Add TUI viewer using cursive

This patch adds a new viewer, tui, that provides an interactive
interface using cursive.  This viewer makes it possible to follow links
to other documentation items and to open external links in a web
browser.

CHANGELOG.md

@@ -12,6 +12,8 @@ SPDX-License-Identifier: MIT
   the configuration file.
   - Add `merge` dependency in version 0.1.0.
 - Add syntax highlighting for code snippets in the doc comments.
+- Add interactive tui viewer that adds support for following links from the
+  documentation.
 
 ## v0.3.0 (2020-09-11)
 

Cargo.lock

@@ -7,6 +7,22 @@ name = "adler"
 version = "0.2.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "ahash"
+version = "0.3.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "const-random 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "ahash"
+version = "0.4.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "const-random 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "ansi_term"
 version = "0.12.1"
@@ -20,6 +36,16 @@ name = "anyhow"
 version = "1.0.31"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "arc-swap"
+version = "0.4.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
+name = "array-macro"
+version = "1.0.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "assert_cmd"
 version = "1.0.1"
@@ -66,6 +92,11 @@ name = "bitflags"
 version = "1.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "bumpalo"
+version = "3.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "byteorder"
 version = "1.3.4"
@@ -88,6 +119,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "num-integer 0.1.43 (registry+https://github.com/rust-lang/crates.io-index)",
  "num-traits 0.2.12 (registry+https://github.com/rust-lang/crates.io-index)",
+ "time 0.1.43 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -113,6 +145,24 @@ dependencies = [
  "winapi 0.3.9 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "const-random"
+version = "0.1.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "const-random-macro 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro-hack 0.5.16 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "const-random-macro"
+version = "0.1.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "getrandom 0.1.14 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro-hack 0.5.16 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "crc32fast"
 version = "1.2.0"
@@ -121,6 +171,25 @@ dependencies = [
  "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "crossbeam-channel"
+version = "0.4.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "crossbeam-utils 0.7.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "maybe-uninit 2.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "crossbeam-utils"
+version = "0.7.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "autocfg 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
+ "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "cssparser"
 version = "0.27.2"
@@ -146,6 +215,80 @@ dependencies = [
  "syn 1.0.34 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "cursive"
+version = "0.15.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "ahash 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
+ "crossbeam-channel 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cursive_core 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "enumset 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.72 (registry+https://github.com/rust-lang/crates.io-index)",
+ "log 0.4.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "maplit 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "ncurses 5.99.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "signal-hook 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "term_size 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicode-segmentation 1.6.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicode-width 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "cursive_core"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "ahash 0.4.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "chrono 0.4.13 (registry+https://github.com/rust-lang/crates.io-index)",
+ "crossbeam-channel 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "enum-map 0.6.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "enumset 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.72 (registry+https://github.com/rust-lang/crates.io-index)",
+ "log 0.4.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "owning_ref 0.4.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "signal-hook 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicode-segmentation 1.6.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicode-width 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "xi-unicode 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "darling"
+version = "0.10.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "darling_core 0.10.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "darling_macro 0.10.2 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "darling_core"
+version = "0.10.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "fnv 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
+ "ident_case 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.18 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
+ "strsim 0.9.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.34 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "darling_macro"
+version = "0.10.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "darling_core 0.10.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.34 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "derive_more"
 version = "0.99.9"
@@ -184,6 +327,45 @@ name = "encode_unicode"
 version = "0.3.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "enum-map"
+version = "0.6.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "array-macro 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "enum-map-derive 0.4.3 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "enum-map-derive"
+version = "0.4.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "proc-macro2 1.0.18 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.34 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "enumset"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "enumset_derive 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-traits 0.2.12 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "enumset_derive"
+version = "0.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "darling 0.10.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.18 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.34 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "env_logger"
 version = "0.7.1"
@@ -306,6 +488,21 @@ dependencies = [
  "syn 1.0.34 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "ident_case"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
+name = "idna"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "matches 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicode-bidi 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicode-normalization 0.1.13 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "indexmap"
 version = "1.5.1"
@@ -333,6 +530,14 @@ name = "itoa"
 version = "0.4.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "js-sys"
+version = "0.3.45"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "wasm-bindgen 0.2.68 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "kuchiki"
 version = "0.8.0"
@@ -385,6 +590,11 @@ name = "mac"
 version = "0.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "maplit"
+version = "1.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "markup5ever"
 version = "0.10.0"
@@ -417,6 +627,11 @@ name = "matches"
 version = "0.1.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "maybe-uninit"
+version = "2.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "merge"
 version = "0.1.0"
@@ -445,6 +660,16 @@ dependencies = [
  "adler 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "ncurses"
+version = "5.99.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "cc 1.0.58 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.72 (registry+https://github.com/rust-lang/crates.io-index)",
+ "pkg-config 0.3.18 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "new_debug_unreachable"
 version = "1.0.4"
@@ -455,6 +680,26 @@ name = "nodrop"
