Dynamic key generators: plugin system for auto-generated pages

Add dynamic_keys support to PageConfig — a contract-based plugin
system where any executable outputs a JSON array of KeyConfig to stdout.
The daemon runs the generator on a configurable interval and renders
the keys dynamically on the Stream Deck.

Core changes:
- config: DynamicKeyGen struct (command/script, interval, timeout, max_keys)
- config: full validation for dynamic_keys fields
- action: execDynamicKeys() with safe JSON parsing (stderr logged separately,
  env vars STREAMDECK_KEY_COUNT / STREAMDECK_CONFIG_DIR)
- page: activeKeys() merges static + dynamic keys (static wins by index)
- page: startDynamicKeys / stopDynamicKeys lifecycle, per-page results cache
- page: rerenderActivePage() with deadlock-safe lock ordering
- daemon: event handler uses activeKeys() for dynamic key actions

Web UI:
- GET /api/pages returns effective_keys (merged static + cached dynamic)
- app.js: gridKeys uses effective_keys when available
- app.js: guard against editing dynamic keys through the UI
- index.html: "⚡ dynamic" badge + effective key count in page switcher
- polls /api/pages every 10s to keep the UI in sync

Image rendering:
- loadImage: gift.ResizeToFill instead of gift.Resize (preserves aspect
  ratio, crops to fill — no more stretched cover art)

Example & docs:
- config.example.json: games page with dynamic_keys + back button
- README.md: comprehensive Dynamic Key Generators section (architecture
  diagram, config reference, generator contract, merge behavior,
  env vars, error handling, Python + Shell examples, tips)

README.md

@@ -127,6 +127,213 @@ Server down!
 
 If no color is specified, the key uses its configured background or the default black.
 
