photocraft/docs/ui-design.md

# UI design system

## Themes

| Theme | Intent |
|---|---|
| Pro | Photoshop-style Spectrum dark: flat charcoal panels (#323232), dark tab strips, Spectrum blue accent (#378ef0), pill buttons, checkboxes, compact 12 px type |
| Pro Medium | Photoshop-style medium-gray panels and a dark canvas |
| Studio | Dark studio style: near-black, rounded cards, pill tabs, violet accent, toggles |
| Studio Light | Studio on light surfaces |
| Classic | Windows-2000 bevels, square corners, navy selection |
| Adwaita | GNOME's libadwaita light palette on the Studio layout: white header bar and cards on a grey sidebar, GNOME blue accent (#3584e4), 6 / 9 / 12 px radii, grey (not red) close button |
| Adwaita Dark | The libadwaita dark palette on the same layout |
| Solarized Dark | Ethan Schoonover's Solarized palette: base03 canvas, base02 panels, base0 text, Solarized blue accent |

Edit → Preferences → Interface shows an Appearance Mode selector (Sync with system, Dark, Light) above separate light and dark theme cards with PhotoCraft editor previews and radio choices. Auto is opt-in and follows the operating system while the app is running. On Linux it reads the desktop portal once and then listens for its `SettingChanged` signal (no polling, and the UI repaints only when the value changes); `gsettings` runs at most once at start-up, by absolute path, when the portal gives no answer. A missing system appearance falls back to Dark. New installs keep Photoshop's default: Dark mode with Pro Medium (Studio Light is the saved light theme). Existing saved single-theme preferences migrate to a fixed Dark or Light mode with their chosen theme. The header appearance button cycles Auto → Light → Dark; its icon shows a monitor, moon or sun for the selected mode. Window → Theme and `ui.set {"theme":"classic"}` select a theme and fix the mode to its light or dark family.

Window → Theme and macOS PhotoCraft → Appearance also offer Sync with system. Its checkmark follows the saved Auto mode rather than the displayed palette; choosing a manual theme selects its fixed appearance mode.

The toolbar's foreground and background colour chips follow the `Tokens::round_chips` flag. Pro and Classic leave it off and draw Photoshop's overlapping squares with Default Colors and Switch Colors above them. Studio, Studio Light, Solarized Dark, Adwaita and Adwaita Dark (the Studio-layout themes) turn it on and draw large round chips with a curved Switch Colors arrow centred right under them, its heads touching the chips: stacked vertically in one tool column, with Default Colors at their top-right, and side by side in two tool columns, with Default Colors at the toolbar's left edge. Another non-Pro theme can opt in by setting the flag.

## Rules

- **Colours and radii come from tokens.** Read them with `Tokens::get(ctx)`; never hard-code a colour in a widget.
- **Shared widgets live in `widgets.rs`:** `card` (panel group; Pro renders a Photoshop tab strip), `value_field`, `slider`/`slider_row`, `toggle`/`checkbox`, `primary_button`/`secondary_button`, `dropdown` (with a chevron icon), `hairline`/`vline`.
- **Icons:** Lucide SVGs in `assets/icons` (ISC licence), embedded via `icon_data.rs`. Regenerate that file when you add icons.
- **Fonts:** Inter (UI) and JetBrains Mono (numbers), both OFL. Named families `medium` and `semibold` are available via `theme::medium()` and `theme::semibold()`.
- **Photoshop layout grammar (Pro):**
  - Essentials dock order: Color | Swatches, then Properties | Adjustments, then Layers | Channels | Paths (Layers fills the remaining height).
  - Options-bar labels end with a colon ("Size:").
  - Document tabs read "name @ 12.5% (RGB/8)".
  - Toolbar tool groups carry a corner triangle.
- **Verify every visual change** with `ui.screenshot`, at several window sizes and in every theme.

