Consolidate logging with a unified interface

Currently, various messages are displayed while the window system is
running, but their format and usage are inconsistent. Additionally,
depending on the scenario, it may be useful to adjust the color scheme
or disable logging output altogether.

The rxi/log.c [1] offers a robust solution for these needs, and it would
be beneficial to integrate it into the core implementation of the window
system to standardize logging and enhance flexibility.
 - log_trace
 - log_debug
 - log_info
 - log_warn
 - log_error
 - log_fatal

[1] https://github.com/rxi/log.c

Close #47

Makefile

@@ -59,6 +59,7 @@ libtwin.a_includes-y := \
 	src
 
 # Features
+libtwin.a_files-$(CONFIG_LOGGING) += src/log.c
 libtwin.a_files-$(CONFIG_CURSOR) += src/cursor.c
 
 # Image loaders

backend/sdl.c

@@ -143,7 +143,7 @@ twin_context_t *twin_sdl_init(int width, int height)
     }
 
     if (SDL_Init(SDL_INIT_VIDEO) < 0) {
-        printf("error : %s\n", SDL_GetError());
+        log_error("%s", SDL_GetError());
         goto bail;
     }
 
@@ -154,7 +154,7 @@ twin_context_t *twin_sdl_init(int width, int height)
                                SDL_WINDOWPOS_UNDEFINED, width, height,
                                SDL_WINDOW_SHOWN);
     if (!tx->win) {
-        printf("error : %s\n", SDL_GetError());
+        log_error("%s", SDL_GetError());
         goto bail;
     }
 
@@ -163,7 +163,7 @@ twin_context_t *twin_sdl_init(int width, int height)
 
     tx->render = SDL_CreateRenderer(tx->win, -1, SDL_RENDERER_ACCELERATED);
     if (!tx->render) {
-        printf("error : %s\n", SDL_GetError());
+        log_error("%s", SDL_GetError());
         goto bail_pixels;
     }
     SDL_SetRenderDrawColor(tx->render, 255, 255, 255, 255);

configs/Kconfig

@@ -18,6 +18,23 @@ endchoice
 
 menu "Features"
 
+config LOGGING
+    bool "Enable logging"
+    default y
+
+config LOGGING_COLOR
+    bool "Use colors for logging"
+    default y
+    depends on LOGGING
+
+config LOGGING_CALLBACK
+    bool "Enable callback functions"
+    default y
+    depends on LOGGING
+
+comment "Logging is disabled"
+    depends on !LOGGING
+
 config CURSOR
     bool "Manipulate cursor"
     default n

include/twin_private.h

@@ -12,6 +12,11 @@
 
 #include "twin.h"
 
+/* FIXME: Both twin_private.h and log.h are private header files. They should
+ * be moved to src/ directory.
+ */
+#include "../src/log.h"
+
 /* Boilerplate for compiler compatibility */
 #ifndef __has_attribute
 #define __has_attribute(x) 0

src/image-gif.c

@@ -85,13 +85,13 @@ static twin_gif_t *gif_open(const char *fname)
     /* Header */
     read(fd, sigver, 3);
     if (memcmp(sigver, "GIF", 3) != 0) {
-        fprintf(stderr, "invalid signature\n");
+        log_error("Invalid signature");
         goto fail;
     }
     /* Version */
     read(fd, sigver, 3);
     if (memcmp(sigver, "89a", 3) != 0) {
-        fprintf(stderr, "invalid version\n");
+        log_error("Invalid version");
         goto fail;
     }
     /* Width x Height */
@@ -101,7 +101,7 @@ static twin_gif_t *gif_open(const char *fname)
     read(fd, &fdsz, 1);
     /* Presence of GCT */
     if (!(fdsz & 0x80)) {
-        fprintf(stderr, "no global color table\n");
+        log_error("No global color table");
         goto fail;
     }
     /* Color Space's Depth */
@@ -480,7 +480,7 @@ static void read_ext(twin_gif_t *gif)
         read_application_ext(gif);
         break;
     default:
-        fprintf(stderr, "unknown extension: %02X\n", label);
+        log_error("Unknown extension: %02X", label);
     }
 }
 
