@Override
		public boolean isAutoActivateOkay( JTextComponent comp ) {
			int caretPosition = comp.getCaretPosition();
			if( caretPosition <= 0 )
				return false;

			try {
				char ch = comp.getText( caretPosition - 1, 1 ).charAt( 0 );
				return (autoActivateAfterLetters && Character.isLetter( ch )) ||
					(autoActivateChars != null && autoActivateChars.indexOf( ch ) >= 0);
			} catch( BadLocationException | IndexOutOfBoundsException ex ) {
				// ignore
				return false;
			}
		}
A completion provider for keys, which always uses all known/predefined keys.
flatlaf-theme-editor/src/main/java/com/formdev/flatlaf/themeeditor/FlatCompletionProvider.java