Theme Editor: increment/decrement color parts (red, green, blue or alpha) at caret using Ctrl+UP/Ctrl+DOWN

flatlaf-theme-editor/src/main/java/com/formdev/flatlaf/themeeditor/FlatSyntaxTextAreaActions.java

@@ -92,15 +92,24 @@ class FlatSyntaxTextAreaActions
 
 		@Override
 		public void actionPerformedImpl( ActionEvent e, RTextArea textArea ) {
+			if( !incrementRGBColor( textArea ) )
+				incrementNumber( textArea );
+		}
+
+		private void incrementNumber( RTextArea textArea ) {
 			try {
 				int caretPosition = textArea.getCaretPosition();
 				int start = caretPosition;
 				int end = caretPosition;
+
+				// find first digit
 				for( int i = caretPosition - 1; i >= 0; i-- ) {
 					if( !Character.isDigit( textArea.getText( i, 1 ).charAt( 0 ) ) )
 						break;
 					start = i;
 				}
+
+				// find last digit
 				int length = textArea.getDocument().getLength();
 				for( int i = caretPosition; i < length; i++ ) {
 					if( !Character.isDigit( textArea.getText( i, 1 ).charAt( 0 ) ) )
@@ -111,8 +120,11 @@ class FlatSyntaxTextAreaActions
 				if( start == end )
 					return;
 
+				// parse number
 				String str = textArea.getText( start, end - start );
 				long number = Long.parseLong( str );
+
+				// increment/decrement number
 				if( increment )
 					number++;
 				else
@@ -121,12 +133,89 @@ class FlatSyntaxTextAreaActions
 				if( number < 0 )
 					return;
 
+				// update editor
 				textArea.replaceRange( Long.toString( number ), start, end );
 			} catch( BadLocationException | IndexOutOfBoundsException | NumberFormatException ex ) {
 				ex.printStackTrace();
 			}
 		}
 
+		private boolean incrementRGBColor( RTextArea textArea ) {
+			try {
+				int caretPosition = textArea.getCaretPosition();
+				int start = caretPosition;
+				int end = caretPosition;
+
+				// find first '#' or hex digit
+				for( int i = caretPosition - 1; i >= 0; i-- ) {
+					char ch = textArea.getText( i, 1 ).charAt( 0 );
+					if( ch != '#' && !isHexDigit( ch ) )
+						break;
+					start = i;
+				}
+
+				// find last hex digit
+				int length = textArea.getDocument().getLength();
+				for( int i = caretPosition; i < length; i++ ) {
+					if( !isHexDigit( textArea.getText( i, 1 ).charAt( 0 ) ) )
+						break;
+					end = i + 1;
+				}
+
+				// check for valid length (#RGB, #RGBA, #RRGGBB or #RRGGBBAA)
+				int len = end - start;
+				if( len != 4 && len != 5 && len != 7 && len != 9 )
+					return false;
+
+				// check whether starts with '#'
+				if( textArea.getText( start, 1 ).charAt( 0 ) != '#' )
+					return false;
+
+				// find start of color part that should be changed (red, green, blue or alpha)
+				int start2;
+				int hexDigitCount = (len == 4 || len == 5) ? 1 : 2;
+				if( hexDigitCount == 1 ) {
+					// #RGB or #RGBA
+					start2 = caretPosition - 1;
+				} else {
+					// #RRGGBB or #RRGGBBAA
+					int offset = caretPosition - (start + 1);
+					offset += (offset % 2);
+					start2 = start + 1 + offset - 2;
+				}
+				start2 = Math.max( start2, start + 1 );
+
+				// parse number
+				String str = textArea.getText( start2, hexDigitCount );
+				int number = Integer.parseInt( str, 16 );
+
+				// increment/decrement number
+				if( increment )
+					number++;
+				else
+					number--;
+
+				// wrap numbers if less than zero or too large
+				int maxNumber = (hexDigitCount == 1) ? 15 : 255;
+				if( number < 0 )
+					number = maxNumber;
+				else if( number > maxNumber )
+					number = 0;
+
+				// update editor
+				String newStr = String.format( hexDigitCount == 1 ? "%1x" : "%02x", number );
+				textArea.replaceRange( newStr, start2, start2 + hexDigitCount );
+				return true;
+			} catch( BadLocationException | IndexOutOfBoundsException | NumberFormatException ex ) {
+				ex.printStackTrace();
+				return false;
+			}
+		}
+
+		private boolean isHexDigit( char ch ) {
+			return Character.isDigit( ch ) || (ch >= 'a' && ch <= 'f') || (ch >= 'A' && ch <= 'F');
+		}
+
 		@Override
 		public String getMacroID() {
 			return getName();