+### Dynamic Key Generators
+
+Generate an entire page of keys dynamically by running any executable (shell script, Python, Go binary, etc.). Useful for game launchers, music collections, Docker containers, monitoring dashboards — anything where the set of keys is not known at config time.
+
+```
+┌──────────────────────────────────────────────────┐
+│  Generator script (any language)                 │
+│  → queries Lutris DB, Steam API, etc.           │
+│  → outputs JSON array of KeyConfig to stdout     │
+│  → receives STREAMDECK_KEY_COUNT env var         │
+└──────────────┬───────────────────────────────────┘
+               │ stdout: [{"index":0,"icon":"...",...}]
+               ▼
+┌──────────────────────────────────────────────────┐
+│  streamdeck-lets-go daemon                       │
+│  → parses JSON                                   │
+│  → merges with static keys (static wins)         │
+│  → renders keys on the deck                      │
+│  → re-runs on interval (default 60s)             │
+└──────────────────────────────────────────────────┘
+```
+
+#### Config
+
+Add `dynamic_keys` to any page:
+
+```json
+{
+  "name": "Games",
+  "icon": "fa:gamepad",
+  "keys": [
+    {
+      "index": 0,
+      "icon": "fa:arrow-left",
+      "actions": [
+        { "trigger": "tap", "type": "page", "page": "main" }
+      ]
+    }
+  ],
+  "dynamic_keys": {
+    "command": "/home/user/bin/game-list",
+    "interval": "120s",
+    "timeout": "15s",
+    "max_keys": 14
+  }
+}
+```
+
+| Field | Type | Default | Description |
+|---|---|---|---|
+| `command` | string | — | Shell command to execute (mutually exclusive with `script`) |
+| `script` | string | — | Path to an executable script; relative paths resolve against `~/.config/streamdeck-lets-go/` |
+| `interval` | string | `"60s"` | How often to re-run the generator (minimum 1s, maximum 24h) |
+| `timeout` | string | `"15s"` | Maximum execution time before the generator is killed |
+| `max_keys` | int | `deck.NumKeys()` | Maximum number of keys to accept (e.g. `13` to reserve 2 for navigation) |
+
+#### Generator contract
+
+The script **must** print a JSON array of key configs to stdout and exit with code 0. Each element supports the full `KeyConfig` schema:
+
+```json
+[
+  {
+    "index": 0,
+    "icon": "/home/user/.local/share/lutris/coverart/cyberpunk-2077.jpg",
+    "label": "Cyberpunk 2077",
+    "font_size": 12,
+    "icon_scale": 1.0,
+    "background": "#222222",
+    "actions": [
+      {
+        "trigger": "tap",
+        "type": "command",
+        "command": "lutris lutris:rungame/cyberpunk-2077",
+        "background": true
+      }
+    ]
+  }
+]
+```
+
+Every field from a static key is available:
+
+| Field | Type | Description |
+|---|---|---|
+| `index` | int | Key position on the deck (0-based) |
+| `icon` | string | Icon source: `fa:terminal`, `emoji:fire`, `@firefox`, `/absolute/path.png`, relative path |
+| `label` | string | Text shown below the icon |
+| `font_size` | number | Font size in points (default 18, recommended 11–14 for labels) |
+| `icon_scale` | number | Icon scale factor (0.0–1.0, default 0.55) |
+| `background` | string | Hex background color `"#222222"` |
+| `actions` | array | Same action schema as static keys — supports all triggers (`tap`, `long_press`, `double_tap`) and all action types (`command`, `builtin`, `script`, `page`, `keyboard`) |
+| `display` | object | Periodic display block (same as static key `display`) — command/script runs on interval and text is overlaid on the key |
+
+#### Merge behavior
+
+Static `keys` (defined directly on the page) and dynamic keys are **merged** at runtime:
+
+| Priority | Source |
+|---|---|
+| 1 (highest) | Static keys — their indices are reserved |
+| 2 | Dynamic keys — fill indices not occupied by static keys |
+
+This lets you keep navigation buttons fixed while the generator fills the rest of the deck:
+
+```
+Static:   [← back] [  ] [  ] [  ] [  ] [  ] [  ] [  ] [  ] [  ] [  ] [  ] [  ] [  ] [  ]
+            index 0   └────────────────────── dynamic (indices 1–14) ──────────────────────→
+```
+
+#### Environment variables
+
+The generator receives these environment variables:
+
+| Variable | Example | Description |
+|---|---|---|
+| `STREAMDECK_KEY_COUNT` | `15` | Maximum number of keys to output (derived from deck model or `max_keys` config) |
+| `STREAMDECK_CONFIG_DIR` | `/home/user/.config/streamdeck-lets-go` | Path to the config directory — useful for finding companion files |
+
+#### Error handling
+
+| Situation | Behavior |
+|---|---|
+| Script fails (non-zero exit, timeout) | Warning logged; previous keys preserved |
+| Script returns empty array `[]` | Only static keys rendered |
+| Script returns invalid JSON | Warning logged; previous keys preserved |
+| Script outputs debug to stderr | Logged at DEBUG level; stdout JSON parsed cleanly |
+| More keys than `max_keys` | Excess keys silently dropped |
+| Generator updates while page is active | Keys re-rendered in place (no flicker) |
+
+#### Examples
+
+**Python — Lutris game launcher**
+
+Place this at `~/.config/streamdeck-lets-go/scripts/lutris-keys`, make executable (`chmod +x`).
+
+```python
+#!/usr/bin/env python3
+import json, os, sqlite3, pathlib
+
+db = pathlib.Path.home() / '.local/share/lutris/pga.db'
+cover = pathlib.Path.home() / '.local/share/lutris/coverart'
+max_keys = int(os.environ.get('STREAMDECK_KEY_COUNT', 15))
+
+if not db.exists():
+    print('[]')
+    exit(0)
+
+conn = sqlite3.connect(db)
+games = conn.execute(
+    "SELECT slug, name FROM games WHERE installed = 1 ORDER BY name"
+).fetchall()
+conn.close()
+
+keys = []
+for idx, (slug, name) in enumerate(games):
+    if idx >= max_keys:
+        break
+    icon = next(cover.glob(f'{slug}.*'), None)
+    key = {
+        "index": idx,
+        "icon_scale": 1.0,
+        "actions": [{
+            "trigger": "tap",
+            "type": "command",
+            "command": f"lutris lutris:rungame/{slug}",
+            "background": True
+        }]
+    }
+    if icon:
+        key["icon"] = str(icon)
+    keys.append(key)
+
+print(json.dumps(keys))
+```
+
+Reference it in config:
+```json
+{
+  "name": "Games",
+  "dynamic_keys": {
+    "script": "scripts/lutris-keys",
+    "interval": "120s"
+  }
+}
+```
+
+**Shell — Simple test generator**
+
+```bash
+#!/bin/sh
+for i in $(seq 0 $((STREAMDECK_KEY_COUNT - 1))); do
+  [ "$i" -gt 0 ] && echo ","
+  printf '{"index":%d,"icon":"fa:hashtag","label":"Item %d"}' "$i" "$i"
+done
+```
+
+Run with any language you like — the only requirement is a valid JSON array on stdout.
+
+#### Tips
+
+- Use `max_keys` to reserve space for static navigation buttons
+- Enable `show_label_background: true` in the global config if labels on full-bleed icons are hard to read
+- Test your generator standalone before wiring it up: `STREAMDECK_KEY_COUNT=15 ./my-generator`
+- For large data sources, pass pagination params through the command string: `"command": "scripts/albums --page 0"`
+- Dynamic keys support `display` blocks — nest monitoring data inside generated keys
+
 ### Gesture timing
 
