.Bounds().Dy(),
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true,
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gopherImage.Pix,
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)
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// And finally, we make a vertex slice, which is basically a dynamically sized
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// vertex array. The length of the slice is 6 and the capacity is the same.
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//
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// The slice inherits the vertex format of the supplied shader. Also, it should
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// only be used with that shader.
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slice = glhf.MakeVertexSlice(shader, 6, 6)
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// Before we use a slice, we need to Begin it. The same holds for all objects in
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// GLHF.
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slice.Begin()
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// We assign data to the vertex slice. The values are in the order as in the vertex
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// format of the slice (shader). Each two floats correspond to an attribute of type
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// glhf.Vec2.
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slice.SetVertexData([]float32{
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-1, -1, 0, 1,
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+1, -1, 1, 1,
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+1, +1, 1, 0,
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-1, -1, 0, 1,
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+1, +1, 1, 0,
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-1, +1, 0, 0,
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})
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// When we're done with the slice, we End it.
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slice.End()
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})
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shouldQuit := false
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for !shouldQuit {
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mainthread.Call(func() {
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// ... GLFW stuff ...
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// Clear the window.
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glhf.Clear(1, 1, 1, 1)
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// Here we Begin/End all necessary objects and finally draw the vertex
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// slice.
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shader.Begin()
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texture.Begin()
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slice.Begin()
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slice.Draw()
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slice.End()
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texture.End()
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shader.End()
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// ... GLFW stuff ...
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})
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}
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```
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## FAQ
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### Which version of OpenGL does GLHF use?
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It uses OpenGL 3.3 and uses
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[`github.com/go-gl/gl/v3.3-core/gl`](https://github.com/go-gl/gl/tree/master/v3.3-core/gl).
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### Why do I have to use `github.com/faiface/mainthread` package with GLHF?
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First of all, OpenGL has to be done from one thread and many operating systems require, that the one
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thread will be the main thread of your application.
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But why that specific package? GLHF uses the `mainthread` package to do the garbage collection of
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OpenGL objects, which is super convenient. So in order for it to work correctly, you have to
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initialize the `mainthread` package through `mainthread.Run`. However, once you call this function
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there is no way to run functions on the main thread, except for through the `mainthread` package.
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### Why is the important XY feature not included?
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I probably didn't need it yet. If you want that features, create an issue or implement it and do a
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pull request.
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### Does GLHF create windows for me?
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No. You have to use another library for windowing, e.g.
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[github.com/go-gl/glfw/v3.2/glfw](https://github.com/go-gl/glfw/tree/master/v3.2/glfw).
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### Why no tests?
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If you find a way to automatically test OpenGL, I may add tests.
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