Awesome

objc-font-lock - Highlight Objective-C method calls

Author: Anders Lindgren<br> Version: 0.0.4<br> URL: https://github.com/Lindydancer/objc-font-lock<br>

This package highlights Objective-C method calls.

Background

Objective-C use a syntax for method calls it has inherited from Smalltalk. Unfortunately, this syntax is frustratingly hard to read -- when browsing through code, method calls tend to "disappear" as they are different from normal C function calls.

By highlighting method calls, it is possible to read the same piece of code faster and more accurate.

By default, the open and close bracket is highlighted using a bright warning face, the entire method call is highligthed using the standard highlight face, and each Objective-C function name component is highlighted using the font-lock function name face.

For a more sober appearance, you can configure the package to, for example, only highlight the function name components.

The following screenshot demonstrates the highlighting effect of this package:

Installation

Place this package in a directory in the load-path. To activate it, use customize or place the following lines in a suitable init file:

   (require 'objc-font-lock-mode)
   (objc-font-lock-global-mode 1)

Customization

Method calls are highlighted as follows:

                        Controlling variable:           Default:
[expr func: expr]
^               ^-- objc-font-lock-bracket-face       Warning face
      ^^^^--------- objc-font-lock-function-name-face Function name face
^^^^^^^^^^^^^^^^^-- objc-font-lock-background-face    Highlight

To change the face used, change the face variable. By setting it to "nil", the corresponding part of the method call will not be highlighted. For example:

;; Don't highlight brackets.
(setq objc-font-lock-bracket-face nil)
;; Use `secondary-selection` (a builtin face) as background.
(setq objc-font-lock-background-face 'secondary-selection)

Under the hood

This package parse the content of brace pairs to decide if they form an Objective-C method call, and what the parts are. It is neither aware of the context in which the brackets appear, nor what included symbols corresponds to. Despite these limitations, this package highlight most typical constructs used in real-world Objective-C.

Implementation

An Objective-C method call is on one the following forms:

[expression func]
[expression func: expression func: expression....]

This package use font-lock rules with a function performing the matcher (rather than an regexp). The matcher will find a bracket pair (skipping those that are used for plain C arrays or are located in a string or comment). Anchored sub-rules will match and highlight individual parts. The function names an brackets are highlighted using one rule placed before the standard Font Lock rules. The background is highlighted using another placed last.

To recognize an expression, the Emacs built-in expression parser, forward-sexp, is used for plain trivial expressions (like identifiers and numbers) and expressions inside parentheses. On top of this, this package checks for complex expressions by looking for casts and infix operators.

The pre- and postincrement and -decrement operators don't fall into the above pattern. However, any code containing them should be fontified exactly like they would, if they weren't there. Hence, they are treated as "whitespace".

Without knowing if an identifier denotes a type or not, a construct like [(alpha)beta] is ambiguous. It can either be interpreted as a method call, where the object alpha is sent the message beta. However, it can also be seen as an array subscript, where the expression beta is cast to the type alpha. This package treats any construct that looks like a cast as though it is a cast.

Converted from objc-font-lock.el by el2markdown.