 version = "0.1.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "num"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "num-complex 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-integer 0.1.43 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-iter 0.1.41 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-rational 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-traits 0.2.12 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "num-complex"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "num-traits 0.2.12 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "num-integer"
 version = "0.1.43"
@@ -464,6 +709,26 @@ dependencies = [
  "num-traits 0.2.12 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "num-iter"
+version = "0.1.41"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "autocfg 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-integer 0.1.43 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-traits 0.2.12 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "num-rational"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "autocfg 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-integer 0.1.43 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-traits 0.2.12 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "num-traits"
 version = "0.2.12"
@@ -492,6 +757,14 @@ dependencies = [
  "pkg-config 0.3.18 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "owning_ref"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "stable_deref_trait 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "pager"
 version = "0.15.0"
@@ -501,6 +774,11 @@ dependencies = [
  "libc 0.2.72 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "percent-encoding"
+version = "2.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "phf"
 version = "0.8.0"
@@ -726,6 +1004,7 @@ dependencies = [
  "anyhow 1.0.31 (registry+https://github.com/rust-lang/crates.io-index)",
  "assert_cmd 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "atty 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cursive 0.15.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "env_logger 0.7.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "html2text 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "insta 0.16.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -744,7 +1023,10 @@ dependencies = [
  "tempfile 3.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "terminal_size 0.1.13 (registry+https://github.com/rust-lang/crates.io-index)",
  "text-style 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "textwrap 0.12.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "toml 0.5.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "url 2.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "webbrowser 0.5.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "xdg 2.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -865,6 +1147,24 @@ dependencies = [
  "stable_deref_trait 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "signal-hook"
+version = "0.1.16"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "libc 0.2.72 (registry+https://github.com/rust-lang/crates.io-index)",
+ "signal-hook-registry 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "signal-hook-registry"
+version = "1.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "arc-swap 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.72 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "siphasher"
 version = "0.3.3"
@@ -903,6 +1203,11 @@ dependencies = [
  "quote 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "strsim"
+version = "0.9.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "structopt"
 version = "0.3.15"
@@ -989,6 +1294,15 @@ dependencies = [
  "utf-8 0.7.5 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "term_size"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "libc 0.2.72 (registry+https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.3.9 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "terminal_size"
 version = "0.1.13"
@@ -1012,6 +1326,7 @@ version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "ansi_term 0.12.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cursive 0.15.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "syntect 4.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1023,6 +1338,14 @@ dependencies = [
  "unicode-width 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "textwrap"
+version = "0.12.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "unicode-width 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "thin-slice"
 version = "0.1.1"
@@ -1037,6 +1360,11 @@ dependencies = [
  "winapi 0.3.9 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "tinyvec"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "toml"
 version = "0.5.6"
@@ -1050,6 +1378,22 @@ name = "treeline"
 version = "0.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "unicode-bidi"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "matches 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "unicode-normalization"
+version = "0.1.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "tinyvec 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "unicode-segmentation"
 version = "1.6.0"
@@ -1065,6 +1409,16 @@ name = "unicode-xid"
 version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "url"
+version = "2.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "idna 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "matches 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "percent-encoding 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
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 "checksum string_cache_codegen 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)" = "f24c8e5e19d22a726626f1a5e16fe15b132dcf21d10177fa5a45ce7962996b97"
+"checksum strsim 0.9.3 (registry+https://github.com/rust-lang/crates.io-index)" = "6446ced80d6c486436db5c078dde11a9f73d42b57fb273121e160b84f63d894c"
 "checksum structopt 0.3.15 (registry+https://github.com/rust-lang/crates.io-index)" = "de2f5e239ee807089b62adce73e48c625e0ed80df02c7ab3f068f5db5281065c"
 "checksum structopt-derive 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)" = "510413f9de616762a4fbeab62509bf15c729603b72d7cd71280fbca431b1c118"
 "checksum syn 1.0.34 (registry+https://github.com/rust-lang/crates.io-index)" = "936cae2873c940d92e697597c5eee105fb570cd5689c695806f672883653349b"
@@ -1268,27 +1733,42 @@ dependencies = [
 "checksum syntect 4.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "b57a45fdcf4891bc79f635be5c559210a4cfa464891f969724944c713282eedb"
 "checksum tempfile 3.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "7a6e24d9338a0a5be79593e2fa15a648add6138caa803e2d5bc782c371732ca9"
 "checksum tendril 0.4.1 (registry+https://github.com/rust-lang/crates.io-index)" = "707feda9f2582d5d680d733e38755547a3e8fb471e7ba11452ecfd9ce93a5d3b"
+"checksum term_size 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)" = "1e4129646ca0ed8f45d09b929036bafad5377103edd06e50bf574b353d2b08d9"
 "checksum terminal_size 0.1.13 (registry+https://github.com/rust-lang/crates.io-index)" = "9a14cd9f8c72704232f0bfc8455c0e861f0ad4eb60cc9ec8a170e231414c1e13"
 "checksum termios 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)" = "6f0fcee7b24a25675de40d5bb4de6e41b0df07bc9856295e7e2b3a3600c400c2"
 "checksum text-style 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "01ecc55ab699ed1b4d0ebe64d7a8ee2611f55d0de4042e9c1ee5a81dee89e332"
 "checksum textwrap 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)" = "d326610f408c7a4eb6f51c37c330e496b08506c9457c9d34287ecc38809fb060"
+"checksum textwrap 0.12.1 (registry+https://github.com/rust-lang/crates.io-index)" = "203008d98caf094106cfaba70acfed15e18ed3ddb7d94e49baec153a2b462789"
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+"checksum xi-unicode 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "e71b85d8b1b8bfaf4b5c834187554d201a8cd621c2bbfa33efd41a3ecabd48b2"
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 "checksum xml5ever 0.16.1 (registry+https://github.com/rust-lang/crates.io-index)" = "0b1b52e6e8614d4a58b8e70cf51ec0cc21b256ad8206708bcff8139b5bbd6a59"
 "checksum yaml-rust 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)" = "39f0c922f1a334134dc2f7a8b67dc5d25f0735263feec974345ff706bcf20b0d"

Cargo.toml

@@ -19,6 +19,7 @@ exclude = [".builds/*", "tests/html/*", "tests/snapshots/*"]
 ansi_term = "0.12.1"
 anyhow = "1.0.31"
 atty = "0.2.14"
+cursive = "0.15.0"
 html2text = "0.2.1"
 kuchiki = "0.8.0"
 log = "0.4.11"
@@ -28,7 +29,10 @@ pager = "0.15.0"
 serde_json = "1.0.56"
 serde_tuple = "0.5.0"
 terminal_size = "0.1.13"
+textwrap = "0.12.1"
 toml = "0.5.6"
+url = "2.1.1"
+webbrowser = "0.5.5"
 xdg = "2.2.0"
 
