Highlight TUI content previews

Cargo.lock

@@ -2,6 +2,12 @@
 # It is not intended for manual editing.
 version = 4
 
+[[package]]
+name = "adler2"
+version = "2.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "320119579fcad9c21884f5c4861d16174d0e06250625266f50fe6898340abefa"
+
 [[package]]
 name = "aho-corasick"
 version = "1.1.4"
@@ -157,13 +163,31 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "bincode"
+version = "1.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b1f45e9417d87227c7a56d22e471c6206462cba514c7590c09aff4cf6d1ddcad"
+dependencies = [
+ "serde",
+]
+
 [[package]]
 name = "bit-set"
 version = "0.5.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0700ddab506f33b20a03b13996eccd309a48e5ff77d0d95926aa0210fb4e95f1"
 dependencies = [
- "bit-vec",
+ "bit-vec 0.6.3",
+]
+
+[[package]]
+name = "bit-set"
+version = "0.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "08807e080ed7f9d5433fa9b275196cfc35414f66a0c79d864dc51a0d825231a3"
+dependencies = [
+ "bit-vec 0.8.0",
 ]
 
 [[package]]
@@ -172,6 +196,12 @@ version = "0.6.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "349f9b6a179ed607305526ca489b34ad0a41aed5f7980fa90eb03160b69598fb"
 
+[[package]]
+name = "bit-vec"
+version = "0.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5e764a1d40d510daf35e07be9eb06e75770908c27d411ee6c92109c9840eaaf7"
+
 [[package]]
 name = "bitflags"
 version = "1.3.2"
@@ -370,6 +400,15 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "crc32fast"
+version = "1.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9481c1c90cbf2ac953f07c8d4a58aa3945c425b7185c9154d67a65e4230da511"
+dependencies = [
+ "cfg-if",
+]
+
 [[package]]
 name = "critical-section"
 version = "1.2.0"
@@ -491,6 +530,12 @@ dependencies = [
  "syn 2.0.119",
 ]
 
+[[package]]
+name = "diff"
+version = "0.1.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "56254986775e3233ffa9c4d7d3faaf6d36a2c09d30b20687e9f88bc8bafc16c8"
+
 [[package]]
 name = "digest"
 version = "0.10.7"
@@ -564,10 +609,21 @@ version = "0.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b95f7c0680e4142284cf8b22c14a476e87d61b004a3a0861872b32ef7ead40a2"
 dependencies = [
- "bit-set",
+ "bit-set 0.5.3",
  "regex",
 ]
 
+[[package]]
+name = "fancy-regex"
+version = "0.16.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "998b056554fbe42e03ae0e152895cd1a7e1002aec800fdc6635d20270260c46f"
+dependencies = [
+ "bit-set 0.8.0",
+ "regex-automata",
+ "regex-syntax",
+]
+
 [[package]]
 name = "fast-srgb8"
 version = "1.0.0"
@@ -609,6 +665,16 @@ version = "0.4.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0ce7134b9999ecaf8bcd65542e436736ef32ddca1b3e06094cb6ec5755203b80"
 
+[[package]]
+name = "flate2"
+version = "1.1.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "843fba2746e448b37e26a819579957415c8cef339bf08564fe8b7ddbd959573c"
+dependencies = [
+ "crc32fast",
+ "miniz_oxide",
+]
+
 [[package]]
 name = "fnv"
 version = "1.0.7"
@@ -689,6 +755,12 @@ version = "0.3.33"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b231ed28831efb4a61a08580c4bc233ec56bc009f4cd8f52da2c3cb97df0c109"
 
+[[package]]
+name = "futures-timer"
+version = "3.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "af43fadb8a98512d547e37b4e92e0ced13e205c061b87b4623eff01d918d6968"
+
 [[package]]
 name = "futures-util"
 version = "0.3.33"
@@ -715,6 +787,15 @@ dependencies = [
  "version_check",
 ]
 
+[[package]]
+name = "getopts"
+version = "0.2.24"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cfe4fbac503b8d1f88e6676011885f34b7174f46e59956bba534ba83abded4df"
+dependencies = [
+ "unicode-width",
+]
+
 [[package]]
 name = "getrandom"
 version = "0.2.17"
@@ -818,7 +899,9 @@ dependencies = [
  "crossterm",
  "gotcha_gitea",
  "ratatui",
+ "syntect",
  "tokio",
+ "tui-markdown",
 ]
 
