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text.go
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text.go
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package three
import "github.com/go-gl/gl"
// Text defines a 2D text geometry and its appearance.
type Text struct {
vertexBuffer gl.Buffer
uvBuffer gl.Buffer
material Texter
geometry *TextGeometry
}
// NewText creates a new 2D text object that can be added to
// the scene.
//
// NOTE: This method overrides the texture for the given texture
// to the texture from the font.
func NewText(geometry *TextGeometry, material Texter) *Text {
material.SetTexture(geometry.Font.texture)
t := Text{
material: material,
geometry: geometry,
}
t.vertexBuffer = newTextVertexBuffer(t.geometry)
t.uvBuffer = newUvBuffer(t.geometry.UVs, true)
return &t
}
// Geometry returns the geometry object for this
// text object.
func (t *Text) Geometry() *TextGeometry {
return t.geometry
}
// Material returns the appearance defintion for this
// text object.
func (t *Text) Material() Texter {
return t.material
}
// SetText updates the text that is drawn.
// This will update the underlying vertex and uv buffer.
// BUG(tobscher) Vertex and UV buffers are deleted and re-created; not updated.
func (t *Text) SetText(text string) {
t.geometry.Text = text
t.geometry.updateVertices(text)
t.vertexBuffer.Delete()
t.uvBuffer.Delete()
t.vertexBuffer = newTextVertexBuffer(t.geometry)
t.uvBuffer = newUvBuffer(t.geometry.UVs, true)
}
func newTextVertexBuffer(geometry *TextGeometry) gl.Buffer {
result := []float32{}
vertices := geometry.Vertices
for _, vertex := range vertices {
result = append(result, vertex.X(), vertex.Y())
}
glBuffer := gl.GenBuffer()
glBuffer.Bind(gl.ARRAY_BUFFER)
gl.BufferData(gl.ARRAY_BUFFER, len(result)*2*4, result, gl.STATIC_DRAW)
return glBuffer
}