sdl: render.go: Fix computation of slice returned by LockTexture

thomas-holmes · veeableful · commit e322b42a52f9 · 2017-11-26T23:17:00.000+08:00
diff --git a/sdl/render.go b/sdl/render.go
@@ -307,7 +307,8 @@ func (texture *Texture) Lock(rect *Rect) ([]byte, int, error) {
 
 	pitch := int32(_pitch)
 	if rect != nil {
-		length = int((pitch / w) * rect.W * rect.H)
+		bytesPerPixel := pitch / w
+		length = int(bytesPerPixel * (w*rect.H - rect.X - (w - rect.X - rect.W)))
 	} else {
 		length = int(pitch * h)
 	}

Original file line number	Diff line number	Diff line change
`@@ -307,7 +307,8 @@ func (texture Texture) Lock(rect Rect) ([]byte, int, error) {`
`307`	`307`
`308`	`308`	`pitch := int32(_pitch)`
`309`	`309`	`if rect != nil {`
`310`		`- length = int((pitch / w) * rect.W * rect.H)`
	`310`	`+ bytesPerPixel := pitch / w`
	`311`	`+ length = int(bytesPerPixel * (w*rect.H - rect.X - (w - rect.X - rect.W)))`
`311`	`312`	`} else {`
`312`	`313`	`length = int(pitch * h)`
`313`	`314`	`}`