 Configured in the web UI (Settings → Gesture Timing) or in `config.json`:

action.go

@@ -3,10 +3,12 @@ package main
 import (
 	"bytes"
 	"context"
+	"encoding/json"
 	"fmt"
 	"log/slog"
 	"os"
 	"os/exec"
+	"path/filepath"
 	"strings"
 	"time"
 
@@ -99,6 +101,52 @@ func execDisplayCapture(d *config.DisplayCfg, timeout time.Duration) (string, er
 	return output, err
 }
 
+func execDynamicKeys(dg *config.DynamicKeyGen, timeout time.Duration, keyCount int) ([]config.KeyConfig, error) {
+	ctx, cancel := context.WithTimeout(context.Background(), timeout)
+	defer cancel()
+
+	var cmd *exec.Cmd
+	if dg.Command != "" {
+		cmd = exec.CommandContext(ctx, "sh", "-c", dg.Command)
+	} else {
+		script := dg.Script
+		if !filepath.IsAbs(script) {
+			script = filepath.Join(configDir(), script)
+		}
+		cmd = exec.CommandContext(ctx, script)
+	}
+
+	// Set environment variables for the script
+	cmd.Env = append(os.Environ(),
+		fmt.Sprintf("STREAMDECK_KEY_COUNT=%d", keyCount),
+		fmt.Sprintf("STREAMDECK_CONFIG_DIR=%s", configDir()),
+	)
+
+	var stdout, stderr bytes.Buffer
+	cmd.Stdout = &stdout
+	cmd.Stderr = &stderr
+
+	err := cmd.Run()
+
+	// Log stderr separately (don't merge into stdout for JSON parsing)
+	if stderr.Len() > 0 {
+		slog.Debug("dynamic_keys script stderr", "output", stderr.String())
+	}
+
+	if err != nil {
+		return nil, fmt.Errorf("execute dynamic_keys: %w", err)
+	}
+
+	// Parse JSON from stdout
+	var keys []config.KeyConfig
+	output := stdout.String()
+	if err := json.Unmarshal([]byte(output), &keys); err != nil {
+		return nil, fmt.Errorf("parse dynamic_keys JSON: %w", err)
+	}
+
+	return keys, nil
+}
+
 func execBuiltin(a *config.Action, deck *Deck, pm *PageManager) error {
 	parts := strings.SplitN(a.Builtin, ":", 2)
 	if len(parts) < 1 {