 [[package]]
@@ -1121,6 +1204,15 @@ dependencies = [
  "either",
 ]
 
+[[package]]
+name = "itertools"
+version = "0.15.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8b4baf93f58d4425749ca49a51c50ebab072c5df6994d08fed93541c331481dc"
+dependencies = [
+ "either",
+]
+
 [[package]]
 name = "itoa"
 version = "1.0.18"
@@ -1241,6 +1333,12 @@ dependencies = [
  "bitflags 2.13.1",
 ]
 
+[[package]]
+name = "linked-hash-map"
+version = "0.5.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0717cef1bc8b636c6e1c1bbdefc09e6322da8a9321966e8928ef80d20f7f770f"
+
 [[package]]
 name = "linux-raw-sys"
 version = "0.12.1"
@@ -1342,6 +1440,16 @@ version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "68354c5c6bd36d73ff3feceb05efa59b6acb7626617f4962be322a825e61f79a"
 
+[[package]]
+name = "miniz_oxide"
+version = "0.8.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1fa76a2c86f704bdb222d66965fb3d63269ce38518b83cb0575fca855ebb6316"
+dependencies = [
+ "adler2",
+ "simd-adler32",
+]
+
 [[package]]
 name = "mio"
 version = "1.2.2"
@@ -1598,6 +1706,19 @@ version = "0.2.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b4596b6d070b27117e987119b4dac604f3c58cfb0b191112e24771b2faeac1a6"
 
+[[package]]
+name = "plist"
+version = "1.10.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7da1d65da6dd5d1e44199ac0f58712d241c0f439f80adea8924d832384087f85"
+dependencies = [
+ "base64",
+ "indexmap",
+ "quick-xml",
+ "serde",
+ "time",
+]
+
 [[package]]
 name = "portable-atomic"
 version = "1.14.0"
@@ -1619,6 +1740,25 @@ version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "439ee305def115ba05938db6eb1644ff94165c5ab5e9420d1c1bcedbba909391"
 
+[[package]]
+name = "pretty_assertions"
+version = "1.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3ae130e2f271fbc2ac3a40fb1d07180839cdbbe443c7a27e1e3c13c5cac0116d"
+dependencies = [
+ "diff",
+ "yansi",
+]
+
+[[package]]
+name = "proc-macro-crate"
+version = "3.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e67ba7e9b2b56446f1d419b1d807906278ffa1a658a8a5d8a39dcb1f5a78614f"
+dependencies = [
+ "toml_edit",
+]
+
 [[package]]
 name = "proc-macro2"
 version = "1.0.107"
@@ -1628,6 +1768,34 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "pulldown-cmark"
+version = "0.13.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e9f068eba8e7071c5f9511831b44f32c740d5adf574e990f946ddb53db2f314e"
+dependencies = [
+ "bitflags 2.13.1",
+ "getopts",
+ "memchr",
+ "pulldown-cmark-escape",
+ "unicase",
+]
+
+[[package]]
+name = "pulldown-cmark-escape"
+version = "0.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "007d8adb5ddab6f8e3f491ac63566a7d5002cc7ed73901f72057943fa71ae1ae"
+
+[[package]]
+name = "quick-xml"
+version = "0.41.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e660451e55124f798a69a5af3f49ccfbefbd41910eefd25caf2393e1f3473ec1"
+dependencies = [
+ "memchr",
+]
+
 [[package]]
 name = "quinn"
 version = "0.11.11"
@@ -1773,7 +1941,7 @@ dependencies = [
  "compact_str",
  "critical-section",
  "hashbrown 0.17.1",
- "itertools",
+ "itertools 0.14.0",
  "kasuari",
  "lru",
  "palette",
@@ -1838,7 +2006,7 @@ dependencies = [
  "hashbrown 0.17.1",
  "indoc",
  "instability",
- "itertools",
+ "itertools 0.14.0",
  "line-clipping",
  "ratatui-core",
  "serde",
@@ -1886,6 +2054,12 @@ version = "0.8.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d6f6ff9a378485b298a5286656da665ba74413d36db0979633275d2e708145d4"
 
+[[package]]
+name = "relative-path"
+version = "1.9.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ba39f3699c378cd8970968dcbff9c43159ea4cfbd88d43c00b22f2ef10a435d2"
+
 [[package]]
 name = "reqwest"
 version = "0.13.4"
@@ -1953,6 +2127,35 @@ dependencies = [
  "windows-sys 0.61.2",
 ]
 
