changes to launchdf to handle relocatable install

instead of assuming colocation, this version will (when both DF and DFHack are installed in Steam) automatically inject DFHack into DF

environments where not both apps are installed in Steam are (hopefully) unaffected

Author: ab9rf

package/launchdf.cpp

@@ -10,6 +10,8 @@
 #include "steam_api.h"
 
 #include <string>
+#include <filesystem>
+#include <fstream>
 
 #define xstr(s) str(s)
 #define str(s) #s
@@ -245,14 +247,19 @@ int main(int argc, char* argv[]) {
     }
 
     bool nowait = false;
+    bool installmode = false;
 #ifdef WIN32
     std::wstring cmdline(lpCmdLine);
     if (cmdline.find(L"--nowait") != std::wstring::npos)
         nowait = true;
+    if (cmdline.find(L"--install") != std::wstring::npos)
+        installmode = true;
 #else
     for (int idx = 0; idx < argc; ++idx) {
         if (strcmp(argv[idx], "--nowait") == 0)
             nowait = true;
+        if (strcmp(argv[idx], "--install") == 0)
+            installmode = true;
     }
 #endif
 
@@ -294,22 +301,75 @@ int main(int argc, char* argv[]) {
     char buf[2048] = "";
 
     int b1 = SteamApps()->GetAppInstallDir(DFHACK_STEAM_APPID, (char*)&buf, 2048);
-    std::string dfhack_install_folder = (b1 != -1) ? std::string(buf) : "";
+    std::filesystem::path dfhack_install_folder = (b1 != -1) ? std::string(buf) : "";
 
     int b2 = SteamApps()->GetAppInstallDir(DF_STEAM_APPID, (char*)&buf, 2048);
-    std::string df_install_folder = (b2 != -1) ? std::string(buf) : "";
+    std::filesystem::path df_install_folder = (b2 != -1) ? std::string(buf) : "";
 
+    if (df_install_folder != dfhack_install_folder)
+    {
+#ifdef WIN32
+        constexpr auto dfhooks_dll_name = "dfhooks.dll";
+        constexpr auto dfhook_dfhack_dll_name = "dfhooks_dfhack.dll";
+#else
+        constexpr auto dfhooks_dll_name = "libdfhooks.so";
+        constexpr auto dfhook_dfhack_dll_name = "libdfhooks_dfhack.so";
+#endif
+        // DF and DFHack are not co-installed (modern case)
+        // inject dfhooks.dll and dfhooks_dfhack.ini into DF install folder
+        std::filesystem::path dfhooks_dll_src = dfhack_install_folder / dfhooks_dll_name;
+        std::filesystem::path dfhooks_dll_dst = df_install_folder / dfhooks_dll_name;
+        std::filesystem::path dfhooks_ini_dst = df_install_folder / "dfhooks_dfhack.ini";
+        std::filesystem::path dfhooks_dfhack_dll_src = dfhack_install_folder / "hack" / dfhook_dfhack_dll_name;
 
-    if (df_install_folder != dfhack_install_folder) {
-        // DF and DFHack are not installed in the same library
+        std::error_code ec;
+
+        std::filesystem::copy(dfhooks_dll_src, dfhooks_dll_dst, std::filesystem::copy_options::update_existing, ec);
+        if (!ec)
+        {
+            std::string indirection;
+            if (std::filesystem::exists(dfhooks_ini_dst))
+            {
+                std::ifstream ini(dfhooks_ini_dst);
+                std::getline(ini, indirection);
+            }
+
+            if (indirection != dfhooks_dfhack_dll_src.string())
+            {
+                std::ofstream ini(dfhooks_ini_dst);
+                ini << dfhooks_dfhack_dll_src.string() << std::endl;
+            }
+        }
+        else
+        {
 #ifdef WIN32
-        MessageBoxW(NULL, L"DFHack and Dwarf Fortress must be installed in the same Steam library.\nAborting.", NULL, 0);
+            std::wstring message{
+                L"Failed to inject DFHack into Dwarf Fortress\n\n"
+                L"Details:\n" + std::filesystem::relative(dfhooks_dll_src).wstring() +
+                L" -> " + std::filesystem::relative(dfhooks_dll_dst).wstring() +
+                L"\n\nError code: " + std::to_wstring(ec.value()) +
+                L"\nError message: " + std::filesystem::relative(ec.message()).wstring()
+            };
+
+            MessageBoxW(NULL, message.c_str(), NULL, 0);
 #else
-        notify("DFHack and Dwarf Fortress must be installed in the same Steam library.\nAborting.");
+            std::string message{
+                "Failed to inject DFHack into Dwarf Fortress\n\n"
+                "Details:\n" + std::filesystem::relative(dfhooks_dll_src).string() +
+                " -> " + std::filesystem::relative(dfhooks_dll_dst).string() +
+                "\n\nError code: " + std::to_string(ec.value()) +
+                "\nError message: " + std::filesystem::relative(ec.message()).string()
+            };
+
+            notify(message.c_str());
 #endif
-        exit(1);
+            exit(1);
+        }
     }
 
+    if (installmode)
+        exit(0);
+
     if (!wrap_launch(launch_via_steam))
         exit(1);