Add live preview to theme picker (#1798)

* Add theme picker with live preview

* Add live theme preview to :theme command

* cargo fmt

* Fix clippy warnings

* Remove picker variant

* Remove unused import

* Cleanup

* Change current_theme to last_theme

* Fix accidental comment flash deletion

* Typo

* Remove theme cache

* Add some comments

* Refactor some theme handling

TIL flatmap on Option is called  and_then

* Remove unnecessary renames

* Constrain last_theme theme preview lifecycle

* Switch to bitflag implementation

* Better handling of last_theme

* Sort theme names

* Better memory juggling

* Missed a branch

* Remove name from theme, switch bitand to &

* cargo fmt

* Update helix-view/src/editor.rs

* Switch boolean to enum

* Remove bitflag impl

* cargo fmt

* Remove un-needed type arg

* cargo fmt

helix-term/src/application.rs

@@ -108,13 +108,7 @@ impl Application {
                     .ok()
                     .filter(|theme| (true_color || theme.is_16_color()))
             })
-            .unwrap_or_else(|| {
+            .unwrap_or_else(|| theme_loader.default_theme(true_color));
-                if true_color {
-                    theme_loader.default()
-                } else {
-                    theme_loader.base16_default()
-                }
-            });
 
         let syn_loader_conf = user_syntax_loader().unwrap_or_else(|err| {
             eprintln!("Bad language config: {}", err);
@@ -373,13 +367,7 @@ impl Application {
                     })
                     .ok()
                     .filter(|theme| (true_color || theme.is_16_color()))
-                    .unwrap_or_else(|| {
+                    .unwrap_or_else(|| self.theme_loader.default_theme(true_color)),
-                        if true_color {
-                            self.theme_loader.default()
-                        } else {
-                            self.theme_loader.base16_default()
-                        }
-                    }),
             );
         }
 

helix-term/src/commands/typed.rs

@@ -15,11 +15,11 @@ pub struct TypableCommand {
     pub completer: Option<Completer>,
 }
 
-fn quit(
+fn quit(cx: &mut compositor::Context, args: &[Cow<str>], event: PromptEvent) -> anyhow::Result<()> {
-    cx: &mut compositor::Context,
+    if event != PromptEvent::Validate {
-    args: &[Cow<str>],
+        return Ok(());
-    _event: PromptEvent,
+    }
-) -> anyhow::Result<()> {
+
     ensure!(args.is_empty(), ":quit takes no arguments");
 
     // last view and we have unsaved changes
@@ -35,8 +35,12 @@ fn quit(
 fn force_quit(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     ensure!(args.is_empty(), ":quit! takes no arguments");
 
     cx.editor.close(view!(cx.editor).id);
@@ -44,11 +48,11 @@ fn force_quit(
     Ok(())
 }
 
