Switch Docker to Alpine and build kge.

Update build environment to Alpine, enable GUI support, and refine developer guide

- Migrated Dockerfile base image from Ubuntu 22.04 to Alpine 3.19 for a smaller and faster container.
- Added dependencies for GUI support (SDL2, OpenGL/Mesa, Freetype, etc.) and updated CMake options.
- Enhanced `DEVELOPER_GUIDE.md` with new instructions for GUI builds, updated dependencies, and simplified custom build workflows.
- Addressed Alpine-specific ncurses library path issues in CMake configuration.

CMakeLists.txt

@@ -68,15 +68,17 @@ if (BUILD_GUI)
 endif ()
 
 # NCurses for terminal mode
-set(CURSES_NEED_NCURSES)
-set(CURSES_NEED_WIDE)
+set(CURSES_NEED_NCURSES TRUE)
+set(CURSES_NEED_WIDE TRUE)
 find_package(Curses REQUIRED)
 include_directories(${CURSES_INCLUDE_DIR})
 
-# On Linux, explicitly link ncursesw for wide-character support
-if (CMAKE_SYSTEM_NAME STREQUAL "Linux")
-    find_library(NCURSESW_LIBRARY NAMES ncursesw REQUIRED)
-    set(CURSES_LIBRARIES ${NCURSESW_LIBRARY})
+# On Alpine Linux, CMake's FindCurses looks in wrong paths
+# Manually find the correct ncurses library
+if (EXISTS "/etc/alpine-release")
+    find_library(NCURSESW_LIB NAMES ncursesw PATHS /usr/lib /lib REQUIRED)
+    set(CURSES_LIBRARIES ${NCURSESW_LIB})
+    message(STATUS "Alpine Linux detected, using ncurses at: ${NCURSESW_LIB}")
 endif ()
 
 set(SYNTAX_SOURCES

Dockerfile

@@ -1,20 +1,23 @@
 # Minimal Dockerfile for building and testing kte on Linux
 # This container provides a build environment with all dependencies.
 # Mount the source tree at /kte when running the container.
-FROM ubuntu:22.04
-
-# Avoid interactive prompts during package installation
-ENV DEBIAN_FRONTEND=noninteractive
+FROM alpine:3.19
 
 # Install build dependencies
-RUN apt-get update && apt-get install -y \
-    build-essential \
+RUN apk add --no-cache \
+    g++ \
     cmake \
-    libncursesw5-dev \
-    && rm -rf /var/lib/apt/lists/*
+    make \
+    ncurses-dev \
+    sdl2-dev \
+    mesa-dev \
+    freetype-dev \
+    libx11-dev \
+    libxext-dev
 
 # Set working directory where source will be mounted
 WORKDIR /kte
 
 # Default command: build and run tests
-CMD ["sh", "-c", "cmake -B build -DBUILD_GUI=OFF -DBUILD_TESTS=ON && cmake --build build --target kte && cmake --build build --target kte_tests && ./build/kte_tests"]
+# Add DirectFB include path for SDL2 compatibility on Alpine
+CMD ["sh", "-c", "cmake -B build -DBUILD_GUI=ON -DBUILD_TESTS=ON -DCMAKE_CXX_FLAGS='-I/usr/include/directfb' && cmake --build build --target kte && cmake --build build --target kge && cmake --build build --target kte_tests && ./build/kte_tests"]

docs/DEVELOPER_GUIDE.md

@@ -309,7 +309,7 @@ This is particularly useful for:
 
 - **macOS/Windows developers** testing Linux compatibility
 - **CI/CD pipelines** ensuring cross-platform builds
-- **Reproducible builds** with a known Ubuntu 22.04 environment
+- **Reproducible builds** with a known Alpine Linux 3.19 environment
 
 #### Prerequisites
 
@@ -328,8 +328,9 @@ podman machine start
 
 #### Building the Docker Image
 
-The Dockerfile only installs build dependencies (g++ 11.4.0, CMake 3.22,
-libncursesw5-dev). It does not copy or build the source code.
+The Dockerfile installs all build dependencies including GUI support (
+g++ 13.2.1, CMake 3.27.8, ncurses-dev, SDL2, OpenGL/Mesa, Freetype). It
+does not copy or build the source code.
 
 From the project root:
 
@@ -352,8 +353,9 @@ docker run --rm -v "$(pwd):/kte" kte-linux
 # Expected output: "98 tests passed, 0 failed"
 ```
 
-The default command builds kte in terminal-only mode (`-DBUILD_GUI=OFF`)
-and runs the full test suite.
+The default command builds both `kte` (terminal) and `kge` (GUI)
+executables with full GUI support (`-DBUILD_GUI=ON`) and runs the
+complete test suite.
 
 #### Custom Build Commands
 
@@ -362,13 +364,18 @@ and runs the full test suite.
 docker run --rm -it -v "$(pwd):/kte" kte-linux /bin/bash
 
 # Then inside the container:
-cmake -B build -DBUILD_GUI=OFF -DBUILD_TESTS=ON
-cmake --build build --target kte
+cmake -B build -DBUILD_GUI=ON -DBUILD_TESTS=ON
+cmake --build build --target kte      # Terminal version
+cmake --build build --target kge      # GUI version
 cmake --build build --target kte_tests
 ./build/kte_tests
 
 # Or run kte directly
 ./build/kte --help
+
+# Terminal-only build (smaller, faster)
+cmake -B build -DBUILD_GUI=OFF -DBUILD_TESTS=ON
+cmake --build build --target kte
 ```
 
 #### Running kte Interactively
@@ -408,7 +415,7 @@ sudo usermod -aG docker $USER
 ```
 
 **Build fails with ncurses errors**:
-The Dockerfile explicitly installs `libncursesw5-dev` (wide-character
+The Dockerfile explicitly installs `ncurses-dev` (wide-character
 ncurses). If you modify the Dockerfile, ensure this dependency remains.
 
 **"No such file or directory" errors**: