feat(demos): add a callback for benchmark (#3353)

* feat(demos): add a callback for benchmark to indicate testing is finished

* update doc and fix code-format

* fix code-format issue

* Update demos/benchmark/lv_demo_benchmark.c

Co-authored-by: Gabor Kiss-Vamosi <kisvegabor@gmail.com>

* change function name accordingly.

* Update demos/benchmark/README.md

Co-authored-by: Gabor Kiss-Vamosi <kisvegabor@gmail.com>

demos/benchmark/README.md

@@ -15,6 +15,7 @@ On to top of the screen the title of the current test step, and the result of th
 - After `lv_init()` and initializing the drivers call `lv_demo_benchmark()`
 - If you only want to run a specific scene for any purpose (e.g. debug, performance optimization etc.), you can call `lv_demo_benchmark_run_scene()` instead of `lv_demo_benchmark()`and pass the scene number.
 - If you enabled trace output by setting macro `LV_USE_LOG` to `1` and trace level `LV_LOG_LEVEL` to `LV_LOG_LEVEL_USER` or higher, benchmark results are printed out in `csv` format.
+- If you want to know when the testing is finished, you can register a callback function via `lv_demo_benchmark_register_finished_handler()` before calling `lv_demo_benchmark()` or `lv_demo_benchmark_run_scene()`. 
 
 
 ## Interpret the result
@@ -36,25 +37,72 @@ By default, only the changed areas are refreshed. It means if only a few pixels
 
 If you are doing performance analysis for 2D image processing optimization, LCD latency (flushing data to LCD) introduced by `disp_flush()` might dilute the performance results of the LVGL drawing process, hence make it harder to see your optimization results (gain or loss). To avoid such problem, please:
 
-1. Temporarily remove the code for flushing data to LCD inside `disp_flush()`. For example:
+1. Use a flag to control the LCD flushing inside `disp_flush()`. For example:
 
 ```c
+static volatile bool is_flush_enabled = true;
+
+void disp_enable(void)
+{
+    is_flush_enabled = true;
+}
+
+void disp_disable(void)
+{
+    is_flush_enabled = false;
+}
+
 static void disp_flush(lv_disp_drv_t * disp_drv, const lv_area_t * area, lv_color_t * color_p)
 {
-#if 0 //!< remove LCD latency
-    GLCD_DrawBitmap(area->x1,               //!< x
-                    area->y1,               //!< y
-                    area->x2 - area->x1 + 1,    //!< width
-                    area->y2 - area->y1 + 1,    //!< height
-                    (const uint8_t *)color_p);
-#endif
+    if(is_flush_enabled) {
+        GLCD_DrawBitmap(area->x1,                   //!< x
+                        area->y1,                   //!< y
+                        area->x2 - area->x1 + 1,    //!< width
+                        area->y2 - area->y1 + 1,    //!< height
+                        (const uint8_t *)color_p);
+    }
+
     /*IMPORTANT!!!
      *Inform the graphics library that you are ready with the flushing*/
     lv_disp_flush_ready(disp_drv);
 }
 ```
 
-2. Use trace output to get the benchmark results by:
+2. Disable flushing before calling `lv_demo_benchmark()` or `lv_demo_benchmark_run_scene()`, for example:
+
+```c
+extern void disp_enable(void);
+extern void disp_disable(void);
+
+static void on_benchmark_finished(void)
+{
+    disp_enable();
+}
+
+int main(void)
+{    
+    lv_init();
+    lv_port_disp_init();
+    lv_port_indev_init();
+
+    LV_LOG("Running LVGL Benchmark...");
+    LV_LOG("Please stand by...");
+    LV_LOG("NOTE: You will NOT see anything until the end.");
+
+    disp_disable();
+    
+    lv_demo_benchmark_set_finished_cb(&on_benchmark_finished);
+    lv_demo_benchmark();
+    
+    //lv_demo_benchmark_run_scene(43);      // run scene no 31
+
+    ...
+}
+```
+
+
+
+3. Alternatively, you can use trace output to get the benchmark results in csv format by:
    - Setting macro `LV_USE_LOG` to `1` 
    - Setting trace level `LV_LOG_LEVEL` to `LV_LOG_LEVEL_USER` or higher.
 

demos/benchmark/lv_demo_benchmark.c

@@ -69,6 +69,7 @@ typedef struct {
 
 static lv_style_t style_common;
 static bool opa_mode = true;
+static finished_cb_t * benchmark_finished_cb = NULL;
 
