hlgl/hlgl.go

package main

import (
	"math"

	"github.com/go-gl/gl/v4.1-core/gl"
	"github.com/go-gl/mathgl/mgl32"
)

type HLRectangle struct {
	X      int
	Y      int
	Width  int
	Height int
}

type HLColorRGBA struct {
	R int
	G int
	B int
	A int
}

var defaultShader *Shader
var projectionMatrix mgl32.Mat4

func InitHLGL(projection mgl32.Mat4) {
	projectionMatrix = projection

	vertexShaderSource := `
    #version 410 core
    layout(location = 0) in vec3 position;
    uniform mat4 u_Projection;
    void main() {
        gl_Position = u_Projection * vec4(position, 1.0);
    }
    `
	fragmentShaderSource := `
    #version 410 core
    out vec4 color;
    uniform vec4 u_Color;
    void main() {
        color = u_Color;
    }
    `
	var err error
	defaultShader, err = NewShader(vertexShaderSource, fragmentShaderSource)
	if err != nil {
		panic("Failed to initialize default shader: " + err.Error())
	}
}

func DrawRectangleWH(x, y, width, height int, color HLColorRGBA) {
	defaultShader.Use()
	defaultShader.SetUniform4f("u_Color", float32(color.R)/255.0, float32(color.G)/255.0, float32(color.B)/255.0, float32(color.A)/255.0)
	defaultShader.SetUniformM("u_Projection", projectionMatrix)

	var vertices = []float32{
		float32(x), float32(y), 0.0,
		float32(x), float32(y + height), 0.0,
		float32(x + width), float32(y), 0.0,

		float32(x + width), float32(y), 0.0,
		float32(x), float32(y + height), 0.0,
		float32(x + width), float32(y + height), 0.0,
	}

	vao := NewVertexArray()
	vbo := NewVertexBuffer(vertices)
	vao.AddBuffer(vbo, []int32{3})
	vao.Bind()

	gl.DrawArrays(gl.TRIANGLES, 0, 6)

	vao.Unbind()
	vbo.Unbind()
}

func DrawRoundedRectangle(x, y, width, height, radius float32, color HLColorRGBA) {
	var vertices []float32
	segments := 12 // maybe change it

	defaultShader.Use()
	defaultShader.SetUniform4f("u_Color", float32(color.R)/255.0, float32(color.G)/255.0, float32(color.B)/255.0, float32(color.A)/255.0)
	defaultShader.SetUniformM("u_Projection", projectionMatrix)

	vertices = append(vertices, x+radius, y, 0.0, x+width-radius, y, 0.0, x+width-radius, y+height, 0.0)
	vertices = append(vertices, x+radius, y, 0.0, x+width-radius, y+height, 0.0, x+radius, y+height, 0.0)

	corners := []struct {
		cx, cy, startAngle float32
	}{
		{x + radius, y + radius, 0},                        // borrom left
		{x + width - radius, y + radius, -math.Pi / 2},     // bottom right
		{x + width - radius, y + height - radius, math.Pi}, // top right
		{x + radius, y + height - radius, math.Pi / 2},     // top left
	}
	for _, corner := range corners {
		for i := 0; i <= segments; i++ {
			angle := corner.startAngle + float32(i)/float32(segments)*(math.Pi/2)
			vertices = append(vertices, corner.cx+float32(math.Cos(float64(angle)))*radius)
			vertices = append(vertices, corner.cy+float32(math.Sin(float64(angle)))*radius)
			vertices = append(vertices, 0.0)
		}
	}

	vao := NewVertexArray()
	vbo := NewVertexBuffer(vertices)
	vao.AddBuffer(vbo, []int32{3})
	vao.Bind()

	gl.DrawArrays(gl.TRIANGLE_FAN, 0, int32(len(vertices)/3))

	vao.Unbind()
	vbo.Unbind()
}