ui: Usability improvements

src/main.rs

@@ -13,8 +13,12 @@ use regex::Regex;
 
 use vmtest::{Config, Target, Ui, VMConfig, Vmtest};
 
+const HELP_ENV_VARS: &str = r#"Environment variables:
+  VMTEST_NO_UI    Set to disable UI  [default: unset]
+"#;
+
 #[derive(Parser, Debug)]
-#[clap(version)]
+#[clap(version, disable_colored_help=true, after_help=HELP_ENV_VARS)]
 struct Args {
     /// Path to config file
     #[clap(short, long)]

src/ui.rs

@@ -1,4 +1,5 @@
 use std::cmp::min;
+use std::env;
 use std::sync::mpsc::{channel, Receiver};
 use std::thread;
 
@@ -26,9 +27,19 @@ struct Stage {
     expand: bool,
 }
 
-/// Helper to clear lines depending on whether or not a tty is attached
+/// Returns whether the "windowed" UI is enabled or not.
+/// If disabled, output is (mostly) just passed through.
+fn ui_enabled(term: &Term) -> bool {
+    if env::var_os("VMTEST_NO_UI").is_some() {
+        return false;
+    }
+
+    term.features().is_attended()
+}
+
+/// Helper to clear lines depending on whether or not UI is enabled
 fn clear_last_lines(term: &Term, n: usize) {
-    if term.features().is_attended() {
+    if ui_enabled(term) {
         term.clear_last_lines(n).unwrap();
     }
 }
@@ -68,7 +79,7 @@ impl Stage {
     /// We kinda hack this to return 1 if we're not writing to terminal.
     /// Should really find a cleaner solution.
     fn window_size(&self) -> usize {
-        if self.term.features().is_attended() {
+        if ui_enabled(&self.term) {
             min(self.lines.len(), WINDOW_LENGTH)
         } else {
             min(self.lines.len(), 1)
@@ -91,25 +102,38 @@ impl Stage {
 
         // Compute new visible lines
         let trimmed_line = line.trim_end();
-        let stripped_line = strip_ansi_codes(trimmed_line);
-        let styled_line = match &custom {
-            Some(s) => s.apply_to(stripped_line),
-            None => style(stripped_line).dim(),
+        let styled_line = if ui_enabled(&self.term) {
+            // If UI is enabled, we do custom window with our own styling.
+            // Therefore, we need to strip away any existing formatting.
+            let stripped = strip_ansi_codes(trimmed_line);
+
+            // Clip output to fit in terminal.
+            //
+            // Note this _does_not_ handle characters that expand to multiple columns,
+            // like tabs or other fancy unicode. This is known to corrupt UI visuals. There
+            // is no real solution to this without doing a mini terminal emulator AFAIK.
+            // The workaround is to set VMTEST_NO_UI.
+            let width = self.term.size_checked().map(|(_, w)| w).unwrap_or(u16::MAX);
+            let clipped = truncate_str(&stripped, width as usize, "...");
+
+            // Apply styling
+            let styled = match &custom {
+                Some(s) => s.apply_to(clipped),
+                None => style(clipped).dim(),
+            };
+
+            styled.to_string()
+        } else {
+            // If output is not attended, we do pass through
+            trimmed_line.to_string()
         };
-        self.lines.push(styled_line.to_string());
+        self.lines.push(styled_line);
         // Unwrap should never fail b/c we're sizing with `min()`
         let window = self.lines.windows(self.window_size()).last().unwrap();
 
-        // Get terminal width, if any
-        let width = match self.term.size_checked() {
-            Some((_, w)) => w,
-            _ => u16::MAX,
-        };
-
         // Print visible lines
         for line in window {
-            let clipped = truncate_str(line, width as usize - 3, "...");
-            self.term.write_line(&format!("{}", clipped)).unwrap();
+            self.term.write_line(line).unwrap();
         }
     }
 
@@ -125,7 +149,7 @@ impl Stage {
 impl Drop for Stage {
     fn drop(&mut self) {
         clear_last_lines(&self.term, self.window_size());
-        if self.expand && self.term.features().is_attended() {
+        if self.expand && ui_enabled(&self.term) {
             for line in &self.lines {
                 self.term
                     .write_line(line)