On 10/13/20, Mike Miller <python-id...@mgmiller.net> wrote: > > The legacy Windows console has another limitation in that I don't believe it > has a single API call to clear the whole thing. One must iterate over the > whole > buffer and write spaces to each cell, or some similar craziness.
No, it's not really similar craziness -- at least not from the client program's perspective. The implementation in the console host itself is probably something like that. CMD's CLS is implemented with three API calls: GetConsoleScreenBufferInfo to get the screen-buffer dimensions and default text attributes, ScrollConsoleScreenBufferW to shift the buffer out, and SetConsoleCursorPosition to move the cursor to (0,0). https://docs.microsoft.com/en-us/windows/console/scrollconsolescreenbuffer The following debugger session is while stepped into CMD's eCls() function that implements the CLS command. This is just before it calls ScrollConsoleScreenBufferW, with parameters 1-4 in registers rcx, rdx, r8, and r9, and parameter 5 on the stack. lpScrollRectangle (rdx): the entire screen buffer (sized 125 x 9001) is to be scrolled. 0:000> ?? ((SMALL_RECT *)@rdx) struct _SMALL_RECT * 0x000000e9`be8ff8b8 +0x000 Left : 0n0 +0x002 Top : 0n0 +0x004 Right : 0n125 +0x006 Bottom : 0n9001 dwDestinationOrigin (r9): the target row is -9001, so the contents of the entire buffer are shifted out. 0:000> ?? (short)(@r9 >> 16) short 0n-9001 lpFill (rsp / stack): use a space with the default attributes (in my case background color 0 and foreground color 7, in the current 16-color palette). 0:000> ?? ((CHAR_INFO **)@rsp)[4]->Char.UnicodeChar wchar_t 0x20 ' ' 0:000> ?? ((CHAR_INFO **)@rsp)[4]->Attributes unsigned short 7 _______________________________________________ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email to python-ideas-le...@python.org https://mail.python.org/mailman3/lists/python-ideas.python.org/ Message archived at https://mail.python.org/archives/list/python-ideas@python.org/message/SYMJ4HM6ZUBA3HMS5QXIDVSMQDRECHFP/ Code of Conduct: http://python.org/psf/codeofconduct/
