Getting list of characters rendered in current frame

[invrainbow]

Per #5176, I'm trying to dynamically load new glyphs as needed in order to support arbitrary Unicode input. I was thinking I could:

1. Draw everything as usual
2. Right before calling ImGui::Render(), get a list of all characters rendered this frame, and rebuild the atlas
3. Call ImGui::Render()

Is that possible? If not, I suppose I could wrap every string I send to ImGui in a macro like IMGUI_STR(...) that manually keeps track of the characters. But that would be very tedious.

[rokups]

It is not practical to implement on-demand glyph loading outside of core library.
There were multiple attempts to implement this already:

• Add an ability to update font atlas texture #3761
• (WIP) Dynamic glyph rasterization and unlimited number of font textures #3471
• https://github.com/rokups/imgui/commits/rk/incremental-atlas-baking

None of which are a complete solution. If you decide to salvage that code you are on your own.
If you decide you want to try your own idea, you may modify ImDrawList::AddText() or ImFont::RenderText() to save all rendered characters somewhere and do your thing.

[ocornut]

Your suggested suggestion wouldn't work anyway, if you rebuild the atlas before Render() all the submitted UV coordinates will be invalidated. One of the key element is #3761 which I would like to focus on soon.