 LV_IMG_DECLARE(img_benchmark_cogwheel_argb);
 LV_IMG_DECLARE(img_benchmark_cogwheel_rgb);
@@ -90,6 +91,7 @@ static void arc_create(lv_style_t * style);
 static void fall_anim(lv_obj_t * obj);
 static void rnd_reset(void);
 static int32_t rnd_next(int32_t min, int32_t max);
+static void report_cb(lv_timer_t * timer);
 
 static void rectangle_cb(void)
 {
@@ -663,6 +665,39 @@ void lv_demo_benchmark(void)
     scene_next_task_cb(NULL);
 }
 
+
+void lv_demo_benchmark_run_scene(int_fast16_t scene_no)
+{
+    benchmark_init();
+
+    if(((scene_no >> 1) >= dimof(scenes))) {
+        /* invalid scene number */
+        return ;
+    }
+
+    opa_mode = scene_no & 0x01;
+    scene_act = scene_no >> 1;
+
+    if(scenes[scene_act].create_cb) {
+        lv_label_set_text_fmt(title, "%"LV_PRId32"/%d: %s%s", scene_act * 2 + (opa_mode ? 1 : 0), (int)(dimof(scenes) * 2) - 2,
+                              scenes[scene_act].name, opa_mode ? " + opa" : "");
+        lv_label_set_text(subtitle, "");
+
+        rnd_reset();
+        scenes[scene_act].create_cb();
+
+        lv_timer_t * t = lv_timer_create(report_cb, SCENE_TIME, NULL);
+        lv_timer_set_repeat_count(t, 1);
+    }
+}
+
+
+void lv_demo_benchmark_set_finished_cb(finished_cb_t * finished_cb);
+{
+    benchmark_finished_cb = finished_cb;
+}
+
+
 /**********************
  *   STATIC FUNCTIONS
  **********************/
@@ -711,6 +746,10 @@ static void generate_report(void)
 
     uint32_t opa_speed_pct = (fps_opa_unweighted * 100) / fps_normal_unweighted;
 
+    if(NULL != benchmark_finished_cb) {
+        (*benchmark_finished_cb)();
+    }
+
     lv_obj_clean(lv_scr_act());
     scene_bg = NULL;
 
@@ -857,6 +896,10 @@ static void generate_report(void)
 
 static void report_cb(lv_timer_t * timer)
 {
+    if(NULL != benchmark_finished_cb) {
+        (*benchmark_finished_cb)();
+    }
+
     if(opa_mode) {
         if(scene_act >= 0) {
             if(scenes[scene_act].time_sum_opa == 0) scenes[scene_act].time_sum_opa = 1;
@@ -891,31 +934,6 @@ static void report_cb(lv_timer_t * timer)
     }
 }
 
-void lv_demo_benchmark_run_scene(int_fast16_t scene_no)
-{
-    benchmark_init();
-
-    if(((scene_no >> 1) >= dimof(scenes))) {
-        /* invalid scene number */
-        return ;
-    }
-
-    opa_mode = scene_no & 0x01;
-    scene_act = scene_no >> 1;
-
-    if(scenes[scene_act].create_cb) {
-        lv_label_set_text_fmt(title, "%"LV_PRId32"/%d: %s%s", scene_act * 2 + (opa_mode ? 1 : 0), (int)(dimof(scenes) * 2) - 2,
-                              scenes[scene_act].name, opa_mode ? " + opa" : "");
-        lv_label_set_text(subtitle, "");
-
-        rnd_reset();
-        scenes[scene_act].create_cb();
-
-        lv_timer_t * t = lv_timer_create(report_cb, SCENE_TIME, NULL);
-        lv_timer_set_repeat_count(t, 1);
-    }
-}
-
 static void scene_next_task_cb(lv_timer_t * timer)
 {
     LV_UNUSED(timer);

demos/benchmark/lv_demo_benchmark.h

@@ -22,6 +22,8 @@ extern "C" {
 /**********************
  *      TYPEDEFS
  **********************/
+typedef void finished_cb_t(void);
+
 
 /**********************
  * GLOBAL PROTOTYPES
@@ -30,6 +32,8 @@ void lv_demo_benchmark(void);
 
 void lv_demo_benchmark_run_scene(int_fast16_t scene_no);
 
+void lv_demo_benchmark_set_finished_cb(finished_cb_t * finished_cb);
+
 /**********************
  *      MACROS
  **********************/