Custom themes support

.github/workflows/check-cli.yml

@@ -34,7 +34,7 @@ jobs:
 
       - name: Run checks (common)
         working-directory: ./common
-        run: yarn check
+        run: yarn check && yarn build
 
       - name: Run checks (gallery)
         working-directory: ./gallery

README.md

@@ -62,11 +62,78 @@ This will:
   - Ubuntu/Debian: `sudo apt install ffmpeg`
   - Windows: [Download from ffmpeg.org](https://ffmpeg.org/download.html)
 
+## Development
+
+This is a monorepo using Yarn workspaces. To set up the development environment:
+
+1. **Clone the repository**
+
+   ```bash
+   git clone https://github.com/SimplePhotoGallery/core.git
+   cd spg-core
+   ```
+
+2. **Install dependencies**
+
+   ```bash
+   yarn install
+   ```
+
+3. **Build the `common` package** (required for TypeScript/ESLint to resolve `@simple-photo-gallery/common`)
+
+   ```bash
+   yarn workspace @simple-photo-gallery/common build
+   ```
+
+4. **Build the gallery package** (optional, for testing CLI changes)
+
+   ```bash
+   yarn workspace simple-photo-gallery build
+   ```
+
+5. **Run the CLI in development mode**
+   ```bash
+   yarn workspace simple-photo-gallery gallery
+   ```
+
+### Workspace Packages
+
+- **`common/`** - Shared types, schemas, and utilities used by both the CLI and themes
+  - Gallery types and Zod validation schemas
+  - Theme utilities (data loading, path resolution, markdown parsing)
+  - Client-side utilities (PhotoSwipe, blurhash, CSS helpers)
+  - See [common/README.md](common/README.md) for full API documentation
+- **`gallery/`** - CLI tool (`simple-photo-gallery`)
+  - Includes base theme template bundled at `gallery/src/modules/create-theme/templates/base/`
+- **`themes/modern/`** - Default theme package (reference implementation)
+
+### Building Packages
+
+Each workspace package can be built individually:
+
+- `yarn workspace @simple-photo-gallery/common build`
+- `yarn workspace simple-photo-gallery build`
+- `yarn workspace @simple-photo-gallery/theme-modern build`
+
 ## Supported Formats
 
 **Images:** JPEG, PNG, WebP, GIF, TIFF  
 **Videos:** MP4, MOV, AVI, WebM, MKV
 
+## Architecture
+
+This project uses a multi-theme architecture:
+- **Common package** provides shared utilities for all themes
+- **Themes** focus only on layout and presentation
+- **CLI** handles gallery generation and theme orchestration
+
+See the [Architecture Documentation](./docs/architecture.md) for details on how the system works, including:
+- Package structure and dependencies
+- Data flow from photos to static HTML
+- Theme system design and resolution
+- Multi-theme support implementation
+- Guidelines for adding new features
+
 ## Detailed Documentation
 
 For advanced usage, customization, and deployment options, see the comprehensive [documentation](./docs/README.md):
@@ -76,7 +143,11 @@ For advanced usage, customization, and deployment options, see the comprehensive
   - [`build`](./docs/commands/build.md) - Generate static HTML galleries
   - [`thumbnails`](./docs/commands/thumbnails.md) - Generate optimized thumbnails
   - [`clean`](./docs/commands/clean.md) - Remove gallery files
+  - [`create-theme`](./docs/commands/create-theme.md) - Scaffold a new theme package
+  - [`telemetry`](./docs/commands/telemetry.md) - Manage anonymous telemetry preferences
 - **[Gallery Configuration](./docs/configuration.md)** - Manual editing of `gallery.json` and advanced features like sections
+- **[Custom Themes](./docs/themes.md)** - Create and use custom themes
+- **[Common Package API](./common/README.md)** - Utilities and types for theme development
 - **[Deployment Guide](./docs/deployment.md)** - Guidelines for hosting your gallery
 
 ## Python Version

common/README.md

@@ -0,0 +1,16 @@
+# @simple-photo-gallery/common
+
+Shared utilities and types for Simple Photo Gallery themes and CLI.
+
+## Installation
+
+```bash
+npm install @simple-photo-gallery/common
+```
+
+## Package Exports
+
+- `.` - Gallery types and Zod validation schemas
+- `./theme` - Theme utilities for data loading and resolution
+- `./client` - Browser-side utilities (PhotoSwipe, blurhash, CSS)
+- `./styles/photoswipe` - PhotoSwipe CSS bundle

