Surface width and height values distinction question

[evanolds]

In the OnRender method in Effect, are the following values always the same:

EnvironmentParameters.SourceSurface.Width

DstArgs.Surface.Width

SrcArgs.Surface.Width

?

Also, in the Effect class (the non-template one) are the following values always the same:

srcArgs.Width

srcArgs.Surface.Width

EnvironmentParameters.SourceSurface.Width

?

The same question goes for the height values, but I assume the answer is the same. If there is any context in which these values would differ, can you please explain when and why?

The reason I ask is I want to process the image in such a way that modifying a given pixel may be dependent on another pixel elsewhere in the image. If there is a contract saying only use pixels within the bounds of the source surface, but that surface doesn't necessarily represent the working image in its entirety, then I'd want pixels that, in theory, lie outside of this surface.

I guess what I'm really asking is, do we ever get a surface delivered to our effect which is not the entire image? I don't know if you (Rick) do currently or plan to in future versions split large images up into multiple surfaces for visibility culling or other reasons, but I just want to make sure that it's safe to develop code under the assumption that the above values are always equivalent.

[Rick Brewster]

The width/height values will always be the same.

When/if Paint.NET shifts to a tiled memory manager, there will be a new interface for effect plugins to use. Legacy effects would work through an adapter layer that will hide this detail, essentially by grabbing one big tile for the whole image. In this situation, legacy effects will require more memory to use but they will still work.