How to get coordinates of first displayed line in windows relatively to DATA-BUFFER ?

[schlebe]

Description of the new feature

where DATA-BUFFER contains all rows displayed and all rows that has been displayed before and that are currently only visible in scrolling console vertically.

My question with more explanation can be found on StackOverflow on https://stackoverflow.com/questions/79725603/on-windows-terminal-in-visual-c-how-can-i-overwrite-previous-lines

Proposed technical implementation details

No response

[DHowett]

I see that you are combining the Windows Console APIs with the use of Virtual Terminal sequences.

I wonder if you would be able to use the Virtual Terminal sequences for cursor positioning, rather than trying to move the cursor directly in the coordinate system.

You can move the cursor up one line relative to the current position (X stays the same, Y decrements) with \x1b[1A.

CSI Ps A Cursor Up Ps Times (default = 1) (CUU).

You can move the cursor to the beginning of the previous line (X = 0, Y decrements) with \x1b[1F

CSI Ps F Cursor Preceding Line Ps Times (default = 1) (CPL).

Does that help?

[schlebe]

No !
Using proposed Virtual Terminal sequences don't help me.

Why ?

Because some times length of filename is greater than 1 row !
CSI Ps A or CSI Ps F don't move the cursor 1 line as written in documentation but only 1 row !

I think that there exists some confusion in documentation that use "Line" word to describe "Row" objects !
For me, a line is a string of character terminated by "\n" or "\r\n".

I have also tested using Save/Restore ANSI and not ANSI cursor position but this doesn't work correclty.

Here is a part of my test code

    COORD oCurrentCoord;
    HANDLE hStdout = GetStdHandle(STD_OUTPUT_HANDLE);
    int iPreviousLineLen; 
    
    // clear screen
    wprintf(L"\x1b[2J");
    // set cursor on first line
    wprintf(L"\x1b[0;0H");

    PrintToConsole("// BS2EDT.Sources");
    PrintToConsole("//   Commands");
    PrintToConsole("//     LineCommands");

    oCurrentCoord = GetConsoleCursorPositionx();
    PrintToConsole("++ CmdDeleteLine.cpp");

    SetConsoleCursorPositionx(oCurrentCoord);
    PrintToConsole("++ CmdSplitLine.cpp");

    oCurrentCoord = GetConsoleCursorPositionx();
    oCurrentCoord.Y -= 1;
    SetConsoleCursorPositionx(oCurrentCoord);
    PrintToConsole("++ CmdSwitchLine.cpp");

    // print one line upper
    wprintf(L"\x1b[1F");
    // save cursor position for next file
    wprintf(L"\x1b7");
    PrintToConsole("++ CmdWriteFile.cpp");

    // save cursor position
    wprintf(L"\x1b8");
    PrintToConsole("++ CmdWriteText.cpp");

    PrintToConsole("");
    PrintToConsole("// BS2EDT.Sources");
    PrintToConsole("//   Commands");
    PrintToConsole("//     LineCommands");

    oCurrentCoord = GetConsoleCursorPositionx();
    PrintToConsole("++ CmdDeleteLine.Very-Long-File-Name.Very-Long-File-Name.Very-Long-File-Name.Very-Long-FileName.Very-Long-FileName.Very-Long-FileName.cpp");

    SetConsoleCursorPositionx(oCurrentCoord);
    PrintToConsole("++ CmdSplitLine.Very-Long-File-Name.Very-Long-File-Name.Very-Long-File-Name.Very-Long-FileName.Very-Long-FileName.Very-Long-FileName.cpp");

    oCurrentCoord = GetConsoleCursorPositionx();
    oCurrentCoord.Y -= 1;
    SetConsoleCursorPositionx(oCurrentCoord);
    PrintToConsole("++ CmdSwitchLine.Very-Long-File-Name.Very-Long-File-Name.Very-Long-File-Name.Very-Long-FileName.Very-Long-FileName.Very-Long-FileName.cpp");

    // print one line upper
    wprintf(L"\x1b[1F");
    // save cursor position for next file
    //wprintf(L"\x1b7");
    wprintf(L"\x1b[s");
    PrintToConsole("++ CmdWriteLine.Very-Long-File-Name.Very-Long-File-Name.Very-Long-File-Name.Very-Long-FileName.Very-Long-FileName.Very-Long-FileName.cpp");

    // save cursor position
    //wprintf(L"\x1b8");
    wprintf(L"\x1b[u");
    PrintToConsole("++ CmdWriteText.Very-Long-File-Name.Very-Long-File-Name.Very-Long-File-Name.Very-Long-FileName.Very-Long-FileName.Very-Long-FileName.cpp");

    // set cursor on last line
    wprintf(L"\x1b[28;0H");

    PrintToConsole("// BS2EDT.Sources");
    PrintToConsole("//   Commands");
    PrintToConsole("//     LineCommands");

    oCurrentCoord = GetConsoleCursorPositionx();
    PrintToConsole("++ CmdDeleteLine.cpp");