+[[package]]
+name = "rstest"
+version = "0.26.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f5a3193c063baaa2a95a33f03035c8a72b83d97a54916055ba22d35ed3839d49"
+dependencies = [
+ "futures-timer",
+ "futures-util",
+ "rstest_macros",
+]
+
+[[package]]
+name = "rstest_macros"
+version = "0.26.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9c845311f0ff7951c5506121a9ad75aec44d083c31583b2ea5a30bcb0b0abba0"
+dependencies = [
+ "cfg-if",
+ "glob",
+ "proc-macro-crate",
+ "proc-macro2",
+ "quote",
+ "regex",
+ "relative-path",
+ "rustc_version",
+ "syn 2.0.119",
+ "unicode-ident",
+]
+
 [[package]]
 name = "rtoolbox"
 version = "0.0.5"
@@ -2291,6 +2494,12 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "simd-adler32"
+version = "0.3.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3a219298ac11a56ea9a6d2120044824d6f01aeb034955e7af7bc16858527deea"
+
 [[package]]
 name = "simd_cesu8"
 version = "1.2.0"
@@ -2439,6 +2648,27 @@ dependencies = [
  "syn 2.0.119",
 ]
 
+[[package]]
+name = "syntect"
+version = "5.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "656b45c05d95a5704399aeef6bd0ddec7b2b3531b7c9e900abbf7c4d2190c925"
+dependencies = [
+ "bincode",
+ "fancy-regex 0.16.2",
+ "flate2",
+ "fnv",
+ "once_cell",
+ "plist",
+ "regex-syntax",
+ "serde",
+ "serde_derive",
+ "serde_json",
+ "thiserror 2.0.19",
+ "walkdir",
+ "yaml-rust",
+]
+
 [[package]]
 name = "tempfile"
 version = "3.27.0"
@@ -2495,7 +2725,7 @@ dependencies = [
  "anyhow",
  "base64",
  "bitflags 2.13.1",
- "fancy-regex",
+ "fancy-regex 0.11.0",
  "filedescriptor",
  "finl_unicode",
  "fixedbitset",
@@ -2590,6 +2820,7 @@ dependencies = [
  "powerfmt",
  "serde_core",
  "time-core",
+ "time-macros",
 ]
 
 [[package]]
@@ -2598,6 +2829,16 @@ version = "0.1.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9e1c906769ad99c88eaa54e728060edef082f8e358ff32030cb7c7d315e81109"
 
+[[package]]
+name = "time-macros"
+version = "0.2.32"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7e689342a48d2ea927c87ea50cabf8594854bf940e9310208848d680d668ed85"
+dependencies = [
+ "num-conv",
+ "time-core",
+]
+
 [[package]]
 name = "tinystr"
 version = "0.8.3"
@@ -2697,6 +2938,18 @@ dependencies = [
  "serde_core",
 ]
 
+[[package]]
+name = "toml_edit"
+version = "0.25.13+spec-1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6975367e4d2ef766d86af01ffad14b622fecc8d4357a998fbc4deb6e9bacaf9b"
+dependencies = [
+ "indexmap",
+ "toml_datetime",
+ "toml_parser",
+ "winnow",
+]
+
 [[package]]
 name = "toml_parser"
 version = "1.1.3+spec-1.1.0"
@@ -2764,9 +3017,21 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "63e71662fa4b2a2c3a26f570f037eb95bb1f85397f3cd8076caed2f026a6d100"
 dependencies = [
  "pin-project-lite",
+ "tracing-attributes",
  "tracing-core",
 ]
 
+[[package]]
+name = "tracing-attributes"
+version = "0.1.31"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7490cfa5ec963746568740651ac6781f701c9c5ea257c58e057f3ba8cf69e8da"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.119",
+]
+
 [[package]]
 name = "tracing-core"
 version = "0.1.36"
@@ -2782,6 +3047,20 @@ version = "0.2.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e421abadd41a4225275504ea4d6566923418b7f05506fbc9c0fe86ba7396114b"
 