## Adding icons

```sh
curl -sfL -o assets/icons/<name>.svg https://raw.githubusercontent.com/lucide-icons/lucide/main/icons/<name>.svg
# regenerate the embedded table
{ printf '%s\n' '//! Lucide icons (ISC licence), embedded and tinted at runtime.' '' 'pub static ICONS: &[(&str, &[u8])] = &['; \
  for f in assets/icons/*.svg; do n=$(basename $f .svg); echo "    (\"$n\", include_bytes!(\"../../../assets/icons/$n.svg\")),"; done; echo '];'; } \
  > crates/ui-egui/src/icon_data.rs
```

## Interaction models (match Photoshop CC)

| Feature | Module | Behaviour |
|---|---|---|
| Type tool | `type_tool.rs` | Click: point text with the placeholder "Lorem Ipsum" selected. Drag: paragraph box. Inline caret and selection drawn from the text engine layout. ⌥/⌘ word and line navigation, ↩ newline, ⌘↩ or Esc commits, a click outside commits. One history step per session (`coalesce`). A new layer is named after its text; an empty one is deleted. |
| Free Transform | `transform_tool.rs` | ⌘T. Corners and edges scale proportionally (⇧ frees them: an edge then stretches one axis); ⌥ scales about the reference point; ⌘-corner distorts; dragging outside rotates (⇧ snaps to 15°); dragging inside moves. Preview = document without the moving pixels + a textured 24×24 mesh. ↩ or a double-click commits via `edit.transform {rect, quad}`. |
| Quick layer pick | `quick_pick.rs` | macOS: ⌘⌥⌃-click with any tool selects the topmost visible layer with pixels under the pointer (`layer.pickAt`) without switching tools; the drag and release are swallowed. Windows/Linux have no third modifier distinct from the ⌃⌥ brush resize, so the gesture is a no-op there (use the Move tool's Auto-Select). A failed pick is a status-bar error. |
| Layers rows | `panels.rs` | Double-click: on the name renames in place; on the Background makes it a normal layer; on an adjustment or fill thumbnail opens its Properties; on a Smart Object thumbnail opens its contents (Edit Contents); anywhere else on the row opens Layer Style. |
| Layer masks | `panels.rs` | Clicking the mask thumbnail targets the mask (corner-bracket frame; the tab reads "Layer, Layer Mask/8"). Brush, eraser (paints background colour), gradient, bucket and moving the selected pixels (⌘-drag, `select.float`; the hole takes the background colour) then send `"target": "mask"`. Adjustment and fill layers target their mask automatically. |
| Levels / Curves | `tone.rs` | Histogram of the image *below* the adjustment. Curves: click to add a point, drag out to delete. Every change is a coalesced `layer.setAdjustment`, so one drag = one undo step and the canvas updates at full resolution on the GPU. |

While editing type, hold Ctrl (Windows/Linux) or Command (macOS) for an oriented transform
frame. Drag inside to move, a corner to scale (Shift keeps proportions; Alt/Option scales about
the reference point), a middle handle to skew, or just outside the frame to rotate (Shift snaps
to 15°). Drag the reference point to move the rotation centre. These Type gestures follow
[Adobe's type guide](https://helpx.adobe.com/photoshop/using/creating-type.html), independently
of the Free Transform preference: Ctrl/Cmd never distorts a Type corner.

Without Ctrl/Cmd, paragraph handles resize the container and reflow its text. Temporary
transforms keep its logical dimensions and all character/paragraph styles. A drag begun with
Ctrl/Cmd owns the pointer until button release, even if the modifier is released first. Its
preview does not change the document; release applies one coalesced `type.edit`, and typing
continues in the same layer. Escape during a drag cancels that preview; focus loss or changes
to its source also discard it. Holding the modifier, moving the reference point, or returning
the pointer to its start creates no history entry. Ctrl/Cmd+T while typing still toggles the
Character panel.

Where the font lacks a symbol (e.g. ∠ ↦ ▔), draw it with the painter or use a Lucide icon; never ship
missing-glyph boxes. Check every new panel with the offscreen snapshot tool (`docs/development.md`).

## Title bar

The app's top bar (`panels::title_bar`) starts with the brand mark (the app icon, `brand.rs`), then the menus, the document title and the workspace controls, like Photoshop's Ps tile and menu row.

