Simple text editor help

I have to do a simple text editor using the c language. But I don't know how to get started. The program should begin with a blank screen, waiting for the user to write something.The last line will be the "situation" line which explains what the program is doing or asking us to do. The user is also able to move the cursor using the arrow keys and the user is also able to load text files to the program from his hard drive and also make a text file of something the user has written in the program. He can load something by pressing CTRL-O or he can press CTRL-S to save something followed by the name of the text file. Our professor said that we have to use the library screenUtils to make the cursor move. How should I start? I'm trying to make this work but nothing really works.
This is an example of how the screen should look like:
http://i53.tinypic.com/1zwm3a0.jpg

First, google up your library, (which I just tried and could not locate in a quick search), then if needed, you miight want to start here, with the basics of console windows, if your OS is Windows:
Win32 Console Applications 1

I'm not sure how to check for Ctrl+O. If you don't find anything in a search of the forum, I'd jump onto Google. That's really an OS thing, rather than a part of standard C.

And of course, your library may cover a lot of this, so you don't have to.

So I found out what the screenUtils library does. Unfortunately it doesn't do anything with the CTRL+O commands. It has 3 functions:
void gotoxy(int x, int y); To move the cursor to a specific place on the screen.

void clrscr(void); To clear the screen and place the cursor on position (0,0).

void setColor(color text, color back); To change the color of the letters and the background.

What is your operating system?

WinXP on an iMac...

Cursor moving is platform specific. Sane libraries that I know and you could use Windows' system calls or what ever they are, conio.h, or curses, which is the most portable from these.

^O is ASCII 0x0f, ^S is ASCII 0x13. For ^foo where foo belongs to [A-Z], the ASCII value is (foo - 'A' + 1).

His assignment states that he has to use the other library, so using conio.h is not OK for him.

Back to the Win32 console tutorial (it's a very good one), and get started with creating your console window as per the picture you posted.

Last time I did this (many DOS days ago), I used a large single dimension char array, which extended beyond the size of the text window, quite a bit. That allowed text to scroll and look natural.

I'd guessed that a 2 dimension char array with rows and columns would work better, but it was actually more of a pain to mess with, than a 1 dimension char array.

@fronty, is ^ the symbol for the Ctrl key or the Alt key or ?

Sorry, I didn't read the original post too well. But if he has to use that library, I guess there won't be much need for Win32 console library.

I wouldn't think about how I would display things. I would start by designing internal data structures used to hold the file, because it will be hell easier to write UI code which displays the menu stuff and the file contents from internal data structures, than first writing the UI and then trying adapt the internal datastructures to the UI code.

And ^ means control.

The link I gave him isn't for a console library - it's shows how to use the Windows console, without a library. In his case, a very limited library.

With Win32 console library I referred to the system library of Windows which offers functions to control a console.

Quote:

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Originally Posted by Fink

I have to do a simple text editor using the c language. But I don't know how to get started. The program should begin with a blank screen, waiting for the user to write something.The last line will be the "situation" line which explains what the program is doing or asking us to do. The user is also able to move the cursor using the arrow keys and the user is also able to load text files to the program from his hard drive and also make a text file of something the user has written in the program. He can load something by pressing CTRL-O or he can press CTRL-S to save something followed by the name of the text file. Our professor said that we have to use the library screenUtils to make the cursor move. How should I start? I'm trying to make this work but nothing really works.
This is an example of how the screen should look like:
http://i53.tinypic.com/1zwm3a0.jpg

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Holy crap... I hope this isn't due on Monday...

I have to give it in two weeks which I think is a lot of time to make this work. How should I ask the user to put a character? Should I do it with scanf? I'm sorry but I'm not the brightest c programmer. I'm thinking on putting the scanf (if needed) in a loop and if the user puts an arrow key I will use the gotoxy(int x, int y) function. But how will I make the thing with the last line work?

Sorry for my bad english.

