Various additions:

- Added sub-bitmaps.
- Color implements color.Color interface.
- Added methods to retrieve font dimensions and its rendered text.
- Added DrawPolyline method.

allegro5/bitmap.go

@@ -16,6 +16,7 @@ type Bitmap struct {
 	bitmap *C.ALLEGRO_BITMAP
 	width  int
 	height int
+	subs   []*Bitmap
 }
 
 type DrawOptions struct {
@@ -66,7 +67,7 @@ func newBitmap(width, height int, mut func(m FlagMutation), flags []NewBitmapFla
 	if nil == b {
 		return nil, errors.New("error creating bitmap")
 	}
-	return &Bitmap{b, width, height}, nil
+	return &Bitmap{b, width, height, nil}, nil
 }
 
 // NewBitmap creates a new bitmap of given width and height and optional flags
@@ -133,7 +134,7 @@ func NewBitmapFromImage(im image.Image, video bool) (*Bitmap, error) {
 		})
 		C.al_convert_bitmap(b)
 	}
-	return &Bitmap{b, width, height}, nil
+	return &Bitmap{b, width, height, nil}, nil
 }
 
 // LoadBitmap tries to load the image at the specified path as a bitmap
@@ -146,7 +147,7 @@ func LoadBitmap(path string) (*Bitmap, error) {
 	}
 	width := int(C.al_get_bitmap_width(b))
 	height := int(C.al_get_bitmap_height(b))
-	return &Bitmap{b, width, height}, nil
+	return &Bitmap{b, width, height, nil}, nil
 }
 
 // Draw draws the bitmap at the given location
@@ -206,6 +207,22 @@ func (b *Bitmap) DrawOptions(left, top float32, options DrawOptions) {
 	}
 }
 
+// Sub creates a sub-bitmap of the original bitmap
+func (b *Bitmap) Sub(x, y, w, h int) *Bitmap {
+	var sub = C.al_create_sub_bitmap(b.bitmap, C.int(x), C.int(y), C.int(w), C.int(h))
+	if nil == sub {
+		return nil
+	}
+	var bmp = &Bitmap{sub, w, h, nil}
+	b.subs = append(b.subs, bmp)
+	return bmp
+}
+
+// Subs returns the slice of sub-bitmaps
+func (b *Bitmap) Subs() []*Bitmap {
+	return b.subs
+}
+
 func (b *Bitmap) Width() int {
 	return b.width
 }
@@ -220,5 +237,13 @@ func (b *Bitmap) SetAsTarget() {
 
 // Destroy destroys the bitmap
 func (b *Bitmap) Destroy() {
-	C.al_destroy_bitmap(b.bitmap)
+	var bmp = b.bitmap
+	if nil == bmp {
+		return
+	}
+	b.bitmap = nil
+	for _, sub := range b.subs {
+		sub.Destroy()
+	}
+	C.al_destroy_bitmap(bmp)
 }

allegro5/color.go

@@ -2,15 +2,30 @@ package allegro5
 
 // #include <allegro5/allegro.h>
 import "C"
+import "image/color"
+
+var _ color.Color = &Color{}
 
 type Color struct {
-  color C.ALLEGRO_COLOR
+	color C.ALLEGRO_COLOR
 }
 
 func NewColor(r, g, b byte) Color {
-  return Color{C.al_map_rgb(C.uchar(r), C.uchar(g), C.uchar(b))}
+	return Color{C.al_map_rgb(C.uchar(r), C.uchar(g), C.uchar(b))}
 }
 
-func NewColorAlpha(r, g, b, a byte) Color {  
-  return Color{C.al_map_rgba(C.uchar(r), C.uchar(g), C.uchar(b), C.uchar(a))}
-}
+func NewColorAlpha(r, g, b, a byte) Color {
+	return Color{C.al_map_rgba(C.uchar(r), C.uchar(g), C.uchar(b), C.uchar(a))}
+}
+
+// RGBA implements the color.Color interface.
+func (c Color) RGBA() (r, g, b, a uint32) {
+	var cr, cg, cb, ca C.uchar
+	C.al_unmap_rgba(c.color, &cr, &cg, &cb, &ca)
+	a = uint32(ca)
+	r = uint32(cr) * a
+	g = uint32(cg) * a
+	b = uint32(cb) * a
+	a *= a
+	return
+}

allegro5/font.go

@@ -12,6 +12,9 @@ import (
 
 type Font struct {
 	font *C.ALLEGRO_FONT
+	hght float32
+	asc  float32
+	desc float32
 }
 
 type HorizontalAlignment int
@@ -30,7 +33,7 @@ func LoadTTFFont(path string, size int) (*Font, error) {
 	if nil == f {
 		return nil, fmt.Errorf("unable to load ttf font '%s'", path)
 	}
-	return &Font{f}, nil
+	return &Font{f, 0, 0, 0}, nil
 }
 
 func (f *Font) drawFlags(a HorizontalAlignment) C.int {
@@ -53,6 +56,45 @@ func (f *Font) Draw(left, top float32, color Color, align HorizontalAlignment, t
 	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))

allegro5/primitives.go

@@ -3,6 +3,7 @@ package allegro5
 // #include <allegro5/allegro.h>
 // #include <allegro5/allegro_primitives.h>
 import "C"
+import "unsafe"
 
 func DrawFilledRectangle(x1, y1, x2, y2 float32, c Color) {
 	C.al_draw_filled_rectangle(C.float(x1), C.float(y1), C.float(x2), C.float(y2), c.color)
@@ -16,6 +17,10 @@ func DrawLine(x1, y1, x2, y2 float32, c Color, thickness float32) {
 	C.al_draw_line(C.float(x1), C.float(y1), C.float(x2), C.float(y2), c.color, C.float(thickness))
 }
 
+func DrawPolyline(vertices []float32, c Color, thickness float32) {
+	C.al_draw_polyline((*C.float)(unsafe.Pointer(&vertices[0])), 8, C.int(len(vertices)>>1), C.ALLEGRO_LINE_JOIN_ROUND, C.ALLEGRO_LINE_CAP_ROUND, c.color, C.float(thickness), 1)
+}
+
 func DrawRectangle(x1, y1, x2, y2 float32, c Color, thickness float32) {
 	C.al_draw_rectangle(C.float(x1), C.float(y1), C.float(x2), C.float(y2), c.color, C.float(thickness))
 }