fix(draw) underflow in subpixel font drawing

Fixes: #2273
lvgl · Jun 15, 2021 · 6d5ac70 · 6d5ac70
1 parent 3abe517
commit 6d5ac70
Showing 1 changed file with 8 additions and 6 deletions.
diff --git a/src/draw/lv_draw_label.c b/src/draw/lv_draw_label.c
@@ -664,6 +664,14 @@ static void draw_letter_subpx(lv_coord_t pos_x, lv_coord_t pos_y, lv_font_glyph_
     int32_t col_bit;
     col_bit = bit_ofs & 0x7; /*"& 0x7" equals to "% 8" just faster*/
 
+    lv_area_t map_area;
+    map_area.x1 = col_start / 3 + pos_x;
+    map_area.x2 = col_end / 3  + pos_x - 1;
+    map_area.y1 = row_start + pos_y;
+    map_area.y2 = map_area.y1;
+
+    if(map_area.x2 <= map_area.x1) return;
+
     int32_t mask_buf_size = box_w * box_h > _LV_MASK_BUF_MAX_SIZE ? _LV_MASK_BUF_MAX_SIZE : g->box_w * g->box_h;
     lv_opa_t * mask_buf = lv_mem_buf_get(mask_buf_size);
     int32_t mask_p = 0;
@@ -682,12 +690,6 @@ static void draw_letter_subpx(lv_coord_t pos_x, lv_coord_t pos_y, lv_font_glyph_
     /*If the letter is partially out of mask the move there on draw_buf*/
     disp_buf_buf_tmp += (row_start * disp_buf_width) + col_start / 3;
 
-    lv_area_t map_area;
-    map_area.x1 = col_start / 3 + pos_x;
-    map_area.x2 = col_end / 3  + pos_x - 1;
-    map_area.y1 = row_start + pos_y;
-    map_area.y2 = map_area.y1;
-
     uint8_t other_mask_cnt = lv_draw_mask_get_cnt();
 
     uint8_t font_rgb[3];