    SetConsoleCursorPositionx(oCurrentCoord);
    PrintToConsole("++ CmdSplitLine.cpp");

    oCurrentCoord = GetConsoleCursorPositionx();
    oCurrentCoord.Y -= 1;
    SetConsoleCursorPositionx(oCurrentCoord);
    PrintToConsole("++ CmdSwitchLine.cpp");

    // print one line upper
    wprintf(L"\x1b[1F");
    // save cursor position for next file
    //wprintf(L"\x1b7");
    wprintf(L"\x1b[s");
    PrintToConsole("++ CmdWriteFile.cpp");

    // save cursor position
    //wprintf(L"\x1b8");
    wprintf(L"\x1b[u");
    PrintToConsole("++ CmdWriteText.cpp");

and the result

The code of functions used in my test is following

int PrintToConsole(const char* szLine)
    {
    //Clear line completetly before overwriting it with new line
    wprintf(L"\x1b[100K");
    cout << szLine << endl;
    return strlen(szLine);
    }

COORD GetConsoleCursorPositionx()
    {
    HANDLE hStdout = GetStdHandle(STD_OUTPUT_HANDLE);
    CONSOLE_SCREEN_BUFFER_INFO infoConsole;

    GetConsoleScreenBufferInfo(
        hStdout,
        &infoConsole);

    return infoConsole.dwCursorPosition;
    }

void SetConsoleCursorPositionx(COORD dwCursorPosition)
    {
    HANDLE hStdout = GetStdHandle(STD_OUTPUT_HANDLE);

    SetConsoleCursorPosition(hStdout, dwCursorPosition);
    }

[schlebe]

I want to add a little remark.

Today, 5 minutes ago, I have tested my code above using ANSI code

    wprintf(L"\x1b[s"); // save cursor position
    wprintf(L"\x1b[u"); // restore cursor position

... and this work correctly for the 3 cases ...
Displaying "CmdWriteLine" is always overwritten by "CmdWriteText".

This is not the case when I use

   wprintf(L"\x1b7");
   wprintf(L"\x1b8");

I can use your technic with success but the next step in my program is to overwrite "folder" line when no file in folder matchs the searching text !

In this new situation, I find API solution easier that API command sequence !

The problem is that API solution doesn't allow to correct previous recorded cursor position when cursor is at bottom of screen !!!

[schlebe]

I continued to work with your proposed solution but as written before, this solution doesn't work correctly when I try to delete previous line representing a directory.

Here is my new code

    Write     ("// 0. BS2EDT.Documentation");
    ClearPreviousLine(); // delete 0. foler name
    Write     ("// 1. BS2EDT.Sources");
    Write     ("//   2. Commands");
    Write     ("//     3. LineCommands");

    Write     ("++ CmdDeleteLineInArea.cpp");
    OverWrite ("++ CmdSplitLine.cpp");
    OverWrite ("++ CmdWriteLine.Very-Long-File-Name.Very-Long-File-Name.Very-Long-File-Name.Very-Long-FileName.Very-Long-FileName.Very-Long-FileName.cpp");
    OverWrite ("++ CmdSwitchLine.cpp");
    OverWrite ("++ CmdWriteFile.cpp");
    OverWrite ("++ CmdWriteText.cpp");

    ClearPreviousLine(); // delete last .CPP filename displayed 
    ClearPreviousLine(); // delete 3. folder name -> NOK
    ClearPreviousLine(); // delete 2. folder name -> NOK

where

void Write(const char* szLine)
    {
   // save cursor position and write line
    wprintf(L"\x1b[s");
    cout << szLine << endl;
    }

void ClearPreviousLine()
    {
    // restore cursor position  
    wprintf(L"\x1b[u");
    // clear all character from cursor position on 10 lines to be sure to delete long filename  
    wprintf(L"\x1b[10M");
    }

void OverWrite(const char* szLine)
    {
    ClearPreviousLine()
    Write(szLine);
    }

and the result

The 2 last statements doesn't work.

I think that that SAVE sequence can only use 1 time. It seems impossible to have stack S sequence.
You can have SUSUSUSU sequence but not SSUU !
I think that second S delete first one so that first one is lost !

Can you confirm my analyse ?

But that is not written in documentation !!!

I don't have this problem using API !
I have another problem but not this one ;-)

PS: to delete all character from restored cursor to be certain to delete previous name I use now L"\x1b[10M"
Before I used L"\x1b[100K" but 100 is not a correct value for integer.
I tried to use L"\x1b[2K" but it doesn't work when line is greater that 1 row !
I searched then a sequence to delete all screen from cursor position but I don't find it !
But this is another issue/question that I can post on StackOverflow.

[schlebe]

I come back to inform you that when cursor is positioning on last line on console view, line greater than 1 row are not correctly overwritten !

Here is my code ...

