How to clear emoji font cache in iOS application (keyboard extension)
问题 Keyboard extension in iOS is memory limited, when the memory cost is above 50+M, keyboard process will be killed. However, when I am developing the emoji panel in keyboard extension, the emoji panel has to render 800+ emoji icons. From this How to clear font cache filled with emoji characters? I know that, keyboad has to spend 10M memory for emoji rendering for the hundreds emoji icons. So I have two questions here: how the iOS system draw the emoji icons, why they have to be converted to png