-fn open(
+fn open(cx: &mut compositor::Context, args: &[Cow<str>], event: PromptEvent) -> anyhow::Result<()> {
-    cx: &mut compositor::Context,
+    if event != PromptEvent::Validate {
-    args: &[Cow<str>],
+        return Ok(());
-    _event: PromptEvent,
+    }
-) -> anyhow::Result<()> {
+
     ensure!(!args.is_empty(), "wrong argument count");
     for arg in args {
         let (path, pos) = args::parse_file(arg);
@@ -114,8 +118,12 @@ fn buffer_gather_paths_impl(editor: &mut Editor, args: &[Cow<str>]) -> Vec<Docum
 fn buffer_close(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     let document_ids = buffer_gather_paths_impl(cx.editor, args);
     buffer_close_by_ids_impl(cx.editor, &document_ids, false)
 }
@@ -123,8 +131,12 @@ fn buffer_close(
 fn force_buffer_close(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     let document_ids = buffer_gather_paths_impl(cx.editor, args);
     buffer_close_by_ids_impl(cx.editor, &document_ids, true)
 }
@@ -141,8 +153,12 @@ fn buffer_gather_others_impl(editor: &mut Editor) -> Vec<DocumentId> {
 fn buffer_close_others(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     let document_ids = buffer_gather_others_impl(cx.editor);
     buffer_close_by_ids_impl(cx.editor, &document_ids, false)
 }
@@ -150,8 +166,12 @@ fn buffer_close_others(
 fn force_buffer_close_others(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     let document_ids = buffer_gather_others_impl(cx.editor);
     buffer_close_by_ids_impl(cx.editor, &document_ids, true)
 }
@@ -163,8 +183,12 @@ fn buffer_gather_all_impl(editor: &mut Editor) -> Vec<DocumentId> {
 fn buffer_close_all(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     let document_ids = buffer_gather_all_impl(cx.editor);
     buffer_close_by_ids_impl(cx.editor, &document_ids, false)
 }
@@ -172,8 +196,12 @@ fn buffer_close_all(
 fn force_buffer_close_all(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     let document_ids = buffer_gather_all_impl(cx.editor);
     buffer_close_by_ids_impl(cx.editor, &document_ids, true)
 }
@@ -181,8 +209,12 @@ fn force_buffer_close_all(
 fn buffer_next(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     goto_buffer(cx.editor, Direction::Forward);
     Ok(())
 }
@@ -190,8 +222,12 @@ fn buffer_next(
 fn buffer_previous(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     goto_buffer(cx.editor, Direction::Backward);
     Ok(())
 }
@@ -242,24 +278,36 @@ fn write_impl(
 fn write(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     write_impl(cx, args.first(), false)
 }
 
 fn force_write(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     write_impl(cx, args.first(), true)
 }
 
 fn new_file(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     cx.editor.new_file(Action::Replace);
 
     Ok(())
@@ -268,8 +316,12 @@ fn new_file(
 fn format(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     let doc = doc!(cx.editor);
     if let Some(format) = doc.format() {
         let callback =
@@ -282,8 +334,12 @@ fn format(
 fn set_indent_style(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     use IndentStyle::*;
 
     // If no argument, report current indent style.
@@ -321,8 +377,12 @@ fn set_indent_style(
 fn set_line_ending(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     use LineEnding::*;
 
     // If no argument, report current line ending setting.
@@ -391,8 +451,12 @@ fn set_line_ending(
 fn earlier(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     let uk = args.join(" ").parse::<UndoKind>().map_err(|s| anyhow!(s))?;
 
     let (view, doc) = current!(cx.editor);
@@ -407,8 +471,12 @@ fn earlier(
 fn later(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     let uk = args.join(" ").parse::<UndoKind>().map_err(|s| anyhow!(s))?;
     let (view, doc) = current!(cx.editor);
     let success = doc.later(view.id, uk);
@@ -424,6 +492,10 @@ fn write_quit(
     args: &[Cow<str>],
     event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     write_impl(cx, args.first(), false)?;
     helix_lsp::block_on(cx.jobs.finish())?;
     quit(cx, &[], event)
@@ -434,6 +506,10 @@ fn force_write_quit(
     args: &[Cow<str>],
     event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     write_impl(cx, args.first(), true)?;
     force_quit(cx, &[], event)
 }
@@ -463,10 +539,14 @@ pub(super) fn buffers_remaining_impl(editor: &mut Editor) -> anyhow::Result<()>
 fn write_all_impl(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
     quit: bool,
     force: bool,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     let mut errors = String::new();
     let auto_format = cx.editor.config().auto_format;
     let jobs = &mut cx.jobs;
@@ -520,6 +600,10 @@ fn write_all(
     args: &[Cow<str>],
     event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     write_all_impl(cx, args, event, false, false)
 }
 
@@ -528,6 +612,10 @@ fn write_all_quit(
     args: &[Cow<str>],
     event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     write_all_impl(cx, args, event, true, false)
 }
 
@@ -536,6 +624,10 @@ fn force_write_all_quit(
     args: &[Cow<str>],
     event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     write_all_impl(cx, args, event, true, true)
 }
 
