Disable Print Screen?

[TerryRitchie]

Does anyone have any ideas on how a QB64PE program can disable the print screen function when running?

Ideally I would like to be able to hook the keyboard's PRINT SCREEN key to intercept keypresses while at the same time disabling the operating system from grabbing a screen shot. However, disabling the operating system's ability to perform screen shots while the program is running would be just as useful.

Any thoughts, ideas?

[TerryRitchie]

One method I came up with was using _CLIPBOARDIMAGE to "poison the well" so to speak. Any program I write would need to write garbage to the clipboard periodically like the example below

Code: (Select All)

'Poison the well

image = _NEWIMAGE(100, 100, 32)
_DEST image
PRINT
PRINT
PRINT "     NO!"

_DEST 0

DO
    SLEEP 1
    _CLIPBOARDIMAGE = image
LOOP UNTIL INKEY$ <> ""
SYSTEM

[mnrvovrfc]

However, disabling the operating system's ability to perform screen shots while the program is running would be just as useful.

Many users expect to record entire videos of what they are doing in an operating system desktop session. With the big talk about the whole of Linux moving from "X-dot-org" to Wayland, it might become impossible to do what you are requesting. However, under Wayland it's already tough enough to record desktop sessions into video.

Some people especially on Linux would not touch a program that disables [PRT SC] or any other key, would consider it spyware. If it comes directly from you this could affect your reputation as educator. An user could press the key without thinking much about it, or because he/she wants to show off to his/her friends on Facebook or wherever else online. If the program doesn't respond to some "system" keypress there better be a good reason why. But this might be the minority of the population using Windows anyway.

It's bothersome that [CTRL][ALT][DEL] on Linux with GNOME desktop only opens the "shutdown" dialog. It does not reboot the computer, and it does not bring a dialog asking the user how to end the current desktop session.

I would like to get a reason from the devs of AutoHotKey, besides "It's too hard!" why it has never been ported to Linux. There is an old version of AutoIt that somebody sort of fixed so it works on Linux reasonably, but it relies way too much on Python and it would probably be forbidden in Wayland session.

[Steffan-68]

One method I came up with was using _CLIPBOARDIMAGE to "poison the well" so to speak. Any program I write would need to write garbage to the clipboard periodically like the example below

Code: (Select All)

'Poison the well

image = _NEWIMAGE(100, 100, 32)
_DEST image
PRINT
PRINT
PRINT "     NO!"

_DEST 0

DO
    SLEEP 1
    _CLIPBOARDIMAGE = image
LOOP UNTIL INKEY$ <> ""
SYSTEM

This could also work under Windows.

Code: (Select All)

SCREEN _NEWIMAGE(800, 600, 32)

DO

    CLS

    COLOR _RGB32(177, 177, 177)

    PRINT "Monitoring clipboard..."

    IF img& < -1 THEN _FREEIMAGE img&

    img& = _CLIPBOARDIMAGE

    IF img& < -1 THEN

        Shell "cmd /c echo off | clip"

       END IF

    _DISPLAY

    _LIMIT 10

LOOP

But starting with Win 10, the clipboard can store more than one page.

[SMcNeill]

https://learn.microsoft.com/en-us/archiv...s-and-more

[SMcNeill]

Code: (Select All)

//////////////////
// When window is activated/deactivated, disable/enable Alt-PrintScreen.
// (IDHOT_SNAPWINDOW)
//
void CMainFrame::OnActivate(UINT nState, CWnd* pWndOther,
   BOOL bMinimized)
{
   CFrameWnd::OnActivate(nState, pWndOther, bMinimized);
   if (nState)
      RegisterHotKey(m_hWnd, IDHOT_SNAPWINDOW, MOD_ALT, VK_SNAPSHOT);
   else
      UnregisterHotKey(m_hWnd, IDHOT_SNAPWINDOW);
}

I think right there is what would be really relevant for you, but read the article itself, also.

[TerryRitchie]

But starting with Win 10, the clipboard can store more than one page.

Yeah, I was wondering about that issue too.

[TerryRitchie]

Code: (Select All)

//////////////////
// When window is activated/deactivated, disable/enable Alt-PrintScreen.
// (IDHOT_SNAPWINDOW)
//
void CMainFrame::OnActivate(UINT nState, CWnd* pWndOther,
   BOOL bMinimized)
{
   CFrameWnd::OnActivate(nState, pWndOther, bMinimized);
   if (nState)
      RegisterHotKey(m_hWnd, IDHOT_SNAPWINDOW, MOD_ALT, VK_SNAPSHOT);
   else
      UnregisterHotKey(m_hWnd, IDHOT_SNAPWINDOW);
}

I think right there is what would be really relevant for you, but read the article itself, also.

Thanks for the info Steve, I'll take a look.

[SMcNeill]

Finally having a little time to sit down and relax -- and try not to fall asleep with my stomach bursting with Christmas Eve Lunch -- I think I put the pieces together here for what you're looking for:

Code: (Select All)

'BOOL UnregisterHotKey(

'  [in, optional] HWND hWnd,

'  [in]          int  id

');



'BOOL RegisterHotKey(

'  [in, optional] HWND hWnd,

'  [in]          int  id,

'  [in]          UINT fsModifiers,

'  [in]          UINT vk

');



Const Alt = 1

Const VK_Snapshot = &H2C





Declare Dynamic Library "user32"

    Function RegisterHotKey%% (ByVal WindowHandle As _Offset, Byval id As Long, Byval keyModifiers As _Unsigned Long, Byval keyValue As _Unsigned Long)

    Function UnregisterHotKey%% (ByVal WindowHandle As _Offset, Byval id As Long)

End Declare



Dim Internal_Key_Name As Long



Dim WH As _Offset: WH = _WindowHandle



result = RegisterHotKey(0, 1, Alt, VK_Snapshot) '0 is null, so defaults to this program.  1 is the id value that we assign to... I dunno!  It just works!  LOL.

If result Then

    Print "Alt-Printscreen is enabled in this program."

    Print "Attempting to disable it..."

    result = UnregisterHotKey(0, 1)

    If result Then

        Print "We should now have disabled Alt-Printscreen in this application"

    Else

        Print "No luck.  Sorry dude.  Try again later!"

    End If

Else

    Print "No can do!  Either alt-printscreen is already broken or assigned elsewhere, or else we just goofed up somewhere!"

    Print "Sorry dude.  Try again later!"

End If

[SMcNeill]

(That 1, I think is some sort of internal register that we first configure with the RegisterHotKey so that it represents Alt+Printscreen.  It's why we use that same value with unregister so we unregister that combo of keystrokes from our program, with that singular value.)