Make build system fully configurable

With the inclusion of kconfiglib [1], the build system is now fully
configurable like "menuconfig" when building the Linux kernel. It allows
users to select the desired backend, choose whether to build
applications, and specify supported image loaders. This flexibility is
also useful for developers to integrate additional backends such as
Linux framebuffer and DRM device support.

[1] https://pypi.org/project/kconfiglib/

.gitignore

@@ -9,6 +9,11 @@ libbackend.a
 .libbackend.a
 libapps.a
 .libapps.a
+.config
+.config.old
+config.h
+__pycache__
+*.pyc
 
 # Tools
 tools/ttf/twin-ttf

Kconfig

@@ -0,0 +1,67 @@
+mainmenu "Mado System Configuration"
+
+config CONFIGURED
+    bool
+    default y
+
+choice
+    prompt "Backend Selection"
+    default BACKEND_SDL
+
+config BACKEND_FBDEV
+    bool "Linux framebuffer support"
+
+config BACKEND_SDL
+    bool "SDL video output support"
+
+endchoice
+
+menu "Image Loaders"
+
+config LOADER_PNG
+    bool "Enable PNG loader"
+    default y
+
+config LOADER_JPEG
+    bool "Enable JPEG loader"
+    default y
+
+endmenu
+
+menu "Demo Applications"
+
+config DEMO_APPLICATIONS
+    bool "Build demo applications"
+    default y
+
+config DEMO_MULTI
+    bool "Build multi demo"
+    default y
+    depends on DEMO_APPLICATIONS
+
+config DEMO_HELLO
+    bool "Build Hello world demo"
+    default y
+    depends on DEMO_APPLICATIONS
+
+config DEMO_CLOCK
+    bool "Build clock demo"
+    default y
+    depends on DEMO_APPLICATIONS
+
+config DEMO_CALCULATOR
+    bool "Build calculator demo"
+    default y
+    depends on DEMO_APPLICATIONS
+
+config DEMO_LINE
+    bool "Build line demo"
+    default y
+    depends on DEMO_APPLICATIONS
+
+config DEMO_SPLINE
+    bool "Build spline demp"
+    default y
+    depends on DEMO_APPLICATIONS 
+
+endmenu

Makefile

@@ -1,17 +1,21 @@
-# FIXME: make these entries configurable
-CONFIG_BACKEND_SDL ?= y
-CONFIG_LOADER_JPEG ?= y
-CONFIG_LOADER_PNG ?= y
+-include .config
+
+check_goal := $(strip $(MAKECMDGOALS))
+ifneq ($(check_goal), config)
+ifneq "$(CONFIG_CONFIGURED)" "y"
+$(error You must first run 'make config')
+endif
+endif
 
 # Rules
 
 target-y :=
 target.o-y :=
 TARGET_LIBS :=
 
-target.a-y = \
-	libapps.a \
-	libtwin.a
+target.a-y :=
+target.a-$(CONFIG_DEMO_APPLICATIONS) += libapps.a
+target.a-y += libtwin.a
 
 # Core library
 
@@ -68,17 +72,18 @@ endif
 
 # Applications
 
-libapps.a_files-y = \
-	apps/calc.c \
-	apps/spline.c \
-	apps/clock.c \
-	apps/line.c \
-	apps/hello.c \
-	apps/demo.c
+libapps.a_files-y := apps/dummy.c
+libapps.a_files-$(CONFIG_DEMO_MULTI) += apps/demo.c
+libapps.a_files-$(CONFIG_DEMO_HELLO) += apps/hello.c
+libapps.a_files-$(CONFIG_DEMO_CLOCK) += apps/clock.c
+libapps.a_files-$(CONFIG_DEMO_CALCULATOR) += apps/calc.c
+libapps.a_files-$(CONFIG_DEMO_LINE) += apps/line.c
+libapps.a_files-$(CONFIG_DEMO_SPLINE) += apps/spline.c
 
 libapps.a_includes-y := include
 
 # Graphical backends
+
 BACKEND := none
 
 ifeq ($(CONFIG_BACKEND_SDL), y)
@@ -88,13 +93,27 @@ libtwin.a_cflags-y += $(shell sdl2-config --cflags)
 TARGET_LIBS += $(shell sdl2-config --libs)
 endif
 
-# Platform-specific executables
+# Standalone application
+
+ifeq ($(CONFIG_DEMO_APPLICATIONS), y)
 target-y += demo-$(BACKEND)
 demo-$(BACKEND)_depends-y += $(target.a-y)
 demo-$(BACKEND)_files-y = apps/main.c
 demo-$(BACKEND)_includes-y := include
 demo-$(BACKEND)_ldflags-y := \
 	$(target.a-y) \
 	$(TARGET_LIBS)
+endif
+
+CFLAGS += -include config.h
 
+check_goal := $(strip $(MAKECMDGOALS))
+ifneq ($(check_goal), config)
 include mk/common.mk
+endif
+
+# Menuconfig
+.PHONY: config
+config:
+	@tools/kconfig/menuconfig.py
+	@tools/kconfig/genconfig.py

