Would it be reasonable for functions that accept text_begin/text_end to allow text_begin equals text_end equals NULL?

[alien-brother]

Version/Branch of Dear ImGui:

Version 1.90.4, Branch: master (I guess?)

Back-ends:

(Unrelated to backends) imgui_impl_win32.cpp + imgui_impl_dx11.cpp

Compiler, OS:

(Unrelated to compiler and OS) MSVC 2022, Windows 11

Full config/build information:

Unrelated to configuration

Details:

I'm looking at ImDrawList::AddText(), but there are other functions that accept a text range. The code that handles text_begin/text_end looks like this:

    if (text_end == NULL)
        text_end = text_begin + strlen(text_begin);
    if (text_begin == text_end)
        return;

If text_begin equals text_end equals NULL, the code will call strlen() on NULL. This can reasonably happen when text_begin and text_end are directly taken from an std::string_view as data() and data() + size(), since a default-constructed std::string_view has NULL as data() as size() of 0. I believe, adding 0 to a null pointer is valid.

Instead, AddText (and other functions) could do something like

    if (text_end == NULL && text_begin != NULL)
        text_end = text_begin + strlen(text_begin);
    if (text_begin == text_end)
        return;

Obviously, the caller can work around this by placing the condition text_begin != NULL before the call.

Screenshots/Video:

No response

Minimal, Complete and Verifiable Example code:

std::string_view empty_view;
ImGui::GetWindowDrawList()->AddText(ImGui::GetCursorScreenPos(), IM_COL32(0, 0, 0, 0), empty_view.data(), empty_view.data() + empty_view.size());

[ocornut]

Yes, in this situation I think we can support it, same as #3615

[ocornut]

I have pushed the fix for this 37b37fc
And the test: ocornut/imgui_test_engine@a3b0296

Thank you!

[alien-brother]

Thanks. This helps get rid of some boilerplate code.

[alien-brother]

Another existing API that does not allow text_begin == text_end == NULL is ImFont::CalcTextSizeA().
https://github.com/ocornut/imgui/blob/master/imgui_draw.cpp#L3915