Quote:

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Originally Posted by Fink

I have to give it in two weeks which I think is a lot of time to make this work. How should I ask the user to put a character? Should I do it with scanf? I'm sorry but I'm not the brightest c programmer. I'm thinking on putting the scanf (if needed) in a loop and if the user puts an arrow key I will use the gotoxy(int x, int y) function. But how will I make the thing with the last line work?

Sorry for my bad english.

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Yes, you're going to have to work this character by character in a loop.

You will need a rather large array of strings (a buffer) to hold the text and a fair bit of logic to position the cursor and text on the screen in some useable manner. Probably the simplest approach would be an array of about 10,000 strings at least 80 characters long.

Your code is going to have to do secondary tasks such as word wrapping and unwrapping, line breaks and paragraph breaks, dealing with backspacing, deletions, insertions, screen scrolling, etc. All done on a character by character basis, in real time, while the operator is typing.

It's been a long time since I did one of these and I'd suggest you get busy, 'cause you ain't gonna do it in an afternoon.

You do NOT have any time to spare. These kinds of assignments always take way longer than you think they will.

You can't use scanf() - all that normal keyboard input functions used for C, is buffered, (meaning you have to hit enter for it to be entered). You need to check out how windows can provide unbuffered input. Also in the MS library. Indeed, you should bookmark it for frequent reference.

Quote:

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Originally Posted by Adak

You do NOT have any time to spare. These kinds of assignments always take way longer than you think they will.

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WAY longer.

This guy's Prof. reminds me of one of my Bosses from years ago... This guy was a horrendous money waster and a flat out idiot. He would come to me and say "Can you do _______". I'd say "yes of course it can be done but it's going to take some time". So I'd get busy on the project, get it up to a prototype, something he could see... Then of course there'd be the software side of it. Well --and this guy never missed-- as soon as he saw the prototype he'd give it to the customer who, of course, immediately complained that it didn't work. My boss would bring it back and say "It doesn't work..." Every time I would try to explain that it needs the software before it's going to work... Without fail, he would toss it in the garbage and give the customer a refund, usually on the day I finished the software... In over 10 years and despite repeated explainations, nobody ever got him to understand that hardware and software work hand in hand. He probably scrapped about 50 perfectly good --patentable-- projects over the years.

Two weeks is no where near enough time to write, debug and deliver even a very basic text editor...

One tip: Don't use array for holding the contents. It won't work.
Another tip: Gap or list.

Quote:

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Originally Posted by fronty

One tip: Don't use array for holding the contents. It won't work.
Another tip: Gap or list.

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Of course an array can be used to hold text content...

Code:

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char TextBuf[1000][81];

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One thousand lines 80 characters wide.

That won't be very practical. If you delete the first character in a line, you have to shift other 79 characters back one place, and when the user enters a new character in the beginning of the line, you have to shift them back. IF you don't use some kind of delay in the changes to the actual buffer, or use another buffer containing a copy of current line or something somewhere else. Still that doesn't work well when user enters completely new line. You have to shoft all the lines further in the buffer.

I still say gap buffer or list. First one is traditionally used in emacsen and the latter is used very well in fancy eds also known as vis and are easy to implement.

So I'm doing some tests here, but I'm stuck. How will the computer know if one of the arrow keys is pressed?
I'm thinking something like that:
if(string=="user presses right arrow")
{
x++;
gotoxy(x,y);
}
but what will the code for "user presses right arrow be? I'm thinking of putting the ASCII code for the arrow keys but I can't find anything.
Just for testing I'm using a string and not an array or something else.

That depends on how you're getting input. If you're doing a keyboard poll, you'd have to check whether right-arrow is in a key-down state. If you're getting signals, then you're "strange" keys have special values that depend on what library you're using.

Hmmm....I never heard my professor tell us anything about this stuff, it can't be that difficult. Right now I'm using stdlib,stdio and screentUtils libraries.

You're not going to get arrow keys (or control-whatever key combinations) using stdio. stdio only gives you line-buffered input -- your program doesn't see anything until the user presses Enter, and then all it sees is the final result in one rush.