+[[package]]
+name = "tui-markdown"
+version = "0.3.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c6779056a6ae2d46013edb3692be1eb55d2e1d3f0d1d454042163efe1b64baca"
+dependencies = [
+ "itertools 0.15.0",
+ "pretty_assertions",
+ "pulldown-cmark",
+ "ratatui-core",
+ "rstest",
+ "tracing",
+]
+
 [[package]]
 name = "typenum"
 version = "1.20.1"
@@ -2818,7 +3097,7 @@ version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "16b380a1238663e5f8a691f9039c73e1cdae598a30e9855f541d29b08b53e9a5"
 dependencies = [
- "itertools",
+ "itertools 0.14.0",
  "unicode-segmentation",
  "unicode-width",
 ]
@@ -3373,6 +3652,21 @@ version = "0.6.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1ffae5123b2d3fc086436f8834ae3ab053a283cfac8fe0a0b8eaae044768a4c4"
 
+[[package]]
+name = "yaml-rust"
+version = "0.4.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "56c1936c4cc7a1c9ab21a1ebb602eb942ba868cbd44a99cb7cdc5892335e1c85"
+dependencies = [
+ "linked-hash-map",
+]
+
+[[package]]
+name = "yansi"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cfe53a6657fd280eaa890a3bc59152892ffa3e30101319d168b781ed6529b049"
+
 [[package]]
 name = "yoke"
 version = "0.8.3"

TESTING.md

@@ -47,9 +47,10 @@ representative repositories.
 - [ ] The five numbered panes open Home, Issues, Repos, PRs, and Milestones;
       the selected pane and row remain visibly distinct at narrow and wide
       terminal sizes.
-- [ ] `j`/`k`, arrows, `g`/`G`, Page Up/Down, Enter, Backspace, and `q` provide
+- [ ] `j`/`k`, arrows, `g`/`G`, Page Up/Down, Enter, and Backspace provide
-      mutt-style list and history navigation; `n`/`p` and scrolling past a
+      mutt-style list and history navigation; `q` exits immediately from every
-      boundary traverse paginated API results without losing history.
+      non-editor depth. `n`/`p` and scrolling past a boundary traverse
+      paginated API results without losing history.
 - [ ] Clicking a pane switches it, clicking a list row selects it,
       double-clicking opens it, and the mouse wheel scrolls the list.
 - [ ] Home activity filters cycle with `v`; activity targets route to their
@@ -57,6 +58,12 @@ representative repositories.
 - [ ] Repository favorites toggle with `*`, sort first per pane, and persist
       after relaunch. Commits switch branches with `b`; file trees, text and
       binary files, commit changes, pull changes, and per-file diffs open.
+- [ ] Source files use grammar-based syntax colors selected by filename or
+      shebang, with unknown text remaining legible. Commit and pull diffs show
+      metadata, hunks, additions, and deletions in distinct syntax colors.
+- [ ] Home activity content plus issue, pull request, milestone, and comment
+      Markdown pseudo-renders headings, emphasis, strong text, lists, links,
+      inline code, and fenced code while preserving metadata line breaks.
 - [ ] Issue and pull filters apply. Issues can be created, edited,
       closed/reopened, and deleted after confirmation; issue comments can be
       added and the current user's comments edited.

crates/tui/Cargo.toml

@@ -14,4 +14,6 @@ path = "src/main.rs"
 crossterm = "0.29"
 gotcha_gitea = { path = "../gitea" }
 ratatui = { version = "0.30", default-features = false, features = ["crossterm_0_29", "layout-cache", "macros", "underline-color"] }
+syntect = { version = "5.3", default-features = false, features = ["default-fancy"] }
 tokio.workspace = true
+tui-markdown = { version = "0.3", default-features = false }

crates/tui/src/app.rs

@@ -1324,7 +1324,7 @@ impl App {
             ),
         );
         screen.detail = format!(
-            "State: {state}\nAuthor: {}\nUpdated: {}\n\n{}\n\n[e] edit  [c] comment  [x] state  [d] delete",
+            "State: {state}  \nAuthor: {}  \nUpdated: {}\n\n{}\n\n[e] edit  [c] comment  [x] state  [d] delete",
             issue
                 .user
                 .as_ref()
@@ -1545,7 +1545,7 @@ impl App {
         screen.page = page;
         screen.has_more = details.has_more;
         screen.detail = format!(
-            "State: {}\n{} → {}\nFiles: {}  +{} -{}\n\n{}",
+            "State: {}  \n{} → {}  \nFiles: {}  +{} -{}\n\n{}",
             gotcha_gitea::pull_state(&pull),
             pull.head
                 .as_ref()
@@ -1642,7 +1642,7 @@ impl App {
         screen.page = page;
         screen.has_more = details.has_more;
         screen.detail = format!(
-            "State: {}\nDue: {}\nOpen: {}  Closed: {}\n\n{}\n\n[e] edit  [x] state  [d] delete",
+            "State: {}  \nDue: {}  \nOpen: {}  Closed: {}\n\n{}\n\n[e] edit  [x] state  [d] delete",
             milestone.state.as_deref().unwrap_or("unknown"),
             milestone.due_on.as_deref().unwrap_or("none"),
             milestone.open_issues.unwrap_or_default(),