 [dependencies.env_logger]
@@ -50,7 +54,7 @@ features = ["parsing", "regex-onig", "assets", "dump-load"]
 
 [dependencies.text-style]
 version = "0.2.0"
-features = ["ansi_term", "syntect"]
+features = ["ansi_term", "cursive", "syntect"]
 
 [dev-dependencies]
 assert_cmd = "1.0.1"

INSTALL.md

@@ -16,7 +16,23 @@ rusty-man packages are available for these distributions:
 
 ### Build Requirements
 
-To compile rusty-man, you need Rust 1.40 or later.
+To compile rusty-man, you need Rust 1.40 or later.  The `tui` backend requires
+the ncurses library in the default search path and a C compiler.
+
+If you don’t want to use ncurses, you can select another [`cursive`][] backend
+by replacing this line in `Cargo.toml`:
+
+```toml
+cursive = "0.15.0"
+```
+
+with this:
+
+```toml
+cursive = { version = "0.15.0", default-features = false, feature = ["termion-backend"] }
+```
+
+[`cursive`]: https://lib.rs/cursive
 
 ### Installing from Git
 

README.md

@@ -53,6 +53,17 @@ Found mulitple matches for u8 – select one of:
 
 For more usage information, run `rusty-man --help`.
 
+## Viewers
+
+rusty-man has three viewers (select one with the `--viewer` option) that
+determine the output format:
+- `plain` prints the documentation to the standard output without formatting.
+  This is the default for non-interactive use.
+- `rich` prints the documentation to the standard output with formatting and
+  optional syntax highlighting.  This is the default for interactive use.
+- `tui` is an interactive terminal interface.  You can read the documentation
+  and follow links.
+
 ## Installation
 
 To install rusty-man from source, clone this repository and use cargo to build
@@ -60,8 +71,10 @@ the project, or use `cargo install`.  See the [`INSTALL.md`][] file for more
 information.  rusty-man is also available as a package for these distributions:
 - Arch Linux: [`rusty-man`][pkg-aur] in the Arch User Repository
 
-rusty-man should run on all platforms, but the `rich` viewer is only available
+rusty-man is developed for Unix-like systems.  It should run on other platforms
-for ANSI terminals.  If you have trouble running rusty-man on your platform or
+too, but with some limitations:  The `rich` viewer uses ANSI escape codes,
+which are not supported on older Windows versions.  The `tui` viewer requires
+the ncurses library.  If you have trouble running rusty-man on your platform or
 if you want to help porting rusty-man to other platforms, please let me know.
 
 ## Integrations

src/main.rs

@@ -65,9 +65,9 @@ fn main() -> anyhow::Result<()> {
                 "Could not find examples for {}",
                 &args.keyword
             );
-            viewer.open_examples(args.viewer_args, &doc, examples)
+            viewer.open_examples(sources, args.viewer_args, &doc, examples)
         } else {
-            viewer.open(args.viewer_args, &doc)
+            viewer.open(sources, args.viewer_args, &doc)
         }
     } else {
         // item selection cancelled by user

src/viewer/mod.rs

@@ -2,18 +2,26 @@
 // SPDX-License-Identifier: MIT
 
 mod text;
+mod tui;
 mod utils;
 
 use std::fmt;
 
 use crate::args;
 use crate::doc;
+use crate::source;
 
 pub trait Viewer: fmt::Debug {
-    fn open(&self, args: args::ViewerArgs, doc: &doc::Doc) -> anyhow::Result<()>;
+    fn open(
+        &self,
+        sources: Vec<Box<dyn source::Source>>,
+        args: args::ViewerArgs,
+        doc: &doc::Doc,
+    ) -> anyhow::Result<()>;
 
     fn open_examples(
         &self,
+        sources: Vec<Box<dyn source::Source>>,
         args: args::ViewerArgs,
         doc: &doc::Doc,
         examples: Vec<doc::Example>,
@@ -24,6 +32,7 @@ pub fn get_viewer(s: &str) -> anyhow::Result<Box<dyn Viewer>> {
     let viewer: Box<dyn Viewer> = match s.to_lowercase().as_ref() {
         "plain" => Box::new(text::TextViewer::new(text::TextMode::Plain)),
         "rich" => Box::new(text::TextViewer::new(text::TextMode::Rich)),
+        "tui" => Box::new(tui::TuiViewer::new()),
         _ => anyhow::bail!("The viewer {} is not supported", s),
     };
     Ok(viewer)

src/viewer/text/mod.rs

@@ -8,6 +8,7 @@ use std::io;
 
 use crate::args;
 use crate::doc;
+use crate::source;
 use crate::viewer::{self, utils};
 
 #[derive(Clone, Debug)]
@@ -41,12 +42,18 @@ impl TextViewer {
 }
 
 impl viewer::Viewer for TextViewer {
-    fn open(&self, args: args::ViewerArgs, doc: &doc::Doc) -> anyhow::Result<()> {
+    fn open(
+        &self,
+        _sources: Vec<Box<dyn source::Source>>,
+        args: args::ViewerArgs,
+        doc: &doc::Doc,
+    ) -> anyhow::Result<()> {
         self.exec(args, |mut viewer| viewer.render_doc(doc))
     }
 
     fn open_examples(
         &self,
+        _sources: Vec<Box<dyn source::Source>>,
         args: args::ViewerArgs,
         doc: &doc::Doc,
         examples: Vec<doc::Example>,

