Scroll bar of child disappears when child becomes too large (Floating Point Issue)

[WerWolv]

Version/Branch of Dear ImGui:

Version: v1.79
Branch: master + docking + tables

Back-end/Renderer/Compiler/OS

Back-ends: imgui_impl_opengl3.cpp + imgui_impl_glfw.cpp
Compiler: GCC
Operating System: Windows / Linux

My Issue/Question:

Hi. I'm using the Hex editor window found here: https://github.com/ocornut/imgui_club in my project.
When loading huge files into the hex editor, it will try to create a child big enough to wrap all those bytes. Issue being, when the child becomes too large (bigger than 2.1 billion pixels), the signed 32 bit integers used inside ImGui overflow causing the scroll bar to not render at all anymore and scrolling to be disabled.
The reason I'm submitting this issue here is because it looks like a general issue with ImGui.

My question is, is there a better way of handling this or is this something that needs to be fixed inside ImGui?
Thanks!

Standalone, minimal, complete and verifiable example:

// Here's some code anyone can copy and paste to reproduce your issue
ImGui::Begin("Example Bug");
ImGui::BeginChild("##scrolling", ImVec(0, 0xDFFF'FFFF);
ImGui::EndChild();
ImGui::End();

[ocornut]

(cross-post)

This doesn't technically solve the proposed repro (ImGui::BeginChild("##scrolling", ImVec(0, 0xDFFF'FFFF); however,
I have pushed variety of tweaks/fixes to improve large ranges from multiple angles.
Basically in the situation where a very large range window always use the clipper, things will tend to work much better into higher range. I am not considering this a full fix.

With those changes, e.g. in the Tables>Advanced demo

• One million items now works without an issue
• Ten millions items works with a small offset but not juggling or jumping around.
• With a 28-px high font, memory editor works reasonably well with a 30-bits range. Higher will likely cause the missing scrollbar.

a76bc52 Clipper: store initial precision loss and apply delta in clipper.

027a7ba Clipper: use line size instead of cursor comparison when ranges are large.

6e141a9 Internals: made ScrollbarEx() use ImS64 to facilitate use with larger ranges (not fully tested)
This is mostly to allow people reusing that code for custom scrollbars.

(+ unrelated fixed a small bug while doing this 926addb and 20e040c)