Highlighting and Selecting text with Python curses

Question

This is my first post to stack overflow. I've been lurking this site for information for years, and it's always helpful, so I thought that I would post my first question.

I've been searching for some similar examples, but can't seem to find anything.

Ultimately, I'm trying to write a simple text ui for finding false positives and false negatives in a text extraction program. The false positive module is a simple yes/no selection, and displaying colored text and using getch() is easy enough. The False negative portion however, is a becoming difficult.

So this is what I want to do:

1. Display a string onto the screen (forget scrolling for now.... ugh) It will only be a string with no newlines.
2. The user sees the text, and pushes 'h' to enter highlight mode.
3. The user can then control the cursor to move it over a portion of the text (still displayed), and select 'v' to begin highlighting (I trying to make this as close to vi as I can)
4. The user then uses control keys (arrows, hjkl) to move the cursor from a starting point to and end point, highlighting the text on the way. This highlighted portion should be a word which is a false negative
5. The user presses some key ('y' probably), and the selected text is colored, or stays highlighted, and the highlighted text is save to some variable that I'll handle later.
6. The user exits highlight mode and proceeds.

Any ideas to even START? I'm trying simple things like keeping text on the screen and moving the cursor around, but to no avail.

I'm aware of the curses.textpad.TextBox() module, but it performs editing like insertion and deletion, which I don't want to do. Perhaps there is a way to disable it.

I have other questions, but I'll keep this specific for now.

Thanks!!

Neal

Edit: To be more specific, I'm not looking for help writing the whole program, just help moving the cursor over displayed text, highlighting it, and selecting it and saVing it in a variable.

Answer 1

I would like to update this question in case anybody else is searching the web for this and stumbles upon this question.

Okay, so the answer was actually quite simple and required reading all the functions listed on the python curses documentation.

What I did was make a 3 state machine: State 1: Normal mode (displays text only), State 2: highlight mode, allow the cursor to move around the window, and State 3: highlighter mode, which gives only limited movement from left to right over texts and highlights the text as it's moving.

To accomplish this task, it just takes some basic curses function calls.

I made separate windows, but I'll just assume a single window for explaination.

Do display text in the window, stick with the:

window.addstr()
window.refresh()

For moving the cursor around:

#get current cursor position
curr_y, curr_x = window.getyx()

# depending on direction, update the cursor with
next_y, next_x = get_next_direction()

# place cursor in new position
window.move(next_y, next_x)

window.refresh()

Once the cursor is over the starting point for highlighting, press 'v' enter the highlighter state, and limit the movement of the cursor, change the attribute of the selected text:

# get current cursor position
curr_y, curr_x = window.getyx()

# save position for later use
start_y = curr_y; start_x = curr_x

# loop until 'v' is pressed again
while highlight_state:
    # change the attribute of the current character, for 1 character only, to reverse
    window.chgat(curr_y,curr_x, 1, curses.A_REVERSE)
    curr_y, curr_x = get_next_direction()

# save end state, this is buggy obviously, but you get the point
end_y = curr_y; end_x = curr_X

Now extract that information from start to end

# get integer representation of char at positiong

outstr = ''
#from start to end
char_as_int = windows.inch(y,x)
char = char_as_int & 0000FF
attr = char_as_int & FFFF00 #not useful here, but maybe later

outstr += char

That's it! I also tried another way to save the highlighted material which was basically transformat the x,y coordinates to the index of the string that was being display, but that let to issue in string representation (newlines, tabs, and so on), plus was just harder to do.

If anyone has comments of a more efficient/ cleaner method, please respond!

Answer 2

I don't know anything about ncurses, but using Tkinter or one of the other GUI toolkits, it could be done with a canvas. You would first set the scroll region, then bind the "h" key so it sets a highlight variable to True, bind a mouse click to a function that retrieves the location to start, bind the left and right arrows to move left or right one letter, and move the cursor and reverse the colors of the next letter as well as keep track of how many letters you are from the starting point, which also tells you the end location, and bind "y" to copy the text.

It is not as complicated as it might seem as each part is a fairly simple function. All of this would of course depend on the font size, and I would suggest displaying the text with a fixed font so each letter occupies the same width. Once again, I do not know ncurses, but it would be similiar with any toolkit. If you can work it around so that the user can select one entire line with a mouse click, it makes the coding much easier. Post back with some code if you do indeed decide to go with Tkinter or wxPython and want some additional help.