feat(draw): add layer memory allocation config support (#7038)

Co-authored-by: Gabor Kiss-Vamosi <kisvegabor@gmail.com>
Co-authored-by: liamHowatt <liamjmh0@gmail.com>
Co-authored-by: Liam <30486941+liamHowatt@users.noreply.github.com>

Kconfig

@@ -202,6 +202,15 @@ menu "LVGL configuration"
 				it is buffered into a "simple" layer before rendering. The widget can be buffered in smaller chunks.
 				"Transformed layers" (if `transform_angle/zoom` are set) use larger buffers and can't be drawn in chunks.
 
+		config LV_DRAW_LAYER_MAX_MEMORY
+			int "The maximum amount of memory that can be used for layers"
+			default 0
+			help
+				Limit the max allocated memory for simple and transformed layers.
+				It should be at least `LV_DRAW_LAYER_SIMPLE_BUF_SIZE` sized but if transformed layers are also used
+				it should be enough to store the largest widget too (width x height x 4 area).
+				Set it to 0 to have no limit.
+
 		config LV_DRAW_THREAD_STACK_SIZE
 			int "Stack size of draw thread in bytes"
 			default 8192

lv_conf_template.h

@@ -144,6 +144,12 @@
 /** The target buffer size for simple layer chunks. */
 #define LV_DRAW_LAYER_SIMPLE_BUF_SIZE    (24 * 1024)    /**< [bytes]*/
 
+/* Limit the max allocated memory for simple and transformed layers.
+ * It should be at least `LV_DRAW_LAYER_SIMPLE_BUF_SIZE` sized but if transformed layers are also used
+ * it should be enough to store the largest widget too (width x height x 4 area).
+ * Set it to 0 to have no limit. */
+#define LV_DRAW_LAYER_MAX_MEMORY 0  /**< No limit by default [bytes]*/
+
 /** Stack size of drawing thread.
  * NOTE: If FreeType or ThorVG is enabled, it is recommended to set it to 32KB or more.
  */

src/draw/lv_draw.c

@@ -36,7 +36,7 @@ static void lv_cleanup_task(lv_draw_task_t * t, lv_display_t * disp);
 
 static inline uint32_t get_layer_size_kb(uint32_t size_byte)
 {
-    return size_byte < 1024 ? 1 : size_byte >> 10;
+    return (size_byte + 1023) >> 10;
 }
 
 /**********************
@@ -448,6 +448,15 @@ void * lv_draw_layer_alloc_buf(lv_layer_t * layer)
     int32_t h = lv_area_get_height(&layer->buf_area);
     uint32_t layer_size_byte = h * lv_draw_buf_width_to_stride(w, layer->color_format);
 
+#if LV_DRAW_LAYER_MAX_MEMORY > 0
+    /* Do not allocate the layer if the sum of allocated layer sizes
+     * will exceed `LV_DRAW_LAYER_MAX_MEMORY` */
+    if((_draw_info.used_memory_for_layers + layer_size_byte) > LV_DRAW_LAYER_MAX_MEMORY) {
+        LV_LOG_WARN("LV_DRAW_LAYER_MAX_MEMORY was reached when allocating the layer.");
+        return NULL;
+    }
+#endif
+
     layer->draw_buf = lv_draw_buf_create(w, h, layer->color_format, 0);
 
     if(layer->draw_buf == NULL) {
@@ -456,8 +465,8 @@ void * lv_draw_layer_alloc_buf(lv_layer_t * layer)
         return NULL;
     }
 
-    _draw_info.used_memory_for_layers_kb += get_layer_size_kb(layer_size_byte);
+    _draw_info.used_memory_for_layers += layer_size_byte;
-    LV_LOG_INFO("Layer memory used: %" LV_PRIu32 " kB\n", _draw_info.used_memory_for_layers_kb);
+    LV_LOG_INFO("Layer memory used: %" LV_PRIu32 " kB", get_layer_size_kb(_draw_info.used_memory_for_layers));
 
     if(lv_color_format_has_alpha(layer->color_format)) {
         lv_draw_buf_clear(layer->draw_buf, NULL);
@@ -535,8 +544,14 @@ static void lv_cleanup_task(lv_draw_task_t * t, lv_display_t * disp)
             int32_t h = lv_area_get_height(&layer_drawn->buf_area);
             uint32_t layer_size_byte = h * layer_drawn->draw_buf->header.stride;
 
-            _draw_info.used_memory_for_layers_kb -= get_layer_size_kb(layer_size_byte);
+            if(_draw_info.used_memory_for_layers >= layer_size_byte) {
-            LV_LOG_INFO("Layer memory used: %" LV_PRIu32 " kB\n", _draw_info.used_memory_for_layers_kb);
+                _draw_info.used_memory_for_layers -= layer_size_byte;
+            }
+            else {
+                _draw_info.used_memory_for_layers = 0;
+                LV_LOG_WARN("More layers were freed than allocated");
+            }
+            LV_LOG_INFO("Layer memory used: %" LV_PRIu32 " kB", get_layer_size_kb(_draw_info.used_memory_for_layers));
             lv_draw_buf_destroy(layer_drawn->draw_buf);
             layer_drawn->draw_buf = NULL;
         }

src/draw/lv_draw_private.h

@@ -178,7 +178,7 @@ struct _lv_draw_unit_t {
 typedef struct {
     lv_draw_unit_t * unit_head;
     uint32_t unit_cnt;
-    uint32_t used_memory_for_layers_kb;
+    uint32_t used_memory_for_layers; /* measured as bytes */
 #if LV_USE_OS
     lv_thread_sync_t sync;
 #else

src/lv_conf_internal.h

@@ -352,6 +352,18 @@
     #endif
 #endif
 
+/* Limit the max allocated memory for simple and transformed layers.
+ * It should be at least `LV_DRAW_LAYER_SIMPLE_BUF_SIZE` sized but if transformed layers are also used
+ * it should be enough to store the largest widget too (width x height x 4 area).
+ * Set it to 0 to have no limit. */
+#ifndef LV_DRAW_LAYER_MAX_MEMORY
+    #ifdef CONFIG_LV_DRAW_LAYER_MAX_MEMORY
+        #define LV_DRAW_LAYER_MAX_MEMORY CONFIG_LV_DRAW_LAYER_MAX_MEMORY
+    #else
+        #define LV_DRAW_LAYER_MAX_MEMORY 0  /**< No limit by default [bytes]*/
+    #endif
+#endif
+
 /** Stack size of drawing thread.
  * NOTE: If FreeType or ThorVG is enabled, it is recommended to set it to 32KB or more.
  */