How do I invoke the freehand line tool (f key) programmatically in an attached cell containing a canvas?

Question

I created the following code that overlays an attached cell containing a large canvas on top of a notebook. This allows me to use the drawing tools on top of my notebook so that I can annotate code with my handwriting.

CreateWindow[DocumentNotebook[CellGroup[{
    "Testing Writing Canvas Overlay",
    "Step 1. Click Draw Above", 
    "Step 2.  Invoke the locked freehand line drawing tool by pressing the f key twice.", "Step 3. Draw Something",
    "Step 4.  Click Reset to Delete AttachCell"}],
  CellGrouping -> Manual,
  WholeCellGroupOpener -> True],
 DockedCells -> Cell[BoxData@ToBoxes@Row[{Button["Draw",
        SelectionMove[ButtonNotebook[], Before, Notebook];
         SelectionMove[ButtonNotebook[], Next, Cell];
        obj = 
         AttachCell[SelectedCells[][[1]], 
          Style[Graphics[{}, AspectRatio -> Full, 
            ImageSize -> 
             AbsoluteCurrentValue[EvaluationNotebook[], 
               WindowSize]*{2, 2}], Deployed -> False, 
           Editable -> True], Left, 75, Left];
        SelectionMove[obj, All, CellContents]],
       Button["Reset", 
        NotebookDelete[
         Cells[EvaluationNotebook[], AttachedCell -> True]]]}]]]

I would like to skip step 2 (as shown in the notebook). In other words, I would like to include an extra line of code that allows me to draw immediately upon pressing the "Draw" button. I don't want to have to press the f key at all.

It seems like I need to either simulate two keypresses of the f key somehow or invoke some frontendtoken twice to start the locked freehand line tool. Any ideas?

Answer 1

This works....

Needs["JLink`"];
ReinstallJava[];

robotclass = JavaNew["java.awt.Robot"];
LoadJavaClass["java.awt.event.InputEvent"];
LoadJavaClass["java.awt.event.KeyEvent"];
LoadJavaClass["java.awt.Event"];

keypress = (Function[k, 
      robotclass[keyPress[Symbol["KeyEvent`VKU" <> k]]]] /@ {##};
    Function[k, 
      robotclass[
       keyRelease[Symbol["KeyEvent`VKU" <> k]]]] /@ {##}) &;
CreateWindow[
 DocumentNotebook[
  CellGroup[{"Testing Writing Canvas Overlay", 
    "Step 1. Click Draw Above", "Step 2. Draw Something", 
    "Step 3.  Invoke the locked freehand line drawing tool by \
pressing the f key twice.", 
    "Step 4.  Click Reset to Delete AttachCell"}], 
  CellGrouping -> Manual, WholeCellGroupOpener -> True], 
 DockedCells -> 
  Cell[BoxData@
    ToBoxes@Row[{Button["Draw", 
        SelectionMove[ButtonNotebook[], Before, Notebook];
        SelectionMove[ButtonNotebook[], Next, Cell];
        obj = 
         AttachCell[SelectedCells[][[1]], 
          Style[Graphics[{}, AspectRatio -> Full, 
            ImageSize -> 
             AbsoluteCurrentValue[EvaluationNotebook[], 
               WindowSize]*{2, 20}], Deployed -> False, 
           Editable -> True], Left, 75, Left];
        SelectionMove[obj, All, CellContents];
        keypress["F", "F"];], 
       Button["Reset", 
        NotebookDelete[
         Cells[EvaluationNotebook[], AttachedCell -> True]]]}]]]