Update .github/workflows/documentation.yaml

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

.github/copilot-instructions.md

@@ -0,0 +1,212 @@
+# FTXUI - Functional Terminal (X) User Interface
+
+FTXUI is a cross-platform C++ library for terminal-based user interfaces with a functional programming approach, inspired by React.
+
+**ALWAYS reference these instructions first and fallback to search or bash commands only when you encounter unexpected information that does not match the information here.**
+
+## Working Effectively
+
+### Build System Setup and Commands
+- Bootstrap and build the repository:
+  ```bash
+  # Basic build (library only) - fast
+  cmake -S . -B build -DCMAKE_BUILD_TYPE=Release
+  cmake --build build --parallel $(nproc)
+  # Build time: ~30 seconds. NEVER CANCEL. Set timeout to 120+ seconds.
+  
+  # Build with examples  
+  cmake -S . -B build -DCMAKE_BUILD_TYPE=Release -DFTXUI_BUILD_EXAMPLES=ON
+  cmake --build build --parallel $(nproc)
+  # Build time: ~70 seconds. NEVER CANCEL. Set timeout to 180+ seconds.
+  
+  # Build with examples and tests
+  cmake -S . -B build -DCMAKE_BUILD_TYPE=Release -DFTXUI_BUILD_EXAMPLES=ON -DFTXUI_BUILD_TESTS=ON
+  cmake --build build --parallel $(nproc)
+  # Build time: ~113 seconds (includes GoogleTest download). NEVER CANCEL. Set timeout to 300+ seconds.
+  ```
+
+- Alternative build with Ninja (faster):
+  ```bash
+  cmake -S . -B build -G Ninja -DCMAKE_BUILD_TYPE=Release -DFTXUI_BUILD_EXAMPLES=ON
+  ninja -C build
+  # Build time: ~62 seconds. NEVER CANCEL. Set timeout to 180+ seconds.
+  ```
+
+- Run unit tests:
+  ```bash
+  # Configure with tests enabled first, then:
+  cd build && ctest --output-on-failure
+  # Test time: ~4 seconds (302 tests). NEVER CANCEL. Set timeout to 60+ seconds.
+  ```
+
+### Bazel Support
+- FTXUI also supports Bazel build system
+- **WARNING**: Bazel may fail due to network connectivity issues in sandboxed environments
+- If Bazel is available:
+  ```bash
+  bazel build //...  # Build everything
+  bazel test //...   # Run tests
+  ```
+
+## Validation
+
+### Manual Testing After Changes
+- **ALWAYS manually validate changes by building and running examples after making code modifications**
+- Run example applications to verify functionality:
+  ```bash
+  # Build an example first
+  cmake --build build --target ftxui_example_border
+  
+  # Run examples (they are interactive, use timeout to terminate)
+  timeout 2s build/examples/dom/ftxui_example_border
+  timeout 2s build/examples/dom/ftxui_example_color_gallery
+  timeout 2s build/examples/component/ftxui_example_button
+  ```
+- Examples should produce visual terminal output with borders, colors, and UI components
+- **CRITICAL**: Always run at least one DOM example and one Component example to verify both modules work
+
+### Code Quality and Formatting
+- Always run formatting before committing:
+  ```bash
+  ./tools/format.sh
+  # Format time: ~7 seconds. NEVER CANCEL. Set timeout to 60+ seconds.
+  ```
+- The format script adds license headers and runs clang-format on all source files
+- **Required**: Run formatting or the CI (.github/workflows/build.yaml) will fail
+
+### Build Validation Requirements
+- ALWAYS build with both `-DFTXUI_BUILD_EXAMPLES=ON` and `-DFTXUI_BUILD_TESTS=ON` when making changes
+- Run the complete test suite with `ctest --output-on-failure`
+- All 302 tests must pass
+- **Scenario Testing**: Run at least these validation scenarios:
+  1. Build library only (basic validation)
+  2. Build with examples and run 2-3 different examples
+  3. Build with tests and run complete test suite
+  4. Run formatting tool to ensure code style compliance
+
+## Project Structure
+
+### Key Directories
+```
+/home/runner/work/FTXUI/FTXUI/
+├── include/ftxui/           # Public header files
+│   ├── component/           # Interactive component headers
+│   ├── dom/                 # DOM element headers  
+│   ├── screen/              # Screen and rendering headers
+│   └── util/                # Utility headers
+├── src/ftxui/               # Implementation files
+│   ├── component/           # Interactive components (buttons, menus, etc.)
+│   ├── dom/                 # DOM elements (layout, styling, text)
+│   ├── screen/              # Screen rendering and terminal handling
+│   └── util/                # Utilities
+├── examples/                # Example applications
