Save srb2path to %LOCALAPPDATA%\SRB2Kart\lastwaddir, and chdir here if srb2.srb cannot be found

Windows code goes brrr

src/d_main.c

@@ -845,6 +845,24 @@ static inline void D_CleanFile(char **filearray)
 // Identify the SRB2 version, and IWAD file to use.
 // ==========================================================================
 
+static boolean AddIWAD(char *srb2wad1, char *srb2wad2)
+{
+	if (srb2wad2 != NULL && FIL_ReadFileOK(srb2wad2))
+	{
+		D_AddFile(srb2wad2, startupwadfiles);
+		return true;
+	}
+	else if (srb2wad1 != NULL && FIL_ReadFileOK(srb2wad1))
+	{
+		D_AddFile(srb2wad1, startupwadfiles);
+		return true;
+	}
+	else
+	{
+		return false;
+	}
+}
+
 static void IdentifyVersion(void)
 {
 	char *srb2wad1, *srb2wad2;
@@ -896,12 +914,17 @@ static void IdentifyVersion(void)
 	configfile[sizeof configfile - 1] = '\0';
 
 	// Load the IWAD
-	if (srb2wad2 != NULL && FIL_ReadFileOK(srb2wad2))
-		D_AddFile(srb2wad2, startupwadfiles);
-	else if (srb2wad1 != NULL && FIL_ReadFileOK(srb2wad1))
-		D_AddFile(srb2wad1, startupwadfiles);
+	if (AddIWAD(srb2wad1, srb2wad2))
+	{
+		I_SaveCurrentWadDirectory();
+	}
 	else
-		I_Error("SRB2.SRB/SRB2.WAD not found! Expected in %s, ss files: %s or %s\n", srb2waddir, srb2wad1, srb2wad2);
+	{
+		if (!( I_UseSavedWadDirectory() && AddIWAD(srb2wad1, srb2wad2) ))
+		{
+			I_Error("SRB2.SRB/SRB2.WAD not found! Expected in %s, ss files: %s or %s\n", srb2waddir, srb2wad1, srb2wad2);
+		}
+	}
 
 	if (srb2wad1)
 		free(srb2wad1);

src/i_system.h

@@ -318,6 +318,15 @@ const CPUInfoFlags *I_CPUInfo(void);
 */
 const char *I_LocateWad(void);
 
+/**	\brief Save current wad directory to appdata
+*/
+void I_SaveCurrentWadDirectory(void);
+
+/**	\brief Change directory to last known directory saved in appdata
+		\return whether the directory could be saved
+*/
+boolean I_UseSavedWadDirectory(void);
+
 /**	\brief First Joystick's events
 */
 void I_GetJoystickEvents(void);

src/sdl/i_system.c

@@ -34,6 +34,7 @@
 #ifdef _WIN32
 #define RPC_NO_WINDOWS_H
 #include <windows.h>
+#include <shlobj.h>
 #include "../doomtype.h"
 typedef BOOL (WINAPI *p_GetDiskFreeSpaceExA)(LPCSTR, PULARGE_INTEGER, PULARGE_INTEGER, PULARGE_INTEGER);
 typedef BOOL (WINAPI *p_IsProcessorFeaturePresent) (DWORD);
@@ -3758,6 +3759,66 @@ static const char *locateWad(void)
 	return NULL;
 }
 
+#ifdef _WIN32
+static FILE * openAppDataFile(const char *filename, const char *mode)
+{
+	FILE * file = NULL;
+	char   kdir[MAX_PATH];
+
+	if (SHGetFolderPathAndSubDirA(NULL, CSIDL_LOCAL_APPDATA|CSIDL_FLAG_CREATE,
+				NULL, 0, "SRB2Kart", kdir) == S_OK)
+	{
+		strcat(kdir, "\\");
+		strcat(kdir, filename);
+		file = fopen(kdir, mode);
+	}
+
+	return file;
+}
+#endif
+
+void I_SaveCurrentWadDirectory(void)
+{
+#ifdef _WIN32
+	char   path[MAX_PATH];
+	FILE * file = openAppDataFile("lastwaddir", "w");
+	if (file != NULL)
+	{
+		if (strcmp(srb2path, ".") == 0)
+		{
+			GetCurrentDirectoryA(sizeof path, path);
+			fputs(path, file);
+		}
+		else
+		{
+			fputs(srb2path, file);
+		}
+		fclose(file);
+	}
+#endif
+}
+
+boolean I_UseSavedWadDirectory(void)
+{
+	boolean ok = false;
+#ifdef _WIN32
+	char   path[MAX_PATH];
+	FILE * file = openAppDataFile("lastwaddir", "r");
+	if (file != NULL)
+	{
+		if (fgets(path, sizeof path, file) != NULL)
+		{
+			I_OutputMsg(
+					"Going to the last known directory with srb2.srb: %s\n",
+					path);
+			ok = SetCurrentDirectoryA(path);
+		}
+		fclose(file);
+	}
+#endif
+	return ok;
+}
+
 const char *I_LocateWad(void)
 {
 	const char *waddir;