If you want to be able to type arrow keys and actually have it work, then you'll need to get closer to the hardware.

Quote:

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Originally Posted by fronty

I still say gap buffer or list. First one is traditionally used in emacsen and the latter is used very well in fancy eds also known as vis and are easy to implement.

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This is a beginner exercise. This guy has less than 2 weeks to write an editor.

Simple wins over better this time.

Quote:

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Originally Posted by Fink

Hmmm....I never heard my professor tell us anything about this stuff, it can't be that difficult. Right now I'm using stdlib,stdio and screentUtils libraries.

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That's interesting... Do you have a copy of the exact assignment he gave you?

Text editors are not what I would call a "beginner exercise"....

Arrays can work OK, but I wouldn't use 10,000 lines for this. Three or four times the number of chars you show on a single page of your editor, should be fine.

@fronty: yes, you shift char's - no, it's not professional - yes, it will do for a beginner's exercise.

Quote:

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Originally Posted by CommonTater

This is a beginner exercise. This guy has less than 2 weeks to write an editor.

Simple wins over better this time.

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I think using linked list containing every line on a node inside some very simple malloc'd dynamic array implementation won't be very hard, even simpler with hard coded maximum line length like in your implementation. This will make creating and destroying lines work better and won't be hard to implement. Similar situation with gap buffer, it isn't really far from simple array implementation, but makes operations work better. It won't be hard for a beginner if he know basic data structures.

Hi guys! I m obviously a co-student of fink and i have the same assignment... We could use a character arrow but not any dynamic solution since we haven't taught anything about pointers(we only use them -but without really knowing- in loading and saving text(fopen,etc).

Quote:

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Originally Posted by pSyXaS

Hi guys! I m obviously a co-student of fink and i have the same assignment... We could use a character arrow but not any dynamic solution since we haven't taught anything about pointers(we only use them -but without really knowing- in loading and saving text(fopen,etc).

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Is there a question coming? Or is this it?

Mainly it's an explanation about the assignment data, but i also haven't done anything... I generally imagine it as a character arrow in which there will be some "if"(for example if the user hits backspace-8 in ascii table- go to the previous place). My most important problem is how to make the status bar...

Do you mind if I ask how far you are into this course?

Do you mean what we have taught so far?

Yeah... Like I'm thinking if you're in second year or something this may be a reasonable project but it's one flat out dirty trick to dump it on someone in the first month.

It's a first semester course in which we have learnt the basics of C and more specificaly data types,I/O,loop and if(and switch-case) statements,Functions,arrays and structures... I m at the 3rd semester but i haven't passed the course so i reattend it...

You are being really vague about the assignment. I think you have no clue what the assignment actually requires. Since your class is only intro stuff, your assignment wouldn't be as complicated as the OP's would be since his would have to do the output dynamically on the screen. I'm just going to guess here that your text editor would just consist of typing something into the buffer then print it out.
Go read the tutorial from this forum. And you may want to start a new thread with the exact assignment AND the code that you have attempted. What you are doing is basically this: I am clueless about what's going on, I wish someone has some code that fit the descriptions.

I don't know about my co-student that started the thread but my problem is very specific i think and doesn't require-in my opinion again- the code that i have or don't have... I never asked for a code i just asked for a thought about how i could create a status bar at the last line of a program...

How about asking for some help from the guy whose salary you pay to teach you?

Specify what the parameters of the status bar, are. That is, status of what?. Status bars I'm familiar with are just a simple graphical representation (but may be done in terminal mode too), of a simple mathematical calculation of some kind.

Quote:

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Originally Posted by Adak

Specify what the parameters of the status bar, are. That is, status of what?. Status bars I'm familiar with are just a simple graphical representation (but may be done in terminal mode too), of a simple mathematical calculation of some kind.

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I'm guessing he means something like the mode line in Emacs, or the bottom line in nano.

Since I've never seen either one, I'll back out of here.