+│   ├── component/           # Interactive component examples
+│   └── dom/                 # DOM element examples
+├── cmake/                   # CMake configuration files
+├── tools/                   # Development tools (formatting, etc.)
+└── .github/workflows/       # CI/CD configuration
+```
+
+### Core Library Modules
+FTXUI is organized into three main modules that depend on each other:
+```
+┌component──┐  (Interactive UI components)
+│┌dom──────┐│  (Layout and styling elements)  
+││┌screen─┐││  (Terminal rendering and input)
+└┴┴───────┴┴┘
+```
+
+1. **screen**: Low-level terminal handling, colors, pixels, input
+2. **dom**: Layout elements (hbox, vbox, text, borders, etc.)
+3. **component**: Interactive components (buttons, menus, input fields)
+
+### CMake Build Options
+| Option                            | Description                      | Default |
+|-----------------------------------|----------------------------------|---------|
+| FTXUI_BUILD_EXAMPLES              | Build example applications       | OFF     |
+| FTXUI_BUILD_DOCS                  | Build documentation             | OFF     |  
+| FTXUI_BUILD_TESTS                 | Build and enable tests          | OFF     |
+| FTXUI_BUILD_MODULES               | Build C++20 modules             | OFF     |
+| FTXUI_ENABLE_INSTALL              | Generate install targets        | ON      |
+| FTXUI_MICROSOFT_TERMINAL_FALLBACK | Windows terminal compatibility  | ON/OFF  |
+
+## Common Tasks
+
+### Building Examples
+```bash
+# Build specific examples
+cmake --build build --target ftxui_example_border
+cmake --build build --target ftxui_example_button
+cmake --build build --target ftxui_example_menu
+
+# List all available examples
+find build -name "ftxui_example_*" -type f
+```
+
+### Running Tests
+```bash
+# Run all tests
+cd build && ctest
+
+# Run tests with verbose output
+cd build && ctest --verbose
+
+# Run specific test pattern
+cd build && ctest -R "Button" --verbose
+```
+
+### Working with Source Code
+- **Component Development**: Modify files in `src/ftxui/component/` for interactive elements
+- **DOM Development**: Modify files in `src/ftxui/dom/` for layout and styling
+- **Screen Development**: Modify files in `src/ftxui/screen/` for terminal rendering
+- **Adding Examples**: Add new `.cpp` files in `examples/component/` or `examples/dom/`
+- **Header Files**: Public APIs are in `include/ftxui/[module]/`
+
+### Integration Patterns
+When adding FTXUI to a project, use CMake FetchContent (recommended):
+```cmake
+include(FetchContent)
+FetchContent_Declare(ftxui
+  GIT_REPOSITORY https://github.com/ArthurSonzogni/ftxui
+  GIT_TAG v6.1.9
+)
+FetchContent_MakeAvailable(ftxui)
+
+target_link_libraries(your_target PRIVATE
+    ftxui::component  # For interactive components
+    ftxui::dom        # For layout elements  
+    ftxui::screen     # For basic rendering
+)
+```
+
+## Troubleshooting
+
+### Build Issues
+- If CMake configuration fails, ensure C++20 support: `cmake --version` (need 3.12+)
+- If Ninja build fails, fall back to Make: `cmake -S . -B build` (without `-G Ninja`)
+- If tests fail to build, GoogleTest download might have failed - check network connectivity
+- Build artifacts are in `build/` directory - delete with `rm -rf build` to clean
+
+### Example Issues  
+- Examples are interactive terminal applications - use `timeout` to terminate them
+- If examples don't display correctly, terminal might not support colors/Unicode
+- Examples require terminal size of at least 80x24 for proper display
+
+### Formatting Issues
+- Format script requires clang-format to be installed
+- If format script fails, check that source files are not read-only
+- Format script modifies files in-place - commit changes afterwards
+
+## Critical Reminders
+
+- **NEVER CANCEL long-running builds** - they may take 2-3 minutes
+- **ALWAYS run the formatting tool** before committing changes  
+- **ALWAYS build and test examples** when making component/dom changes
+- **SET APPROPRIATE TIMEOUTS**: 300+ seconds for builds, 60+ seconds for tests
+- **BUILD TIMING EXPECTATIONS**:
+  - Basic library: ~30 seconds
+  - With examples: ~70 seconds  
+  - With examples + tests: ~113 seconds (first time, includes GoogleTest download)
+  - Subsequent builds: ~60-70 seconds
+  - Tests execution: ~4 seconds
+  - Formatting: ~7 seconds