- **Windows and Linux:** the window has no OS decorations, so there is one bar, not two stacked. The top bar is the title bar (`titlebar.rs`): Minimize, Maximize/Restore and Close (red on hover, `caption_close` tokens) sit flush in the window's top-right corner, the free gap between the menus and the controls drags the window and a double-click there maximizes it, and invisible 5 pt edges (12 pt corners) resize it. Close runs File › Exit, so unsaved documents are asked about first.
- **macOS:** the traffic lights sit over the integrated title strip (`integrated_titlebar`).
- **Narrow windows** drop controls that are also in a menu before anything overlaps: Discord (Help › Discord), then the theme toggle, then search (Edit › Search), then the workspace switcher narrows (Window › Workspace).

## Menus

`menu_catalog.rs` holds Photoshop's menu tree (standard command names, order, separators, default shortcuts). Items whose id matches an engine or UI command are live; others render disabled until implemented. Give new commands the catalogue's id (for example `image.imageSize`) and they light up in the right place automatically.

Menus never run off the window: the menu bar's menus and submenus scroll with arrows (`menu_nav::level`), and long right-click menus (Layers, canvas tools, Channels, Paths, document tabs) wrap their rows in `widgets::menu_scroll`, so they move up to fit and scroll only when taller than the visible window.

## Automation for visual checks

Use `ui.click {x,y}`, `ui.move`, `ui.key` and `ui.type` (synthetic input in screen points) to open menus, popups and context menus, then `ui.screenshot`.

## Font menus

The Type options bar, Character panel, Character/Paragraph Style editors and Glyphs panel
share a searchable family picker. Each visible row shows an `AaBbCc` sample rendered by
PhotoCraft's text engine in that family (script/symbol fonts use characters they support).
Samples are cached with a bounded cache and follow display scale and theme text colour.
Builds without system fonts preview the bundled fonts.
While the menu is open, Up/Down applies the previous/next matching family and scrolls it into
view; Enter accepts the selection and closes the menu. Escape closes it, keeping already
applied changes (Edit › Undo restores text-layer font changes).

## Preferences

Preferences has **Apply**, **OK** and **Cancel**. Apply saves the edited sections and keeps the
dialog open; it is disabled when the values match the saved preferences. OK saves and closes.
Cancel discards only changes made since the last successful Apply. A failed Apply leaves the
draft open for correction. Settings marked for the next launch still require a restart.
On Windows and Linux, System Title Bar displays “Applies at next launch.” beneath its checkbox,
including before editing and after Apply. Saving this preference does not restart the app or
change the current window's decorations; the next launch reads the saved choice.

## High DPI and 4K displays

Edit → Preferences → Interface → UI Scale applies immediately. Auto follows the operating
system's display scale, including fractional scales such as 125%, 150% and 175% (on Linux,
Wayland's fractional scale or X11's `Xft.dpi`). Only when the system reports no scaling (100%) on
a 4K or larger monitor does Auto use 200%, so text and controls remain readable. Detection uses the current monitor,
including portrait displays, and updates when the window moves between monitors. If monitor
size is unavailable, Auto follows system DPI. The fixed choices (75% to 300%) set an absolute UI
scale, allowing large 4K displays to use smaller controls when desired. Canvas zoom shortcuts
continue to control the document independently of UI scaling.

Interface → UI Font Size changes interface text independently of UI Scale and canvas zoom.
Tiny, Small (the default), Medium and Large use 10/12, 1, 14/12 and 16/12 of the theme's original
font sizes, preserving the relative sizes of headings, captions and numeric fields. Apply or OK
updates text immediately; the choice persists across launches and theme changes. CJK fallback
fonts use the same size, including fonts loaded after the preference changes.

## Localisation

Strings in code stay English and are the default lookup keys. `crates/ui-egui/src/i18n` maps them
to display text at render time from one catalog per language (`i18n/<code>.tsv`; the format is
documented in the header of `ja.tsv`). Command ids, menu paths used for logic, the control channel,
the CLI and MCP always use the English ids and labels.