config.example.json

@@ -40,6 +40,19 @@
             }
           ]
         },
+        {
+          "index": 2,
+          "icon": "fa:gamepad",
+          "label": "Games",
+          "font_size": 11,
+          "actions": [
+            {
+              "trigger": "tap",
+              "type": "page",
+              "page": "games"
+            }
+          ]
+        },
         {
           "index": 7,
           "icon": "fa:chevron-right",
@@ -58,6 +71,23 @@
           ]
         }
       ]
+    },
+    {
+      "name": "games",
+      "icon": "fa:gamepad",
+      "keys": [
+        {
+          "index": 0,
+          "icon": "fa:arrow-left",
+          "actions": [
+            { "trigger": "tap", "type": "page", "page": "main" }
+          ]
+        }
+      ],
+      "dynamic_keys": {
+        "script": "scripts/lutris-keys",
+        "interval": "120s"
+      }
     }
   ],
   "auto_switch": [],

daemon.go

@@ -184,7 +184,7 @@ func Run(ctx context.Context, cfg *config.Config, opts RunOptions) error {
 			if page == nil {
 				continue
 			}
-			for _, k := range page.Keys {
+			for _, k := range primaryPM.activeKeys() {
 				if k.Index == evt.Index {
 					if len(k.Actions) > 0 {
 						ge.HandleEvent(evt, k.Actions)

internal/config/config.go

@@ -43,10 +43,19 @@ type PageConfig struct {
 	Name        string          `json:"name"`
 	Icon        string          `json:"icon,omitempty"`
 	Keys        []KeyConfig     `json:"keys"`
+	DynamicKeys *DynamicKeyGen  `json:"dynamic_keys,omitempty"`
 	Background  string          `json:"background,omitempty"`
 	Screensaver *ScreensaverCfg `json:"screensaver,omitempty"`
 }
 
+type DynamicKeyGen struct {
+	Command  string `json:"command,omitempty"`
+	Script   string `json:"script,omitempty"`
+	Interval string `json:"interval,omitempty"`
+	Timeout  string `json:"timeout,omitempty"`
+	MaxKeys  int    `json:"max_keys,omitempty"`
+}
+
 type KeyConfig struct {
 	Index      int           `json:"index"`
 	Icon       string        `json:"icon,omitempty"`
@@ -293,6 +302,35 @@ func (c *Config) Validate() error {
 				}
 			}
 		}
+
+		if p.DynamicKeys != nil {
+			if p.DynamicKeys.Command == "" && p.DynamicKeys.Script == "" {
+				return fmt.Errorf("page %s: dynamic_keys requires command or script", p.Name)
+			}
+			if p.DynamicKeys.Command != "" && p.DynamicKeys.Script != "" {
+				return fmt.Errorf("page %s: dynamic_keys command and script are mutually exclusive", p.Name)
+			}
+			if p.DynamicKeys.Interval != "" {
+				interval, err := time.ParseDuration(p.DynamicKeys.Interval)
+				if err != nil {
+					return fmt.Errorf("page %s: invalid dynamic_keys interval %q: %w", p.Name, p.DynamicKeys.Interval, err)
+				}
+				if interval < time.Second {
+					return fmt.Errorf("page %s: dynamic_keys interval must be at least 1s", p.Name)
+				}
+				if interval > 24*time.Hour {
+					return fmt.Errorf("page %s: dynamic_keys interval must not exceed 24h", p.Name)
+				}
+			}
+			if p.DynamicKeys.Timeout != "" {
+				if _, err := time.ParseDuration(p.DynamicKeys.Timeout); err != nil {
+					return fmt.Errorf("page %s: invalid dynamic_keys timeout %q: %w", p.Name, p.DynamicKeys.Timeout, err)
+				}
+			}
+			if p.DynamicKeys.MaxKeys < 0 {
+				return fmt.Errorf("page %s: dynamic_keys max_keys must be >= 0", p.Name)
+			}
+		}
 	}
 
 	for _, p := range c.Pages {

page.go

@@ -50,6 +50,10 @@ type PageManager struct {
 	displayMu           sync.RWMutex
 	defaultFont         string
 	showLabelBackground bool
+	dynamicCancel       context.CancelFunc
+	dynamicKeys         []config.KeyConfig
+	dynamicKeysMu       sync.RWMutex
+	dynamicResults      map[string][]config.KeyConfig
 }
 
 func NewPageManager(deck *Deck) *PageManager {
@@ -59,19 +63,88 @@ func NewPageManager(deck *Deck) *PageManager {
 		keyStates:      make(map[int]*keyState),
 		displayOutputs: make(map[int]*DisplayOutput),
 		defaultFont:    "medium",
+		dynamicResults: make(map[string][]config.KeyConfig),
 	}
 }
 
