Port fontp to Rust #248

atheriel · 2017-07-17T23:00:50Z

This is my first pass at porting fontp to Rust, and should be considered a work in progress. I have a few questions:

~~Should I change the naming convention for the font_property_index enum?~~
~~Is there a convention for calling intern from Rust code?~~ See Adds intern and an intern_static! macro #255.
~~Can or should I add is_font_spec() (etc) methods to LispObject in lisp.rs, so that the checking can be moved out of fontp and into those methods?~~

This should close #233.

DavidDeSimone · 2017-07-17T23:08:20Z

rust_src/src/fonts.rs

+// See font_property_index in font.h for details.
+#[allow(non_camel_case_types, dead_code)]
+#[repr(C)]
+enum font_property_index {


This enum will probably want to be defined in the remacs-sys crate instead of here. That crate is where we house the code related to FFI and representing structures that are defined in the C layer.

Ok, I will move it there.

use camelcase names.

Moved, with a new camelcase name.

DavidDeSimone · 2017-07-17T23:08:33Z

rust_src/src/fonts.rs

+        if v.is_pseudovector(PseudovecType::PVEC_FONT) {
+            if extra_type.eq(Qnil) {
+                LispObject::constant_t()
+            } else if extra_type.eq(LispObject::from_raw(unsafe { Qfont_spec })) {


Yeah I don't like the raw unsafe Q... usage here. Personally I like the idea of having safe methods implemented for LispObject like "is_font_spec", etc.

I thoought it would be "safe enough" to get at these symbols this way -- is there another option?

Let me clarify:

Accessing these symbols the way you are doing is fine, but we have to use unsafe blocks in Lisp binding code. If we have another lisp binding that needs to do similar logic, we will need to add more unsafe blocks. In general, I think a Rust code base is at it's best when it minimizes unsafe code blocks.

We can improve this situation by adding a safe wrapper around unsafe code (since the code here is "unsafe" due to its interaction with C). For example something like:

impl LispObject { pub fn is_font_spec(&self) -> bool { self.eq(unsafe { /* ... */ }); } }

That's fair. I think that fontp is the only place that uses of Qfont_spec and friends in this manner in the codebase, though. Is it worth writing a safe interface (for example, creating a FontEntity::from_object()-style enum method)?

That's a fair point, I'm personally fine either way.

I wrote a little enum to abstract this pattern out.

DavidDeSimone · 2017-07-17T23:08:38Z

rust_src/src/fonts.rs

+        } else {
+            // As with the C version, checking that object is a font takes priority
+            // over checking that extra_type is well-formed.
+            Qnil


We generally prefer calls to LispObject::constant_nil() over raw Qnil usage.

DavidDeSimone · 2017-07-17T23:10:06Z

Thanks for the contribution! This is looking good to me so far, I've left a few inline comments on a couple things I saw.

atheriel · 2017-07-18T00:25:32Z

Ok, I've added some is_font_* methods to LispObject.

atheriel · 2017-07-18T00:47:39Z

I will probably wait on #244 before moving the struct to remacs-sys.

birkenfeld · 2017-07-18T04:15:44Z

rust_src/src/fonts.rs

+#[lisp_fn(min = "1")]
+pub fn fontp(object: LispObject, extra_type: LispObject) -> LispObject {
+    if object.is_font() {
+        if extra_type.eq(LispObject::constant_nil()) {


shorter: extra_type.is_nil()

birkenfeld · 2017-07-18T04:17:58Z

rust_src/src/lisp.rs

@@ -559,6 +560,27 @@ impl LispObject {
            v.is_pseudovector(PseudovecType::PVEC_FONT)
        })
    }
+
+    pub fn is_font_spec(self) -> bool {


Instead of adding these to LispObject, I would create an as_font method on is_vectorlike that returns a "LispFontRef" or similar.

is_spec, is_entity etc can the be methods on that struct.