src/viewer/text/rich.rs

@@ -40,7 +40,7 @@ impl utils::ManRenderer for RichTextRenderer {
         } else {
             indent
         };
-        let decorator = utils::RichDecorator::new(super::list_link);
+        let decorator = utils::RichDecorator::new(super::list_link, utils::LinkMode::List);
         let lines = html2text::parse(s.html.as_bytes())
             .render(self.line_length - indent, decorator)
             .into_lines();

src/viewer/tui/mod.rs

@@ -0,0 +1,376 @@
+// SPDX-FileCopyrightText: 2020 Robin Krahl <robin.krahl@ireas.org>
+// SPDX-License-Identifier: MIT
+
+mod views;
+
+use std::convert;
+
+use anyhow::Context as _;
+use cursive::view::{Resizable as _, Scrollable as _};
+use cursive::views::{Dialog, LinearLayout, PaddedView, Panel, TextView};
+use cursive::{event, theme};
+
+use crate::args;
+use crate::doc;
+use crate::source;
+use crate::viewer::{self, utils, utils::ManRenderer as _};
+
+use views::{CodeView, HtmlView};
+
+#[derive(Clone, Debug)]
+pub struct TuiViewer {}
+
+impl TuiViewer {
+    pub fn new() -> TuiViewer {
+        TuiViewer {}
+    }
+
+    fn render<F>(
+        &self,
+        sources: Vec<Box<dyn source::Source>>,
+        args: args::ViewerArgs,
+        doc: &doc::Doc,
+        f: F,
+    ) -> anyhow::Result<()>
+    where
+        F: Fn(&mut TuiManRenderer) -> Result<(), convert::Infallible>,
+    {
+        let mut s = create_cursive(sources, args)?;
+        let mut renderer = context(&mut s).create_renderer(&doc);
+        f(&mut renderer)?;
+        let view = renderer.into_view();
+        s.add_fullscreen_layer(view);
+        s.run();
+        Ok(())
+    }
+}
+
+impl viewer::Viewer for TuiViewer {
+    fn open(
+        &self,
+        sources: Vec<Box<dyn source::Source>>,
+        args: args::ViewerArgs,
+        doc: &doc::Doc,
+    ) -> anyhow::Result<()> {
+        self.render(sources, args, doc, |renderer| renderer.render_doc(doc))
+    }
+
+    fn open_examples(
+        &self,
+        sources: Vec<Box<dyn source::Source>>,
+        args: args::ViewerArgs,
+        doc: &doc::Doc,
+        examples: Vec<doc::Example>,
+    ) -> anyhow::Result<()> {
+        self.render(sources, args, doc, |renderer| {
+            renderer.render_examples(doc, &examples)
+        })
+    }
+}
+
+pub struct Context {
+    pub sources: Vec<Box<dyn source::Source>>,
+    pub args: args::ViewerArgs,
+    pub highlighter: Option<utils::Highlighter>,
+}
+
+impl Context {
+    pub fn new(
+        sources: Vec<Box<dyn source::Source>>,
+        args: args::ViewerArgs,
+    ) -> anyhow::Result<Context> {
+        let highlighter = utils::get_highlighter(&args)?;
+        Ok(Context {
+            sources,
+            args,
+            highlighter,
+        })
+    }
+
+    pub fn create_renderer(&self, doc: &doc::Doc) -> TuiManRenderer {
+        TuiManRenderer::new(
+            doc,
+            self.args.max_width.unwrap_or(100),
+            self.highlighter.as_ref(),
+        )
+    }
+}
+
+pub struct TuiManRenderer<'s> {
+    doc_name: doc::Fqn,
+    doc_ty: doc::ItemType,
+    layout: LinearLayout,
+    max_width: usize,
+    highlighter: Option<&'s utils::Highlighter>,
+}
+
+impl<'s> TuiManRenderer<'s> {
+    pub fn new(
+        doc: &doc::Doc,
+        max_width: usize,
+        highlighter: Option<&'s utils::Highlighter>,
+    ) -> TuiManRenderer<'s> {
+        TuiManRenderer {
+            doc_name: doc.name.clone(),
+            doc_ty: doc.ty,
+            layout: LinearLayout::vertical(),
+            max_width,
+            highlighter,
+        }
+    }
+
+    fn into_view(self) -> impl cursive::View {
+        let title = format!("{} {}", self.doc_ty.name(), self.doc_name);
+        let scroll = self.layout.scrollable().full_screen();
+        Panel::new(scroll).title(title)
+    }
+}
+
+impl<'s> utils::ManRenderer for TuiManRenderer<'s> {
+    type Error = convert::Infallible;
+
+    fn print_title(&mut self, _left: &str, _center: &str, _right: &str) -> Result<(), Self::Error> {
+        Ok(())
+    }
+
+    fn print_heading(&mut self, indent: u8, text: &str) -> Result<(), Self::Error> {
+        let heading = TextView::new(text).effect(theme::Effect::Bold);
+        self.layout.add_child(indent_view(indent, heading));
+        Ok(())
+    }
+
+    fn print_code(&mut self, indent: u8, code: &doc::Code) -> Result<(), Self::Error> {
+        if let Some(highlighter) = self.highlighter {
+            let code = CodeView::new(&code.to_string(), highlighter);
+            self.layout.add_child(indent_view(indent, code));
+        } else {
+            let text = TextView::new(code.to_string());
+            self.layout.add_child(indent_view(indent, text));
+        }
+        Ok(())
+    }
+
+    fn print_text(&mut self, indent: u8, text: &doc::Text) -> Result<(), Self::Error> {
+        let indent = usize::from(indent);
+        let mut text = HtmlView::new(
+            &text.html,
+            self.highlighter.cloned(),
+            self.max_width.saturating_sub(indent),
+        );
+        let doc_name = self.doc_name.clone();
+        let doc_ty = self.doc_ty;
+        text.set_on_link(move |s, link| handle_link(s, &doc_name.clone(), doc_ty, link));
+        self.layout.add_child(indent_view(indent, text));
+        Ok(())
+    }
+
+    fn println(&mut self) -> Result<(), Self::Error> {
+        self.layout.add_child(TextView::new(" "));
+        Ok(())
+    }
+}
+
+fn indent_view<V>(indent: impl Into<usize>, view: V) -> PaddedView<V> {
+    PaddedView::lrtb(indent.into(), 0, 0, 0, view)
+}
+
+fn create_cursive(
+    sources: Vec<Box<dyn source::Source>>,
+    args: args::ViewerArgs,
+) -> anyhow::Result<cursive::Cursive> {
+    let mut cursive = cursive::default();
+
+    cursive.set_user_data(Context::new(sources, args)?);
+
+    cursive.add_global_callback('q', |s| s.quit());
+    cursive.add_global_callback(event::Key::Backspace, |s| {
+        let screen = s.screen_mut();
+        if screen.len() > 1 {