@@ -556,24 +648,36 @@ fn quit_all_impl(editor: &mut Editor, force: bool) -> anyhow::Result<()> {
 fn quit_all(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     quit_all_impl(cx.editor, false)
 }
 
 fn force_quit_all(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     quit_all_impl(cx.editor, true)
 }
 
 fn cquit(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     let exit_code = args
         .first()
         .and_then(|code| code.parse::<i32>().ok())
@@ -586,8 +690,12 @@ fn cquit(
 fn force_cquit(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     let exit_code = args
         .first()
         .and_then(|code| code.parse::<i32>().ok())
@@ -600,35 +708,61 @@ fn force_cquit(
 fn theme(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
-    let theme = args.first().context("Theme not provided")?;
+    let true_color = cx.editor.config.load().true_color || crate::true_color();
+    match event {
+        PromptEvent::Abort => {
+            cx.editor.unset_theme_preview();
+        }
+        PromptEvent::Update => {
+            if let Some(theme_name) = args.first() {
+                if let Ok(theme) = cx.editor.theme_loader.load(theme_name) {
+                    if !(true_color || theme.is_16_color()) {
+                        bail!("Unsupported theme: theme requires true color support");
+                    }
+                    cx.editor.set_theme_preview(theme);
+                };
+            };
+        }
+        PromptEvent::Validate => {
+            let theme_name = args.first().with_context(|| "Theme name not provided")?;
             let theme = cx
                 .editor
                 .theme_loader
-        .load(theme)
+                .load(theme_name)
-        .with_context(|| format!("Failed setting theme {}", theme))?;
+                .with_context(|| "Theme does not exist")?;
-    let true_color = cx.editor.config().true_color || crate::true_color();
             if !(true_color || theme.is_16_color()) {
                 bail!("Unsupported theme: theme requires true color support");
             }
             cx.editor.set_theme(theme);
+        }
+    };
+
     Ok(())
 }
 
 fn yank_main_selection_to_clipboard(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     yank_main_selection_to_clipboard_impl(cx.editor, ClipboardType::Clipboard)
 }
 
 fn yank_joined_to_clipboard(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     let doc = doc!(cx.editor);
     let default_sep = Cow::Borrowed(doc.line_ending.as_str());
     let separator = args.first().unwrap_or(&default_sep);
@@ -638,16 +772,24 @@ fn yank_joined_to_clipboard(
 fn yank_main_selection_to_primary_clipboard(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     yank_main_selection_to_clipboard_impl(cx.editor, ClipboardType::Selection)
 }
 
 fn yank_joined_to_primary_clipboard(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     let doc = doc!(cx.editor);
     let default_sep = Cow::Borrowed(doc.line_ending.as_str());
     let separator = args.first().unwrap_or(&default_sep);
@@ -657,32 +799,48 @@ fn yank_joined_to_primary_clipboard(
 fn paste_clipboard_after(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     paste_clipboard_impl(cx.editor, Paste::After, ClipboardType::Clipboard, 1)
 }
 
 fn paste_clipboard_before(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     paste_clipboard_impl(cx.editor, Paste::Before, ClipboardType::Clipboard, 1)
 }
 
 fn paste_primary_clipboard_after(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     paste_clipboard_impl(cx.editor, Paste::After, ClipboardType::Selection, 1)
 }
 
 fn paste_primary_clipboard_before(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     paste_clipboard_impl(cx.editor, Paste::Before, ClipboardType::Selection, 1)
 }
 