common/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@simple-photo-gallery/common",
-  "version": "1.0.6",
+  "version": "2.1.0",
   "description": "Shared utilities and types for Simple Photo Gallery",
   "license": "MIT",
   "author": "Vladimir Haltakov, Tomasz Rusin",
@@ -16,7 +16,16 @@
       "types": "./dist/gallery.d.ts",
       "import": "./dist/gallery.js",
       "require": "./dist/gallery.cjs"
-    }
+    },
+    "./theme": {
+      "types": "./dist/theme.d.ts",
+      "import": "./dist/theme.js"
+    },
+    "./client": {
+      "types": "./dist/client.d.ts",
+      "import": "./dist/client.js"
+    },
+    "./styles/photoswipe": "./dist/styles/photoswipe/photoswipe.css"
   },
   "files": [
     "dist"
@@ -33,12 +42,26 @@
     "prepublish": "yarn build"
   },
   "dependencies": {
+    "marked": "^16.0.0",
     "zod": "^4.0.14"
   },
+  "peerDependencies": {
+    "blurhash": "^2.0.5",
+    "photoswipe": "^5.4.4"
+  },
+  "peerDependenciesMeta": {
+    "blurhash": {
+      "optional": true
+    },
+    "photoswipe": {
+      "optional": true
+    }
+  },
   "devDependencies": {
     "@eslint/eslintrc": "^3.3.1",
     "@eslint/js": "^9.30.1",
     "@types/node": "^24.0.10",
+    "@types/photoswipe": "^4.1.6",
     "@typescript-eslint/eslint-plugin": "^8.38.0",
     "@typescript-eslint/parser": "^8.38.0",
     "eslint": "^9.30.1",

common/src/client.ts

@@ -0,0 +1 @@
+export * from './client/index';

common/src/client/blurhash.ts

@@ -0,0 +1,39 @@
+import { decode } from 'blurhash';
+
+/**
+ * Decode a single blurhash and draw it to a canvas element.
+ *
+ * @param canvas - The canvas element with a data-blur-hash attribute
+ * @param width - The width to decode at (default: 32)
+ * @param height - The height to decode at (default: 32)
+ */
+export function decodeBlurhashToCanvas(canvas: HTMLCanvasElement, width: number = 32, height: number = 32): void {
+  const blurHashValue = canvas.dataset.blurHash;
+  if (!blurHashValue) return;
+
+  const pixels = decode(blurHashValue, width, height);
+  const ctx = canvas.getContext('2d');
+  if (pixels && ctx) {
+    const imageData = new ImageData(new Uint8ClampedArray(pixels), width, height);
+    ctx.putImageData(imageData, 0, 0);
+  }
+}
+
+/**
+ * Decode and render all blurhash canvases on the page.
+ * Finds all canvas elements with data-blur-hash attribute and draws the decoded image.
+ *
+ * @param selector - CSS selector for canvas elements (default: 'canvas[data-blur-hash]')
+ * @param width - The width to decode at (default: 32)
+ * @param height - The height to decode at (default: 32)
+ */
+export function decodeAllBlurhashes(
+  selector: string = 'canvas[data-blur-hash]',
+  width: number = 32,
+  height: number = 32,
+): void {
+  const canvases = document.querySelectorAll<HTMLCanvasElement>(selector);
+  for (const canvas of canvases) {
+    decodeBlurhashToCanvas(canvas, width, height);
+  }
+}

common/src/client/css-utils.ts

@@ -0,0 +1,71 @@
+/**
+ * CSS utility functions for client-side theming and color manipulation.
+ * These utilities are browser-only and require DOM access.
+ */
+
+/**
+ * Normalizes hex color values to 6-digit format (e.g., #abc -> #aabbcc).
+ * Returns null if the hex value is invalid.
+ *
+ * @param hex - The hex color value to normalize (with or without #)
+ * @returns The normalized 6-digit hex color with # prefix, or null if invalid
+ */
+export function normalizeHex(hex: string): string | null {
+  hex = hex.replace('#', '');
+  if (hex.length === 3) hex = [...hex].map((c) => c + c).join('');
+  return hex.length === 6 && /^[0-9A-Fa-f]{6}$/.test(hex) ? `#${hex}` : null;
+}
+
+/**
+ * Parses and validates a color value.
+ * Supports CSS color names, hex values, rgb/rgba, and 'transparent'.
+ * Returns null if the color is invalid.
+ *
+ * @param colorParam - The color string to parse
+ * @returns The validated color string, or null if invalid
+ */
+export function parseColor(colorParam: string | null): string | null {
+  if (!colorParam) return null;
+  const normalized = colorParam.toLowerCase().trim();
+  if (normalized === 'transparent') return 'transparent';
+
+  const testEl = document.createElement('div');
+  testEl.style.color = normalized;
+  if (testEl.style.color) return normalized;
+
+  return normalizeHex(colorParam);
+}
+
+/**
+ * Sets or removes a CSS custom property (variable) on an element.
+ * Removes the property if value is null.
+ *
+ * @param element - The HTML element to modify
+ * @param name - The CSS variable name (e.g., '--my-color')
+ * @param value - The value to set, or null to remove
+ */
+export function setCSSVar(element: HTMLElement, name: string, value: string | null): void {
+  if (value) {
+    element.style.setProperty(name, value);
+  } else {
+    element.style.removeProperty(name);
+  }
+}
+
+/**
+ * Derives a color with adjusted opacity from an existing color.
+ * Converts rgb to rgba if needed, or adjusts existing rgba opacity.
+ *
+ * @param color - The source color (rgb, rgba, or other CSS color)
+ * @param opacity - The target opacity (0-1)
+ * @returns The color with adjusted opacity, or original if not rgb/rgba
+ */
+export function deriveOpacityColor(color: string, opacity: number): string {
+  if (color.startsWith('rgba')) {
+    return color.replace(/,\s*[\d.]+\)$/, `, ${opacity})`);
+  }
+  if (color.startsWith('rgb')) {
+    return color.replace('rgb', 'rgba').replace(')', `, ${opacity})`);
+  }
+  return color;
+}

