Text Wrapping in C on Thermo Mini Printer

Question

I would really like some help with one of my projects. I am a graphic design student and have little to no programming experience. I have created a program for a thermo mini printer that identifies tweets made on twitter based on specific hashtags used and prints them automatically.

However, it's based on a line length of 32 chars and will split words in half instead of moving the entire word to another line. A friend of mine suggested word wrapping but I can't find anything online to help me and most code I've found tends to be for c++ or c#.

The code so far can be found below:

// Build an ArrayList to hold all of the words that
// we get from the imported tweets

ArrayList<String> words = new ArrayList();
Twitter twitter;
import processing.serial.*;

Serial myPort;  // Create object from Serial class
int val;        // Data received from the serial port

void setup() {
    String portName = Serial.list()[0];
    myPort = new Serial(this, portName, 9600);
    //Set the size of the stage, and the background to black.
    size(550,550);
    background(0);
    smooth();

    //Make the twitter object and prepare the query
    twitter = new TwitterFactory(cb.build()).getInstance();
}

void draw() {

    Query query = new Query("#R.I.P");
    query.setRpp(1);

    //Try making the query request.
    try {
        QueryResult result = twitter.search(query);
        ArrayList tweets = (ArrayList) result.getTweets();

        for (int i = 0; i < tweets.size(); i++) {
            Tweet t = (Tweet) tweets.get(i);
            String user = t.getFromUser();
            String msg = t.getText();
            Date d = t.getCreatedAt();
            println("Tweet by " + user + " at " + d + ": " + msg);
            msg = msg.replace("\n"," ");
            myPort.write(msg+"\n");
        };
    }
    catch (TwitterException te) {
        println("Couldn't connect: " + te);
    };
    println("------------------------------------------------------");
    delay(20000);
}

Answer 1

Since you have the length of the line, it's not that hard...

Iterate over the string, one character at a time. If you see a space save the position as e.g. last_space. If your iteration goes over the max line length, then go to the last_space position and convert the space to a newline, reset the position counter to zero, and start over from that position.

---

Maybe implement it something like this:

#include <stdio.h>
#include <string.h>
#include <ctype.h>

#define LINE_LENGTH 32

char text[256] = "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer ac risus elit, id pellentesque magna. Curabitur tempor rutrum enim, sit amet interdum turpis venenatis vel. Praesent eu urna eros. Mauris sagittis tempor felis, ac feugiat est elementum sed. Praesent et augue in nibh pharetra egestas quis et lectus. Lorem ipsum.";

static void wrap(char *text, const int length)
{
    int last_space = 0;
    int counter = 0;

    for (int current = 0; text[current] != '\0'; current++, counter++)
    {
        if (isspace(text[current]))  // TODO: Add other delimiters here
            last_space = current;

        if (counter >= length)
        {
            text[last_space] = '\n';
            counter = 0;
        }
    }
}

int main(void)
{
    printf("Before wrap:\n%s\n", text);

    wrap(text, LINE_LENGTH);

    printf("\nAfter wrap:\n%s\n", text);

    return 0;
}

Important note: The wrap function modifies the buffer passed in as the text argument. That means it can not handle literal strings as those are read-only. It works by replacing a space with a newline. If you modify the function to add more than one character, then a better solution would by to (re)allocate a new buffer big enough to hold the modified string.