Using _wfopen() under Windows+MSVC because fopen() doesn't support UTF-8 encoding. Wrapped as ImFileOpen(). (#917)

imgui.cpp

@@ -1293,6 +1293,22 @@ void ImGui::ColorConvertHSVtoRGB(float h, float s, float v, float& out_r, float&
     }
 }
 
+FILE* ImFileOpen(const char* filename, const char* mode)
+{
+#ifdef _MSC_VER
+    // We need a fopen() wrapper because MSVC/Windows fopen doesn't handle UTF-8 filenames. Converting both strings from UTF-8 to wchar format (using a single allocation, because we can)
+    const int filename_wsize = ImTextCountCharsFromUtf8(filename, NULL) + 1;
+    const int mode_wsize = ImTextCountCharsFromUtf8(mode, NULL) + 1;
+    ImVector<ImWchar> buf;
+    buf.resize(filename_wsize + mode_wsize);
+    ImTextStrFromUtf8(&buf[0], filename_wsize, filename, NULL);
+    ImTextStrFromUtf8(&buf[filename_wsize], mode_wsize, mode, NULL);
+    return _wfopen((wchar_t*)&buf[0], (wchar_t*)&buf[filename_wsize]);
+#else
+    return fopen(filename, mode);
+#endif
+}
+
 // Load file content into memory
 // Memory allocated with ImGui::MemAlloc(), must be freed by user using ImGui::MemFree()
 void* ImLoadFileToMemory(const char* filename, const char* file_open_mode, int* out_file_size, int padding_bytes)
@@ -1302,7 +1318,7 @@ void* ImLoadFileToMemory(const char* filename, const char* file_open_mode, int*
         *out_file_size = 0;
 
     FILE* f;
-    if ((f = fopen(filename, file_open_mode)) == NULL)
+    if ((f = ImFileOpen(filename, file_open_mode)) == NULL)
         return NULL;
 
     long file_size_signed;
@@ -2501,7 +2517,7 @@ static void SaveSettings()
 
     // Write .ini file
     // If a window wasn't opened in this session we preserve its settings
-    FILE* f = fopen(filename, "wt");
+    FILE* f = ImFileOpen(filename, "wt");
     if (!f)
         return;
     for (int i = 0; i != g.Settings.Size; i++)
@@ -5784,7 +5800,7 @@ void ImGui::LogToFile(int max_depth, const char* filename)
             return;
     }
 
-    g.LogFile = fopen(filename, "ab");
+    g.LogFile = ImFileOpen(filename, "ab");
     if (!g.LogFile)
     {
         IM_ASSERT(g.LogFile != NULL); // Consider this an error

imgui_internal.h

@@ -89,6 +89,7 @@ IMGUI_API int           ImTextCountUtf8BytesFromStr(const ImWchar* in_text, cons
 // Helpers: Misc
 IMGUI_API ImU32         ImHash(const void* data, int data_size, ImU32 seed = 0);    // Pass data_size==0 for zero-terminated strings
 IMGUI_API void*         ImLoadFileToMemory(const char* filename, const char* file_open_mode, int* out_file_size = NULL, int padding_bytes = 0);
+IMGUI_API FILE*         ImOpenFile(const char* filename, const char* file_open_mode);         
 IMGUI_API bool          ImIsPointInTriangle(const ImVec2& p, const ImVec2& a, const ImVec2& b, const ImVec2& c);
 static inline bool      ImCharIsSpace(int c)            { return c == ' ' || c == '\t' || c == 0x3000; }
 static inline int       ImUpperPowerOfTwo(int v)        { v--; v |= v >> 1; v |= v >> 2; v |= v >> 4; v |= v >> 8; v |= v >> 16; v++; return v; }