+func (pm *PageManager) activeKeys() []config.KeyConfig {
+	pm.mu.RLock()
+	page := pm.pages[pm.active]
+	pm.mu.RUnlock()
+	if page == nil {
+		return nil
+	}
+
+	pm.dynamicKeysMu.RLock()
+	dyn := pm.dynamicKeys
+	pm.dynamicKeysMu.RUnlock()
+
+	if dyn == nil {
+		return page.Keys
+	}
+
+	used := make(map[int]bool, len(page.Keys))
+	result := make([]config.KeyConfig, 0, len(page.Keys)+len(dyn))
+	for _, k := range page.Keys {
+		used[k.Index] = true
+		result = append(result, k)
+	}
+	for _, k := range dyn {
+		if !used[k.Index] {
+			result = append(result, k)
+		}
+	}
+	return result
+}
+
+// GetEffectiveKeys returns merged (static + cached dynamic) keys for a page.
+// Used by the web UI to preview generated keys.
+func (pm *PageManager) GetEffectiveKeys(name string) []config.KeyConfig {
+	pm.mu.RLock()
+	page := pm.pages[name]
+	pm.mu.RUnlock()
+	if page == nil {
+		return nil
+	}
+
+	pm.dynamicKeysMu.RLock()
+	cached := pm.dynamicResults[name]
+	pm.dynamicKeysMu.RUnlock()
+
+	if cached == nil {
+		return page.Keys
+	}
+
+	used := make(map[int]bool, len(page.Keys))
+	result := make([]config.KeyConfig, 0, len(page.Keys)+len(cached))
+	for _, k := range page.Keys {
+		used[k.Index] = true
+		result = append(result, k)
+	}
+	for _, k := range cached {
+		if !used[k.Index] {
+			result = append(result, k)
+		}
+	}
+	return result
+}
+
 func (pm *PageManager) LoadPages(pages []config.PageConfig) {
 	pm.mu.Lock()
-	defer pm.mu.Unlock()
 	pm.pages = make(map[string]*config.PageConfig, len(pages))
 	for i := range pages {
 		pm.pages[pages[i].Name] = &pages[i]
 	}
+	pm.mu.Unlock()
+
+	pm.dynamicKeysMu.Lock()
+	pm.dynamicResults = make(map[string][]config.KeyConfig)
+	pm.dynamicKeysMu.Unlock()
 }
 
 func (pm *PageManager) ActivatePage(name string) error {
+	pm.stopDynamicKeys()
+
 	pm.mu.Lock()
 	defer pm.mu.Unlock()
 
@@ -117,6 +190,12 @@ func (pm *PageManager) ActivatePage(name string) error {
 		pm.renderKey(i, &k)
 	}
 
+	if page.DynamicKeys != nil {
+		go func() {
+			pm.startDynamicKeys(page.DynamicKeys)
+		}()
+	}
+
 	return nil
 }
 
@@ -149,13 +228,7 @@ func (pm *PageManager) GetPage(name string) *config.PageConfig {
 }
 
 func (pm *PageManager) RenderKey(keyIndex int) {
-	pm.mu.RLock()
+	for _, k := range pm.activeKeys() {
-	defer pm.mu.RUnlock()
-	page := pm.pages[pm.active]
-	if page == nil {
-		return
-	}
-	for _, k := range page.Keys {
 		if k.Index == keyIndex {
 			pm.renderKey(keyIndex, &k)
 			return
@@ -164,13 +237,7 @@ func (pm *PageManager) RenderKey(keyIndex int) {
 }
 
