in gdb tui mode scroll the command window

Use cgdb instead.

Let GDBW denote the command window,
let SRCW denote the source window
let TTYW denote the input window.

Cgdb basic usage

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ESC key in GDBW: switch to SRCW
i key in SRCW: switch to GDBW
T key in SRCW: switch on/off TTYW
PgUp/PgDn key in GDBW: scroll GDBW
PgUp/PgDn key in SRCW: scroll SRCW
-/= in SRCW: decrease/increase SRCW size

Patch: GDBW output is truncated.
cgdb/scroller.cpp:146
https://github.com/cgdb/cgdb/pull/269

refer to:
https://github.com/cgdb/cgdb/blob/master/doc/cgdb.texi