OLEACC: Microsoft Active Accessibility

[José Roca]

The following example demonstrates how to create an instance of the IAccessible interface for the object located at the cursor position by calling the AccessibleObjectFromPoint API function, and how to navigate though its child objects.

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' ########################################################################################
' IAccessible demo.
' ########################################################################################

' SED_PBWIN - Use the PBWIN compiler
#COMPILE EXE
#DIM ALL
#INCLUDE "OLEACC.INC"

%CHILDID_SELF = 0
%IDC_TEXTBOX = 1001

' ========================================================================================
' Structure to store the position
' ========================================================================================
TYPE IAccessibleRect
   left AS LONG
   top AS LONG
   width AS LONG
   height AS LONG
END TYPE
' ========================================================================================

' ========================================================================================
' Get object from point
' ========================================================================================
FUNCTION IAccessible_GetObjectFromPoint (BYREF IAR AS IAccessibleRect, BYREF strAccName AS STRING, BYREF strAccValue AS STRING, BYREF strChildren AS STRING) AS LONG

   LOCAL hr AS LONG
   LOCAL pt AS POINTAPI
   LOCAL pIAccessible AS IAccessible
   LOCAL varChild AS VARIANT
   LOCAL pxLeft AS LONG
   LOCAL pyTop AS LONG
   LOCAL pcxWidth AS LONG
   LOCAL pcyHeight AS LONG

   hr = GetCursorPos(pt)
   IF hr = 0 THEN EXIT FUNCTION

   hr = AccessibleObjectFromPoint(pt, pIAccessible, varChild)
   IF hr <> %S_OK THEN EXIT FUNCTION

   pIAccessible.accLocation(pxLeft, pyTop, pcxWidth, pcyHeight, varChild)
   IF OBJRESULT = %S_OK THEN
      IAR.left = pxLeft
      IAR.top = pyTop
      IAR.width = pcxWidth
      IAR.height = pcyHeight
   END IF

   LOCAL bstrAccName AS STRING
   bstrAccName = pIAccessible.accName(varChild)
   IF OBJRESULT = %S_OK THEN
      ' Some versions of the Scintilla control, return the string as ANSI,
      ' not UNICODE! It also returns the text being edited as the name!
      ' This is why I'm using IsTextUnicode here; it should not be needed.
      IF IsTextUnicode(STRPTR(bstrAccName), LEN(bstrAccName), BYVAL %NULL) THEN
         strAccName = ACODE$(bstrAccName)
      ELSE
         strAccName = bstrAccName
      END IF
   END IF

   LOCAL bstrAccValue AS STRING
   bstrAccValue = pIAccessible.accValue(varChild)
   IF OBJRESULT = %S_OK THEN
      IF IsTextUnicode(STRPTR(bstrAccValue), LEN(bstrAccValue), BYVAL %NULL) THEN
         strAccValue = ACODE$(bstrAccValue)
      ELSE
         strAccValue = strAccValue
      END IF
   END IF

   ' Navigate children objects to retrieve its names
   LOCAL varStart AS VARIANT
   varStart = %CHILDID_SELF AS LONG
   varChild = pIAccessible.accNavigate(%NAVDIR_FIRSTCHILD, varStart)
   DO
      IF OBJRESULT <> %S_OK OR VARIANTVT(varChild) = %VT_EMPTY THEN EXIT DO
      bstrAccName = pIAccessible.accName(varChild)
      strChildren += "Child " & FORMAT$(VARIANT#(varChild))
      strChildren += " = " & ACODE$(bstrAccName) & $CRLF
      varStart = varChild
      varChild = pIAccessible.accNavigate(%NAVDIR_NEXT, varStart)
   LOOP

   ' Release the interface
   pIAccessible = NOTHING

   FUNCTION = %TRUE

END FUNCTION
' ========================================================================================

' ========================================================================================
' Main dialog callback
' ========================================================================================
CALLBACK FUNCTION DlgProc() AS LONG

   STATIC hTimer AS LONG
   LOCAL  hr AS LONG
   LOCAL  IAR AS IAccessibleRect
   LOCAL  strAccName AS STRING
   LOCAL  strAccValue AS STRING
   LOCAL  strOutput AS STRING
   LOCAL  strChildren AS STRING

   SELECT CASE CBMSG

      CASE %WM_INITDIALOG
         SetWindowPos CBHNDL, %HWND_TOPMOST, 0, 0, 0, 0, %SWP_NOSIZE OR %SWP_NOMOVE
         hTimer = SetTimer(CBHNDL, 123, 200, 0)

      CASE %WM_TIMER
        hr = IAccessible_GetObjectFromPoint(IAR, strAccName, strAccValue, strChildren)
        strOutput = "x = " & FORMAT$(IAR.left) & " y = " & FORMAT$(IAR.top) & " Width = " & FORMAT$(IAR.width) & " Height = " & FORMAT$(IAR.height) & $CRLF
        strOutput += "Name = " & strAccName & $CRLF & "Value = " & strAccValue & $CRLF
        strOutput += strChildren
        CONTROL SET TEXT CBHNDL, %IDC_TEXTBOX, strOutput

      CASE %WM_DESTROY
         KillTimer CBHNDL, hTimer
         SetWindowPos CBHNDL, %HWND_NOTOPMOST, 0, 0, 0, 0, %SWP_NOSIZE OR %SWP_NOMOVE

      CASE %WM_COMMAND
         SELECT CASE CBCTL
            CASE %IDCANCEL
               IF CBCTLMSG = %BN_CLICKED THEN DIALOG END CBHNDL, 0
         END SELECT

   END SELECT

END FUNCTION
' ========================================================================================

' ========================================================================================
' Main
' ========================================================================================
FUNCTION PBMAIN () AS LONG

  LOCAL hDlg AS DWORD

  DIALOG NEW 0, "IAccessible Demo",,, 350, 150, %WS_CAPTION OR %WS_SYSMENU, 0 TO hDlg
  CONTROL ADD TEXTBOX, hDlg, %IDC_TEXTBOX, "", 4, 4, 340, 140,%ES_MULTILINE OR %ES_WANTRETURN OR %WS_VSCROLL, %WS_EX_CLIENTEDGE
  DIALOG SHOW MODAL hDlg CALL DlgProc

END FUNCTION
' ========================================================================================


A reference guide, adapted to the PowerBASIC syntax, is available in my web site: http://www.jose.it-berater.org/oleacc/iframe/index.htm