.github/workflows/documentation.yaml

@@ -12,6 +12,10 @@ jobs:
     steps:
       - name: "Checkout repository"
         uses: actions/checkout@v3
+        with:
+          fetch-depth: 0   # Need full history.
+          fetch-tags: true # Need tags.
+
 
       - name: "Install cmake"
         uses: lukka/get-cmake@latest
@@ -30,19 +34,23 @@ jobs:
           sudo apt-get install graphviz;
 
       - name: "Build documentation"
+        run: |
+          python3 ./tools/build_multiversion_doc.py
+
+      - name: "Build examples"
         run: >
+          mkdir -p multiversion_docs/main/examples;
           mkdir build;
           cd build;
           emcmake cmake ..
           -DCMAKE_BUILD_TYPE=Release
-          -DFTXUI_BUILD_DOCS=ON
+          -DFTXUI_BUILD_DOCS=OFF
           -DFTXUI_BUILD_EXAMPLES=ON
           -DFTXUI_BUILD_TESTS=OFF
           -DFTXUI_BUILD_TESTS_FUZZER=OFF
           -DFTXUI_ENABLE_INSTALL=OFF
           -DFTXUI_DEV_WARNINGS=OFF;
           cmake --build . --target doc;
-          cmake --build . ;
           rsync -amv
           --include='*/'
           --include='*.html'
@@ -52,13 +60,13 @@ jobs:
           --include='*.wasm'
           --exclude='*'
           examples
-          doc/doxygen/html;
+          ../multiversion_docs/main/examples;
 
       - name: "Deploy"
         uses: peaceiris/actions-gh-pages@v3
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
-          publish_dir: build/doc/doxygen/html/
+          publish_dir: multiversion_docs
           enable_jekyll: false
           allow_empty_commit: false
           force_orphan: true

.gitignore

@@ -28,6 +28,7 @@ out/
 # .github directory:
 !.github/**/*.yaml
 !.github/**/*.yml
+!.github/**/*.md
 
 # cmake directory:
 !cmake/**/*.in
@@ -69,4 +70,6 @@ out/
 
 # tools directory:
 !tools/**/*.sh
+!tools/**/*.py
 !tools/**/*.cpp
+build/

build/_deps/googlebenchmark-subbuild/CMakeLists.txt

@@ -1,42 +0,0 @@
-# Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
-# file Copyright.txt or https://cmake.org/licensing for details.
-
-cmake_minimum_required(VERSION 3.31.6)
-
-# Reject any attempt to use a toolchain file. We must not use one because
-# we could be downloading it here. If the CMAKE_TOOLCHAIN_FILE environment
-# variable is set, the cache variable will have been initialized from it.
-unset(CMAKE_TOOLCHAIN_FILE CACHE)
-unset(ENV{CMAKE_TOOLCHAIN_FILE})
-
-# We name the project and the target for the ExternalProject_Add() call
-# to something that will highlight to the user what we are working on if
-# something goes wrong and an error message is produced.
-
-project(googlebenchmark-populate NONE)
-
-
-# Pass through things we've already detected in the main project to avoid
-# paying the cost of redetecting them again in ExternalProject_Add()
-set(GIT_EXECUTABLE [==[/usr/bin/git]==])
-set(GIT_VERSION_STRING [==[2.51.0]==])
-set_property(GLOBAL PROPERTY _CMAKE_FindGit_GIT_EXECUTABLE_VERSION
-  [==[/usr/bin/git;2.51.0]==]
-)
-
-
-include(ExternalProject)
-ExternalProject_Add(googlebenchmark-populate
-                     "UPDATE_DISCONNECTED" "False" "GIT_REPOSITORY" "https://github.com/google/benchmark" "EXTERNALPROJECT_INTERNAL_ARGUMENT_SEPARATOR" "GIT_TAG" "015d1a091af6937488242b70121858bce8fd40e9" "GIT_PROGRESS" "TRUE"
-                    SOURCE_DIR          "/home/runner/work/FTXUI/FTXUI/build/_deps/googlebenchmark-src"
-                    BINARY_DIR          "/home/runner/work/FTXUI/FTXUI/build/_deps/googlebenchmark-build"
-                    CONFIGURE_COMMAND   ""
-                    BUILD_COMMAND       ""
-                    INSTALL_COMMAND     ""
-                    TEST_COMMAND        ""
-                    USES_TERMINAL_DOWNLOAD  YES
-                    USES_TERMINAL_UPDATE    YES
-                    USES_TERMINAL_PATCH     YES
-)
-
-