+            screen.pop_layer();
+        }
+    });
+
+    let mut theme = theme::Theme::default();
+    theme.shadow = false;
+    theme.palette[theme::PaletteColor::Background] = theme::Color::TerminalDefault;
+    theme.palette[theme::PaletteColor::View] = theme::Color::TerminalDefault;
+    theme.palette[theme::PaletteColor::Primary] = theme::Color::TerminalDefault;
+    cursive.set_theme(theme);
+
+    Ok(cursive)
+}
+
+fn context(s: &mut cursive::Cursive) -> &mut Context {
+    s.user_data()
+        .expect("Missing context in cursive application")
+}
+
+fn report_error(s: &mut cursive::Cursive, error: anyhow::Error) {
+    let context: Vec<_> = error
+        .chain()
+        .skip(1)
+        .map(|e| format!("    {}", e.to_string()))
+        .collect();
+
+    let mut msg = error.to_string();
+    if !context.is_empty() {
+        msg.push_str("\n\nContext:\n");
+        msg.push_str(&context.join("\n"));
+    }
+
+    let dialog = Dialog::info(msg).title("Error");
+    s.add_layer(dialog);
+}
+
+fn handle_link(s: &mut cursive::Cursive, doc_name: &doc::Fqn, doc_ty: doc::ItemType, link: String) {
+    let result = resolve_link(doc_name, doc_ty, link).and_then(|link| open_link(s, link));
+    if let Err(err) = result {
+        report_error(s, err);
+    }
+}
+
+fn find_doc(
+    sources: &[Box<dyn source::Source>],
+    ty: Option<doc::ItemType>,
+    name: &doc::Fqn,
+) -> anyhow::Result<doc::Doc> {
+    for source in sources {
+        if let Some(doc) = source.find_doc(name, ty)? {
+            return Ok(doc);
+        }
+    }
+    Err(anyhow::anyhow!(
+        "Could not find documentation for item: {}",
+        name
+    ))
+}
+
+fn open_link(s: &mut cursive::Cursive, link: ResolvedLink) -> anyhow::Result<()> {
+    match link {
+        ResolvedLink::Doc(ty, name) => {
+            let doc = find_doc(&context(s).sources, ty, &name)?;
+            let mut renderer = context(s).create_renderer(&doc);
+            renderer.render_doc(&doc).unwrap();
+            let view = renderer.into_view();
+            s.add_fullscreen_layer(view);
+            Ok(())
+        }
+        ResolvedLink::External(link) => webbrowser::open(&link)
+            .map(|_| {})
+            .context("Failed to open web browser"),
+    }
+}
+
+enum ResolvedLink {
+    Doc(Option<doc::ItemType>, doc::Fqn),
+    External(String),
+}
+
+fn resolve_link(
+    doc_name: &doc::Fqn,
+    doc_ty: doc::ItemType,
+    link: String,
+) -> anyhow::Result<ResolvedLink> {
+    // TODO: support docs.rs and doc.rust-lang.org links
+    match url::Url::parse(&link) {
+        Ok(_) => Ok(ResolvedLink::External(link)),
+        Err(url::ParseError::RelativeUrlWithoutBase) => resolve_doc_link(doc_name, doc_ty, &link)
+            .with_context(|| format!("Could not parse relative link URL: {}", &link)),
+        Err(e) => {
+            Err(anyhow::Error::new(e).context(format!("Could not parse link URL: {}", &link)))
+        }
+    }
+}
+
+fn resolve_doc_link(
+    doc_name: &doc::Fqn,
+    doc_ty: doc::ItemType,
+    link: &str,
+) -> anyhow::Result<ResolvedLink> {
+    // TODO: use a proper URL parser instead of manually parsing the URL
+    let (link, fragment) = {
+        let parts: Vec<_> = link.splitn(2, '#').collect();
+        if parts.len() > 1 {
+            (parts[0], Some(parts[1]))
+        } else {
+            (parts[0], None)
+        }
+    };
+    let parts: Vec<_> = link
+        .split('/')
+        .filter(|s| !s.is_empty())
+        .filter(|s| *s != ".")
+        .collect();
+
+    let (mut ty, mut name) = if doc_ty != doc::ItemType::Module && !parts.is_empty() {
+        (None, doc_name.parent())
+    } else {
+        (Some(doc_ty), Some(doc_name.to_owned()))
+    };
+
+    for part in parts {
+        // We support "..", "index.html", "<module>" and "<type>.<name>.html".
+        match part {
+            ".." => {
+                ty = None;
+                name = name.context("Exceeded root level")?.parent();
+            }
+            "index.html" => {}
+            _ => {
+                if let Some((part_ty, part_name)) = parse_url_part(part, Some(".html")) {
+                    // part == "type.name.html"
+                    ty = Some(part_ty.parse()?);
+                    name = if let Some(name) = name {
+                        Some(name.child(&part_name))
+                    } else {
+                        Some(part_name.to_owned().into())
+                    };
+                } else {
+                    // part == "<module>"
+                    ty = Some(doc::ItemType::Module);
+                    name = if let Some(name) = name {
+                        Some(name.child(&part))
+                    } else {
+                        Some(part.to_owned().into())
+                    };
+                }
+            }
+        }
+    }
+
+    if let Some(fragment) = fragment {
+        // If the fragment is "<type>.:name>", we add it to the name, otherwise we ignore it
+        // because it just points to some other element on the page.
+        if let Some((fragment_ty, fragment_name)) = parse_url_part(fragment, None) {
+            ty = Some(fragment_ty.parse()?);
+            name = if let Some(name) = name {
+                Some(name.child(&fragment_name))
+            } else {
+                Some(fragment_name.to_owned().into())
+            };
+        }
+    }
+
+    Ok(ResolvedLink::Doc(
+        ty,
+        name.context("Cannot handle link to root")?,
+    ))
+}
+
+fn parse_url_part<'s>(s: &'s str, suffix: Option<&str>) -> Option<(&'s str, &'s str)> {
+    let s = if let Some(suffix) = suffix {
+        if s.ends_with(suffix) {
+            &s[..s.len() - suffix.len()]
+        } else {
+            return None;
+        }
+    } else {
+        s
+    };
+    let parts: Vec<_> = s.split('.').collect();
+    if parts.len() == 2 {
+        Some((parts[0], parts[1]))
+    } else {
+        None
+    }
+}