 func (pm *PageManager) ReRenderDisplayKey(keyIndex int, output string) {
-	pm.mu.RLock()
+	for _, k := range pm.activeKeys() {
-	page := pm.pages[pm.active]
-	pm.mu.RUnlock()
-	if page == nil {
-		return
-	}
-	for _, k := range page.Keys {
 		if k.Index == keyIndex && k.Display != nil {
 			pm.renderKeyOutput(keyIndex, k.Display, output, nil)
 			return
@@ -260,6 +327,8 @@ func (pm *PageManager) renderKey(idx int, k *config.KeyConfig) {
 }
 
 func (pm *PageManager) stopPeriodicKeys() {
+	pm.stopDynamicKeys()
+
 	pm.mu.Lock()
 	defer pm.mu.Unlock()
 	for _, ks := range pm.keyStates {
@@ -296,11 +365,136 @@ func (pm *PageManager) startPeriodicKeys() {
 			keys = append(keys, displayKey{index: k.Index, display: k.Display, ctx: ctx})
 		}
 	}
+	dg := page.DynamicKeys
 	pm.mu.Unlock()
 
 	for _, dk := range keys {
 		go pm.runDisplayKey(dk.index, dk.display, dk.ctx)
 	}
+
+	if dg != nil {
+		pm.startDynamicKeys(dg)
+	}
+}
+
+func (pm *PageManager) stopDynamicKeys() {
+	pm.dynamicKeysMu.Lock()
+	if pm.dynamicCancel != nil {
+		pm.dynamicCancel()
+		pm.dynamicCancel = nil
+	}
+	pm.dynamicKeys = nil
+	pm.dynamicKeysMu.Unlock()
+}
+
+func (pm *PageManager) startDynamicKeys(dg *config.DynamicKeyGen) {
+	ctx, cancel := context.WithCancel(context.Background())
+
+	pm.dynamicKeysMu.Lock()
+	if pm.dynamicCancel != nil {
+		pm.dynamicCancel()
+	}
+	pm.dynamicCancel = cancel
+	pm.dynamicKeysMu.Unlock()
+
+	numKeys := dg.MaxKeys
+	if numKeys <= 0 {
+		numKeys = pm.deck.NumKeys()
+	}
+
+	var interval time.Duration
+	if dg.Interval != "" {
+		interval, _ = time.ParseDuration(dg.Interval)
+	}
+	if interval == 0 {
+		interval = 60 * time.Second
+	}
+
+	go pm.runDynamicKeyGenerator(ctx, dg, numKeys, interval)
+}
+
+func (pm *PageManager) runDynamicKeyGenerator(ctx context.Context, dg *config.DynamicKeyGen, numKeys int, interval time.Duration) {
+	timeout := 15 * time.Second
+	if dg.Timeout != "" {
+		if t, err := time.ParseDuration(dg.Timeout); err == nil && t > 0 {
+			timeout = t
+		}
+	}
+
+	pm.updateDynamicKeys(dg, timeout, numKeys)
+
+	ticker := time.NewTicker(interval)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case <-ticker.C:
+			pm.updateDynamicKeys(dg, timeout, numKeys)
+		case <-ctx.Done():
+			return
+		}
+	}
+}
+
+func (pm *PageManager) updateDynamicKeys(dg *config.DynamicKeyGen, timeout time.Duration, numKeys int) {
+	keys, err := execDynamicKeys(dg, timeout, numKeys)
+	if err != nil {
+		slog.Warn("dynamic_keys generator failed", "error", err)
+		return
+	}
+
+	if len(keys) > numKeys {
+		keys = keys[:numKeys]
+	}
+
+	pm.mu.RLock()
+	pageName := pm.active
+	pm.mu.RUnlock()
+
+	pm.dynamicKeysMu.Lock()
+	if pm.dynamicCancel == nil {
+		pm.dynamicKeysMu.Unlock()
+		return
+	}
+	pm.dynamicKeys = keys
+	pm.dynamicResults[pageName] = keys
+	pm.dynamicKeysMu.Unlock()
+
+	slog.Info("dynamic_keys updated", "count", len(keys), "page", pageName)
+
+	pm.rerenderActivePage()
+}
+
+func (pm *PageManager) rerenderActivePage() {
+	pm.mu.RLock()
+	bg := ""
+	if page := pm.pages[pm.active]; page != nil {
+		bg = page.Background
+	}
+	pm.mu.RUnlock()
+
+	if bg != "" {
+		if img, err := loadImage(bg, 0, 0); err == nil {
+			pm.deck.FillPanel(img)
+		}
+	}
+
+	keys := pm.activeKeys()
+	keyByIndex := make(map[int]config.KeyConfig, len(keys))
+	for _, k := range keys {
+		keyByIndex[k.Index] = k
+	}
+
+	for i := 0; i < pm.deck.NumKeys(); i++ {
+		k, ok := keyByIndex[i]
+		if !ok {
+			if bg == "" {
+				pm.deck.ClearKey(i)
+			}
+			continue
+		}
+		pm.renderKey(i, &k)
+	}
 }
 
