Refactor terminal support

CHANGELOG.md

@@ -8,6 +8,11 @@ This project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html
 ### Added
 - `mdcat` builds on Windows now (see [GH-34][]).
 
+### Changed
+- Refactor internal terminal representation, replacing the terminal enum with a
+  new `Terminal` trait and dynamic dispatch.
+- Only include terminal backends supported on the platform.
+
 [GH-34]: https://github.com/lunaryorn/mdcat/pull/34
 
 ## [0.8.0] – 2018-02-15

Cargo.toml

@@ -10,18 +10,29 @@ version = "0.8.1-pre"
 categories = ["command-line-utilities", "text-processing"]
 license = "Apache-2.0"
 authors = ["Sebastian Wiesner <sebastian@swsnr.de>"]
+build = "build.rs"
 
 [badges]
 travis-ci = { repository = "lunaryorn/mdcat" }
 maintenance = { status = "actively-developed" }
 
+[features]
+default = []
+
+iterm2 = ["mime", "base64"]
+terminology = ["immeta"]
+
 [dependencies]
 atty = "^0.2"
 failure = "^0.1"
 reqwest = "^0.8"
 term_size = "^0.3"
 url = "^1.6"
 
+mime = {version = "^0.3", optional = true}
+base64 = {version = "^0.9", optional = true}
+immeta = {version = "^0.4", optional = true}
+
 [dependencies.clap]
 version = "^2.29"
 default-features = false
@@ -37,13 +48,6 @@ version = "^2"
 default-features = false
 features = ["parsing", "assets", "dump-load"]
 
-[target.'cfg(target_os = "macos")'.dependencies]
-mime = "^0.3"
-base64 = "^0.9"
-
-[target.'cfg(all(unix, not(target_os = "macos")))'.dependencies]
-immeta = "^0.4"
-
 [package.metadata.release]
 sign-commit = true
 upload-doc = false

build.rs

@@ -0,0 +1,28 @@
+// Copyright 2018 Sebastian Wiesner <sebastian@swsnr.de>
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+
+// 	http://www.apache.org/licenses/LICENSE-2.0
+
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+fn enable_feature(feature: &str) {
+    println!("rustc-cfg={}", feature);
+}
+
+fn main() {
+    #[cfg(target_os = "macos")]
+    {
+        enable_feature("iterm2");
+    }
+    #[cfg(all(unix, not(target_os = "macos")))]
+    {
+        enable_feature("terminology");
+    }
+}