drbawb/koko

an infinite canvas

koko's Issues

hah. opengl support is borked.

Now that I'm back on my Mac for a minute I found an entertaining bug... as I understand it:

• DirectX, like SDL, has the notion that the y-coordinate grows downwards in memory.
• Whereas OpenGL (as SDL uses it) has the y-coordinate growing upward in memory.

When swapping cold regions out I rip the texture out of VRAM and RLE it for space savings
by setting the render target to the texture and calling Renderer#read_pixel_data().

Then when that gets swapped back in I just call Texture#update().

Apparently #update() handles the flipping, but #read_pixel_data() doesn't. (... or possibly vice versa.) So when I swap the region back in on a system using OpenGL: that region is upside down.

---

Not really sure how to fix this apart from:

1. Don't rely on serializing the draw state to/from VRAM. (e.g: my initial "shadow draw" idea)
2. Detect what platform koko is running on and swap in an RLE impl that reverses the row-order. (This does work, but it seems exceptionally hacky to me. Why use SDL2 exactly if I have to start writing platform specific code anyways? 😞 )