Ok, I've taken this approach.

birkenfeld · 2017-07-19T03:47:51Z

rust_src/src/fonts.rs

+}
+
+impl FontExtraType {
+    pub fn from_object_or_error(extra_type: LispObject) -> FontExtraType {


I'd prefer from_symbol_or_error.

birkenfeld · 2017-07-19T03:48:59Z

rust_src/src/fonts.rs

+            FontExtraType::Object
+        } else {
+            // TODO: This should actually be equivalent to
+            // intern("font-extra-type"), not Qsymbolp.


In order to call intern, you can add it to the imported functions in remacs-sys. Signature should be straightforward.

This turns out to be more difficult than it first appears. See #255.

birkenfeld · 2017-07-19T03:49:17Z

rust_src/remacs-sys/lib.rs

@@ -1096,3 +1096,47 @@ extern "C" {
        nchars_return: *mut ptrdiff_t,
    ) -> ptrdiff_t;
 }
+
+/// Contains C definitions from the font.h header.
+pub mod font {


Good idea to add some modules to structure this crate!

birkenfeld · 2017-07-23T04:20:46Z

Can be updated to use intern() now.

Signed-off-by: Aaron Jacobs <atheriel@gmail.com>

atheriel · 2017-07-23T16:26:57Z

Updated to use intern(). Is there anything else extant on this PR?

birkenfeld · 2017-07-24T04:04:17Z

Nope, looks, good!

twmr · 2017-07-24T16:14:18Z

rust_src/src/fonts.rs

+use vectors::LispVectorlikeRef;
+
+// A font is not a type in and of itself, it's just a group of three kinds of
+// pseudovector. This newtype allows us to define methods that yield the actual


This could be improved.

plural of pseudovectors

missing space between new and type.

First you mention that a font is not a type and then you continue with "This new type"

I'm glad someone is reading the docstrings :) Not quite sure I agree about the plural -- a font is "one of three kinds of pseudovector", so fonts are "a group of three kinds of pseudovector". Might be wrong here, though.

The term "newtype" refers to the Rust pattern of struct X(Y). It's not a typo. A "font" does not have its own structure in the C code. It refers to three possible structs. Hence a font is not "a type in and of itself". It's just a label for a group of structures. So I'm not actually defining any structure here, I just want to add some methods to LispVectorlikeRef -- hence the newtype.

DavidDeSimone reviewed Jul 17, 2017

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birkenfeld reviewed Jul 18, 2017

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birkenfeld reviewed Jul 19, 2017

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atheriel added 6 commits July 23, 2017 12:18

Port fontp to Rust.

bec9fa5

Signed-off-by: Aaron Jacobs <atheriel@gmail.com>

Add is_font_* methods to LispObject.

02222c4

Signed-off-by: Aaron Jacobs <atheriel@gmail.com>

Add a FontExtraType enum to compartmentalize font types.

e6b3bc6

Signed-off-by: Aaron Jacobs <atheriel@gmail.com>

Add a LispFontRef type and move is_font_* methods to it.

dd4b589

Signed-off-by: Aaron Jacobs <atheriel@gmail.com>

Move font_property_index and associated consts to remacs-sys.

9e0185d

Signed-off-by: Aaron Jacobs <atheriel@gmail.com>

Raise the correct wrong_type_argument in fontp.

728579b

Signed-off-by: Aaron Jacobs <atheriel@gmail.com>

birkenfeld approved these changes Jul 24, 2017

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birkenfeld merged commit 7016d43 into remacs:master Jul 24, 2017

terlar mentioned this pull request Jul 24, 2017

Compiling complains about: unresolved import remacs_sys::wrong_type_argument #270

Closed

twmr reviewed Jul 24, 2017

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Port fontp to Rust #248

Port fontp to Rust #248

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Port fontp to Rust #248

Port fontp to Rust #248

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birkenfeld commented Jul 23, 2017

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atheriel commented Jul 17, 2017 •

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