How to change render backend

[CaiDingxian]

How to change gtk render backend like windows gdi rendering (software) or opengl es rendering (hardware).

My hello world applicaiton that contain 10 simple ComboBox,consume 70M+ RAM on start ,and up to 200M+ after I click every ComboBox.it seems to high,and I wonder if it's related to render backend impl.

(imgui render a large table that contains 1000+ items and a super complex demo UI compoents tree panel,comsume 80M RAM，No offense，I waiting for a professional answer)