Deprecation warning about mixed enums when compiling with C++20 (and newer)

[mich-dy]

I'm using the ImGuiFileDialog in my own project, and I compiled all code with C++20/23/26 to test forward-compatibility.
And I ran into a deprecation warning in the file dialog code when using C++20:

/.../build/_deps/filedialog-src/ImGuiFileDialog.cpp:3997:130: warning: bitwise operation between different enumeration types ‘ImGuiSelectableFlags_’ and ‘ImGuiSelectableFlagsPrivate_’ is deprecated [-Wdeprecated-enum-enum-conversion]
 3997 |                             if (ImGui::Selectable(infos_ptr->fileNameExt.c_str(), &selected, ImGuiSelectableFlags_SpanAllColumns | ImGuiSelectableFlags_SpanAvailWidth)) {

There is no urgent action needed since the code still compiles, but it might break at some point in the future.
So, please see this issue just as a reminder :)

[kyle-paul]

I encountered the same issue with C++20. The reason is that ImGuiSelectableFlags_SpanAllColumns belongs to the ImGuiSelectableFlags_ enum, while ImGuiSelectableFlags_SpanAvailWidth is part of the ImGuiSelectableFlagsPrivate_ enum. The ImGuiSelectableFlags_ enum has a value range from 0 to 1 << 5, whereas ImGuiSelectableFlagsPrivate_ ranges from 1 << 20 to 1 << 27. Since these ranges do not overlap, performing a bitwise OR operation between these two flags does not cause any logical conflicts.

Here’s how I fixed it:

Use static_cast<int> to ensure compatibility:

static_cast<int>(ImGuiSelectableFlags_SpanAllColumns) | static_cast<int>(ImGuiSelectableFlags_SpanAvailWidth)

You can verify this with the following simple test:

#include <iostream>

int main() {
    int a = 1 << 1;  // 2^1
    std::cout << a << "\n";

    int b = 1 << 24; // 2^24 = 16777216
    std::cout << b << "\n";

    std::cout << (a | b) << "\n";  // 16777218

    int c = static_cast<int>(a) | static_cast<int>(b);  // 16777218
    std::cout << c;

    return 0;
}