Cannot find docs for „callstack" feature

[Radrogyl]

Maybe I am just blind, but I cannot seem to find any documentation on how to use the „callstack“ feature mentioned in egui’s Cargo.toml file:

[features]
Show a debug-ui on hover including the stacktrace to the hovered item.
This is very useful in finding the code that creates a part of the UI.
Does not work on web.
callstack = ["dep:backtrace“]

I use the eframe template and added the feature to egui in the dependencies. But it doesn’t show any of the debug-ui when I hover over any of the stuff present in the template app. Is there anything else I need to do to make it work? Is there any documentation on this I missed?

[darekwojciechowski]

The feature alone doesn't show anything, debug_on_hover is false by default. What callstack switches on is a different option, debug_on_hover_with_all_modifiers, so you only get the tooltip while holding every modifier at once (Ctrl + Shift + Alt + Super) and hovering. Try that first, it tells you whether the feature actually compiled in.

To have it on all the time:

ctx.set_debug_on_hover(true);

Two ways to end up with nothing at all: release builds, since the whole DebugOptions struct sits behind #[cfg(debug_assertions)], and web, since it's native only.