Optionally skip scissor in `t3d_viewport_attach`?

[lmcd]

I'm setting minus dimensions in t3d_viewport_set_area to render an object on a different part of the screen but preserving the perspective as if it was rendered elsewhere.

However doing this trips an assert in rdpq_set_scissor, which doesn't allow minus numbers. I've commented out this call and get precisely the result I want. Could there be a version of t3d_viewport_attach that skips the scissor call?

[HailToDodongo]

the scissor should always be set, but it sounds more like a bug that i don't just clamp it.
I'll fix that

[HailToDodongo]

Looking at it now there are some problems, i can clamp the negative side but not the positive one.
So if you move it in that direction it could lead to OOB memory writes by drawing beyond the framebuffer.
Sadly the CPU at that point can't know the actual dimension of what it is physically drawing to.
Being able to omit a scissor may also cause accidental misuse of the API.

I'll have to think about this a bit more, but maybe defining an extra position in the viewport to define the center point for the 3D pipeline would be an alternative.
That could then be shifted around without having to touch the actual screen dimension/offset

[lmcd]

I initially figured I could just change the camera matrix or something, but I couldn't get a single thing to work that would allow me to render something at an arbitrary place on screen with the same perspective as if it was at 0, 0, 0.

In the end, by luck, I figured out that the T3D_CMD_SCREEN_SIZE part of t3d_viewport_attach did exactly this. This is more of a menu system than free-roaming gameplay, so I can stop things from going into bad memory territory and have seen no issues so far.