@@ -617,7 +617,7 @@ twin_pixmap_t *_twin_gif_to_pixmap(const char *filepath, twin_format_t fmt)
         return NULL;
     FILE *infile = fopen(filepath, "rb");
     if (!infile) {
-        fprintf(stderr, "Failed to open %s\n", filepath);
+        log_error("Failed to open %s", filepath);
         return NULL;
     }
     twin_animation_t *gif = _twin_animation_from_gif_file(filepath);

src/image-jpeg.c

@@ -51,7 +51,7 @@ twin_pixmap_t *_twin_jpeg_to_pixmap(const char *filepath, twin_format_t fmt)
 
     FILE *infile = fopen(filepath, "rb");
     if (!infile) {
-        fprintf(stderr, "Failed to open %s\n", filepath);
+        log_error("Failed to open %s", filepath);
         return NULL;
     }
 
@@ -61,7 +61,7 @@ twin_pixmap_t *_twin_jpeg_to_pixmap(const char *filepath, twin_format_t fmt)
     struct twin_jpeg_err_mgr jerr = {.mgr.error_exit = twin_jpeg_error_exit};
     cinfo.err = jpeg_std_error(&jerr.mgr);
     if (setjmp(jerr.jbuf)) {
-        fprintf(stderr, "Failed to decode %s\n", filepath);
+        log_error("Failed to decode %s", filepath);
         if (pix)
             twin_pixmap_destroy(pix);
         jpeg_destroy_decompress(&cinfo);

src/image.c

@@ -66,7 +66,7 @@ static twin_image_format_t image_type_detect(const char *path)
     twin_image_format_t type = IMAGE_TYPE_unknown;
     FILE *file = fopen(path, "rb");
     if (!file) {
-        fprintf(stderr, "Failed to open %s\n", path);
+        log_error("Failed to open %s", path);
         return IMAGE_TYPE_unknown;
     }
 

src/log.c

@@ -0,0 +1,170 @@
+/*
+ * Copyright (c) 2020 rxi
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include <stdio.h>
+
+#include "log.h"
+
+#define MAX_CALLBACKS 32
+
+typedef struct {
+    log_func_t fn;
+    void *udata;
+    int level;
+} callback_t;
+
+static struct {
+    void *udata;
+    log_lock_func_t lock;
+    int level;
+    bool quiet;
+    callback_t callbacks[MAX_CALLBACKS];
+} L;
+
+static const char *level_strings[] = {
+    "TRACE", "DEBUG", "INFO", "WARN", "ERROR", "FATAL",
+};
+
+#if defined(CONFIG_LOGGING_COLOR)
+static const char *level_colors[] = {
+    "\x1b[94m", "\x1b[36m", "\x1b[32m", "\x1b[33m", "\x1b[31m", "\x1b[35m",
+};
+#endif
+
+static void stdout_callback(log_event_t *ev)
+{
+    char buf[16];
+    buf[strftime(buf, sizeof(buf), "%H:%M:%S", ev->time)] = '\0';
+#if defined(CONFIG_LOGGING_COLOR)
+    fprintf(ev->udata, "%s %s%-5s\x1b[0m \x1b[90m%s:%d:\x1b[0m ", buf,
+            level_colors[ev->level], level_strings[ev->level], ev->file,
+            ev->line);
+#else
+    fprintf(ev->udata, "%s %-5s %s:%d: ", buf, level_strings[ev->level],
+            ev->file, ev->line);
+#endif
+    vfprintf(ev->udata, ev->fmt, ev->ap);
+    fprintf(ev->udata, "\n");
+    fflush(ev->udata);
+}
+
+static void file_callback(log_event_t *ev)
+{
+    char buf[64];
+    buf[strftime(buf, sizeof(buf), "%Y-%m-%d %H:%M:%S", ev->time)] = '\0';
+    fprintf(ev->udata, "%s %-5s %s:%d: ", buf, level_strings[ev->level],
+            ev->file, ev->line);
+    vfprintf(ev->udata, ev->fmt, ev->ap);
+    fprintf(ev->udata, "\n");
+    fflush(ev->udata);
+}
+
+static void lock(void)
+{
+    if (L.lock)
+        L.lock(true, L.udata);
+}
+
+static void unlock(void)
+{
+    if (L.lock)
+        L.lock(false, L.udata);
+}
+
+const char *log_level_string(int level)
+{
+    return level_strings[level];
+}
+
+void log_set_lock(log_lock_func_t fn, void *udata)
+{
+    L.lock = fn;
+    L.udata = udata;
+}
+
+void log_set_level(int level)
+{
+    L.level = level;
+}
+
+void log_set_quiet(bool enable)
+{
+    L.quiet = enable;
+}
+
+int log_add_callback(log_func_t fn, void *udata, int level)
+{
+    for (int i = 0; i < MAX_CALLBACKS; i++) {
+        if (!L.callbacks[i].fn) {
+            L.callbacks[i] = (callback_t){fn, udata, level};
+            return 0;
+        }
+    }
+    return -1;
+}
+
+int log_add_fp(FILE *fp, int level)
+{
+    return log_add_callback(file_callback, fp, level);
+}
+
+static void init_event(log_event_t *ev, void *udata)
+{
+    if (!ev->time) {
+        time_t t = time(NULL);
+        ev->time = localtime(&t);
+    }
+    ev->udata = udata;
+}
+
+void log_impl(int level, const char *file, int line, const char *fmt, ...)
+{
+    log_event_t ev = {
+        .fmt = fmt,
+        .file = file,
+        .line = line,
+        .level = level,
+    };
+
+    lock();
+
+    if (!L.quiet && level >= L.level) {
+        init_event(&ev, stderr);
+        va_start(ev.ap, fmt);
+        stdout_callback(&ev);
+        va_end(ev.ap);
+    }
+
+#ifdef CONFIG_LOGGING_CALLBACK
+    for (int i = 0; i < MAX_CALLBACKS && L.callbacks[i].fn; i++) {
+        callback_t *cb = &L.callbacks[i];
+        if (level >= cb->level) {
+            init_event(&ev, cb->udata);
+            va_start(ev.ap, fmt);
+            cb->fn(&ev);
+            va_end(ev.ap);
+        }
+    }
+#endif
+
+    unlock();
+}

