The editor

A code editor bound to the strategy source, compiled on every change through the same path Run uses, with the verdict as a chip, an inline banner naming the line, and an amber dot while the buffer has drifted from its last save.

crates/vike-studio/src/editor.rs's EditorPane is one widget — egui_code_editor's CodeEditor bound to the strategy source string — and the pieces around it are what make it an editor rather than a text box: a compile status, an error banner, a save baseline, and the workspace that restores it.

What you see

The editor renders in the Gruvbox colour theme with line numbers at a 13-pixel font, and it fills whatever height the panel leaves. rows_for_height is the sizing rule and its doc carries the measurement: the widget's real row pitch is about font_size × 1.16, measured from a screenshot capture — 45 rows over roughly 680 logical pixels at font 13 — after a first-guess factor of 1.5 left a dead gap of about a fifth of the panel. The result is clamped to 8..=400 rows so a degenerate height never yields a zero-row editor.

Highlighting is Rust's. crates/vike-studio/src/syntax.rs's header states the reason: Rhai's surface — fn, let, const, if/else, while, return, // comments, strings, numbers — is a subset of Rust's, so the built-in Rust syntax highlights it well; a bespoke Rhai syntax that colours the host verbs specially is a documented follow-up.

A fresh Studio opens on DEFAULT_SCRIPT, an SMA crossover: FAST = 5, SLOW = 20, QTY = 1.0, long above and short below, reaching the target through market(...) by the delta from position(). On later launches the workspace restores the last buffer instead — unless that buffer was empty, in which case the starter script is kept rather than the editor blanked (saved and workspace).

The compile status

compile_status compiles the buffer as a RhaiStrategy — the same compile path run_slice uses — and collapses the outcome to Ok/Err(message). Rhai has no notion of warnings, so this is a strict green/red split. The shell recompiles in StudioState::poll only when the source has drifted since the last compile: a single compile costs milliseconds, but compiling every frame regardless of keystrokes would still be wasteful. The restored script is compiled eagerly at construction, so the first frame never shows a stale status.

The verdict has two renderings. The chip beside the "Editor" title reads ● compiles in green, or ● error · line N in red — ● error when no line is recoverable — with the full message on hover either way. Under the header — above the editor, not below it, so the editor's row estimate can never push it off the panel bottom — a failing compile also gets an inline banner: ✗ line N · message, or ✗ message when no line is recoverable.

Where the line number comes from

error_line parses it out of the message text. vike_script::ScriptError is a stringified rhai error with no structured position to read, and the parser's doc records the empirical fact it relies on: verified against rhai 1.25.1, both parse errors and top-level runtime errors end with a (line N, position M) suffix. It never assumes the suffix is present — a message without one, or a malformed one, yields None and the banner shows the message alone. format_compile_error drops the redundant suffix from the body once the prefix already carries the line.

Saving, and the amber dot

StudioState::saved_source is the buffer as of the last Save, Load or template load; while editor.source differs from it, an amber ● unsaved chip sits beside the compile chip with the hover "Unsaved changes — Ctrl+S saves to the Saved list". Ctrl+S snapshots the buffer under the name in the Saved pane's box. With an empty box it re-saves under the last saved name, falling back to untitled only when the session has never saved — the shell's comment records the misfiling this replaced: save momo-1, keep editing, Ctrl+S again, and the edits landed under untitled while momo-1 kept the stale code. Loading a saved entry or a template re-baselines the dot.

The buffer is also part of the workspace snapshot, written to disk once per drift rather than once per frame, so the editor reopens where you left it.

Collapsing

The ◀ button collapses the editor to a 28-pixel rail with a ▶ to expand it. The collapsed rail is a different panel from the expanded editor on purpose: egui persists panel width by id, and sharing one would store the 28-pixel width and reopen the editor as a minimum-width sliver instead of at the width you dragged.

What the buffer becomes

When the Strategy tool says "Rhai script", the toolbar chip reads 🧩 rhai and every Run, Sweep and Walk-Forward compiles this buffer; a sweep compiles it once per grid point with that point's param() overrides bound (crates/vike-studio-core/src/run.rs's build_strategy_with). The language, the order verbs a script may call, and the resource ceilings the engine enforces are the scripting tree's: writing a strategy, the order vocabulary, limits.