add blit_atlas method

for some additional convenience when blitting BitmapAtlas tiles

examples/slimed/src/entities/systems.rs

@@ -707,10 +707,10 @@ fn render_system_sprites(context: &mut Core) {
             // now render them in the correct order ...
             for (entity, position, blit_method) in context.sprite_render_list.iter() {
                 let sprite = sprites.get(entity).unwrap();
-                context.system.video.blit_region(
+                context.system.video.blit_atlas(
                     *blit_method,
-                    sprite.atlas.bitmap(),
-                    &sprite.atlas[sprite.index],
+                    &sprite.atlas,
+                    sprite.index,
                     position.x as i32 - camera.x,
                     position.y as i32 - camera.y,
                 );

libretrogd/src/graphics/bitmap/blit.rs

@@ -750,11 +750,25 @@ impl Bitmap {
         self.blit_region(method, src, &src_region, x, y);
     }
 
+    #[inline]
+    pub fn blit_atlas(&mut self, method: BlitMethod, src: &BitmapAtlas, index: usize, x: i32, y: i32) {
+        if let Some(src_region) = src.get(index) {
+            self.blit_region(method, src.bitmap(), src_region, x, y);
+        }
+    }
+
     #[inline]
     pub unsafe fn blit_unchecked(&mut self, method: BlitMethod, src: &Bitmap, x: i32, y: i32) {
         let src_region = Rect::new(0, 0, src.width, src.height);
         self.blit_region_unchecked(method, src, &src_region, x, y);
     }
+
+    #[inline]
+    pub unsafe fn blit_atlas_unchecked(&mut self, method: BlitMethod, src: &BitmapAtlas, index: usize, x: i32, y: i32) {
+        if let Some(src_region) = src.get(index) {
+            self.blit_region_unchecked(method, src.bitmap(), &src_region, x, y);
+        }
+    }
 }
 
 #[cfg(test)]

libretrogd/src/graphics/bitmapatlas.rs

@@ -101,6 +101,11 @@ impl BitmapAtlas {
         self.tiles.len()
     }
 
+    #[inline]
+    pub fn get(&self, index: usize) -> Option<&Rect> {
+        self.tiles.get(index)
+    }
+
     pub fn bitmap(&self) -> &Bitmap {
         &self.bitmap
     }
@@ -110,7 +115,7 @@ impl Index<usize> for BitmapAtlas {
     type Output = Rect;
 
     fn index(&self, index: usize) -> &Self::Output {
-        &self.tiles[index]
+        self.get(index).unwrap()
     }
 }