The State command is used in conjunction with NewCanvas to initialize a default state that can be subsequently used by the SetState script action.

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

Check := proc(canvas)
   local state := GetElements(canvas,"state")[1];
   local ans := GetElements(canvas,'custom'="Input")[1];
   local sc := Script();
   SetActive(sc,ans);
   Annotate(sc,`if`(is(sqrt(state:-value[1]^2+state:-value[2]^2) = ans:-math),"Correct","Incorrect"));
   ToString(sc);
end proc:

TryAnother := proc(canvas)
   # find and clear the input box
   local elem := GetElements(canvas,'custom'="Input");
   local sc := Script();
   SetActive(sc,elem[1]);
   SetMath(sc,"");
   Annotate(sc,"-- Enter Hypotenuse");
   # generate a new plot
   randomize();
   local l1 := rand(1..5)();
   local l2 := rand(1..5)();
   SetState(sc,[l1,l2]);
   elem := GetElements(canvas,"plot");
   SetActive(sc,elem[1]);
   SetPlot(sc,DrawTriangle(l1,l2));
   ToString(sc);
end proc:

DrawTriangle := proc( len1, len2 )
   plots:-display( [
       plots:-polygonplot( [[1,1],[1,1+len1],[1+len2,1],[1,1]], 'style'='line' ),
       plots:-textplot( [[1,len1/2+1,len1,'align'='left'],[len2/2+1,1,len2,'align'='below']] )
   ], 'view'=[0.5 .. len2+1.5,0.5 .. len1+1.5], 'axes'='boxed');
end proc:

$\mathrm{cv}≔\mathrm{NewCanvas}\left(\left[''Calculate\; the\; Hypotenuse''\,\mathrm{StaticPlot}\left(\mathrm{DrawTriangle}\left(1\,2\right)\right)\,\mathrm{Math}\left(0\,'\mathrm{custom}'=''Input''\,'\mathrm{annotation}'=''--\; Enter\; Hypotenuse''\,'\mathrm{border}'=\mathrm{true}\right)\,\mathrm{ScriptButton}\left(''Check''\,\mathrm{Check}\right)\,\mathrm{ScriptButton}\left(''Try\; Another''\,\mathrm{TryAnother}\,'\mathrm{include}'=\left[\mathrm{DrawTriangle}\right]\right)\,\mathrm{State}\left(\left[1\,2\right]\right)\right]\right)\:$

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

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

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