in ev3-api/src/ev3api_lcd.c [46:49]
ER ev3_lcd_fill_rect(int32_t x, int32_t y, int32_t w, int32_t h, lcdcolor_t color) { bitmap_bitblt(NULL, 0, 0, lcd_screen, x, y, w, h, color == EV3_LCD_BLACK ? ROP_SET : ROP_CLEAR); return E_OK; }