Added functions for detecting known folders per-platform. Not tested on Windows yet, but who cares?

source/mijin/platform/folders.cpp

@@ -0,0 +1,106 @@
+
+#include "./folders.hpp"
+
+
+#include "../detect.hpp"
+#include "../debug/assert.hpp"
+
+#include <cstdlib>
+
+#if MIJIN_TARGET_OS == MIJIN_OS_WINDOWS
+#   include <Shlobj.h>
+#endif
+
+namespace mijin
+{
+fs::path getKnownFolder(KnownFolder folder) MIJIN_NOEXCEPT
+{
+#if MIJIN_TARGET_OS == MIJIN_OS_LINUX
+    switch (folder)
+    {
+    case KnownFolder::USER_HOME:
+        if (const char* val = std::getenv("HOME"); val != nullptr)
+        {
+            return val;
+        }
+        return "/";
+    case KnownFolder::TEMP:
+        for (const char* varname : {"TMPDIR", "TEMP", "TMP"})
+        {
+            if (const char* val = std::getenv(varname); val != nullptr)
+            {
+                return val;
+            }
+        }
+        return "/tmp";
+    case KnownFolder::CACHE_ROOT:
+        if (const char* val = std::getenv("XDG_CACHE_HOME"); val != nullptr)
+        {
+            return val;
+        }
+        return getKnownFolder(KnownFolder::USER_HOME) / ".cache";
+    case KnownFolder::USER_CONFIG_ROOT:
+        if (const char* val = std::getenv("XDG_CONFIG_HOME"); val != nullptr)
+        {
+            return val;
+        }
+        return getKnownFolder(KnownFolder::USER_HOME) / ".config";
+    case KnownFolder::USER_DATA_ROOT:
+        if (const char* val = std::getenv("XDG_DATA_HOME"); val != nullptr)
+        {
+            return val;
+        }
+        return getKnownFolder(KnownFolder::USER_HOME) / ".local/share";
+    }
+    MIJIN_ERROR("Invalid value passed to getKnownFolder().");
+    return {};
+#elif MIJIN_TARGET_OS == MIJIN_OS_WINDOWS
+    // TODO: this is 100% untested on Windows
+
+    auto getKnownFolderPath = [](REFKNOWNFOLDERID rfid) -> fs::path
+    {
+        WSTR path = nullptr;
+        if (!SUCCEEDED(SHGetKnownFolderPath(rfid, KF_FLAG_DEFAULT, nullptr, &path)))
+        {
+            CoTaskMemFree(path);
+            return {};
+        }
+        fs::path result(path);
+        CoTaskMemFree(path);
+        return result;
+    };
+
+    switch (folder)
+    {
+    case KnownFolder::USER_HOME:
+        if (const fs::path path = getKnownFolderPath(FOLDERID_Profile); !path.empty())
+        {
+            return path;
+        }
+        return "C:\\";
+    case KnownFolder::TEMP:
+    case KnownFolder::CACHE_ROOT:
+        for (const char* varname : {"TMPDIR", "TEMP", "TMP"})
+        {
+            if (const char* val = std::getenv(varname); val != nullptr)
+            {
+                return val;
+            }
+        }
+        return getKnownFolder(KnownFolder::USER_DATA_ROOT) / "Temp";
+    case KnownFolder::USER_CONFIG_ROOT:
+    case KnownFolder::USER_DATA_ROOT:
+        if (const fs::path path = getKnownFolderPath(FOLDERID_LocalAppData); !path.empty())
+        {
+            return path;
+        }
+        return getKnownFolder(KnownFolder::USER_HOME) / "AppData" / "Local";
+    }
+    MIJIN_ERROR("Invalid value passed to getKnownFolder().");
+    return {};
+#else
+    MIJIN_ERROR("Known folders not implemented for this platform.");
+    return {}; // don't know :/
+#endif
+}
+}