@@ -710,24 +868,36 @@ fn replace_selections_with_clipboard_impl(
 fn replace_selections_with_clipboard(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     replace_selections_with_clipboard_impl(cx, ClipboardType::Clipboard)
 }
 
 fn replace_selections_with_primary_clipboard(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     replace_selections_with_clipboard_impl(cx, ClipboardType::Selection)
 }
 
 fn show_clipboard_provider(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     cx.editor
         .set_status(cx.editor.clipboard_provider.name().to_string());
     Ok(())
@@ -736,8 +906,12 @@ fn show_clipboard_provider(
 fn change_current_directory(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     let dir = helix_core::path::expand_tilde(
         args.first()
             .context("target directory not provided")?
@@ -760,8 +934,12 @@ fn change_current_directory(
 fn show_current_directory(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     let cwd = std::env::current_dir().context("Couldn't get the new working directory")?;
     cx.editor
         .set_status(format!("Current working directory is {}", cwd.display()));
@@ -772,8 +950,12 @@ fn show_current_directory(
 fn set_encoding(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     let doc = doc_mut!(cx.editor);
     if let Some(label) = args.first() {
         doc.set_encoding(label)
@@ -788,8 +970,12 @@ fn set_encoding(
 fn reload(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     let scrolloff = cx.editor.config().scrolloff;
     let (view, doc) = current!(cx.editor);
     doc.reload(view.id).map(|_| {
@@ -800,8 +986,12 @@ fn reload(
 fn tree_sitter_scopes(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     let (view, doc) = current!(cx.editor);
     let text = doc.text().slice(..);
 
@@ -814,8 +1004,12 @@ fn tree_sitter_scopes(
 fn vsplit(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     let id = view!(cx.editor).doc;
 
     if args.is_empty() {
@@ -833,8 +1027,12 @@ fn vsplit(
 fn hsplit(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     let id = view!(cx.editor).doc;
 
     if args.is_empty() {
@@ -852,8 +1050,12 @@ fn hsplit(
 fn vsplit_new(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     cx.editor.new_file(Action::VerticalSplit);
 
     Ok(())
@@ -862,8 +1064,12 @@ fn vsplit_new(
 fn hsplit_new(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     cx.editor.new_file(Action::HorizontalSplit);
 
     Ok(())
@@ -872,8 +1078,12 @@ fn hsplit_new(
 fn debug_eval(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     if let Some(debugger) = cx.editor.debugger.as_mut() {
         let (frame, thread_id) = match (debugger.active_frame, debugger.thread_id) {
             (Some(frame), Some(thread_id)) => (frame, thread_id),
@@ -894,8 +1104,12 @@ fn debug_eval(
 fn debug_start(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     let mut args = args.to_owned();
     let name = match args.len() {
         0 => None,
@@ -907,8 +1121,12 @@ fn debug_start(
 fn debug_remote(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     let mut args = args.to_owned();
     let address = match args.len() {
         0 => None,
@@ -924,8 +1142,12 @@ fn debug_remote(
 fn tutor(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     let path = helix_loader::runtime_dir().join("tutor.txt");
     cx.editor.open(&path, Action::Replace)?;
     // Unset path to prevent accidentally saving to the original tutor file.
@@ -936,8 +1158,12 @@ fn tutor(
 pub(super) fn goto_line_number(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     ensure!(!args.is_empty(), "Line number required");
 
     let line = args[0].parse::<usize>()?;
@@ -954,8 +1180,12 @@ pub(super) fn goto_line_number(
 fn get_option(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     if args.len() != 1 {
         anyhow::bail!("Bad arguments. Usage: `:get key`");
     }
@@ -976,8 +1206,12 @@ fn get_option(
 fn set_option(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     if args.len() != 2 {
         anyhow::bail!("Bad arguments. Usage: `:set key field`");
     }
@@ -1009,8 +1243,12 @@ fn set_option(
 fn language(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     if args.len() != 1 {
         anyhow::bail!("Bad arguments. Usage: `:set-language language`");
     }
@@ -1023,19 +1261,23 @@ fn language(
     Ok(())
 }
 
