Improve ScopedLock.

esp/cpp/07_lcd-panel/main/display.cpp

@@ -13,7 +13,9 @@
 // To use LV_COLOR_FORMAT_I1, we need an extra buffer to hold the converted data
 uint8_t Display::oled_buffer_[LCD_H_RES * LCD_V_RES / 8];
 
-_lock_t Display::lvgl_api_lock_;
+// LVGL library is not thread-safe, this example calls LVGL APIs from tasks.
+// We must use a mutex to protect it.
+_lock_t ScopedLock::lock_;
 
 Display::Display() :
     io_handle_(nullptr),
@@ -149,9 +151,9 @@ void Display::lvgl_port_task(void *arg)
   ESP_LOGI(TAG, "Starting LVGL task");
   uint32_t time_till_next_ms = 0;
   while (1) {
-    _lock_acquire(&lvgl_api_lock_);
+    _lock_acquire(&ScopedLock::lock_);
     time_till_next_ms = lv_timer_handler();
-    _lock_release(&lvgl_api_lock_);
+    _lock_release(&ScopedLock::lock_);
     usleep(1000 * time_till_next_ms);
   }
 }

esp/cpp/07_lcd-panel/main/display.h

@@ -4,8 +4,10 @@
 #include <esp_lcd_types.h>
 #include <esp_lcd_panel_ssd1306.h>
 #include <driver/i2c_types.h>
+#include <driver/i2c_master.h>
 #include "misc/lv_types.h"
 #include "misc/lv_area.h"
+#include "display/lv_display.h"
 
 #define I2C_BUS_PORT  0
 #define LVGL_TICK_PERIOD_MS    5
@@ -33,11 +35,13 @@ static const char *TAG = "lcd-panel";
 #define PIN_RST                -1
 
 struct ScopedLock {
-  explicit ScopedLock(_lock_t& lock) : lock_(&lock) { _lock_acquire(lock_); }
-  ~ScopedLock() { _lock_release(lock_); }
+  explicit ScopedLock() { _lock_acquire(&lock_); }
 
-private:
-  _lock_t* lock_;
+  ~ScopedLock() { _lock_release(&lock_); }
+
+  // LVGL library is not thread-safe, this example calls LVGL APIs from tasks.
+  // We must use a mutex to protect it.
+  static _lock_t lock_;
 };
 
 class Display {
@@ -59,19 +63,16 @@ public:
                                esp_lcd_panel_io_event_data_t *data,
                                void *user_ctx);
 
-  static void
-  lvgl_flush_cb(lv_display_t *display, const lv_area_t *area, uint8_t *px_map);
+  static void lvgl_flush_cb(lv_display_t *display,
+                            const lv_area_t *area,
+                            uint8_t *px_map);
 
   static void lvgl_increase_tick(void *arg);
 
   static void lvgl_port_task(void *arg);
 
-  // To use LV_COLOR_FORMAT_I1, we need an extra buffer to hold the converted data
+  // For LV_COLOR_FORMAT_I1 we need an extra buffer to hold the converted data.
   static uint8_t oled_buffer_[LCD_H_RES * LCD_V_RES / 8];
-
-  // LVGL library is not thread-safe, this example will call LVGL APIs from different tasks, so use a mutex to protect it
-  static _lock_t lvgl_api_lock_;
-
 protected:
   esp_lcd_panel_io_handle_t io_handle_;
 

esp/cpp/07_lcd-panel/main/main.cpp

@@ -10,7 +10,7 @@ void setup()
   // UI function
   {
     // Lock the mutex due to the LVGL APIs are not thread-safe
-    ScopedLock lock(Display::lvgl_api_lock_);
+    ScopedLock lock;
 
     ESP_LOGI(TAG, "Display LVGL Scroll Text");
     lv_obj_t *scr = lv_display_get_screen_active(d.get());