The SetState command records a string property that can be fetched by GetElements. This allows you to query and update hidden values in a canvas-based application.

$\mathrm{with}\left(\mathrm{DocumentTools}:-\mathrm{Canvas}\right)\:$

Press := proc(canvas)
   local state := GetElements(canvas,"state");
   local sc := Script();
   SetState(sc,1+state[1]:-value);
   ToString(sc);
end proc:

Show := proc(canvas)
   local M := GetElements(canvas,'custom'="Input");
   local state := GetElements(canvas,"state");
   local sc := Script();
   SetActive(sc,M[1]);
   SetMath(sc,state[1]:-value);
   ToString(sc);
end proc:

$\mathrm{cv}≔\mathrm{NewCanvas}\left(\left[''Counter''\,\mathrm{Math}\left(0\,'\mathrm{custom}'=''Input''\right)\,\mathrm{ScriptButton}\left(''Press''\,\mathrm{Press}\right)\,\mathrm{ScriptButton}\left(''Show\; Count''\,\mathrm{Show}\right)\,\mathrm{State}\left(100\right)\right]\right)\:$

$\mathrm{ShowCanvas}\left(\mathrm{cv}\right)$

The DocumentTools[Canvas][Script][SetState] command was introduced in Maple 2022.

For more information on Maple 2022 changes, see Updates in Maple 2022.