build/_deps/googletest-subbuild/CMakeLists.txt

@@ -1,42 +0,0 @@
-# Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
-# file Copyright.txt or https://cmake.org/licensing for details.
-
-cmake_minimum_required(VERSION 3.31.6)
-
-# Reject any attempt to use a toolchain file. We must not use one because
-# we could be downloading it here. If the CMAKE_TOOLCHAIN_FILE environment
-# variable is set, the cache variable will have been initialized from it.
-unset(CMAKE_TOOLCHAIN_FILE CACHE)
-unset(ENV{CMAKE_TOOLCHAIN_FILE})
-
-# We name the project and the target for the ExternalProject_Add() call
-# to something that will highlight to the user what we are working on if
-# something goes wrong and an error message is produced.
-
-project(googletest-populate NONE)
-
-
-# Pass through things we've already detected in the main project to avoid
-# paying the cost of redetecting them again in ExternalProject_Add()
-set(GIT_EXECUTABLE [==[/usr/bin/git]==])
-set(GIT_VERSION_STRING [==[2.51.0]==])
-set_property(GLOBAL PROPERTY _CMAKE_FindGit_GIT_EXECUTABLE_VERSION
-  [==[/usr/bin/git;2.51.0]==]
-)
-
-
-include(ExternalProject)
-ExternalProject_Add(googletest-populate
-                     "UPDATE_DISCONNECTED" "False" "GIT_REPOSITORY" "https://github.com/google/googletest" "EXTERNALPROJECT_INTERNAL_ARGUMENT_SEPARATOR" "GIT_TAG" "23ef29555ef4789f555f1ba8c51b4c52975f0907" "GIT_PROGRESS" "TRUE"
-                    SOURCE_DIR          "/home/runner/work/FTXUI/FTXUI/build/_deps/googletest-src"
-                    BINARY_DIR          "/home/runner/work/FTXUI/FTXUI/build/_deps/googletest-build"
-                    CONFIGURE_COMMAND   ""
-                    BUILD_COMMAND       ""
-                    INSTALL_COMMAND     ""
-                    TEST_COMMAND        ""
-                    USES_TERMINAL_DOWNLOAD  YES
-                    USES_TERMINAL_UPDATE    YES
-                    USES_TERMINAL_PATCH     YES
-)
-
-

cmake/ftxui_install.cmake

@@ -11,9 +11,6 @@ include(CMakePackageConfigHelpers)
 install(
   TARGETS screen dom component
   EXPORT ftxui-targets
-  ARCHIVE DESTINATION "${CMAKE_INSTALL_LIBDIR}"
-  LIBRARY DESTINATION "${CMAKE_INSTALL_LIBDIR}"
-  RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}"
   )
 
 install(

doc/footer.html

@@ -2,16 +2,9 @@
 <!-- start footer part -->
 <!--BEGIN GENERATE_TREEVIEW-->
 <div id="nav-path" class="navpath"><!-- id is needed for treeview function! -->
-  <ul>
-    $navpath
-    <li class="footer">$generatedby <a href="https://www.doxygen.org/index.html"><img class="footer" src="$relpath^doxygen.svg" width="104" height="31" alt="doxygen"/></a> $doxygenversion </li>
-  </ul>
 </div>
 <!--END GENERATE_TREEVIEW-->
 <!--BEGIN !GENERATE_TREEVIEW-->
-<hr class="footer"/><address class="footer"><small>
-$generatedby&#160;<a href="https://www.doxygen.org/index.html"><img class="footer" src="$relpath^doxygen.svg" width="104" height="31" alt="doxygen"/></a> $doxygenversion
-</small></address>
 <!--END !GENERATE_TREEVIEW-->
 </body>
 </html>

include/ftxui/component/receiver.hpp

@@ -4,14 +4,14 @@
 #ifndef FTXUI_COMPONENT_RECEIVER_HPP_
 #define FTXUI_COMPONENT_RECEIVER_HPP_
 
-#include <ftxui/util/warn_windows_macro.hpp>
 #include <algorithm>           // for copy, max
 #include <atomic>              // for atomic, __atomic_base
 #include <condition_variable>  // for condition_variable
-#include <memory>              // for unique_ptr, make_unique
-#include <mutex>               // for mutex, unique_lock
-#include <queue>               // for queue
-#include <utility>             // for move
+#include <ftxui/util/warn_windows_macro.hpp>
+#include <memory>   // for unique_ptr, make_unique
+#include <mutex>    // for mutex, unique_lock
+#include <queue>    // for queue
+#include <utility>  // for move
 
 namespace ftxui {
 

src/ftxui/component/task_runner.hpp

@@ -21,8 +21,8 @@ class TaskRunner {
   auto PostTask(Task task) -> void;
 