 func (pm *PageManager) runDisplayKey(idx int, d *config.DisplayCfg, ctx context.Context) {
@@ -393,15 +587,8 @@ func parseDisplayOutput(output string) (*DisplayOutput, color.Color, color.Color
 }
 
 func (pm *PageManager) renderKeyOutput(idx int, d *config.DisplayCfg, output string, execErr error) {
-	pm.mu.RLock()
-	page := pm.pages[pm.active]
-	pm.mu.RUnlock()
-	if page == nil {
-		return
-	}
-
 	var kc *config.KeyConfig
-	for _, k := range page.Keys {
+	for _, k := range pm.activeKeys() {
 		if k.Index == idx {
 			kCopy := k
 			kc = &kCopy
@@ -499,13 +686,7 @@ func (pm *PageManager) renderKeyOutput(idx int, d *config.DisplayCfg, output str
 }
 
 func (pm *PageManager) RefreshDisplayKey(idx int) {
-	pm.mu.RLock()
+	for _, k := range pm.activeKeys() {
-	page := pm.pages[pm.active]
-	pm.mu.RUnlock()
-	if page == nil {
-		return
-	}
-	for _, k := range page.Keys {
 		if k.Index == idx && k.Display != nil {
 			timeout := 30 * time.Second
 			if k.Display.Timeout != "" {
@@ -892,9 +1073,9 @@ func loadImage(path string, targetSize int, faScale float64) (image.Image, error
 			displaySize = 1
 		}
 
-		// Resize to displaySize
+		// Resize to displaySize preserving aspect ratio (crop to fill)
 		if img.Bounds().Dx() != displaySize || img.Bounds().Dy() != displaySize {
-			g := gift.New(gift.Resize(displaySize, displaySize, gift.LanczosResampling))
+			g := gift.New(gift.ResizeToFill(displaySize, displaySize, gift.LanczosResampling, gift.CenterAnchor))
 			scaled := image.NewRGBA(image.Rect(0, 0, displaySize, displaySize))
 			g.Draw(scaled, img)
 			img = scaled

static/app.js

@@ -52,6 +52,7 @@ document.addEventListener('alpine:init', () => {
       await this.loadConfig()
       await this.loadDecks()
       setInterval(() => this.pollDisplayOutputs(), 3000)
+      setInterval(() => this.loadEffectiveKeys(), 10000)
       this.connectSSE()
     },
 
@@ -101,6 +102,7 @@ document.addEventListener('alpine:init', () => {
         const res = await fetch('/api/config')
         this.config = await res.json()
         this.pages = this.config.pages
+        await this.loadEffectiveKeys()
         if (this.pages.length > 0) {
           const saved = localStorage.getItem('sd_active_page')
           if (saved && this.pages.find(p => p.name === saved)) {
@@ -115,6 +117,19 @@ document.addEventListener('alpine:init', () => {
       }
     },
 
