SetConsoleScreenBufferSize(something < viewport) crashes ConPTY host

A pseudoconsole host is a headless console
Headless consoles have no minimum size
SetConsoleScreenBufferSize(new) checks to make sure the following are true:
- new is within minimum size
- new is within current viewport size
SetConsoleScreenBufferSize only does this check if a console is headful (i.e. not headless)

Lines 509 to 519 in 381b115

    
           if (!ServiceLocator::LocateGlobals().IsHeadless()) 
        
           { 
        
               COORD const coordMin = screenInfo.GetMinWindowSizeInCharacters(); 
        
               // clang-format off 
        
               // Make sure requested screen buffer size isn't smaller than the window. 
        
               RETURN_HR_IF(E_INVALIDARG, (size.X < screenInfo.GetViewport().Width() || 
        
                                           size.Y < screenInfo.GetViewport().Height() || 
        
                                           size.Y < coordMin.Y || 
        
                                           size.X < coordMin.X)); 
        
               // clang-format on 
        
           }

When we're attached to a conpty, it happily resizes the buffer to be smaller than the viewport.
The next time the whole screen is invalidated (or whenever luck strikes, really), the renderer tries to render the whole viewport, which is now outside the bounds of the buffer.

This part of the check should probably be moved outside of the "are we headful" block;

terminal/src/host/getset.cpp

Lines 514 to 515 in 381b115

    
           RETURN_HR_IF(E_INVALIDARG, (size.X < screenInfo.GetViewport().Width() || 
        
                                       size.Y < screenInfo.GetViewport().Height() ||

Trivial repro code:

#include <Windows.h>
int main(int argc, char *argv[])
{
	HANDLE hStdOut = GetStdHandle(STD_OUTPUT_HANDLE);
	SetConsoleScreenBufferSize(hStdOut, {10,10});
	return 0;
}

This purchases a nice plot of land overlooking a cemetery for both WSL interop and Windows Terminal. 😄

 RETURN_HR_IF(E_INVALIDARG, (size.X < screenInfo.GetViewport().Width() || 
                             size.Y < screenInfo.GetViewport().Height())); 

 if (!ServiceLocator::LocateGlobals().IsHeadless()) 
 { 
     COORD const coordMin = screenInfo.GetMinWindowSizeInCharacters(); 
     // clang-format off 
     // Make sure requested screen buffer size isn't smaller than the window. 
     RETURN_HR_IF(E_INVALIDARG, (size.Y < coordMin.Y || 
                                 size.X < coordMin.X)); 
     // clang-format on 
 }

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SetConsoleScreenBufferSize(something < viewport) crashes ConPTY host #3907

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	if (!ServiceLocator::LocateGlobals().IsHeadless())
	{
	COORD const coordMin = screenInfo.GetMinWindowSizeInCharacters();
	// clang-format off
	// Make sure requested screen buffer size isn't smaller than the window.
	RETURN_HR_IF(E_INVALIDARG, (size.X < screenInfo.GetViewport().Width() \|\|
	size.Y < screenInfo.GetViewport().Height() \|\|
	size.Y < coordMin.Y \|\|
	size.X < coordMin.X));
	// clang-format on
	}

SetConsoleScreenBufferSize(something < viewport) crashes ConPTY host #3907

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zadjii-msft commented on Dec 12, 2019

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