common/src/client/hero-fallback.ts

@@ -0,0 +1,98 @@
+/** Options for the hero image fallback behavior */
+export interface HeroImageFallbackOptions {
+  /** CSS selector for the picture element (default: '#hero-bg-picture') */
+  pictureSelector?: string;
+  /** CSS selector for the img element within picture (default: 'img.hero__bg-img') */
+  imgSelector?: string;
+  /** CSS selector for the blurhash canvas element (default: 'canvas[data-blur-hash]') */
+  canvasSelector?: string;
+}
+
+/**
+ * Initialize hero image fallback behavior.
+ * Handles:
+ * - Hiding blurhash canvas when image loads successfully
+ * - Removing source elements and retrying with fallback src on error
+ * - Keeping blurhash visible if final fallback also fails
+ *
+ * @param options - Configuration options for selectors
+ *
+ * @example
+ * ```typescript
+ * import { initHeroImageFallback } from '@simple-photo-gallery/common/client';
+ *
+ * // Use default selectors
+ * initHeroImageFallback();
+ *
+ * // Or with custom selectors
+ * initHeroImageFallback({
+ *   pictureSelector: '#my-hero-picture',
+ *   imgSelector: 'img.my-hero-img',
+ *   canvasSelector: 'canvas.my-blurhash',
+ * });
+ * ```
+ */
+export function initHeroImageFallback(options: HeroImageFallbackOptions = {}): void {
+  const {
+    pictureSelector = '#hero-bg-picture',
+    imgSelector = 'img.hero__bg-img',
+    canvasSelector = 'canvas[data-blur-hash]',
+  } = options;
+
+  const picture = document.querySelector<HTMLPictureElement>(pictureSelector);
+  const img = picture?.querySelector<HTMLImageElement>(imgSelector);
+  const canvas = document.querySelector<HTMLCanvasElement>(canvasSelector);
+
+  if (!img) return;
+
+  const fallbackSrc = img.getAttribute('src') || '';
+  let didFallback = false;
+
+  const hideBlurhash = () => {
+    if (canvas) {
+      canvas.style.display = 'none';
+    }
+  };
+
+  const doFallback = () => {
+    if (didFallback) return;
+    didFallback = true;
+
+    if (picture) {
+      // Remove all <source> elements so the browser does not retry them
+      for (const sourceEl of picture.querySelectorAll('source')) {
+        sourceEl.remove();
+      }
+    }
+
+    // Force reload using the <img> src as the final fallback
+    const current = img.getAttribute('src') || '';
+    img.setAttribute('src', '');
+    img.setAttribute('src', fallbackSrc || current);
+
+    // If fallback also fails, keep blurhash visible
+    img.addEventListener(
+      'error',
+      () => {
+        // Final fallback failed, blurhash stays visible
+      },
+      { once: true },
+    );
+
+    // If fallback succeeds, hide blurhash
+    img.addEventListener('load', hideBlurhash, { once: true });
+  };
+
+  // Check if image already loaded or failed before script runs
+  if (img.complete) {
+    if (img.naturalWidth === 0) {
+      doFallback();
+    } else {
+      hideBlurhash();
+    }
+  } else {
+    img.addEventListener('load', hideBlurhash, { once: true });
+  }
+
+  img.addEventListener('error', doFallback, { once: true });
+}