fix(flex): fix rounding may leave unused space on track with flex_grow (#9217)

src/layouts/flex/lv_flex.c

@@ -67,6 +67,11 @@ static lv_obj_t * get_next_item(lv_obj_t * cont, bool rev, int32_t * item_id);
 static int32_t lv_obj_get_width_with_margin(const lv_obj_t * obj);
 static int32_t lv_obj_get_height_with_margin(const lv_obj_t * obj);
 
+static inline int32_t div_round_closest(int32_t dividend, int32_t divisor)
+{
+    return (dividend + divisor / 2) / divisor;
+}
+
 /**********************
  *  GLOBAL VARIABLES
  **********************/
@@ -363,13 +368,11 @@ static void children_repos(lv_obj_t * cont, flex_t * f, int32_t item_first_id, i
                 grow_max_size -= t->grow_dsc[i].final_size;
             }
         }
-        int32_t grow_unit;
 
         for(i = 0; i < t->grow_item_cnt; i++) {
             if(t->grow_dsc[i].clamped == 0) {
                 LV_ASSERT(grow_value_sum != 0);
-                grow_unit = grow_max_size / grow_value_sum;
-                int32_t size = grow_unit * t->grow_dsc[i].grow_value;
+                int32_t size = div_round_closest(grow_max_size * t->grow_dsc[i].grow_value, grow_value_sum);
                 int32_t size_clamp = LV_CLAMP(t->grow_dsc[i].min_size, size, t->grow_dsc[i].max_size);
 
                 if(size_clamp != size) {

tests/src/test_cases/test_flex_grow.c

@@ -0,0 +1,69 @@
+#if LV_BUILD_TEST
+#include "../lvgl.h"
+
+#include "unity/unity.h"
+
+static lv_obj_t * active_screen = NULL;
+
+void setUp(void)
+{
+    active_screen = lv_screen_active();
+}
+
+void tearDown(void)
+{
+    lv_obj_clean(active_screen);
+}
+
+static void simple_style(lv_obj_t * obj)
+{
+    lv_obj_set_style_pad_row(obj, 0, LV_PART_MAIN);
+    lv_obj_set_style_pad_column(obj, 0, LV_PART_MAIN);
+    lv_obj_set_style_pad_all(obj, 0, LV_PART_MAIN);
+    lv_obj_set_style_border_width(obj, 0, LV_PART_MAIN);
+    lv_obj_set_style_radius(obj, 0, LV_PART_MAIN);
+}
+
+/**
+ * Tests that various flex tracks containing fixed and growing items are
+ * always completely filled, no red background visible.
+ */
+void test_grid_fr(void)
+{
+    simple_style(active_screen);
+
+    lv_obj_t * container = lv_obj_create(active_screen);
+    simple_style(container);
+    lv_obj_set_style_bg_color(container, lv_palette_main(LV_PALETTE_RED), LV_PART_MAIN);
+    lv_obj_set_flex_flow(container, LV_FLEX_FLOW_ROW);
+    lv_obj_set_size(container, LV_PCT(100), LV_SIZE_CONTENT);
+    lv_obj_center(container);
+
+    for(int32_t grow_1 = 1; grow_1 <= 3; grow_1++) {
+        for(int32_t grow_2 = 1; grow_2 <= 3; grow_2++) {
+            for(int32_t fixed = 20; fixed <= 24; fixed++) {
+                lv_obj_t * child_grow_1 = lv_obj_create(container);
+                simple_style(child_grow_1);
+                lv_obj_set_style_bg_color(child_grow_1, lv_palette_main(LV_PALETTE_BLUE), LV_PART_MAIN);
+                lv_obj_set_size(child_grow_1, 1, 10);
+                lv_obj_set_flex_grow(child_grow_1, grow_1);
+                lv_obj_add_flag(child_grow_1, LV_OBJ_FLAG_FLEX_IN_NEW_TRACK);
+
+                lv_obj_t * child_grow_2 = lv_obj_create(container);
+                simple_style(child_grow_2);
+                lv_obj_set_style_bg_color(child_grow_2, lv_palette_main(LV_PALETTE_GREEN), LV_PART_MAIN);
+                lv_obj_set_size(child_grow_2, 1, 10);
+                lv_obj_set_flex_grow(child_grow_2, grow_2);
+
+                lv_obj_t * child_fixed = lv_obj_create(container);
+                simple_style(child_fixed);
+                lv_obj_set_style_bg_color(child_fixed, lv_palette_main(LV_PALETTE_BLUE), LV_PART_MAIN);
+                lv_obj_set_size(child_fixed, fixed, 10);
+            }
+        }
+    }
+
+    TEST_ASSERT_EQUAL_SCREENSHOT("flex_grow.png");
+}
+
+#endif