OpenEuphoria

1. graphics.e on Linux

• Posted by georgeorr May 03, 2009
• 1103 views

I have been experimenting with the position(line,column) procedure and get_position() function from the graphics.e include file for Linux running in a terminal window.

It appears from my tests that get_position() returns a line and column that is based on the line where the cursor was located when the program calling the function began. The position(line,column) procedure seems to locate the cursor at the beginning of the terminal window as I expected.

Is this the intended results of get_position()? If so, is there a way to determine the actual line within the terminal window based on the current position of the cursor?

I have seen other applications using position() and get_position that seem to work, but these seem to define an area of the screen for their use and don't depend on where the cursor is in the terminal window.

I'm probably just missing something simple again. The code for my simple (not very elegant) test case is below. Again this is run in a terminal window on Linux (Ubuntu 9.0.4)) which uses a Gnome desktop. I open a terminal window and run eui pos_test. Then (without closing and restarting the terminal window) I run eui pos_test again. Both times get_position reports the same line and column numbers, even though on the second call it appears the line number should not be the same. The text written after calling position() is written in the same place each time.

I would appreciate any help anyone can provide on this.

Thanks!

George

My code in a file pos_test is

-- test position and get_position 
 
include graphics.e 
 
sequence pos 
integer line, col 
 
puts(1,"\n\n\n\n****") 
pos = get_position() 
line = pos[1] 
col = pos[2] 
 
print(1,pos) 
 
position(line,col) 
 
puts(1,"**********\n\n\n\n") 
 

3. Re: graphics.e on Linux

• Posted by ChrisB (moderator) May 03, 2009
• 1101 views

-- test position and get_position 
 
include graphics.e 
 
sequence pos 
integer line, col 
 
puts(1,"\n\n\n\n****") 
pos = get_position() 
line = pos[1] 
col = pos[2] 
 
print(1,pos) 
 
position(line,col) 
 
puts(1,"**********\n\n\n\n") 
 

Hi

If you ran

-- test position and get_position 
 
include graphics.e 
 
sequence pos 
integer line, col 
 
position(1,1) 
 
puts(1,"\n\n\n\n****") 
pos = get_position() 
line = pos[1] 
col = pos[2] 
 
print(1,pos) 
 
position(line,col) 
 
puts(1,"**********\n\n\n\n") 
 

What would happen? The point being, you shouldn't rely on the interpreter to always return the correct cursor position, until after you've initially set it.

Chris

5. Re: graphics.e on Linux

• Posted by ChrisB (moderator) May 04, 2009
• 1071 views

Hi

After a little experimentation, this would seem to be the case - you can't know the position of the cursor, until after you have called position(). As far as I can tell, this is because there's no way of getting the cursor position from bash, or passing it to an application.

include graphics.e  
  
sequence pos  
integer line, col  
 
pos = get_position()  --doesn't matter where you start, always returns 1,1 
line = pos[1]  
col = pos[2]  
printf(1,"%d,%d\n",{line, col}) 
 
position(15,15) 
puts(1,"***\n-------------------------------->") --returns the real cursor position 
pos = get_position() 
line = pos[1]  
col = pos[2]  
printf(1,"%d,%d\n",{line, col}) 
 

I tried with a (highly experimental and undeveloped) ncurses lib, but you have to open a new 'screen' with that, and kind of defeats the object. There are ways of returning to and from 'cooked' mode with curses, but again I'm not sure how to get the cursor position from the stdscr.

Why don't you just put a box in the middle of the screen, and edit in there?

Chris

7. Re: graphics.e on Linux

• Posted by jimcbrown (admin) May 04, 2009
• 1158 views

IMHO this is a bug in the Unix console code of Euphoria. It should be possible to do this, in fact there is a working example at http://unixwiz.net/techtips/wsize.c (which should be integrated into Euphoria).

-- test position and get_position 
 
include graphics.e 
 
sequence pos 
integer line, col 
 
puts(1,"\n\n\n\n****") 
pos = get_position() 
line = pos[1] 
col = pos[2] 
 
print(1,pos) 
 
position(line,col) 
 
puts(1,"**********\n\n\n\n")