src/viewer/tui/views.rs

@@ -0,0 +1,383 @@
+// SPDX-FileCopyrightText: 2020 Robin Krahl <robin.krahl@ireas.org>
+// SPDX-License-Identifier: MIT
+
+use std::cmp;
+use std::iter;
+use std::rc;
+
+use cursive::{event, theme, utils::markup};
+use html2text::render::text_renderer;
+
+use crate::viewer::utils;
+
+pub struct HtmlView {
+    render_tree: html2text::RenderTree,
+    highlighter: Option<utils::Highlighter>,
+    max_width: usize,
+    rendered_html: Option<RenderedHtml>,
+    focus: Option<usize>,
+    on_link: Option<rc::Rc<dyn Fn(&mut cursive::Cursive, String)>>,
+}
+
+impl HtmlView {
+    pub fn new(html: &str, highlighter: Option<utils::Highlighter>, max_width: usize) -> HtmlView {
+        HtmlView {
+            render_tree: html2text::parse(html.as_bytes()),
+            highlighter,
+            max_width,
+            rendered_html: None,
+            focus: None,
+            on_link: None,
+        }
+    }
+
+    pub fn set_on_link<F>(&mut self, cb: F)
+    where
+        F: Fn(&mut cursive::Cursive, String) + 'static,
+    {
+        self.on_link = Some(rc::Rc::new(cb));
+    }
+
+    fn render(&self, width: usize) -> RenderedHtml {
+        let mut rendered_html = RenderedHtml::new(width);
+        let decorator = utils::RichDecorator::new(show_link, utils::LinkMode::Annotate);
+        let raw_lines = self
+            .render_tree
+            .clone()
+            .render(width, decorator)
+            .into_lines();
+        let highlighted_lines = utils::highlight_html(&raw_lines, self.highlighter.as_ref());
+        for (y, line) in highlighted_lines.enumerate() {
+            rendered_html.push_line(y, line);
+        }
+        rendered_html
+    }
+
+    fn update(&mut self, constraint: cursive::XY<usize>) -> cursive::XY<usize> {
+        let width = cmp::min(self.max_width, constraint.x);
+
+        // If we already have rendered the tree with the same width, we can reuse the cached data.
+        if let Some(rendered_html) = &self.rendered_html {
+            if rendered_html.width == width {
+                return rendered_html.size;
+            }
+        }
+
+        let rendered_html = self.render(width);
+
+        // Due to changed wrapping, the link count may have changed.  So we have to make sure that
+        // our focus is still valid.
+        if let Some(focus) = self.focus {
+            // TODO: Ideally, we would also want to adjust the focus if a previous link was
+            // re-wrapped.
+            if focus >= rendered_html.links.len() {
+                self.focus = Some(rendered_html.links.len() - 1);
+            }
+        }
+
+        let size = rendered_html.size;
+        self.rendered_html = Some(rendered_html);
+        size
+    }
+}
+
+impl cursive::View for HtmlView {
+    fn draw(&self, printer: &cursive::Printer) {
+        let lines = &self
+            .rendered_html
+            .as_ref()
+            .expect("layout not called before draw")
+            .lines;
+        for (y, line) in lines.iter().enumerate() {
+            let mut x = 0;
+            for element in line {
+                let mut style = element.style;
+                if element.link_idx == self.focus && printer.focused {
+                    style = style.combine(theme::PaletteColor::Highlight);
+                }
+                printer.with_style(style, |printer| printer.print((x, y), &element.text));
+                x += element.text.len();
+            }
+        }
+    }
+
+    fn layout(&mut self, constraint: cursive::XY<usize>) {
+        self.update(constraint);
+    }
+
+    fn required_size(&mut self, constraint: cursive::XY<usize>) -> cursive::XY<usize> {
+        self.update(constraint)
+    }
+
+    fn take_focus(&mut self, direction: cursive::direction::Direction) -> bool {
+        let link_count = self
+            .rendered_html
+            .as_ref()
+            .map(|html| html.links.len())
+            .unwrap_or_default();
+        if link_count > 0 {
+            use cursive::direction::{Absolute, Direction, Relative};
+            let focus = match direction {
+                Direction::Abs(abs) => match abs {
+                    Absolute::Up | Absolute::Left | Absolute::None => 0,
+                    Absolute::Down | Absolute::Right => link_count - 1,
+                },
+                Direction::Rel(rel) => match rel {
+                    Relative::Front => 0,
+                    Relative::Back => link_count - 1,
+                },
+            };
+            self.focus = Some(focus);
+            true
+        } else {
+            false
+        }
+    }
+
+    fn on_event(&mut self, event: event::Event) -> event::EventResult {
+        use event::{Event, EventResult, Key};
+
+        let links = if let Some(rendered_html) = &self.rendered_html {
+            if rendered_html.links.is_empty() {
+                return EventResult::Ignored;
+            } else {
+                &rendered_html.links
+            }
+        } else {
+            return EventResult::Ignored;
+        };
+        let focus = if let Some(focus) = self.focus {
+            focus
+        } else {
+            return EventResult::Ignored;
+        };
+
+        match event {
+            Event::Key(Key::Left) => {
+                if focus == 0 {
+                    EventResult::Ignored
+                } else if links[focus].position.y == links[focus - 1].position.y {
+                    self.focus = Some(focus - 1);
+                    EventResult::Consumed(None)
+                } else {
+                    EventResult::Ignored
+                }
+            }
+            Event::Key(Key::Up) => {
+                let y = links[focus].position.y;
+                let next_focus = links[..focus]
+                    .iter()
+                    .enumerate()
+                    .rev()
+                    .find(|(_, link)| link.position.y < y)
+                    .map(|(idx, _)| idx);
+                match next_focus {
+                    Some(focus) => {
+                        self.focus = Some(focus);
+                        EventResult::Consumed(None)
+                    }
+                    None => EventResult::Ignored,
+                }
+            }
+            Event::Key(Key::Down) => {
+                let y = links[focus].position.y;
+                let next_focus = links
+                    .iter()
+                    .enumerate()
+                    .skip(focus)
