wrap some functions which in imp header

[benjerming]

Hi, I am very thankyou import libmupdf into Rust community.
Now I am planning to add a feture to extract various path from fz_device::{fill_path, stroke_path} to fz_pixmap or image file, just mostly like source/fitz/draw-device.c does.
Unfortunately, source/fitz/draw-device.c depend on many functions in private header:

#include "context-imp.h"
#include "color-imp.h"
#include "draw-imp.h"
#include "glyph-imp.h"
#include "pixmap-imp.h"

So I want to import these useful functions in source/fitz directory.
Can this pr be merge into main repo? thanks very much.

[itsjunetime]

I think we generally try to manually write wrappers for all C(++) functions in wrapper.c so that we can catch thrown errors and handle them in C (since unwinding over ffi boundaries is ub iirc), so I don't think we want to manually expose more functions without wrappers.

Also, could you explain the changes to the function blocklists? It isn't immediately evident.

[ginnyTheCat]

since unwinding over ffi boundaries is ub iirc

Unwinding over ffi boundarys just aborts, but what mupdf does is implementing throwing/unwinding using long jump, which is not allowed in rust, but fz_throwing without having a fz_try up in the chain is undefined afaik, since there is no long jump target. Therefore having a wrapper in wrapper.c is essential for all functions that call fz_throw somewhere down the chain.

so I don't think we want to manually expose more functions without wrappers.

We already export all functions we have wrappers (mupdf_* functions) for without wrappers (fz_* functions) as well, you're just i guess just not allowed to call them with input that could error i guess.

[messense]

Now I am planning to add a feture to extract various path from fz_device::{fill_path, stroke_path} to fz_pixmap or image file, just mostly like source/fitz/draw-device.c does.
Unfortunately, source/fitz/draw-device.c depend on many functions in private header:

I'd suggest write it in C wrapper.{h,c} then expose the API in Rust side such that we don't need to expose imp headers.