[NXC UserInteraction Library]

Robots Libraries Lego Mindstorms Date: Mar 2012

Current version: 1.2 :: Follow me on Twitter for updates

The User Interaction (UIn) Library helps you create standard user interfaces (multi-line aligned texts, buttons, menus, etc.) and capture user actions on the NXT Mindstorms brick.

The library works with the intelligent brick buttons and keeps all your sensor ports free for your program to use.

The UIn Library is a single .h file that can be included with your NXC project. It has been tested with NBC version 1.2.1 r4 and requires the NXC extended firmware. Please read the development setup tutorial if you are not sure how to get extended firmware.

Main features

How it works

Download a demo (XCode) project to try out the whole UserInteraction library.

This is an example of using a sliding menu in order to decide which task to exectute. UIn function createSlidingMenu() is called with appropriate arguments and the program waits until user selects an option from the menu. The user choice is then resolved by the calling task. Note that ExitTo(Task newTask) is used in order to close the current task and start a new one. This prevents unpredictable behaviour of the new task when calling UIn and other functions.

#include "UserInteraction.h"

task main() {

    //-- create menu with 2-line option items
    string menuItems[3] = {"First#Option","Second#Option", "Third#Option"};
    int userResponse = createSlidingMenu("Select#an option",menuItems, 0);

    //-- resolve answer from the sliding menu
    switch (userResponse) {
        case 0:
            // Selected 'First Option'
        case 1:
            // Selected 'Second Option'
            // Selected 'Third Option'

task onFirstOption() {}
task onSecondOption() {}
task onThirdOption() {}


Other features

Text drawing functions

Shape-drawing functions

Helper functions

  • int getTextPixelLength (string text_)
  • int getAlignedTextPosition (string text_, UIN_ALIGNMENT alignment_)
  • int normaliseTextXPosition (string text_, int xPosition_)
  • int lastPos(string substr_, string string_)

Math functions

  • int round (float number_)
  • float abs (float number_)


Please comment or email me if you have questions or ideas about new functionality.



Hi Raj, I'm glad you got it sorted, although that is a strange solution as those two macros are defined in the library file itself so you would only add those lines if you wanted to change the values. Anyways, I wish you luck, thanks for downloading the library.
oh, I got it solved by adding following two lines.



my long wish has been answered by your excellent interface library. I'm getting error while compiling your demo code with lot of syntax error.

I'm using Bric Command Center Version 3.3(build in windows xp. I can see that UserInteraction.h does exist on the same directory.

Am I missing anything ?


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