+                    .find(|(_, link)| link.position.y > y)
+                    .map(|(idx, _)| idx);
+                match next_focus {
+                    Some(focus) => {
+                        self.focus = Some(focus);
+                        EventResult::Consumed(None)
+                    }
+                    None => EventResult::Ignored,
+                }
+            }
+            Event::Key(Key::Right) => {
+                if focus + 1 >= links.len() {
+                    EventResult::Ignored
+                } else if links[focus].position.y == links[focus + 1].position.y {
+                    self.focus = Some(focus + 1);
+                    EventResult::Consumed(None)
+                } else {
+                    EventResult::Ignored
+                }
+            }
+            Event::Key(Key::Enter) => {
+                let link = links[focus].target.clone();
+                let cb = self
+                    .on_link
+                    .clone()
+                    .map(|cb| event::Callback::from_fn(move |s| cb(s, link.clone())));
+                EventResult::Consumed(cb)
+            }
+            _ => EventResult::Ignored,
+        }
+    }
+
+    fn important_area(&self, _: cursive::XY<usize>) -> cursive::Rect {
+        if let Some((focus, rendered_html)) = self.focus.zip(self.rendered_html.as_ref()) {
+            let origin = rendered_html.links[focus].position;
+            cursive::Rect::from_size(origin, (rendered_html.links[focus].width, 1))
+        } else {
+            cursive::Rect::from((0, 0))
+        }
+    }
+}
+
+fn show_link(url: &str) -> bool {
+    // We don’t want to show fragment links as we cannot jump to HTML elements by ID
+    !url.starts_with('#')
+}
+
+#[derive(Clone, Debug)]
+struct HtmlElement {
+    text: String,
+    style: theme::Style,
+    link_idx: Option<usize>,
+}
+
+#[derive(Clone, Debug)]
+struct Link {
+    position: cursive::XY<usize>,
+    target: String,
+    width: usize,
+}
+
+#[derive(Clone, Debug)]
+struct RenderedHtml {
+    width: usize,
+    size: cursive::XY<usize>,
+    lines: Vec<Vec<HtmlElement>>,
+    links: Vec<Link>,
+}
+
+impl RenderedHtml {
+    pub fn new(width: usize) -> RenderedHtml {
+        RenderedHtml {
+            width,
+            size: (0, 0).into(),
+            lines: Vec::new(),
+            links: Vec::new(),
+        }
+    }
+
+    pub fn push_link(&mut self, link: Link) -> usize {
+        self.links.push(link);
+        self.links.len() - 1
+    }
+
+    pub fn push_line(&mut self, y: usize, elements: Vec<utils::HighlightedHtmlElement>) {
+        let mut len = 0;
+        let mut line = Vec::new();
+
+        for element in elements {
+            let element = match element {
+                utils::HighlightedHtmlElement::RichString(ts) => {
+                    let tag: Tag = ts.tag.iter().collect();
+                    HtmlElement {
+                        text: ts.s.clone(),
+                        style: tag.style,
+                        link_idx: tag.link_target.map(|target| {
+                            self.push_link(Link {
+                                position: (len, y).into(),
+                                target,
+                                width: ts.s.len(),
+                            })
+                        }),
+                    }
+                }
+                utils::HighlightedHtmlElement::StyledString(s) => {
+                    let s = utils::reset_background(s);
+                    HtmlElement {
+                        text: s.s.to_owned(),
+                        style: s.style.map_or_else(Default::default, From::from),
+                        link_idx: None,
+                    }
+                }
+            };
+
+            len += element.text.len();
+            line.push(element);
+        }
+
+        self.lines.push(line);
+        self.size = self.size.stack_vertical(&(len, 1).into());
+    }
+}
+
+#[derive(Clone, Debug, Default, PartialEq)]
+struct Tag {
+    style: theme::Style,
+    link_target: Option<String>,
+}
+
+impl<'a> iter::FromIterator<&'a text_renderer::RichAnnotation> for Tag {
+    fn from_iter<I: IntoIterator<Item = &'a text_renderer::RichAnnotation>>(iter: I) -> Tag {
+        let mut tag = Tag::default();
+        for annotation in iter {
+            if let text_renderer::RichAnnotation::Link(target) = annotation {
+                tag.link_target = Some(target.clone());
+            }
+            if let Some(style) = get_rich_style(annotation) {
+                tag.style = tag.style.combine(style);
+            }
+        }
+        tag
+    }
+}
+
+fn get_rich_style(annotation: &text_renderer::RichAnnotation) -> Option<theme::Style> {
+    use text_renderer::RichAnnotation;
+
+    match annotation {
+        RichAnnotation::Default => None,
+        RichAnnotation::Link(_) => Some(theme::Effect::Underline.into()),
+        RichAnnotation::Image => None,
+        RichAnnotation::Emphasis => Some(theme::Effect::Italic.into()),
+        RichAnnotation::Strong => Some(theme::Effect::Bold.into()),
+        RichAnnotation::Strikeout => Some(theme::Effect::Strikethrough.into()),
+        RichAnnotation::Code => Some(theme::PaletteColor::Secondary.into()),
+        RichAnnotation::Preformat(_) => None,
+    }
+}
+
+pub struct CodeView {
+    lines: Vec<markup::StyledString>,
+    width: usize,
+}
+
+impl CodeView {
+    pub fn new(code: &str, highlighter: &utils::Highlighter) -> CodeView {
+        let mut lines = Vec::new();
+        let mut width = 0;
+        for line in highlighter.highlight(code) {
+            let s = line
+                .iter()
+                .map(text_style::StyledStr::from)
+                .map(utils::reset_background)
+                .map(markup::StyledString::from)
+                .fold(markup::StyledString::new(), |mut acc, s| {
+                    acc.append(s);
+                    acc
+                });
+            width = cmp::max(width, s.width());
+            lines.push(s);
+        }
+        CodeView { lines, width }
+    }
+}
+
+impl cursive::View for CodeView {
+    fn draw(&self, printer: &cursive::Printer) {
+        for (y, line) in self.lines.iter().enumerate() {
+            printer.print_styled((0, y), line.into());
+        }
+    }
+
+    fn required_size(&mut self, _constraint: cursive::XY<usize>) -> cursive::XY<usize> {
+        (self.width, self.lines.len()).into()
+    }
+}