Languages shipped (`complete_menus` marks a catalog that covers every menu string and `tl!` literal;
the tests enforce it):

- English (`en`), the source language.
- Japanese (`ja`), complete.
- Simplified Chinese (`zh-hans`; see [`localization-zh-hans.md`](localization-zh-hans.md)), complete.
- Traditional Chinese (`zh-hant`), complete, in the vocabulary used in Taiwan; `zh-TW`, `zh-HK`,
  `zh-MO` and `zh-Hant-*` locales all resolve to it. The resolver distinguishes the two Chinese
  scripts, so neither catalog is shown to the other script's locales.
- Spanish (`es`), complete.
- Russian (`ru`), complete, with three plural forms (`one|few|many`, see `plural_russian`).
- Korean (`ko`), complete, with one plural form.
- French (`fr`), complete, with two plural forms (0 and 1 use the singular).
- Czech (`cs`), complete, with three plural forms.
- Indonesian (`id`), complete, with one plural form.

- `tr(lang, s)` plain strings; `tr_ctx` when one English word needs different translations;
  `tr_id(lang, command_id, label)` for menu items (keyed by command id, English label as the
  fallback); `trn(lang, n, one, other)` for plurals; `fmt` fills `{name}` placeholders, which
  translators may reorder.
- The language is Preferences › Interface › Language (`interface.language`: `auto` or a language
  code; `auto` follows the system locale, an unknown code falls back to `auto`).
- Language changes apply without a restart; Preferences previews the chosen language until
  Apply or OK commits it. Cancel restores the committed language. Regional preference tags
  resolve through the same locale matcher. See [`localization.md`](localization.md).
- To add a language: add `<code>.tsv` and one row in `i18n::LANGUAGES` (code, native name, catalog,
  plural rule). The dropdown, locale matching and the catalog tests (well-formed, no duplicates,
  placeholders and ellipses agree, command ids exist) pick it up. Set `complete_menus` once every
  menu string is translated; a test then enforces it. A language with more plural forms lists them
  all in `@plural` entries (Russian: `one|few|many`); the row's plural rule picks the form.
- Translations are clean-room: written from the meaning of the English text in ordinary vocabulary,
  never from another product's localisation resources.

Localised so far: menus, the command palette, dialogs and panels (literals wrapped in `tl!("…")`;
widgets such as `checkbox`, `slider_row`, `dropdown` and the buttons translate their labels
themselves). A test fails when a `tl!` literal, a menu string, a blend mode name, brush section name or a generated
preference label has no entry in a language marked `complete_menus`. Not translated: status-bar
messages and errors (they stay English, also for agents), names that are user data (layers, styles,
documents), strings assembled with `format!` that were not converted to `fmt`/`trn`. Not done yet:
right-to-left layout,
locale-aware number and date formats, automatic language detection on the web build (native
builds read `LANG`/`LC_*`, the macOS preferred languages and the Windows user locale).

Camera Raw has explicit coverage for all ten available languages, including Korean and
Simplified Chinese. Its contextual `cameraRaw` entries distinguish tonal regions,
colour-band names and font-weight Light. The title uses a `{layer}` placeholder; user layer
names and the universal RGB/Lab channel symbols stay unchanged. Collapse IDs use English
source keys, so switching languages preserves open sections. Mixer tabs wrap within the
panel width. Catalog coverage and actual shell language-switch tests enforce these rules.

Native CJK font fallback follows the selected UI script and resets its cache when switching
languages; font delivery on the web remains separate work.

## Arithmetic in numeric fields

Click a numeric value and type an expression, then press Enter or move focus to finish.
Numeric fields accept `+`, `-`, `*`, `/`, remainder `%`, powers `^` or `**`, parentheses,
scientific notation, and `pi` / `tau`. For example, `1920/2` gives `960`, and `(30+15)*2`
gives `90`. Shared value fields apply plain numbers live and arithmetic when editing
finishes, preserving rounded/integer workflows. Field limits and integer rounding
still apply; invalid expressions, division by zero, and non-finite results are rejected.
Expressions are evaluated locally as arithmetic, never as scripts.