SAMPLE: Creating Accelerator Tables Dynamically

• Microsoft Windows Software Development Kit (SDK) for Windows versions 3.0 and 3.1

SUMMARY

Sometimes it is desirable to allow the user to define accelerator keys when running an application. No Windows function provides this functionality, nor does the typical method of using the Resource Compiler (RC) and embedding the accelerator table in the .EXE file. To accomplish this, the programmer must create and manage an accelerator table.

This article outlines one method of creating accelerator tables at run time or "on the fly." The DYNACCEL sample, which is available in the Microsoft Software Library, demonstrates this method.

MORE INFORMATION

DYNACCEL demonstrates creating an accelerator table at run time rather than in the resource file. It creates a table of accelerator keys and their associated command identifiers. It implements a CustomTranslateAccelerator function, which is used in place of Windows' TranslateAccelerator function. It traps any WM_KEYDOWN messages, checks the table to see if the key matches an accelerator key, checks to see if the CTRL or SHIFT key is down as appropriate, and generates a WM_COMMAND message if all conditions are met.

DYNACCEL can be enhanced to use a dynamically sized or updated table or to include other desired functionality because everything is created and maintained within the program.

The following code fragments are used in DYNACCEL to implement an accelerator table at run time. The complete DYNACCEL sample can be found in the Microsoft Software Library.

Download DYNACCEL.EXE, a self-extracting file, from the Microsoft Software Library (MSL) on the following services:

• Microsoft Download Service (MSDL)

        Dial (206) 936-6735 to connect to MSDL
        Download DYNACCEL.EXE (size: 24680 bytes) 
  

• Internet (anonymous FTP)

        ftp ftp.microsoft.com
        Change to the \SOFTLIB\MSLFILES directory
        Get DYNACCEL.EXE (size: 24680 bytes) 
  

  /*
   * Accelerator table data structure. This has been set up arbitrarily
   * and may be altered depending on the desired functionality.
   */
  
  

    BYTE cChar;
    BYTE cVirtKey;
    WORD wID;

/*
 * Array of accelerator keys. For demonstration purposes, these values
 * are predefined by DYNACCEL. An application could read in the
 * user's keystrokes and assign these values at run time or from an
 * INI file.
 */

Accelerator AccTable[TABLELENGTH] =   {
                {'A', VKCTRL, IDDA},        //CTRL+key will activate
                {'B', VKCTRL, IDDB},        //    "     "      "
                {'C', VKCTRL, IDDC},        //    "     "      "
                {'D', VKSHFT, IDDD},        //SHIFT+key will activate
                {'E', VKSHFT, IDDE},        //    "     "      "
                {'F', VKSHFT, IDDF},        //    "     "      "
                {' ', 0, IDD_UNDEFINED},    //not defined
                {' ', 0, IDD_UNDEFINED}
                                      };


/*
 * FUNCTION: CustomTranslateAccelerator(HWND, LPMSG)
 *
 * PURPOSE: Custom TranslateAccelerator for dynamic accelerator
 *          tables.
 */

int CustomTranslateAccelerator(HWND hWnd,
                               LPMSG lpMsg)
{
int i;

   for (i = 0; i < TABLELENGTH; i++)  //check table for a match
      {
      if ((lpMsg->wParam == AccTable[i].cChar)   //key is in table
           && (AccTable[i].wID != IDD_UNDEFINED))  //and is defined

         switch (AccTable[i].cVirtKey)
            {
            case VKCTRL:  //is CONTROL down?
               if (GetKeyState(VK_CONTROL) & 0x1000)
                  return ActivateMenuItem(hWnd, AccTable[i].wID);
               break;

            case VKSHFT:  //is SHIFT down?
               if (GetKeyState(VK_SHIFT) & 0x1000)
                  return ActivateMenuItem(hWnd, AccTable[i].wID);
               break;
            } //end switch
      } //end for loop

   return FALSE;    //key combination not found in accelerator table
}


/*
 * FUNCTION: ActivateMenuItem(HWND, WORD)
 *
 * PURPOSE: Highlight (HILITE) a top level menu item, run the command
 *          associated with a menu item, and unhighlight (UNHILITE)
 *          the top-level menu item.
 */

                      WORD wID)
{

/*
 * Implementation of CustomTranslateAccelerator within WinMain
 */

    while (GetMessage(&msg, NULL, NULL, NULL))
        {
        if (CustomTranslateAccelerator(hwnd, (LPMSG)&msg) == 0)
            {
            TranslateMessage(&msg);
            DispatchMessage(&msg);
            }
        }