The emWin documentation states for the function GUI_MEMDEV_Create_Fixed that the parameter GUI_MEMDEV_NOTRANS allows using the memory device for non-rectangular areas. But there is no description how this non-rectangular area will be specified.
I want to use a memory device for the upper left triangle of my screen fill it with a picture. Finally this triangle should be copied to the LCD screen. Obviously a triangle is non-rectangular. What is the best approach for this?