+    async loadEffectiveKeys() {
+      try {
+        const res = await fetch('/api/pages')
+        const pagesData = await res.json()
+        for (const pd of pagesData) {
+          const page = this.pages.find(p => p.name === pd.name)
+          if (page && pd.effective_keys && pd.effective_keys.length > 0) {
+            page.effective_keys = pd.effective_keys
+          }
+        }
+      } catch (_) {}
+    },
+
     syncSettings() {
       this.settingsForm = {
         brightness: this.getDeviceConfig(this.activeDeckSerial)?.brightness ?? 75,
@@ -151,10 +166,13 @@ document.addEventListener('alpine:init', () => {
     get gridKeys() {
       const page = this.currentPage
       if (!page) return []
+      const sourceKeys = (page.effective_keys && page.effective_keys.length > 0)
+        ? page.effective_keys
+        : (page.keys || [])
       const keys = []
       const n = this.activeDeck.num_keys
       for (let i = 0; i < n; i++) {
-        const kc = page.keys.find(k => k.index === i)
+        const kc = sourceKeys.find(k => k.index === i)
         const dout = this.displayOutputs[i]
         keys.push({
           index: i,
@@ -166,6 +184,7 @@ document.addEventListener('alpine:init', () => {
           displayBg: dout?.background || '',
           displayText: dout?.text || '',
           previewUrl: this.keyPreviewUrl(kc ? kc : {}, dout),
+          isDynamic: !!(page.dynamic_keys && page.effective_keys?.find(k => k.index === i)),
         })
       }
       return keys
@@ -306,6 +325,9 @@ document.addEventListener('alpine:init', () => {
       const page = this.currentPage
       if (!page) return
       const kc = page.keys.find(k => k.index === idx)
+      if (!kc && page.dynamic_keys && page.effective_keys?.find(k => k.index === idx)) {
+        return
+      }
       this.editing = idx
       this.showAdvanced = false
 

static/index.html

@@ -94,8 +94,11 @@
           :style="{ borderColor: p.name === activePage ? 'var(--accent)' : '' }"
           @click="switchPage(p.name); subView = null">
           <span x-text="p.name"></span>
+          <span x-show="p.dynamic_keys"
+            title="Dynamic keys generator"
+            style="color:var(--accent);font-size:11px;margin-left:4px;">⚡</span>
           <span style="float:right;color:var(--text-muted);font-size:11px;"
-            x-text="p.keys.length + ' keys'"></span>
+            x-text="(p.effective_keys?.length || p.keys.length) + ' keys'"></span>
         </button>
       </template>
     </div>

web.go

@@ -339,18 +339,27 @@ func (s *WebServer) handleGetPages(w http.ResponseWriter, r *http.Request) {
 	defer s.mu.RUnlock()
 
 	type pageInfo struct {
-		Name string     `json:"name"`
+		Name          string                `json:"name"`
-		Keys []config.KeyConfig `json:"keys"`
+		Keys          []config.KeyConfig    `json:"keys"`
-		Icon string     `json:"icon,omitempty"`
+		Icon          string                `json:"icon,omitempty"`
+		DynamicKeys   *config.DynamicKeyGen `json:"dynamic_keys,omitempty"`
+		Background    string                `json:"background,omitempty"`
+		EffectiveKeys []config.KeyConfig    `json:"effective_keys,omitempty"`
 	}
 
 	pages := make([]pageInfo, 0, len(s.cfg.Pages))
 	for _, p := range s.cfg.Pages {
-		pages = append(pages, pageInfo{
+		pi := pageInfo{
-			Name: p.Name,
+			Name:        p.Name,
-			Keys: p.Keys,
+			Keys:        p.Keys,
-			Icon: p.Icon,
+			Icon:        p.Icon,
-		})
+			DynamicKeys: p.DynamicKeys,
+			Background:  p.Background,
+		}
+		if p.DynamicKeys != nil && s.pm != nil {
+			pi.EffectiveKeys = s.pm.GetEffectiveKeys(p.Name)
+		}
+		pages = append(pages, pi)
 	}
 
 	w.Header().Set("Content-Type", "application/json")