-fn sort(
+fn sort(cx: &mut compositor::Context, args: &[Cow<str>], event: PromptEvent) -> anyhow::Result<()> {
-    cx: &mut compositor::Context,
+    if event != PromptEvent::Validate {
-    args: &[Cow<str>],
+        return Ok(());
-    _event: PromptEvent,
+    }
-) -> anyhow::Result<()> {
+
     sort_impl(cx, args, false)
 }
 
 fn sort_reverse(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     sort_impl(cx, args, true)
 }
 
@@ -1076,8 +1318,12 @@ fn sort_impl(
 fn reflow(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     let (view, doc) = current!(cx.editor);
 
     const DEFAULT_MAX_LEN: usize = 79;
@@ -1115,8 +1361,12 @@ fn reflow(
 fn tree_sitter_subtree(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     let (view, doc) = current!(cx.editor);
 
     if let Some(syntax) = doc.syntax() {
@@ -1151,8 +1401,12 @@ fn tree_sitter_subtree(
 fn open_config(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     cx.editor
         .open(&helix_loader::config_file(), Action::Replace)?;
     Ok(())
@@ -1161,8 +1415,12 @@ fn open_config(
 fn open_log(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     cx.editor.open(&helix_loader::log_file(), Action::Replace)?;
     Ok(())
 }
@@ -1170,8 +1428,12 @@ fn open_log(
 fn refresh_config(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     cx.editor.config_events.0.send(ConfigEvent::Refresh)?;
     Ok(())
 }
@@ -1179,8 +1441,12 @@ fn refresh_config(
 fn append_output(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     ensure!(!args.is_empty(), "Shell command required");
     shell(cx, &args.join(" "), &ShellBehavior::Append);
     Ok(())
@@ -1189,18 +1455,22 @@ fn append_output(
 fn insert_output(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     ensure!(!args.is_empty(), "Shell command required");
     shell(cx, &args.join(" "), &ShellBehavior::Insert);
     Ok(())
 }
 
-fn pipe(
+fn pipe(cx: &mut compositor::Context, args: &[Cow<str>], event: PromptEvent) -> anyhow::Result<()> {
-    cx: &mut compositor::Context,
+    if event != PromptEvent::Validate {
-    args: &[Cow<str>],
+        return Ok(());
-    _event: PromptEvent,
+    }
-) -> anyhow::Result<()> {
+
     ensure!(!args.is_empty(), "Shell command required");
     shell(cx, &args.join(" "), &ShellBehavior::Replace);
     Ok(())
@@ -1209,8 +1479,12 @@ fn pipe(
 fn run_shell_command(
     cx: &mut compositor::Context,
     args: &[Cow<str>],
-    _event: PromptEvent,
+    event: PromptEvent,
 ) -> anyhow::Result<()> {
+    if event != PromptEvent::Validate {
+        return Ok(());
+    }
+
     let shell = &cx.editor.config().shell;
     let (output, success) = shell_impl(shell, &args.join(" "), None)?;
     if success {
@@ -1787,10 +2061,6 @@ pub fn command_mode(cx: &mut Context) {
             }
         }, // completion
         move |cx: &mut compositor::Context, input: &str, event: PromptEvent| {
-            if event != PromptEvent::Validate {
-                return;
-            }
-
             let parts = input.split_whitespace().collect::<Vec<&str>>();
             if parts.is_empty() {
                 return;
@@ -1811,10 +2081,10 @@ pub fn command_mode(cx: &mut Context) {
                 if let Err(e) = (cmd.fun)(cx, &args[1..], event) {
                     cx.editor.set_error(format!("{}", e));
                 }
-            } else {
+            } else if event == PromptEvent::Validate {
                 cx.editor
                     .set_error(format!("no such command: '{}'", parts[0]));
-            };
+            }
         },
     );
     prompt.doc_fn = Box::new(|input: &str| {

helix-term/src/ui/mod.rs

@@ -237,6 +237,7 @@ pub mod completers {
         ));
         names.push("default".into());
         names.push("base16_default".into());
+        names.sort();
 
         let mut names: Vec<_> = names
             .into_iter()

helix-term/src/ui/picker.rs

@@ -490,7 +490,7 @@ impl<T: Item + 'static> Component for Picker<T> {
             _ => return EventResult::Ignored(None),
         };
 