README.md

@@ -62,6 +62,11 @@ have the [SDL2 library](https://www.libsdl.org/), [libjpeg](https://www.ijg.org/
 * macOS: `brew install sdl2 jpeg libpng`
 * Ubuntu Linux / Debian: `sudo apt install libsdl2-dev libjpeg-dev libpng-dev`
 
+Configure via [Kconfiglib](https://pypi.org/project/kconfiglib/)
+```shell
+$ make config
+```
+
 Build the library and demo program.
 ```shell
 $ make

apps/dummy.c

@@ -0,0 +1 @@
+/* Placeholder */

apps/main.c

@@ -1,5 +1,6 @@
 /*
  * Twin - A Tiny Window System
+ * Copyright (c) 2024 National Cheng Kung University, Taiwan
  * Copyright (c) 2004 Keith Packard <[email protected]>
  * All rights reserved.
  */
@@ -33,6 +34,7 @@
 static twin_pixmap_t *load_background(twin_screen_t *screen,
                                       const char *filename)
 {
+#if defined(CONFIG_LOADER_PNG)
     twin_pixmap_t *raw_background = twin_png_to_pixmap(filename, TWIN_ARGB32);
     if (!raw_background) /* Fallback to a default pattern */
         return twin_make_pattern();
@@ -65,6 +67,9 @@ static twin_pixmap_t *load_background(twin_screen_t *screen,
     twin_pixmap_destroy(raw_background);
 
     return scaled_background;
+#else
+    return twin_make_pattern();
+#endif
 }
 
 static twin_context_t *tx = NULL;
@@ -99,12 +104,24 @@ int main(void)
     twin_screen_set_background(
         tx->screen, load_background(tx->screen, ASSET_PATH "/tux.png"));
 
+#if defined(CONFIG_DEMO_MULTI)
     apps_demo_start(tx->screen, "Demo", 100, 100, 400, 400);
+#endif
+#if defined(CONFIG_DEMO_HELLO)
     apps_hello_start(tx->screen, "Hello, World", 0, 0, 200, 200);
+#endif
+#if defined(CONFIG_DEMO_CLOCK)
     apps_clock_start(tx->screen, "Clock", 10, 10, 200, 200);
+#endif
+#if defined(CONFIG_DEMO_CALCULATOR)
     apps_calc_start(tx->screen, "Calculator", 100, 100, 200, 200);
+#endif
+#if defined(CONFIG_DEMO_LINE)
     apps_line_start(tx->screen, "Line", 0, 0, 200, 200);
+#endif
+#if defined(CONFIG_DEMO_SPLINE)
     apps_spline_start(tx->screen, "Spline", 20, 20, 400, 400);
+#endif
 
     twin_dispatch();
 

tools/kconfig/.gitignore

@@ -0,0 +1,4 @@
+*.py[co]
+build/
+*.egg-info/
+dist/

tools/kconfig/LICENSE

@@ -0,0 +1,13 @@
+Copyright (c) 2011-2019, Ulf Magnusson <[email protected]>
+
+Permission to use, copy, modify, and/or distribute this software for any purpose
+with or without fee is hereby granted, provided that the above copyright notice
+and this permission notice appear in all copies.
+
+THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
+FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
+OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
+THIS SOFTWARE.

tools/kconfig/README.md

@@ -0,0 +1,5 @@
+# Kconfiglib
+
+A flexible Python 2/3 Kconfig implementation and library.
+
+Taken from https://github.com/ulfalizer/Kconfiglib

tools/kconfig/defconfig.py

@@ -0,0 +1,43 @@
+#!/usr/bin/env python3
+
+# Copyright (c) 2019, Ulf Magnusson
+# SPDX-License-Identifier: ISC
+
+"""
+Reads a specified configuration file, then writes a new configuration file.
+This can be used to initialize the configuration from e.g. an arch-specific
+configuration file. This input configuration file would usually be a minimal
+configuration file, as generated by e.g. savedefconfig.
+
+The default output filename is '.config'. A different filename can be passed in
+the KCONFIG_CONFIG environment variable.
+"""
+import argparse
+
+import kconfiglib
+
+
+def main():
+    parser = argparse.ArgumentParser(
+        formatter_class=argparse.RawDescriptionHelpFormatter,
+        description=__doc__)
+
+    parser.add_argument(
+        "--kconfig",
+        default="Kconfig",
+        help="Top-level Kconfig file (default: Kconfig)")
+
+    parser.add_argument(
+        "config",
+        metavar="CONFIGURATION",
+        help="Input configuration file")
+
+    args = parser.parse_args()
+
+    kconf = kconfiglib.Kconfig(args.kconfig, suppress_traceback=True)
+    print(kconf.load_config(args.config))
+    print(kconf.write_config())
+
+
+if __name__ == "__main__":
+    main()