   /// Schedules a task to be executed after a certain duration.
-  auto PostDelayedTask(Task task, std::chrono::steady_clock::duration duration)
-      -> void;
+  auto PostDelayedTask(Task task,
+                       std::chrono::steady_clock::duration duration) -> void;
 
   /// Runs the tasks in the queue, return the delay until the next delayed task
   /// can be executed.

tools/build_multiversion_doc.py

@@ -0,0 +1,222 @@
+#!/usr/bin/env python3
+
+import os
+import subprocess
+import shutil
+import tempfile
+import json
+from pathlib import Path
+from typing import List, Dict
+
+class VersionInfo:
+    """A structure to hold all information about a single documentation version."""
+    def __init__(self, name: str, is_main: bool, output_root: Path):
+        self.name = name
+        self.is_main = is_main
+        # Destination directory for the built docs, relative to the output root.
+        self.dest_dir = output_root if is_main else output_root / "en" / name
+        # The path to this version's index.html, relative to the output root.
+        self.index_path_from_root = self.dest_dir / "index.html"
+
+    def __repr__(self) -> str:
+        return f"VersionInfo(name='{self.name}', dest_dir='{self.dest_dir}')"
+
+def run_command(command: List[str], check: bool = True, cwd: Path = None):
+    """
+    Runs a command, prints its output, and handles errors.
+    """
+    command_str = ' '.join(command)
+    print(f"Executing: {command_str} in {cwd or Path.cwd()}")
+    try:
+        # Using capture_output=True to get stdout/stderr
+        result = subprocess.run(
+            command,
+            capture_output=True,
+            text=True,
+            check=check,
+            cwd=cwd
+        )
+        if result.stdout:
+            print(result.stdout)
+        if result.stderr:
+            print(result.stderr)
+        return result
+    except subprocess.CalledProcessError as e:
+        print(f"ERROR: Command failed with exit code {e.returncode}")
+        print(f"Command: {command_str}")
+        if e.stdout:
+            print("--- STDOUT ---")
+            print(e.stdout)
+        if e.stderr:
+            print("--- STDERR ---")
+            print(e.stderr)
+        raise  # Re-raise the exception to halt the script
+
+def get_version_switcher_js(
+    current_version: VersionInfo,
+    all_versions: List[VersionInfo],
+    current_html_file: Path
+) -> str:
+    """
+    Generates the JavaScript for the version switcher dropdown.
+
+    This version pre-calculates the relative path from the current HTML file
+    to the index.html of every other version, simplifying the JS logic.
+    """
+    version_names = [v.name for v in all_versions]
+
+    # Create a dictionary mapping version names to their relative URLs.
+    relative_paths: Dict[str, str] = {}
+    for version in all_versions:
+        # Calculate the relative path from the *parent directory* of the current HTML file
+        # to the target version's index.html.
+        path = os.path.relpath(version.index_path_from_root, current_html_file.parent)
+        relative_paths[version.name] = path
+
+    # Use json.dumps for safe serialization of data into JavaScript.
+    versions_json = json.dumps(version_names)
+    paths_json = json.dumps(relative_paths)
+    current_version_json = json.dumps(current_version.name)
+
+    return f"""
+document.addEventListener('DOMContentLoaded', function() {{
+  const projectNumber = document.getElementById('projectnumber');
+  if (!projectNumber) {{
+    console.warn('Doxygen element with ID "projectnumber" not found. Cannot add version switcher.');
+    return;
+  }}
+
+  const versions = {versions_json};
+  const version_paths = {paths_json};
+  const currentVersion = {current_version_json};
+
+  // Sort versions: 'main' first, then others numerically descending.
+  versions.sort((a, b) => {{
+    if (a === 'main') return -1;
+    if (b === 'main') return 1;
+    return b.localeCompare(a, undefined, {{ numeric: true, sensitivity: 'base' }});
+  }});
+
+  const select = document.createElement('select');
+  select.onchange = function() {{
+    const selectedVersion = this.value;
+    // Navigate directly to the pre-calculated relative path.
+    if (selectedVersion !== currentVersion) {{
+      window.location.href = version_paths[selectedVersion];
+    }}
+  }};
+
+  versions.forEach(v => {{
+    const option = document.createElement('option');
+    option.value = v;
+    option.textContent = v;
+    if (v === currentVersion) {{
+      option.selected = true;
+    }}
+    select.appendChild(option);
+  }});
+
+  // Replace the Doxygen project number element with our dropdown.
+  projectNumber.replaceWith(select);
+
+  // Apply some styling to make it look good.
+  Object.assign(select.style, {{
+    backgroundColor: 'rgba(0, 0, 0, 0.8)',
+    color: 'white',
+    border: '1px solid rgba(255, 255, 255, 0.2)',
+    padding: '5px',
+    borderRadius: '5px',
+    fontSize: '14px',
+    fontFamily: 'inherit',
+    marginLeft: '10px',
+    cursor: 'pointer'
+  }});
+}});
+"""
+
+def main():
+    """Main function to build multi-version documentation."""
+    root_dir = Path.cwd()
+    output_dir = root_dir / "multiversion_docs"
+
+    print("--- 1. Cleaning up old documentation ---")
+    if output_dir.exists():
+        shutil.rmtree(output_dir)
+    output_dir.mkdir(parents=True, exist_ok=True)
+
+    print("--- 2. Getting versions from git ---")
+    git_tags_result = run_command(["git", "tag", "--list", "v*"])
+    # Create a list of version names, starting with 'main'.
+    version_names = ["main"] + sorted(
+        git_tags_result.stdout.splitlines(),
+        reverse=True
+    )
+    # For demonstration, limit the number of versions. Remove this in production.
+    version_names = version_names[:4]
+    print(f"Versions to build: {', '.join(version_names)}")
+
+    # Pre-compute all version information and paths.
+    versions = [
+        VersionInfo(name, name == "main", output_dir)
+        for name in version_names
+    ]
+
+    with tempfile.TemporaryDirectory() as build_dir_str:
+        build_dir = Path(build_dir_str)
+        # --- 3. Build documentation for each version ---
+        for version in versions:
+            print(f"\n--- Building docs for version: {version.name} ---")
+
+            # Create a temporary directory for this version's source code.
+            version_src_dir = build_dir / f"src_{version.name}"
+            version_src_dir.mkdir()
+
+            # Check out the version's source code from git.
+            archive_path = version_src_dir / "source.tar"
+            run_command([
+                "git", "archive", version.name,
+                "--format=tar", f"--output={archive_path}"
+            ])
+            run_command(["tar", "-xf", str(archive_path)], cwd=version_src_dir)
+            archive_path.unlink()
+
+            # Configure and build the docs using CMake.
+            version_build_dir = build_dir / f"build_{version.name}"
+            version_build_dir.mkdir()
+            run_command([
+                "cmake", str(version_src_dir), "-DFTXUI_BUILD_DOCS=ON"
+            ], cwd=version_build_dir)
+            run_command(["make", "doc"], cwd=version_build_dir)
+
+            # Copy the generated HTML files to the final destination.
+            doxygen_html_dir = version_build_dir / "doc" / "doxygen" / "html"
+            if not doxygen_html_dir.is_dir():
+                print(f"FATAL: Doxygen HTML output not found for version {version.name}")
+                exit(1)
+
+            print(f"Copying files to: {version.dest_dir}")
+            shutil.copytree(doxygen_html_dir, version.dest_dir, dirs_exist_ok=True)
+
+    # --- 4. Inject version switcher into all HTML files ---
+    print("\n--- Injecting version switcher JavaScript ---")
+    for version in versions:
+        if not version.dest_dir.exists():
+            print(f"Warning: Destination directory for {version.name} does not exist. Skipping JS injection.")
+            continue
+        
+        print(f"Processing HTML files in: {version.dest_dir}")
+        for html_file in version.dest_dir.rglob("*.html"):
+            js_script = get_version_switcher_js(version, versions, html_file)
+            script_tag = f'<script>{js_script}</script>'
+
+            content = html_file.read_text(encoding='utf-8')
+            # Inject the script right before the closing body tag.
+            new_content = content.replace("</body>", f"{script_tag}\n</body>")
+            html_file.write_text(new_content, encoding='utf-8')
+
+    print("\n--- 5. Finalizing ---")
+    print("Multi-version documentation generated successfully!")
+    print(f"Output located in: {output_dir.resolve()}")
+
+if __name__ == "__main__":
+    main()