Limit the size of sprite-sheet to 64KB

Screen size is already limited. It makes sense to limit the sprite-sheet too. Creating sprite-sheets bigger than 64KB takes a lot of time, and really does not make sense to have bigger one to create low-res games. If game developer wants to create huge pictures,

Author: elgopher

pi.go

@@ -75,7 +75,8 @@ var GameLoopStopped bool
 // form of mapping: index number->RGB color. Image must have an indexed color mode,
 // because Pi loads the palette from the sprite-sheet.png file itself. Please use a pixel-art editor
 // which supports indexed color mode, such as Aseprite (paid) or LibreSprite (free). Sprite-sheet
-// width and height must be multiplication of 8.
+// width and height must be multiplication of 8. Each sprite is 8x8 pixels. The maximum number of pixels
+// is 65536 (64KB).
 //
 // custom-font.png must also have an indexed color mode. Color with index 0 is treated as background.
 // Any other color as foreground. The size of the image is fixed. It must be 128x128. Each char is 8x8.

pi_test.go

@@ -225,6 +225,13 @@ func TestLoad(t *testing.T) {
 			})
 		})
 	})
+
+	t.Run("should panic when sprite-sheet total number of pixels is higher than 65536", func(t *testing.T) {
+		pi.Reset()
+		assert.Panics(t, func() {
+			pi.UseEmptySpriteSheet(264, 256)
+		})
+	})
 }
 
 func TestTime(t *testing.T) {

screen.go

@@ -180,7 +180,7 @@ func (p *Position) Reset() {
 	p.Y = 0
 }
 
-const maxScreenSize = 1024 * 64
+const maxScreenSize = 65536
 
 // SetScreenSize sets the screen size to specified resolution. The maximum number of pixels is 65536 (64KB).
 // Will panic if screen size is too big or width/height are <= 0.

sprite_sheet.go

@@ -60,6 +60,8 @@ func SprSheet() PixMap {
 	return sprSheet.PixMap
 }
 
+const maxSpriteSheetSize = 65536
+
 func newSpriteSheet(w int, h int) spriteSheet {
 	if w%8 != 0 || w == 0 {
 		panic(fmt.Sprintf("sprite sheet width %d is not a multiplication of 8", w))
@@ -70,6 +72,10 @@ func newSpriteSheet(w int, h int) spriteSheet {
 
 	size := w * h
 
+	if size > maxSpriteSheetSize {
+		panic(fmt.Sprintf("number of pixels for sprite-sheet resolution %dx%d is higher than maximum %d. Please use a smaller one.", w, h, maxSpriteSheetSize))
+	}
+
 	return spriteSheet{
 		PixMap:          NewPixMap(w, h),
 		numberOfSprites: size / (SpriteWidth * SpriteHeight),
@@ -78,7 +84,7 @@ func newSpriteSheet(w int, h int) spriteSheet {
 }
 
 // UseEmptySpriteSheet initializes empty sprite-sheet with given size. Could be used
-// when you don't have sprite-sheet.png in resources.
+// when you don't have sprite-sheet.png in resources. The maximum number of pixels is 65536 (64KB).
 func UseEmptySpriteSheet(w, h int) {
 	sprSheet = newSpriteSheet(w, h)
 }

sprite_sheet_test.go

@@ -47,4 +47,11 @@ func TestUseEmptySpriteSheet(t *testing.T) {
 		expectedSpriteSheetData := make([]byte, 16*8)
 		assert.Equal(t, expectedSpriteSheetData, pi.SprSheet().Pix())
 	})
+
+	t.Run("should panic when total number of pixels is higher than 65536", func(t *testing.T) {
+		pi.Reset()
+		assert.Panics(t, func() {
+			pi.UseEmptySpriteSheet(256, 264)
+		})
+	})
 }