feat(log): add LV_LOG_PRINT_CB to set a default log print cb (#6095)

Co-authored-by: Neo Xu <xuxingliang@xiaomi.com>

lv_conf_template.h

@@ -240,6 +240,11 @@
     *0: User need to register a callback with `lv_log_register_print_cb()`*/
     #define LV_LOG_PRINTF 0
 
+    /*Set callback to print the logs.
+     *E.g `my_print`. The prototype should be `void my_print(lv_log_level_t level, const char * buf)`
+     *Can be overwritten by `lv_log_register_print_cb`*/
+    //#define LV_LOG_PRINT_CB
+
     /*1: Enable print timestamp;
      *0: Disable print timestamp*/
     #define LV_LOG_USE_TIMESTAMP 1
@@ -248,6 +253,7 @@
      *0: Do not print file and line number of the log*/
     #define LV_LOG_USE_FILE_LINE 1
 
+
     /*Enable/disable LV_LOG_TRACE in modules that produces a huge number of logs*/
     #define LV_LOG_TRACE_MEM        1
     #define LV_LOG_TRACE_TIMER      1

src/lv_conf_internal.h

@@ -616,6 +616,11 @@
         #endif
     #endif
 
+    /*Set callback to print the logs.
+     *E.g `my_print`. The prototype should be `void my_print(lv_log_level_t level, const char * buf)`
+     *Can be overwritten by `lv_log_register_print_cb`*/
+    //#define LV_LOG_PRINT_CB
+
     /*1: Enable print timestamp;
      *0: Disable print timestamp*/
     #ifndef LV_LOG_USE_TIMESTAMP
@@ -644,6 +649,7 @@
         #endif
     #endif
 
+
     /*Enable/disable LV_LOG_TRACE in modules that produces a huge number of logs*/
     #ifndef LV_LOG_TRACE_MEM
         #ifdef _LV_KCONFIG_PRESENT

src/lv_init.c

@@ -96,6 +96,11 @@ static inline void lv_global_init(lv_global_t * global)
     global->event_last_register_id = _LV_EVENT_LAST;
     lv_rand_set_seed(0x1234ABCD);
 
+#ifdef LV_LOG_PRINT_CB
+    void LV_LOG_PRINT_CB(lv_log_level_t, const char * txt);
+    global->custom_log_print_cb = LV_LOG_PRINT_CB;
+#endif
+
 #if defined(LV_DRAW_SW_SHADOW_CACHE_SIZE) && LV_DRAW_SW_SHADOW_CACHE_SIZE > 0
     global->sw_shadow_cache.cache_size = -1;
     global->sw_shadow_cache.cache_r = -1;

src/misc/lv_log.c

@@ -102,7 +102,7 @@ void _lv_log_add(lv_log_level_t level, const char * file, int line, const char *
         vprintf(format, args);
         printf(LOG_FILE_LINE_FMT "\n" LOG_FILE_LINE_EXPR);
         fflush(stdout);
-#else
+#endif
         if(custom_print_cb) {
             char buf[512];
             char msg[256];
@@ -111,7 +111,6 @@ void _lv_log_add(lv_log_level_t level, const char * file, int line, const char *
                         lvl_prefix[level], LOG_TIMESTAMP_EXPR func, msg LOG_FILE_LINE_EXPR);
             custom_print_cb(level, buf);
         }
-#endif
 
 #if LV_LOG_USE_TIMESTAMP
         last_log_time = t;