emacs -Q
M-x set-variable RET pop-up-frames RET t
M-x tool-bar-mode ; turn it off, to start from zero
M-x pp-eval-expression RET (frame-parameters)
In frame *Pp Eval Output* search for `tool-bar-lines' => 0 (good).
In original frame (do all of the commands here, except isearch):
M-x tool-bar-mode ; turn it on
M-x pp-eval-expression RET (frame-parameters)
In frame *Pp Eval Output* search for `tool-bar-lines' => 2 (wrong).
In original frame (do all of the commands here, except isearch):
M-x pp-eval-expression RET (set-frame-parameter nil 'tool-bar-lines 1)
M-x pp-eval-expression RET (frame-parameters)
In frame *Pp Eval Output* search for `tool-bar-lines' => 2 (wrong).
In original frame (do all of the commands here, except isearch):
M-x pp-eval-expression RET (set-frame-parameter nil 'tool-bar-lines 3)
M-x pp-eval-expression RET (frame-parameters)
In frame *Pp Eval Output* search for `tool-bar-lines' => 2 (wrong).
etc. It seems that the `tool-bar-lines' is always either 0 or 2.