crates/tui/src/ui.rs

@@ -1,3 +1,5 @@
+use std::{cell::RefCell, sync::LazyLock};
+
 use ratatui::{
     Frame,
     layout::{Alignment, Constraint, Direction, Layout, Rect},
@@ -5,13 +7,24 @@ use ratatui::{
     text::{Line, Span, Text},
     widgets::{Block, Borders, Clear, List, ListItem, ListState, Paragraph, Tabs, Wrap},
 };
+use syntect::{
+    easy::HighlightLines,
+    highlighting::{FontStyle, ThemeSet},
+    parsing::SyntaxSet,
+    util::LinesWithEndings,
+};
 
 use crate::{
-    app::{App, Tab},
+    app::{App, ScreenKind, Tab},
     editor::Editor,
 };
 
 const ACCENT: Color = Color::Cyan;
+static SYNTAXES: LazyLock<SyntaxSet> = LazyLock::new(SyntaxSet::load_defaults_newlines);
+static THEMES: LazyLock<ThemeSet> = LazyLock::new(ThemeSet::load_defaults);
+thread_local! {
+    static HIGHLIGHT_CACHE: RefCell<Option<(String, String, Text<'static>)>> = const { RefCell::new(None) };
+}
 
 pub fn draw(frame: &mut Frame<'_>, app: &mut App) {
     let area = frame.area();
@@ -167,25 +180,127 @@ fn lane_color(lane: usize) -> Color {
 }
 
 fn draw_detail(frame: &mut Frame<'_>, app: &App, area: Rect) {
-    let mut detail = app.screen.detail.clone();
+    let mut detail = render_screen_detail(&app.screen.kind, &app.screen.detail);
     if let Some(item) = app.screen.selected_item()
         && !item.detail.is_empty()
     {
-        if !detail.is_empty() {
+        if !detail.lines.is_empty() {
-            detail.push_str("\n\n────\n\n");
+            detail.lines.extend([
+                Line::default(),
+                Line::styled("────", Style::default().fg(Color::DarkGray)),
+                Line::default(),
+            ]);
         }
-        detail.push_str(&item.detail);
+        detail
+            .lines
+            .extend(render_item_detail(&app.screen.kind, &item.detail).lines);
     }
-    if detail.is_empty() {
+    if detail.lines.is_empty() {
-        detail = "Select an item to see details.".into();
+        detail = Text::from("Select an item to see details.");
     }
-    let paragraph = Paragraph::new(Text::from(detail))
+    let paragraph = Paragraph::new(detail)
         .block(Block::default().borders(Borders::ALL).title(" Preview "))
         .wrap(Wrap { trim: false })
         .scroll((app.screen.detail_scroll, 0));
     frame.render_widget(paragraph, area);
 }
 