#include <windows.h>

#include <iostream>
#include <chrono>
#include <thread>
#include <stack>

using namespace std;

static HANDLE hStdout;
static CONSOLE_SCREEN_BUFFER_INFO infoConsole;

/**********************************************************************
* ActivateVirtualConsole()
***********************************************************************
*/

void ActivateVirtualTerminal()
{
    hStdout = GetStdHandle(STD_OUTPUT_HANDLE);

    DWORD dwMode = 0;
    if (!GetConsoleMode(hStdout, &dwMode))
    {
        //return GetLastError();
    }

    dwMode |= ENABLE_VIRTUAL_TERMINAL_PROCESSING;
    if (!SetConsoleMode(hStdout, dwMode))
    {
        //return GetLastError();
    }
}

void Write(const char* szLine)
{
    wprintf(L"\x1b[s");
    cout << szLine << endl;
}

void ClearPreviousLine()
{
    wprintf(L"\x1b[u");
    wprintf(L"\x1b[10M");
}

void OverWrite(const char* szLine)
{
    ClearPreviousLine();
    Write(szLine);
}

void CheckConsoleCursorInfo()
{
wprintf(L"\x1b[29;0H");

Write("++ CmdDeleteLineInArea.cpp");
OverWrite("++ CmdWriteArea.Very-Long-File-Name.Very-Long-File-Name.Very-Long-File-Name.Very-Long-File-Name.Very-Long-FileName.Very-Long-FileName.Very-Long-FileName.Very-Long-File-Name.Very-Long-File-Name.Very-Long-File-Name.Very-Long-FileName.Very-Long-FileName.Very-Long-FileName.cpp");
OverWrite("++ CmdSplitLine.cpp");
OverWrite("++ CmdWriteLine.Very-Long-File-Name.Very-Long-File-Name.Very-Long-File-Name.Very-Long-FileName.Very-Long-FileName.Very-Long-FileName.cpp");
OverWrite("++ CmdSwitchLine.cpp");
OverWrite("++ CmdWriteFile.cpp");
OverWrite("++ CmdWriteText.cpp");
}

int main()
{
    std::cout << "Test Get/Set cursor position !\n";

    ActivateVirtualTerminal();

    CheckConsoleCursorInfo();
}

and the Print screen of result

Finally, I consider that there are 2 bugs !

1. S/U sequence can not be embbeded ! (see previous messages)
2. S/U sequence doens't work correctly in any situation !

Can you test and confirm that it is bugs and indicate what you do next ?

Personnaly, I consider also that there is a bug on GetConsoleScreenBufferInfo(hStdout,&infoConsole)

When data displayed on screen is moved up, infoConsole.srWindow.Top value must be greater than 0 !

In Microsoft documentation, for infoConsole.srWindow variable it is written

srWindow
A SMALL_RECT structure that contains the console screen buffer coordinates of the upper-left and lower-right corners of the display window.

[j4james]

I think you have misunderstood how the cursor save/restore operations work.

1. They aren't intended to be nested. There is only one cursor save buffer. If you save multiple times it'll just overwrite the last saved position. That is the way it is intended to work.
2. The saved position is a static window coordinate - it doesn't move when the buffer is scrolled. So if you save a position on the last line of the display, and then execute a linefeed that causes the buffer to scroll, your text will have moved up a line, but the saved position will still be on the last line.

Some other issues I noticed in your code and in previous messages:

1. VT coordinates are one-based. So to move the cursor to the top left corner you would use \x1b[1;1H. Using zero will also work, because it's interpreted as the "default" value, and for CUP the defaults are 1;1. However, it's important you understand the base when working with values beyond the origin position.
2. The parameter to the EL command (\x1b[K) is not a length. It can take one of three values: 0 - clears from the cursor position to the end of the line; 1 - clears from the cursor position to the start of the line; 2 - clears the entire line.
3. The \x1b[s and \x1b[u sequences are essentially identical to ESC 7 and ESC 8, but you can't represent the latter sequences in C with \x1b7 and \x1b8 because the compiler will try to interpret that as a single hex value. You can use octal (i.e. \0337 and \0338), or split the string between the escape and the second character (i.e. "\x1b" "7" and "\x1b" "8").

[schlebe]

Thanks to react to my post ;-)

I understand what you write. That is also what I think.

BUT, I regret that SAVE/RESTORE can not be nested. To implement that; I think that you must only replace a COORD variable with a stack<COORD*> variable !

Using API that Microsoft team want to suppress, work perfectly when cursor is not at bottom of console windows !!!

I regret that you don't answer about srWindow variable ! Why this variable is not updated when view is scrolling ?

I think that interaction with console using API or characters sequence can be improved.

Perhaps can I do that myself with little help !

Is GetConsoleScreenBufferInfo() function defined on this GITHUB project ?

If yes, where ?

If no, who can correct this function so that when view scrolls, srWindow variable reflect scrolling position ?

[j4james]

These escape sequences were not developed by Microsoft. They're part of a widely used standard that was defined more than 50 years ago, and have decades worth of applications that depend on their behavior. We can't just redefine them.

As for srWindow not reflecting the scrolling position, I believe that's because it reports the position of the window within the buffer, and in the context of a conpty connection, the buffer is always the same size as the window, so the position will always be 0.

If you use the old conhost console, it may give the impression that it's reflecting the scroll position, but even there it's not going to work consistently. As soon as the buffer is full, the srWindow.Top coordinate will end up with a maximum value that never increases.

So as far as I can see there's nothing broken here. You may not like the way it works, but this is the expected behavior.