Wait for user ROI generation? (doprompt)

I struggled with something similar, here is what worked for me:

	string s_info=TraceInfo(S_graphName, S_traceName, 0)
	string s_Xax=StringByKey("XAXIS",s_info)
	string s_Yax=StringByKey("YAXIS",s_info)	

	KillWindow/Z EncirclePanel
	GetWindow/Z kwTopWin wsize
	variable gx0=(V_left+V_right)/2, gy0=(V_top+V_bottom)/2
	NewPanel/N=EncirclePanel/W=(gx0,gy0,gx0+130,gy0+90) as "ROI"
	SetDrawLayer UserBack
	SetDrawEnv textyjust= 2
	DrawText 5,5,"Click & drag to select,\rthen click continue"
	Button Done,pos={30,35},size={70,20},title="Continue", Proc=ButtonProc
	Button Cancel,pos={30,60},size={70,20},title="Cancel", Proc=ButtonProc
	
	// set hook to bring panel to front after drawing ROI
	SetWindow $S_graphName hook(encircleHook)=hookROI
	
	string s_flags=StringByKey("AXISFLAGS",s_info)
	variable flagBits=GrepString(s_flags, "/R")+2*GrepString(s_flags, "/T")
	switch (flagBits)
		case 0:
			GraphWaveDraw/W=$S_graphName/F/O/B=$s_Xax/L=$s_Yax yROI, xROI
			break
		case 1:
			GraphWaveDraw/W=$S_graphName/F/O/B=$s_Xax/R=$s_Yax yROI, xROI
			break
		case 2:
			GraphWaveDraw/W=$S_graphName/F/O/T=$s_Xax/L=$s_Yax yROI, xROI
			break
		case 3:
			GraphWaveDraw/W=$S_graphName/F/O/T=$s_Xax/R=$s_Yax yROI, xROI
			break
	endswitch
			
	PauseForUser EncirclePanel, $S_graphName
	SetWindow $S_graphName hook(encircleHook)=$""
	
	RemoveFromGraph/Z/W=$S_graphName yROI
	wave/Z xROI=xROI, yROI=yROI
	if (WaveExists(xROI)==0)
		return 0
	endif



// hook is active while drawing to select ROI
// brings panel to front when drawing is complete
// Couldn't figure out how to give a floating panel focus.
function hookROI(s)
	STRUCT WMWinHookStruct &s
	
	if (s.eventCode==8 || s.eventCode==5)
		DoWindow/F EncirclePanel
		return 1
	endif
	return 0
end

// deal with cancel and continue buttons for selection by drawing
function ButtonProc(STRUCT WMButtonAction &s)
		
	if (s.eventCode!=2)
		return 0
	endif
	
	if (stringmatch(s.ctrlName, "Cancel"))
		wave/Z xROI=xROI, yROI=yROI
		if (WaveExists(xROI))
			Redimension/N=0 xROI, yROI
		endif
	endif
	
	KillWindow/Z EncirclePanel
	
	return 0
end

In my case with Image Tools, I have a button to Start the draw action. Clicking the button changes the button's name and userdata for the button. It also puts userdata on the graph window.

usD = GetUserData(k_fullPanel,"buttonsetbckgrnd_tab21","")
strswitch(usD)
	case "start":
		switch(how)
			case 1:		// manual
				Button buttonsetbckgrnd_tab21,win=$k_fullpanel,userdata="end",title="End..."
				SetWindow $k_imgDisplay, userdata(draw)="active"
				SetDrawLayer/W=$k_imgDisplay ProgFront
				GraphWaveDraw/W=$k_imgDisplay/L/T/O imgT_bckgY,imgT_bckgX

The image window has a hook function with this code.

// image window hook function
Function Hf_imgTImageHook(iwH)		// WindowHookFunction
	STRUCT WMWinHookStruct &iwH
	
	variable hookResult = 0
	string wmode
	
	switch(iwH.eventCode)
		case 0:		// activate
			// reset axes if ever switched
			wmode = GetUserData(k_imgDisplay,"","draw")
			if (strlen(wmode) != 0)
				// drawing mode active, ignore active event
				hookResult = 0
			else
				hookResult = 1
			endif
			break
		case 2:		// image being killed
			...
			hookResult = 1
			break
		case 5:		// mouseup
			wmode = GetUserData(k_imgDisplay,"","draw")
			if (strlen(wmode) != 0)
				// drawing mode active here
				...
			else
				// drawing mode inactive here
				...
			endif
			hookResult = 1
			break
	endswitch
	
	return hookResult
end

The End button code is as below.

	case "end":
		DoUpdate/W=$k_imgDisplay
		Button buttonsetbckgrnd_tab21,win=$k_fullpanel,userdata="start",title="Set"
		GraphWaveEdit/W=$k_imgDisplay/T=1 scalewy
		GraphNormal/W=$k_imgDisplay
		SetDrawLayer/W=$k_imgDisplay UserFront
		SetWindow $k_imgDisplay, userdata(draw)=""

The approach could likely be improved when GetWindow would have a flag to return the drawing mode state for a graph or image window, such as ...

GetWindow ... drawmode
0 - normal mode
1 - drawing mode active
2 - edit mode active