Strange behavior of Ncurses

[Urban Söderberg]

Hi Ncurses!

 

We are using Ncurses C++ (6.1) in Linux to handle terminal-communication.

The actual development was made several years ago.

Recently a customer discovered an issue with certain printouts that have repeated/similar lines and with several spaces.

 

Short description of the use-case:

From a webpage a websocket is used to handle communication with our client.

Our client is started and Ncurses is used for input/output.

When a command is run the printout is presented in terminal-screen.

 

 

An example when issue is seen:

File: printout_similar_lines_and_several_spaces.png

Here is the visible data alright but not all data when for example scrolling back in browsers terminal to see the upper part.

Websocket shows that data is written from row 1 to 63 and after this a jump is made to row 1.

Backspaces are seen as well.

When exporting the total received data the printout is corrupt, lines missing and some overwritten.

We see corrupt printout when viewing the received data, file:

full_data_lines_are_missing_due_to_jump_back_to_line_1_ad_backspaces_seen.png

 

Also see attached file: websocket_data_received_from_ncurses.txt

Jump to row 1 is seen and some backspaces etc.

 

How correct printout look like, file: Actual_command_and_its_printout.log

 

 

An example when a printout is alright:

File: printout_unique_lines_few_spaces

Here is the visual data alright.

When checking websocket no jump to row 1 is seen.

Websocket shows that data is written from row 1 to 63 and after that row 63 is used.

When exporting output all rows are present.

 

 

This jump back to row 1 and the backspaces really causes problem to us.

Is there a way to get rid of that handling or is there any correction done in Ncurses?

 

 

Best regards

Urban

Actual_command_and_its_printout.log
Description: Actual_command_and_its_printout.log

full_data_lines_are_missing_due_to_jump_back_to_line_1_ad_backspaces_seen.png
Description: full_data_lines_are_missing_due_to_jump_back_to_line_1_ad_backspaces_seen.png

printout_similar_lines_and_several_spaces.png
Description: printout_similar_lines_and_several_spaces.png

printout_unique_lines_few_spaces.png
Description: printout_unique_lines_few_spaces.png

websocket_data_received_from_ncurses.txt
Description: websocket_data_received_from_ncurses.txt