-        let close_fn = EventResult::Consumed(Some(Box::new(|compositor: &mut Compositor, _| {
+        let close_fn = EventResult::Consumed(Some(Box::new(|compositor: &mut Compositor, _cx| {
             // remove the layer
             compositor.last_picker = compositor.pop();
         })));

helix-view/src/editor.rs

@@ -464,7 +464,6 @@ pub struct Editor {
     pub registers: Registers,
     pub macro_recording: Option<(char, Vec<KeyEvent>)>,
     pub macro_replaying: Vec<char>,
-    pub theme: Theme,
     pub language_servers: helix_lsp::Registry,
     pub diagnostics: BTreeMap<lsp::Url, Vec<lsp::Diagnostic>>,
 
@@ -476,6 +475,12 @@ pub struct Editor {
 
     pub syn_loader: Arc<syntax::Loader>,
     pub theme_loader: Arc<theme::Loader>,
+    /// last_theme is used for theme previews. We store the current theme here,
+    /// and if previewing is cancelled, we can return to it.
+    pub last_theme: Option<Theme>,
+    /// The currently applied editor theme. While previewing a theme, the previewed theme
+    /// is set here.
+    pub theme: Theme,
 
     pub status_msg: Option<(Cow<'static, str>, Severity)>,
     pub autoinfo: Option<Info>,
@@ -500,6 +505,11 @@ pub enum ConfigEvent {
     Update(Box<Config>),
 }
 
+enum ThemeAction {
+    Set,
+    Preview,
+}
+
 #[derive(Debug, Clone)]
 pub struct CompleteAction {
     pub trigger_offset: usize,
@@ -544,6 +554,7 @@ impl Editor {
             breakpoints: HashMap::new(),
             syn_loader,
             theme_loader,
+            last_theme: None,
             registers: Registers::default(),
             clipboard_provider: get_clipboard_provider(),
             status_msg: None,
@@ -613,7 +624,22 @@ impl Editor {
             .unwrap_or(false)
     }
 
+    pub fn unset_theme_preview(&mut self) {
+        if let Some(last_theme) = self.last_theme.take() {
+            self.set_theme(last_theme);
+        }
+        // None likely occurs when the user types ":theme" and then exits before previewing
+    }
+
+    pub fn set_theme_preview(&mut self, theme: Theme) {
+        self.set_theme_impl(theme, ThemeAction::Preview);
+    }
+
     pub fn set_theme(&mut self, theme: Theme) {
+        self.set_theme_impl(theme, ThemeAction::Set);
+    }
+
+    fn set_theme_impl(&mut self, theme: Theme, preview: ThemeAction) {
         // `ui.selection` is the only scope required to be able to render a theme.
         if theme.find_scope_index("ui.selection").is_none() {
             self.set_error("Invalid theme: `ui.selection` required");
@@ -623,7 +649,18 @@ impl Editor {
         let scopes = theme.scopes();
         self.syn_loader.set_scopes(scopes.to_vec());
 
+        match preview {
+            ThemeAction::Preview => {
+                let last_theme = std::mem::replace(&mut self.theme, theme);
+                // only insert on first preview: this will be the last theme the user has saved
+                self.last_theme.get_or_insert(last_theme);
+            }
+            ThemeAction::Set => {
+                self.last_theme = None;
                 self.theme = theme;
+            }
+        }
+
         self._refresh();
     }
 

helix-view/src/theme.rs

@@ -77,6 +77,14 @@ impl Loader {
         names
     }
 
+    pub fn default_theme(&self, true_color: bool) -> Theme {
+        if true_color {
+            self.default()
+        } else {
+            self.base16_default()
+        }
+    }
+
     /// Returns the default theme
     pub fn default(&self) -> Theme {
         DEFAULT_THEME.clone()