In this example, we will insert a canvas, get the math from the canvas, and manually add annotations to the math input.

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

create the canvas:

$\mathrm{cv}≔\mathrm{NewCanvas}\left(\left[''Sample\; Canvas''\,x+y\right]\right)\:$

$\mathrm{ShowCanvas}\left(\mathrm{cv}\,'\mathrm{input}'=\left[\mathrm{box}\left[A\right]\,\mathrm{box}\left[B\right]\right]\right)$

get references to the math data in the canvas:

$\mathrm{data}≔\mathrm{GetMath}\left(\right)\:$

look at the math property of the first element:

$\mathrm{data}\left[1\right]:-\mathrm{math}$

create a script object and add some annotations

$\mathrm{sc}≔\mathrm{Script}\left(\right)\:$

$\mathrm{Annotate}\left(\mathrm{sc}\,''this\; is\; a\; sum''\,\mathrm{data}\left[1\right]\right)$

$\mathrm{Annotate}\left(\mathrm{sc}\,''this\; is\; box\; A''\,\mathrm{data}\left[2\right]\right)$

loop through all of the math and annotate each element with its type

$$\begin{gathered} \mathbf{for}\mathrm{elem}\mathbf{in}\mathrm{data}\mathbf{do} \\ \mathrm{Annotate}\left(\mathrm{sc}\,\left[''This\; contains\; something\; of\; type''\,\mathrm{whattype}\left(\mathrm{elem}\left[\mathrm{math}\right]\right)\right]\,\mathrm{elem}\right) \\ \mathbf{end}\mathbf{do}\: \end{gathered}$$

In this example, we will define an application that allows user input and provides feedback.  The FindPrimes procedure will run when a button is pressed.  It will find all the math in the canvas area, and add annotations to the inputs.

FindPrimes := proc( canvas )
   uses DC=DocumentTools:-Canvas;
   local script := DC:-Script();
   for local m in DC:-GetMath(canvas) do  # get all the math in the canvas
       SetActive(script,m);    # set the location of the annotation
       if m:-math::integer and isprime(m:-math) then
           Annotate(script,"Good job, this is prime");   # annotate based on the given math
      else
           Annotate(script,"This is not prime");
      end if;
  end do;
  ToString(script);
end proc:

Generate the canvas

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

$\mathrm{cv}≔\mathrm{NewCanvas}\left(\left[''Write\; Some\; Prime\; Numbers\; Anywhere''\,\mathrm{ScriptButton}\left(''Check\; Your\; Page''\,\mathrm{FindPrimes}\,\mathrm{position}=\left[500\,50\right]\right)\right]\right)\:$

To test this within Maple, run:

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

To try this on the web using Maple Learn, execute:

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