From a1f157c317cced93bb6a1e9b19451fe4109ab202 Mon Sep 17 00:00:00 2001
From: Sander Schobers <sander@schobers.eu>
Date: Sat, 23 May 2020 08:56:52 +0200
Subject: [PATCH] A sub-bitmap now removes itself from the registration of its
 parent. With this change it is safe to Destroy the sub-bitmap (and afterwards
 destroy the parent bitmap). The implementation is not thread-safe.

---
 bitmap.go  | 21 +++++++++++++++++----
 display.go |  4 ++--
 2 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/bitmap.go b/bitmap.go
index 093539f..9dc30bf 100644
--- a/bitmap.go
+++ b/bitmap.go
@@ -16,6 +16,7 @@ type Bitmap struct {
 	width  int
 	height int
 	subs   []*Bitmap
+	sup    *Bitmap
 }
 
 type DrawOptions struct {
@@ -58,7 +59,7 @@ func newBitmap(width, height int, mut func(m FlagMutation), flags []NewBitmapFla
 	if b == nil {
 		return nil, errors.New("error creating bitmap")
 	}
-	return &Bitmap{b, width, height, nil}, nil
+	return &Bitmap{b, width, height, nil, nil}, nil
 }
 
 // NewBitmap creates a new bitmap of given width and height and optional flags
@@ -123,7 +124,7 @@ func NewBitmapFromImage(src image.Image, video bool) (*Bitmap, error) {
 		})
 		C.al_convert_bitmap(b)
 	}
-	return &Bitmap{b, width, height, nil}, nil
+	return &Bitmap{b, width, height, nil, nil}, nil
 }
 
 // LoadBitmap tries to load the image at the specified path as a bitmap
@@ -136,7 +137,7 @@ 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}, nil
+	return &Bitmap{b, width, height, nil, nil}, nil
 }
 
 // Draw draws the bitmap at the given location
@@ -202,7 +203,7 @@ func (b *Bitmap) Sub(x, y, w, h int) *Bitmap {
 	if sub == nil {
 		return nil
 	}
-	var bmp = &Bitmap{sub, w, h, nil}
+	var bmp = &Bitmap{sub, w, h, nil, b}
 	b.subs = append(b.subs, bmp)
 	return bmp
 }
@@ -267,5 +268,17 @@ func (b *Bitmap) Destroy() {
 	for _, sub := range b.subs {
 		sub.Destroy()
 	}
+	if b.sup != nil {
+		b.sup.removeSub(b)
+	}
 	C.al_destroy_bitmap(bmp)
 }
+
+func (b *Bitmap) removeSub(sub *Bitmap) {
+	for i := 0; i < len(b.subs); i++ {
+		if b.subs[i] == sub {
+			b.subs = append(b.subs[:i], b.subs[i+1:]...)
+			return
+		}
+	}
+}
diff --git a/display.go b/display.go
index 927d9e7..ea85273 100644
--- a/display.go
+++ b/display.go
@@ -150,7 +150,7 @@ func (d *Display) SetWindowTitle(title string) {
 }
 
 func (d *Display) Target() *Bitmap {
-	return &Bitmap{C.al_get_backbuffer(d.display), d.Width(), d.Height(), nil}
+	return &Bitmap{C.al_get_backbuffer(d.display), d.Width(), d.Height(), nil, nil}
 }
 
 // Destroy destroys the display
@@ -160,7 +160,7 @@ func (d *Display) Destroy() {
 
 func CurrentTarget() *Bitmap {
 	var bmp = C.al_get_target_bitmap()
-	return &Bitmap{bmp, int(C.al_get_bitmap_width(bmp)), int(C.al_get_bitmap_height(bmp)), nil}
+	return &Bitmap{bmp, int(C.al_get_bitmap_width(bmp)), int(C.al_get_bitmap_height(bmp)), nil, nil}
 }
 
 func SetNewWindowTitle(title string) {