src/log.h

@@ -0,0 +1,82 @@
+/**
+ * Copyright (c) 2020 rxi
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#ifndef _TWIN_LOGGING_H_
+#define _TWIN_LOGGING_H_
+
+#include <stdarg.h>
+#include <stdbool.h>
+#include <time.h>
+
+typedef struct {
+    va_list ap;
+    const char *fmt;
+    const char *file;
+    struct tm *time;
+    void *udata;
+    int line;
+    int level;
+} log_event_t;
+
+typedef void (*log_func_t)(log_event_t *ev);
+typedef void (*log_lock_func_t)(bool lock, void *udata);
+
+enum { LOGC_TRACE, LOGC_DEBUG, LOGC_INFO, LOGC_WARN, LOGC_ERROR, LOGC_FATAL };
+
+#if defined(CONFIG_LOGGING)
+#define log_trace(...) log_impl(LOGC_TRACE, __FILE__, __LINE__, __VA_ARGS__)
+#define log_debug(...) log_impl(LOGC_DEBUG, __FILE__, __LINE__, __VA_ARGS__)
+#define log_info(...) log_impl(LOGC_INFO, __FILE__, __LINE__, __VA_ARGS__)
+
+#else /* !CONFIG_LOGGING */
+#define log_trace(...) \
+    do {               \
+    } while (0)
+#define log_debug(...) \
+    do {               \
+    } while (0)
+#define log_info(...) \
+    do {              \
+    } while (0)
+#endif /* CONFIG_LOGGING */
+
+#define log_warn(...) log_impl(LOGC_WARN, __FILE__, __LINE__, __VA_ARGS__)
+#define log_error(...) log_impl(LOGC_ERROR, __FILE__, __LINE__, __VA_ARGS__)
+#define log_fatal(...) log_impl(LOGC_FATAL, __FILE__, __LINE__, __VA_ARGS__)
+
+const char *log_level_string(int level);
+void log_set_lock(log_lock_func_t fn, void *udata);
+void log_set_level(int level);
+void log_set_quiet(bool enable);
+int log_add_callback(log_func_t fn, void *udata, int level);
+int log_add_fp(FILE *fp, int level);
+
+#if defined(CONFIG_LOGGING)
+void log_impl(int level, const char *file, int line, const char *fmt, ...);
+#else
+#define log_impl(...)              \
+    do {                           \
+        /* dummy implementation */ \
+    } while (0)
+#endif
+
+#endif /* _TWIN_LOGGING_H_ */