Unix: Use de::Info to configure basedir and libdir

The de::Info parser is utilized to read Unix-specific configuration
files /etc/doomsday/paths and ~/.doomsday/paths for overridden
base and library directories. For instance:

basedir: /opt/deng/share/
libdir: /opt/deng/lib/

This allows a packager to override the compile-time
DENG_BASE_DIR and DENG_LIBRARY_DIR without the user
needing to know about it.

Command line options (-basedir, -appdir, -libdir) still take precedence
over these.

doomsday/engine/portable/src/library.c

@@ -75,17 +75,23 @@ static void getBundlePath(char* path, size_t len)
         return;
     }
 
+    /*
 #ifdef MACOSX
     // This is the default location where bundles are.
     dd_snprintf(path, len, "%s/Bundles", appDir);
 #endif
+    */
+
 #ifdef UNIX
-#ifdef DENG_LIBRARY_DIR
+# ifdef DENG_LIBRARY_DIR
     strncpy(path, DENG_LIBRARY_DIR, len);
-#else
+# else
     // Assume they are in the cwd.
     strncpy(path, appDir, len);
-#endif
+# endif
+
+    // Check Unix-specific config files.
+    DD_Unix_GetConfigValue("paths", "libdir", path, len);
 #endif
 }
 #endif

doomsday/engine/unix/include/dd_uinit.h

@@ -53,6 +53,15 @@ extern application_t app;
 boolean DD_Unix_Init(int argc, char** argv);
 void DD_Shutdown(void);
 
+/**
+ * @note This implementation re-parses the entire config file on each call, so
+ * it is not useful for performance-critical or high volume usage.
+ *
+ * @return @c true, if the found config value was written to @a dest, otherwise
+ * @c false.
+ */
+boolean DD_Unix_GetConfigValue(const char* configFile, const char* key, char* dest, size_t destLen);
+
 #ifdef __cplusplus
 }
 #endif

doomsday/engine/unix/src/dd_uinit.c

@@ -310,6 +310,8 @@ static void determineGlobalPaths(application_t* app)
 #else
         strncpy(ddBasePath, DENG_BASE_DIR, FILENAME_T_MAXLEN);
 #endif
+        // Also check the system config files.
+        DD_Unix_GetConfigValue("paths", "basedir", ddBasePath, FILENAME_T_MAXLEN);
     }
     Dir_CleanPath(ddBasePath, FILENAME_T_MAXLEN);
     Dir_MakeAbsolutePath(ddBasePath, FILENAME_T_MAXLEN);
@@ -427,3 +429,45 @@ void DD_Shutdown(void)
     Library_Shutdown();
     DisplayMode_Shutdown();
 }
+
+boolean DD_Unix_GetConfigValue(const char* configFile, const char* key, char* dest, size_t destLen)
+{
+    Info* info;
+    char buf[512];
+    ddstring_t* p;    
+    boolean success = false;
+
+    // Maybe it is in the user's .doomsday dir.
+    p = Str_New();
+    Str_Appendf(p, "~/.doomsday/%s", configFile);
+    F_MakeAbsolute(p, p);
+    info = Info_NewFromFile(Str_Text(p));
+    if(info)
+    {
+        if(Info_FindValue(info, key, buf, sizeof(buf)))
+        {
+            strncpy(dest, buf, destLen);
+            success = true;
+            goto cleanup;
+        }
+    }
+
+    // Check for a config file for the library path.
+    Str_Clear(p);
+    Str_Appendf(p, "/etc/doomsday/%s", configFile);
+    info = Info_NewFromFile(Str_Text(p));
+    if(info)
+    {
+        if(Info_FindValue(info, key, buf, sizeof(buf)))
+        {
+            strncpy(dest, buf, destLen);
+            success = true;
+            goto cleanup;
+        }
+    }
+
+cleanup:
+    Info_Delete(info);
+    Str_Delete(p);
+    return success;
+}