SvgSurface: make filename param optional

[bilelmoussaoui]

Per the docs https://www.cairographics.org/manual/cairo-SVG-Surfaces.html
This allows drawing parts of a SVG file without saving it to a tmp file.

I'm not sure if what I did is right or not :P

Fixes #293

[GuillaumeGomez]

👍

[bilelmoussaoui]

@GuillaumeGomez Any idea why the CI fails with

error[E0599]: no method named `to_glib_none` found for type `std::option::Option<&std::string::String>` in the current scope

  --> src/svg.rs:44:61

   |

44 |                 ffi::cairo_svg_surface_create(path.as_ref().to_glib_none().0, width, height),

   |                                                             ^^^^^^^^^^^^ method not found in `std::option::Option<&std::string::String>`

It builds and works fine locally here.

[GuillaumeGomez]

Try to change your code as follow:

path.map(|s| s.as_str()).to_glib_none().0

[bilelmoussaoui]

My bad! I was running the tests without --features svg. It should pass this time. Thanks!

[bilelmoussaoui]

It fails because tests are run without --features use_glib 🤦‍♂️

[GuillaumeGomez]

Oh then it depends: is it supposed to be run even without glib or not? If so, please don't use to_glib calls.

[bilelmoussaoui]

It doesn't need to. In such case, what I'm supposed to do?

[GuillaumeGomez]

Like this:

let c_str = CString::new(c_str).unwrap();
// then:
c_str.as_ptr();

[sdroege]

lgtm

[sdroege]

This assumes that path is not an Option and already a Path. Needs the map(), as_ref() part from above too

[sdroege]

The path will be freed once this block is done, and then you store a dangling pointer in path in the outer scope. Just return the Option<CString> from this block, and do the as_ptr() part for both Windows/UNIX just before calling the C function.

[sdroege]

Looks good for real now :)

[GuillaumeGomez]

Then I'll merge for real once CI passed. 😆

[EPashkin]

@bilelmoussaoui Thanks, 👍

[EPashkin]

@sdroege, @GuillaumeGomez Maybe we need to make these function public someday
https://github.com/gtk-rs/glib/blob/master/src/translate.rs#L422-L486

[GuillaumeGomez]

@EPashkin Oh indeed! Do you mind opening an issue for it please? So it can be done for the next release. :)

[sdroege]

That would not help here as otherwise cairo would have to always depend on glib

[EPashkin]

@sdroege Agree about this case, but IMHO here also better add separate path_to_c and use with map to make code more clear

[bilelmoussaoui]

@sdroege Agree about this case, but IMHO here also better add separate path_to_c and use with map to make code more clear

I don't see a valid reason to do that as the function won't be used anywhere else but I agree it makes that part of code less readable.

The failing tests are not related to this change I think.

[EPashkin]

@bilelmoussaoui Why you think that it not related?

failures:

---- svg::test::file stdout ----

thread 'svg::test::file' panicked at 'called `Result::unwrap()` on an `Err` value: "error while writing to output stream"', src/libcore/result.rs:1189:5

failures:

    svg::test::file

test result: FAILED. 39 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out

[EPashkin]

IMHO test with None also will be good

[bilelmoussaoui]

Because I had that issue once, tried to reproduce it and it was gone the next time I ran the tests. Yeah a test with None will be good. Will add that.

[sdroege]

Still fails to write the output file, on Windows and macOS but not on Linux.

[EPashkin]

On Windows SvgSurface::new not work even for direct path

[EPashkin]

Old version works on let surface = SvgSurface::new(100., 100., "_.tmp").unwrap();,
I try to find problem

[EPashkin]

CI passed

[sdroege]

Great, let's get it in then :)

[GuillaumeGomez]

Thanks!