Add some theme name resolving functions.

Makefile.am

@@ -123,7 +123,8 @@ rofi_CFLAGS=\
 	-Werror=missing-prototypes\
 	-DSYSCONFDIR=\"$(sysconfdir)\"\
 	-DTHEME_CONVERTER\
-	-DPLUGIN_PATH=\"${libdir}/rofi\"
+	-DPLUGIN_PATH=\"${libdir}/rofi\"\
+	-DTHEME_DIR=\"${prefix}/share/rofi/themes/\"
 
 rofi_LDADD=\
 	$(glib_LIBS)\

include/theme.h

@@ -443,5 +443,12 @@ gboolean rofi_theme_is_empty ( void );
  * Convert old theme colors into default one.
  */
 void rofi_theme_convert_old ( void );
+
+/**
+ * @param filename File name passed to option.
+ *
+ * @returns path to theme or copy of filename if not found.
+ */
+char *helper_get_theme_path ( const char *filename );
 #endif
 #endif

lexer/theme-lexer.l

@@ -574,7 +574,10 @@ static char * rofi_theme_parse_prepare_file ( const char *file, const char *pare
 }
 gboolean rofi_theme_parse_file ( const char *file )
 {
-    char *filename = rofi_theme_parse_prepare_file ( file, NULL );
+    char *file2 = helper_get_theme_path ( file );
+    char *filename = rofi_theme_parse_prepare_file ( file2, NULL );
+    g_free ( file2 );
+
     yyin = fopen ( filename, "rb" );
     if ( yyin == NULL ) {
         char *str = g_markup_printf_escaped ( "Failed to open theme: <i>%s</i>\nError: <b>%s</b>",

source/helper.c

@@ -964,3 +964,39 @@ int helper_execute_command ( const char *wd, const char *cmd, int run_in_term )
     g_strfreev ( args );
     return retv;
 }
+
+
+char *helper_get_theme_path ( const char *file )
+{
+    char *filename = rofi_expand_path ( file );
+    if ( g_file_test ( filename, G_FILE_TEST_EXISTS ) ) {
+        return filename;
+    }
+    g_free ( filename );
+
+    if ( g_str_has_suffix ( file, ".rasi" ) ) {
+        filename = g_strdup ( file );
+    } else {
+        filename = g_strconcat ( file, ".rasi", NULL );
+    }
+    // Check config directory.
+    const char *cpath = g_get_user_config_dir ();
+    if ( cpath ) {
+        char *themep = g_build_filename ( cpath, "rofi", filename, NULL );
+        if ( g_file_test ( themep, G_FILE_TEST_EXISTS ) ) {
+            g_free ( filename );
+            return themep;
+        }
+        g_free ( themep );
+    }
+
+    char *theme_path = g_build_filename ( THEME_DIR, filename, NULL );
+    if ( theme_path ) {
+        if ( g_file_test ( theme_path, G_FILE_TEST_EXISTS ) ) {
+            g_free ( filename );
+            return theme_path;
+        }
+        g_free ( theme_path );
+    }
+    return filename;
+}