# Implementation: Separate per-filter settings dialogs

## Changes required

### 1. HcieAppState additions
**File:** `crates/hcie-gui-egui/src/app/mod.rs`
- Add to `HcieAppState` (or `HcieApp` if using a struct-level state):
  - `pub filter_selected_id: String`
  - `pub filter_params_open: bool`
  - `pub filter_preview_active: bool`
  - `pub filter_sky_path: String`
- Initialize to defaults in the struct constructor.

### 2. Filter dialog redesign
**File:** `crates/hcie-gui-egui/src/app/filter_dialog.rs`
- Replace the monolithic filter dialog with two windows:
  1. **Main filter dialog** — filter list only + common controls (Close, Undo Last Filter, Apply-to-New-Layer)
  2. **Per-filter settings window** — opened when a filter is selected

### 3. New functions in filter_dialog.rs
- `show_filter_list_window(app, ctx)` — shows the filter category tree
  - Calls `egui_panel_filters::show_filter_list_ui(...)`
  - On filter click: set `app.filter_selected_id`, open `app.filter_params_open = true`
- `show_filter_params_window(app, ctx)` — shows the selected filter's controls
  - Uses `get_filter_panel(filter_id)` to get the panel spec
  - Renders `render_module_panel` for the parameter widgets
  - Renders sky-path input for `sky_replacement`
  - Buttons: **Preview / Stop Preview**, **Apply**, **Reset**, **Close**
  - Close button sets `filter_params_open = false`

### 4. Preview feature
- In `show_filter_params_window`:
  - If `filter_preview_active` is true:
    - On widget change: call `engine.filter_preview_restore()` + `engine.filter_preview_begin()` + `engine.apply_filter_preview(id, params)`
    - Show "Stop Preview" button instead of "Preview"
  - If not previewing:
    - "Preview" button starts preview: `engine.filter_preview_begin()`, then apply once
    - Set `filter_preview_active = true`
  - On window close: if preview active, call `engine.filter_preview_restore()` and clear flag

### 5. Reset feature
- "Reset" button:
  - Re-initialize all widget values to defaults from `get_filter_panel(filter_id)`
  - If preview active, also restore original pixels and stop preview
  - Keep window open

### 6. Apply feature
- "Apply" button:
  - Compile params with `compile_filter_params`
  - If preview active, restore first
  - Call `engine.apply_filter(id, params)`
  - Clear `filter_selected_id`, set `filter_params_open = false`

### 7. is_raster check
- Pass `is_raster` from the engine to both windows
- Main filter list shows the mismatch warning if not raster
- Per-filter window is disabled/hidden if not raster

### 8. FilterType to string ID mapping
**File:** `crates/hcie-gui-egui/src/app/menus.rs`
- Add a helper function `filter_type_to_id(ft: FilterType) -> &'static str`
- Map each menu item's filter type to the corresponding ID string
- Update menu handlers to set both `app.show_filter = true` and `app.filter_selected_id = id`

## Implementation order
1. Add state fields to HcieApp
2. Implement `show_filter_params_window`
3. Implement `show_filter_list_window`
4. Update main filter dialog to use new windows
5. Add preview/reset logic
6. Update menus