Hi @3Run
That is the original example of the ImGui module. I did not write it myself.

You can find all the window flags into 'imgui_enums.h' file. Not sure what are you trying to thought.

About the button width, you need to get the available width so you can create the button with it.
var _width = imgui_get_content_region_avail_width();
if(imgui_h_button("Button text", _width, 0)) {

I am not at home and I can't try it but I think it should work as spected.