[settings] Display only applicable settings in "config" user interface

Display only settings relevant to the current scope.  For example,
"config net0" no longer displays SMBIOS settings, and "config smbios"
displays only SMBIOS settings.

Originally-implemented-by: Glenn Brown <glenn@myri.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/hci/tui/settings_ui.c

 struct setting_widget {
 	/** Settings block */
 	struct settings *settings;
+	/** Number of applicable settings */
+	unsigned int num_settings;
         /** Index of the first visible setting, for scrolling. */
 	unsigned int first_visible;
 	/** Configuration setting */
 	char value[256]; /* enough size for a DHCP string */
 };
 
-/** Number of registered configuration settings */
-#define NUM_SETTINGS table_num_entries ( SETTINGS )
-
 static void load_setting ( struct setting_widget *widget ) __nonnull;
 static int save_setting ( struct setting_widget *widget ) __nonnull;
 static void init_widget ( struct setting_widget *widget,
  */
 static void init_widget ( struct setting_widget *widget,
 			  struct settings *settings ) {
+	struct setting *setting;
+
 	memset ( widget, 0, sizeof ( *widget ) );
 	widget->settings = settings;
+	for_each_table_entry ( setting, SETTINGS ) {
+		if ( setting_applies ( settings, setting ) )
+			widget->num_settings++;
+	}
 	widget->first_visible = SETTINGS_LIST_ROWS;
 	reveal ( widget, 0 );
 }
  */
 static void select_setting ( struct setting_widget *widget,
 			     unsigned int index ) {
-	struct setting *all_settings = table_start ( SETTINGS );
 	unsigned int skip = offsetof ( struct setting_widget, setting );
 
 	/* Reset the widget, preserving static state. */
 	memset ( ( char * ) widget + skip, 0, sizeof ( *widget ) - skip );
-	widget->setting = &all_settings[index];
 	widget->row = SETTINGS_LIST_ROW + index - widget->first_visible;
 	widget->col = SETTINGS_LIST_COL;
+	for_each_table_entry ( widget->setting, SETTINGS ) {
+		if ( ! setting_applies ( widget->settings, widget->setting ) )
+			continue;
+		if ( index-- == 0 )
+			break;
+	}
 
 	/* Read current setting value */
 	load_setting ( widget );
 		   widget->first_visible > 0 ? "..." : "   " );
 	mvaddstr ( SETTINGS_LIST_ROW + SETTINGS_LIST_ROWS,
 		   SETTINGS_LIST_COL + 1,
-		   ( widget->first_visible + SETTINGS_LIST_ROWS < NUM_SETTINGS
-		     ? "..."
-		     : "   " ) );
+		   ( ( widget->first_visible + SETTINGS_LIST_ROWS )
+		     < widget->num_settings ? "..." : "   " ) );
 	
 	/* Draw visible settings. */
 	for ( i = 0; i < SETTINGS_LIST_ROWS; i++ ) {
-		if ( widget->first_visible + i < NUM_SETTINGS ) {
+		if ( ( widget->first_visible + i ) < widget->num_settings ) {
 			select_setting ( widget, widget->first_visible + i );
 			draw_setting ( widget );
 		} else {
 			next = current;
 			switch ( key ) {
 			case KEY_DOWN:
-				if ( next < ( NUM_SETTINGS - 1 ) )
+				if ( next < ( widget.num_settings - 1 ) )
 					reveal ( &widget, ++next );
 				break;
 			case KEY_UP: