Feature request: Rollback untrusted API calls

[ejulien]

Hello,

Context: Our editor can be extended using plugins. Plugin hot-reload+ImGui is extremely fast to iterate with.

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Problem: Unfortunately API misuses are really ruining our party. These come in two flavors:

1. Genuine errors (eg. wrongly scoped End or EndChild call).
2. Script errors interrupting an otherwise valid sequence of ImGui calls.

Both usually end with a C++ assertion being thrown which is less than ideal.

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Solution?: Both scenarios can be adressed in the same manner but solving the first one might be more work.

Handling scenario 2. could look something like:

ImGui::EnterUntrustedSection();

bool success = call_plugin_issuing_ImGui_calls());
if (!success)
    ImGui::RollbackUntrustedSection();

ImGui::ExitUntrustedSection();

if (!success)
    ImGui::Text("So sad");

Script execution failure was reported by the client code but that doesn't cover API misuse.

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The ideal version would validate the untrusted section on exit and roll it back if it did not pass.

ImGui::EnterUntrustedSection();

call_plugin_issuing_ImGui_calls(); // alea jacta est

if (!ImGui::ExitUntrustedSection())
    ImGui::Text("So sad");

Obviously logic already executed in the client code can not be rolled back (eg. if (ImGui::Button) ++my_var;) but that really doesn't matter. As soon as the error is repaired the UI will correctly reflect those changes anyway.

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While not a critical feature to have I wonder how hard it would be to implement on top of the current design?

[ocornut]

Linking to #1651. Could you copy your exact post in #1651 and I'll merge the issues?

We'd be to be very specific about what use case exactly we are trying to fix/rollback.

Let's also be clear that we are never going to be able to correct 100% of the bad use case, nor prevent intentionally malicious users from crashing your app or messing up with your state.

But I agree that if we can fix 90% of the common use case that would be progress for any users of scripting language.

[ejulien]

Done. Sorry, I did not manage to find #1651 when looking for duplicate.