src/viewer/utils.rs

@@ -285,18 +285,29 @@ fn print_heading<M: ManRenderer + ?Sized>(
     viewer.print_heading(indent, text.as_ref())
 }
 
+/// Link handling mode for the [`RichDecorator`].
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum LinkMode {
+    /// Annotate links with `RichAnnotation::Link`.
+    Annotate,
+    /// List links at the end of the block.
+    List,
+}
+
 /// A decorator that generates rich text.
 #[derive(Clone)]
 pub struct RichDecorator {
     link_filter: fn(&str) -> bool,
+    link_mode: LinkMode,
     ignore_next_link: bool,
     links: Vec<String>,
 }
 
 impl RichDecorator {
-    pub fn new(link_filter: fn(&str) -> bool) -> RichDecorator {
+    pub fn new(link_filter: fn(&str) -> bool, link_mode: LinkMode) -> RichDecorator {
         RichDecorator {
             link_filter,
+            link_mode,
             ignore_next_link: false,
             links: Vec::new(),
         }
@@ -311,11 +322,14 @@ impl text_renderer::TextDecorator for RichDecorator {
         if self.ignore_next_link {
             (String::new(), text_renderer::RichAnnotation::Default)
         } else {
-            self.links.push(url.to_owned());
+            let annotation = text_renderer::RichAnnotation::Link(url.to_owned());
-            (
+            match self.link_mode {
-                "[".to_owned(),
+                LinkMode::Annotate => (String::new(), annotation),
-                text_renderer::RichAnnotation::Link(url.to_owned()),
+                LinkMode::List => {
-            )
+                    self.links.push(url.to_owned());
+                    ("[".to_owned(), annotation)
+                }
+            }
         }
     }
 
@@ -323,7 +337,10 @@ impl text_renderer::TextDecorator for RichDecorator {
         if self.ignore_next_link {
             String::new()
         } else {
-            format!("][{}]", self.links.len() - 1)
+            match self.link_mode {
+                LinkMode::Annotate => String::new(),
+                LinkMode::List => format!("][{}]", self.links.len() - 1),
+            }
         }
     }
 
@@ -373,23 +390,25 @@ impl text_renderer::TextDecorator for RichDecorator {
 
     fn finalise(self) -> Vec<text_renderer::TaggedLine<text_renderer::RichAnnotation>> {
         let mut lines = Vec::new();
-        for (idx, link) in self.links.into_iter().enumerate() {
+        if self.link_mode == LinkMode::List {
-            let mut line = text_renderer::TaggedLine::new();
+            for (idx, link) in self.links.into_iter().enumerate() {
-            line.push_str(text_renderer::TaggedString {
+                let mut line = text_renderer::TaggedLine::new();
-                s: format!("[{}] ", idx),
+                line.push_str(text_renderer::TaggedString {
-                tag: text_renderer::RichAnnotation::Default,
+                    s: format!("[{}] ", idx),
-            });
+                    tag: text_renderer::RichAnnotation::Default,
-            line.push_str(text_renderer::TaggedString {
+                });
-                s: link.clone(),
+                line.push_str(text_renderer::TaggedString {
-                tag: text_renderer::RichAnnotation::Link(link),
+                    s: link.clone(),
-            });
+                    tag: text_renderer::RichAnnotation::Link(link),
-            lines.push(line);
+                });
+                lines.push(line);
+            }
         }
         lines
     }
 
     fn make_subblock_decorator(&self) -> Self {
-        RichDecorator::new(self.link_filter)
+        RichDecorator::new(self.link_filter, self.link_mode)
     }
 }