fix(layouts): fix rounding for fr in grid layout (#6255)

tests/src/test_cases/test_grid_fr.c

@@ -0,0 +1,47 @@
+#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);
+}
+
+/**
+ * Tests that green/blue checker pattern of various row and column sizes
+ * completely covers underyling screen, no red background visible.
+ */
+void test_grid_fr(void)
+{
+    static int32_t col_dsc[] = {3 * 9, LV_GRID_FR(1), LV_GRID_FR(2), LV_GRID_FR(3), LV_GRID_FR(4), LV_GRID_TEMPLATE_LAST};
+    static int32_t row_dsc[] = {3 * 3, LV_GRID_FR(1), LV_GRID_FR(1), LV_GRID_FR(1), LV_GRID_FR(1), LV_GRID_TEMPLATE_LAST};
+
+    lv_obj_set_style_bg_color(active_screen, lv_palette_main(LV_PALETTE_RED), LV_PART_MAIN);
+    lv_obj_set_layout(active_screen, LV_LAYOUT_GRID);
+    lv_obj_set_grid_dsc_array(active_screen, col_dsc, row_dsc);
+    lv_obj_set_style_pad_row(active_screen, 0, LV_PART_MAIN);
+    lv_obj_set_style_pad_column(active_screen, 0, LV_PART_MAIN);
+
+    for(int col = 0; col < 5; col++) {
+        for(int row = 0; row < 5; row++) {
+            lv_obj_t * child = lv_obj_create(active_screen);
+            lv_obj_set_size(child, 1, 1);
+            lv_obj_set_grid_cell(child, LV_GRID_ALIGN_STRETCH, col, 1, LV_GRID_ALIGN_STRETCH, row, 1);
+            lv_obj_set_style_bg_color(child, lv_palette_main((row + col) % 2 ? LV_PALETTE_GREEN : LV_PALETTE_BLUE), LV_PART_MAIN);
+            lv_obj_set_style_radius(child, 0, LV_PART_MAIN);
+            lv_obj_set_style_border_width(child, 0, LV_PART_MAIN);
+        }
+    }
+
+    TEST_ASSERT_EQUAL_SCREENSHOT("grid_fr.png");
+}
+
+#endif