+fn render_screen_detail<'a>(kind: &ScreenKind, detail: &'a str) -> Text<'a> {
+    match kind {
+        ScreenKind::File(_, path) => highlight(detail, path),
+        ScreenKind::Text(_, _) if detail.starts_with("diff --git ") => {
+            highlight(detail, "change.diff")
+        }
+        ScreenKind::Text(title, _) => highlight(detail, title),
+        ScreenKind::Issue(_, _) | ScreenKind::Pull(_, _) | ScreenKind::Milestone(_, _) => {
+            render_markdown(detail)
+        }
+        _ => Text::from(detail),
+    }
+}
+
+fn render_item_detail<'a>(kind: &ScreenKind, detail: &'a str) -> Text<'a> {
+    if detail.starts_with("diff --git ") {
+        highlight(detail, "change.diff")
+    } else if matches!(
+        kind,
+        ScreenKind::Home
+            | ScreenKind::Issue(_, _)
+            | ScreenKind::Pull(_, _)
+            | ScreenKind::Milestone(_, _)
+    ) {
+        render_markdown(detail)
+    } else {
+        Text::from(detail)
+    }
+}
+
+fn render_markdown(markdown: &str) -> Text<'_> {
+    tui_markdown::from_str(markdown)
+}
+
+fn highlight(source: &str, path: &str) -> Text<'static> {
+    HIGHLIGHT_CACHE.with_borrow_mut(|cache| {
+        if let Some((cached_path, cached_source, text)) = cache.as_ref()
+            && cached_path == path
+            && cached_source == source
+        {
+            return text.clone();
+        }
+        let text = highlight_uncached(source, path);
+        *cache = Some((path.to_owned(), source.to_owned(), text.clone()));
+        text
+    })
+}
+
+fn highlight_uncached(source: &str, path: &str) -> Text<'static> {
+    let syntax = SYNTAXES
+        .find_syntax_for_file(path)
+        .ok()
+        .flatten()
+        .or_else(|| SYNTAXES.find_syntax_by_first_line(source))
+        .unwrap_or_else(|| SYNTAXES.find_syntax_plain_text());
+    let theme = &THEMES.themes["base16-ocean.dark"];
+    let mut highlighter = HighlightLines::new(syntax, theme);
+    let lines = LinesWithEndings::from(source)
+        .map(|line| match highlighter.highlight_line(line, &SYNTAXES) {
+            Ok(ranges) => {
+                let last = ranges.len().saturating_sub(1);
+                Line::from(
+                    ranges
+                        .into_iter()
+                        .enumerate()
+                        .map(|(index, (style, text))| {
+                            let text = if index == last {
+                                text.trim_end_matches(['\r', '\n'])
+                            } else {
+                                text
+                            };
+                            let mut terminal_style = Style::default().fg(Color::Rgb(
+                                style.foreground.r,
+                                style.foreground.g,
+                                style.foreground.b,
+                            ));
+                            if style.font_style.contains(FontStyle::BOLD) {
+                                terminal_style = terminal_style.add_modifier(Modifier::BOLD);
+                            }
+                            if style.font_style.contains(FontStyle::ITALIC) {
+                                terminal_style = terminal_style.add_modifier(Modifier::ITALIC);
+                            }
+                            if style.font_style.contains(FontStyle::UNDERLINE) {
+                                terminal_style = terminal_style.add_modifier(Modifier::UNDERLINED);
+                            }
+                            Span::styled(text.to_owned(), terminal_style)
+                        })
+                        .collect::<Vec<_>>(),
+                )
+            }
+            Err(_) => Line::from(line.trim_end_matches(['\r', '\n']).to_owned()),
+        })
+        .collect::<Vec<_>>();
+    Text::from(lines)
+}
+
 fn draw_footer(frame: &mut Frame<'_>, app: &App, area: Rect) {
     let status = if let Some(status) = app.visible_status() {
         format!(
@@ -357,4 +472,55 @@ mod tests {
         assert_eq!(buffer[(4, 0)].fg, lane_color(1));
         assert_eq!(buffer[(6, 0)].fg, lane_color(2));
     }
+
+    #[test]
+    fn previews_render_markdown_source_and_diffs_with_styles() {
+        let repository = gotcha_gitea::RepositoryId {
+            owner: "owner".into(),
+            repository: "project".into(),
+        };
+        let markdown = render_item_detail(
+            &ScreenKind::Home,
+            "# Title\n\nSome *emphasis* and **strong text**.",
+        );
+        assert!(
+            markdown.lines[0]
+                .style
+                .add_modifier
+                .contains(Modifier::BOLD)
+        );
+        assert!(
+            markdown
+                .lines
+                .iter()
+                .flat_map(|line| &line.spans)
+                .any(|span| { span.style.add_modifier.contains(Modifier::ITALIC) })
+        );
+
+        let source = render_screen_detail(
+            &ScreenKind::File(repository, "main.rs".into()),
+            "fn main() { println!(\"hello\"); }\n",
+        );
+        let source_colors = source
+            .lines
+            .iter()
+            .flat_map(|line| &line.spans)
+            .filter_map(|span| span.style.fg)
+            .collect::<Vec<_>>();
+        assert!(
+            source_colors
+                .iter()
+                .any(|color| Some(color) != source_colors.first())
+        );
+
+        let diff_source = "diff --git a/main.rs b/main.rs\n@@ -1 +1 @@\n-old\n+new\n";
+        let diff = render_screen_detail(
+            &ScreenKind::Text("main.rs".into(), diff_source.into()),
+            diff_source,
+        );
+        assert_ne!(
+            diff.lines[2].spans[0].style.fg,
+            diff.lines[3].spans[0].style.fg
+        );
+    }
 }