Quote:

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Originally Posted by Adak

Since I've never seen either one, I'll back out of here.

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Basically it's a reverse video bar at the bottom of the screen... line #, column #, filename, stauts messages, etc. When the screen scrolls the bar stays put...

Hello! I am co-student with the guy who started this thread. I'd like to help me.

First of all, I have almost completed this text editor project (type special charactes like arrow keys and move the cursor to a user-specific position, type normal characters and print them in an 80 x 20 console's display area (80 columns x 20 rows), push enter and move the cursor down one line, backspace key's function etc..). I have a problem with the backspace function. Let the cursor be in the first column (0) and in a row bigger than first row (let it be row 1). Let the position of the last character in the previous row 0 be 45 x 00. When I push the backspace key, the cursor moves one position backwards and deletes the preceding character with printf(" "). Unfortunately, the 35 preceding characters are NULL characters and so I have to push the backspace key 35 times to delete the last character of row 0. Any ideas to improve the code? I'm using a two-dimensional array keystrokes[col][row] to store the ASCII values of the keystrokes and the function gotoxy(column,row) to move the cursor.

BACKSPACE if else statements:

Code:

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          if (column>0)
                    {
                            gotoxy(column-1,row);
                            printf(" ");
                            keystrokes[row][column-1]=' ';
                            gotoxy(column-1,row);
                            --column;
                    }
                    else if (column==0 && row>0)
                    {
                          column=79;
                          gotoxy(column,row-1);
                          printf(" ");
                          keystrokes[row-1][column]=' ';
                          gotoxy(column,row-1);
                          --row;
                    }

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So don't automatically go to column 79, but rather to the last actual character of row n-1.

Quote:

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Originally Posted by tabstop

So don't automatically go to column 79, but rather to the last actual character of row n-1.

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Ok, done! Now I want to search for a word into my 2D array. If the word exists, the cursor must be moved in the beginning of the word. How can I do this function? Probably with gotoxy(col,row) and strstr() functions. But how? The strstr() function returns a pointer to the first occurrence of str2 in str1, or NULL if no match is found. How can I move the cursor in the beginning of the word.

Also, if the characters of a word are stored into cells [78][0], [79][0], [0][1], [1][1], [2][1] , how can I search for the word and find it?

If result_from_strstr is a pointer to the middle of the array, and row_n is a pointer to the beginning of the array, then result_from_strstr - row_n tells you the index of that pointer in the array.

If the characters of a word are stored in cells [78][0], [79][0], [0][1], [1][1], and [2][1], then you don't want to find the word in that case. I certainly wouldn't want any editor I use to report "word found" if it happened to find it going down a column. And for that matter, even if you had the characters at [0][78], [0][79], [1][0], [1][1], and [1][2], that's two different words, since you wouldn't split a word over a line break.

Quote:

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Originally Posted by tabstop

If result_from_strstr is a pointer to the middle of the array, and row_n is a pointer to the beginning of the array, then result_from_strstr - row_n tells you the index of that pointer in the array.

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First of all, thanks for the idea! I have a serious problem. This is the code I've written:

Code:

---

int i, row;
void *index;
char *row_n, *result, word[15], keystrokes[20][81];

printf("Word to find: ");
fgets(word, sizeof(word), stdin);

    for (i=0;i<20;i++)    /* 20 lines */
    {
        row_n=keystrokes[i];
        if ((result=strstr(keystrokes[i],word))!=NULL)    /* keystrokes[i]=&keystrokes[i][0] */
        {   
            index=result-row_n;
            row=i;
            gotoxy(index,row);
        }
        else
        {
            printf("There's No Such Word");
        }
    }

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My program crashes when I run this code. Is the code properly written? How can I find the index of that pointer in the array and what about the gotoxy(col,row) function?

Quote:

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Originally Posted by Sartre

Code:

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void *index;

            index=result-row_n;
            gotoxy(index,row);

---

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The variable index should be a int not a pointer.
FYI: You need to remove the trailing linefeed to find a good match.

Tim S.