mirror of https://github.com/liamg/aminal.git
76 lines
2.0 KiB
Go
76 lines
2.0 KiB
Go
package glfont
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import (
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"io"
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"io/ioutil"
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"github.com/go-gl/gl/all-core/gl"
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"github.com/golang/freetype/truetype"
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"golang.org/x/image/font"
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)
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type character struct {
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textureID uint32 // ID handle of the glyph texture
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width int //glyph width
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height int //glyph height
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advance int //glyph advance
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bearingH int //glyph bearing horizontal
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bearingV int //glyph bearing vertical
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}
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//LoadTrueTypeFont builds a set of textures based on a ttf files glyphs
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func LoadTrueTypeFont(program uint32, r io.Reader, scale float32) (*Font, error) {
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data, err := ioutil.ReadAll(r)
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if err != nil {
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return nil, err
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}
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//make Font struct type
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f := new(Font)
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f.scale = scale
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f.characters = map[rune]*character{}
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f.program = program //set shader program
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f.uniformLocationResolution = gl.GetUniformLocation(program, gl.Str("resolution\x00"))
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f.uniformLocationTextColor = gl.GetUniformLocation(program, gl.Str("textColor\x00"))
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// Read the truetype font.
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f.ttf, err = truetype.Parse(data)
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if err != nil {
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return nil, err
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}
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f.SetColor(1.0, 1.0, 1.0, 1.0) //set default white
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_, h := f.MaxSize()
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f.lineHeight = h
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gl.BindTexture(gl.TEXTURE_2D, 0)
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// Configure VAO/VBO for texture quads
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gl.GenVertexArrays(1, &f.vao)
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gl.GenBuffers(1, &f.vbo)
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gl.BindVertexArray(f.vao)
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gl.BindBuffer(gl.ARRAY_BUFFER, f.vbo)
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gl.BufferData(gl.ARRAY_BUFFER, 6*4*4, nil, gl.DYNAMIC_DRAW)
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vertAttrib := uint32(gl.GetAttribLocation(f.program, gl.Str("vert\x00")))
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gl.EnableVertexAttribArray(vertAttrib)
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gl.VertexAttribPointer(vertAttrib, 2, gl.FLOAT, false, 4*4, gl.PtrOffset(0))
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texCoordAttrib := uint32(gl.GetAttribLocation(f.program, gl.Str("vertTexCoord\x00")))
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gl.EnableVertexAttribArray(texCoordAttrib)
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gl.VertexAttribPointer(texCoordAttrib, 2, gl.FLOAT, false, 4*4, gl.PtrOffset(2*4))
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gl.BindBuffer(gl.ARRAY_BUFFER, 0)
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gl.BindVertexArray(0)
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//create new face to measure glyph dimensions
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f.ttfFace = truetype.NewFace(f.ttf, &truetype.Options{
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Size: float64(f.scale),
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DPI: DPI,
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Hinting: font.HintingFull,
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})
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return f, nil
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}
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