NUI from scratch: ui_page, messages, callbacks

NUI is FiveM's name for the in-game browser layer, a real Chromium tab the client renders on top of GTA. Every menu, hud, scoreboard, and pause UI you have ever seen in a server is NUI. So far you have used ox_lib and other framework UIs that wrap NUI for you. (ox_lib is a community library from the Overextended team, not a Cfx.re built-in, but it is everywhere.) This bonus shows the layer underneath: how to declare a page in fxmanifest.lua, how to push state from Lua with SendNUIMessage, how to receive clicks with RegisterNUICallback, and how to capture the cursor with SetNuiFocus. Once you understand these four pieces, you can read any NUI resource and build your own without a framework.