ImGui can't open Windows files in non-ASCII paths when compiling with MinGW

[vircon32]

Version/Branch of Dear ImGui:

master

Back-ends:

Any backend

Compiler, OS:

Windows + MSYS/MinGW

Full config/build information:

No response

Details:

I am building Dear ImGui with MSYS2 and MinGW. I noticed it fails to open TTF files when their Windows path has non ASCII characters. Analyzing the code the problem seems to be in ImFileOpen, in this line:

imgui/imgui.cpp

Line 2285 in c798311

#if defined(_WIN32) && !defined(IMGUI_DISABLE_WIN32_FUNCTIONS) && !defined(__CYGWIN__) && !defined(__GNUC__)

The issue is that, when compiling with MinGW, the macro __GNUC__ is defined. So, despite being in Windows, and therefore needing to use _wfopen(), the plain fopen() gets used instead. In my system I just removed that from the #endif and it now opens files correctly.

Sorry that I don't submit a PR instead, but right now I'm not sure how the MinGW compiler should be properly detected.

Screenshots/Video:

No response

Minimal, Complete and Verifiable Example code:

#include <imgui/imgui.h>
#include <string>

int main()
{
    // init ImGui
    ImGui::CreateContext();
    ImGui::GetIO().IniFilename = NULL;
    
    // add all the standard characters
    ImVector< ImWchar > GlyphRanges;
    ImFontGlyphRangesBuilder GlyphBuilder;
    GlyphBuilder.AddRanges( ImGui::GetIO().Fonts->GetGlyphRangesDefault() );
    GlyphBuilder.BuildRanges( &GlyphRanges );
    
    // load a TTF font from a non ascii path
    std::string FontPath = "C:\\Español\\GuiFont.ttf";
    ImFont* Font = ImGui::GetIO().Fonts->AddFontFromFileTTF( FontPath.c_str(), 16, NULL, GlyphRanges.Data );
    
    // this will now crash because Font is NULL
    ImGui::GetIO().Fonts->Build();
}

[ocornut]

Hello,

Thanks for your report.

The __GNUC__ check was added by 40db2ca:
"Fixed a build issue with non-Cygwin GCC under Windows."

-- #if defined(_WIN32) && !defined(__CYGWIN__)
++ #if defined(_WIN32) && !defined(__CYGWIN__) && !defined(__GNUC__)

The __CYGWIN__ check was added by bbd0a37:
"ImFileOpen: MinGW uses _wfopen() codepath to support UTF-8 filenames (#917)"

-- #ifdef _MSC_VER
++ #if defined(_WIN32) && !defined(__CYGWIN__)

I think it is reasonable to simply add a __MINGW32__ check, added one with 940d954.
Thank you!