macOS: Implement NSTextInputClient (#518)

Fixes #263

src/platform/macos/ffi.rs

@@ -0,0 +1,74 @@
+// TODO: Upstream these
+
+#![allow(non_snake_case, non_upper_case_globals)]
+
+use cocoa::base::{class, id};
+use cocoa::foundation::{NSInteger, NSUInteger};
+use objc;
+
+pub const NSNotFound: NSInteger = NSInteger::max_value();
+
+#[repr(C)]
+pub struct NSRange {
+    pub location: NSUInteger,
+    pub length: NSUInteger,
+}
+
+impl NSRange {
+    #[inline]
+    pub fn new(location: NSUInteger, length: NSUInteger) -> NSRange {
+        NSRange { location, length }
+    }
+}
+
+unsafe impl objc::Encode for NSRange {
+    fn encode() -> objc::Encoding {
+        let encoding = format!(
+            // TODO: Verify that this is correct
+            "{{NSRange={}{}}}",
+            NSUInteger::encode().as_str(),
+            NSUInteger::encode().as_str(),
+        );
+        unsafe { objc::Encoding::from_str(&encoding) }
+    }
+}
+
+pub trait NSMutableAttributedString: Sized {
+    unsafe fn alloc(_: Self) -> id {
+        msg_send![class("NSMutableAttributedString"), alloc]
+    }
+
+    unsafe fn init(self) -> id; // *mut NSMutableAttributedString
+    unsafe fn initWithString(self, string: id) -> id;
+    unsafe fn initWithAttributedString(self, string: id) -> id;
+
+    unsafe fn string(self) -> id; // *mut NSString
+    unsafe fn mutableString(self) -> id; // *mut NSMutableString
+    unsafe fn length(self) -> NSUInteger;
+}
+
+impl NSMutableAttributedString for id {
+    unsafe fn init(self) -> id {
+        msg_send![self, init]
+    }
+
+    unsafe fn initWithString(self, string: id) -> id {
+        msg_send![self, initWithString:string]
+    }
+
+    unsafe fn initWithAttributedString(self, string: id) -> id {
+        msg_send![self, initWithAttributedString:string]
+    }
+
+    unsafe fn string(self) -> id {
+        msg_send![self, string]
+    }
+
+    unsafe fn mutableString(self) -> id {
+        msg_send![self, mutableString]
+    }
+
+    unsafe fn length(self) -> NSUInteger {
+        msg_send![self, length]
+    }
+}