zntg/allg5/font.go

package allg5

// #include <allegro5/allegro.h>
// #include <allegro5/allegro_font.h>
// #include <allegro5/allegro_ttf.h>
import "C"

import (
	"fmt"
	"unsafe"
)

type Font struct {
	font *C.ALLEGRO_FONT
	hght float32
	asc  float32
	desc float32
}

type HorizontalAlignment int

const (
	AlignLeft HorizontalAlignment = iota
	AlignCenter
	AlignRight
)

func LoadTTFFont(path string, size int) (*Font, error) {
	p := C.CString(path)
	defer C.free(unsafe.Pointer(p))

	f := C.al_load_ttf_font(p, C.int(size), 0)
	if nil == f {
		return nil, fmt.Errorf("unable to load ttf font '%s'", path)
	}
	return &Font{f, 0, 0, 0}, nil
}

func (f *Font) drawFlags(a HorizontalAlignment) C.int {
	switch a {
	case AlignLeft:
		return C.ALLEGRO_ALIGN_LEFT
	case AlignCenter:
		return C.ALLEGRO_ALIGN_CENTRE
	case AlignRight:
		return C.ALLEGRO_ALIGN_RIGHT
	}
	return C.ALLEGRO_ALIGN_LEFT
}

func (f *Font) Draw(left, top float32, color Color, align HorizontalAlignment, text string) {
	t := C.CString(text)
	defer C.free(unsafe.Pointer(t))

	flags := f.drawFlags(align)
	C.al_draw_text(f.font, color.color, C.float(left), C.float(top), flags, t)
}

// Ascent returns the ascent of the font
func (f *Font) Ascent() float32 {
	if 0 == f.asc {
		f.asc = float32(C.al_get_font_ascent(f.font))
	}
	return f.asc
}

// Descent returns the descent of the font.
func (f *Font) Descent() float32 {
	if 0 == f.desc {
		f.desc = float32(C.al_get_font_descent(f.font))
	}
	return f.desc
}

// Height returns the height of the font
func (f *Font) Height() float32 {
	if 0 == f.hght {
		f.hght = f.Ascent() + f.Descent()
	}
	return f.hght
}

// TextDimensions returns the bounding box of the rendered text.
func (f *Font) TextDimensions(text string) (x, y, w, h float32) {
	t := C.CString(text)
	defer C.free(unsafe.Pointer(t))

	var bbx, bby, bbw, bbh C.int
	C.al_get_text_dimensions(f.font, t, &bbx, &bby, &bbw, &bbh)
	x = float32(bbx)
	y = float32(bby)
	w = float32(bbw)
	h = float32(bbh)
	return
}

// TextWidth returns the width of the rendered text.
func (f *Font) TextWidth(text string) float32 {
	t := C.CString(text)
	defer C.free(unsafe.Pointer(t))

	return float32(C.al_get_text_width(f.font, t))
}

func (f *Font) Destroy() {
	C.al_destroy_font(f.font)
}