L_ShowMagGlass

#include "l_bitmap.h"

L_LTDIS_API L_INT L_ShowMagGlass(hWnd, bShowMagGlass)

Shows or hides the magnifying glass on the screen.

Returns

Comments

The function is used to control the display of the magnifying glass on the screen. Since the user is responsible for displaying the magnifying glass and moving it on the screen in a manual update, this function is used in conjunction with L_SetMagGlassPos function.

This function can be called with bShowMagGlass set to TRUE when the left mouse button is pressed to show the magnifying glass. It can be called with bShowMagGlass set to FALSE when the left mouse button is released to hide the magnifying glass.

Required DLLs and Libraries

Platforms

Win32, x64, Mobile.

See Also

Example

This example starts the Magnifying Glass in the Manual Update mode, then calls the necessary functions such like L_SetMagGlassPos and L_ShowMagGlass to handle the painting of the Magnifying Glass.

static L_BOOL   bLeftButton = FALSE; 
static HCURSOR  hMagGlassCursor = NULL;

#define IDC_MAGGLASS_CURSOR 1234

 L_INT StartMagnifyingGlass(L_HWND          hWnd,
                            pBITMAPHANDLE pBitmap,
                            pBITMAPHANDLE pUpdateBitmap,
                            RECT*         prcView,
                            HINSTANCE     hInst)
{
   L_INT             nRet;
   L_TCHAR           szMsg[256]= TEXT("");
   MAGGLASSOPTIONS   MagGlassOpt;

   // Starting the Magnifying Glass
   memset(&MagGlassOpt, 0, sizeof(MAGGLASSOPTIONS));
   MagGlassOpt.uStructSize    = sizeof(MAGGLASSOPTIONS);
   MagGlassOpt.nWidth         = 100;
   MagGlassOpt.nHeight        = 100;
   MagGlassOpt.nZoom          = 400;
   MagGlassOpt.clrPen         = RGB(255,0,0);
   MagGlassOpt.hMagCursor     = NULL;
   MagGlassOpt.clrBack        = RGB(128,128,128);
   MagGlassOpt.bEllipse       = FALSE;
   MagGlassOpt.nBorderSize    = 1;
   MagGlassOpt.b3D            = TRUE;
   MagGlassOpt.uPaintFlags    = 0;
   MagGlassOpt.pMask          = NULL;
   MagGlassOpt.uMaskCount     = 0;
   MagGlassOpt.nCrosshair     = CROSSHAIR_FINE;
   MagGlassOpt.bIgnoreRgn     = TRUE;
   MagGlassOpt.bCenter        = TRUE;
   MagGlassOpt.uMagGlassFlags = MAGGLASS_MANUAL_UPDATE;

   nRet = L_StartMagGlass (hWnd, pBitmap, prcView, &MagGlassOpt, NULL, NULL);
   if (nRet != SUCCESS) 
   {
      wsprintf(szMsg, TEXT("Error Starting the Magnifying Glass, Error: %d"), nRet); 
      MessageBox(hWnd, szMsg, TEXT("Error"), MB_ICONEXCLAMATION | MB_OK); 
      return nRet; 
   }

   // Updating the Magnifying Glass bitmap with another bitmap that has the 
   // same width and height. 
   nRet = L_UpdateMagGlassBitmap(hWnd, pUpdateBitmap, TRUE); 
   if (nRet != SUCCESS) 
   {
      wsprintf(szMsg, TEXT("Error Trying to update the Magnifying Glass bitmap, Error: %d"), nRet); 
      MessageBox(hWnd, szMsg, TEXT("Error"), MB_ICONEXCLAMATION | MB_OK); 
      return nRet; 
   }

   L_UpdateMagGlassPaintFlags(hWnd, DISPLAYMODE_SCALETOGRAY); //enable ScaleToGray for MagGlass

   hMagGlassCursor = LoadCursor(hInst, MAKEINTRESOURCE(IDC_MAGGLASS_CURSOR));
   return SUCCESS; 
}

L_BOOL Child_OnSetCursor(L_HWND hWnd, L_HWND hWndCursor, L_UINT codeHitTest, L_UINT msg)
{
   if (codeHitTest != HTCLIENT) 
      return (FORWARD_WM_SETCURSOR(hWnd, hWndCursor, codeHitTest, msg, DefMDIChildProc));

   if (L_WindowHasMagGlass(hWnd) && !bLeftButton)
      SetCursor(hMagGlassCursor);

   return TRUE; 
}

L_VOID Child_OnLButtonDown(L_HWND     hWnd,
                           L_BOOL   fDoubleClick,
                           L_INT    x,
                           L_INT    y,
                           L_UINT   keyFlags)
{
   UNREFERENCED_PARAMETER(fDoubleClick);
   UNREFERENCED_PARAMETER(x);
   UNREFERENCED_PARAMETER(y);
   UNREFERENCED_PARAMETER(keyFlags);
   L_INT    nRet; 
   L_TCHAR   szMsg[256]=TEXT(""); 

   if (!L_WindowHasMagGlass(hWnd)) 
      return; 

   SetCapture(hWnd); 
   ShowCursor(FALSE); 

   nRet = L_SetMagGlassPos (hWnd, x, y); 
   if (nRet != SUCCESS) 
   {
      wsprintf(szMsg, TEXT("Error Displaying Magnifying Glass, Error: %d"), nRet); 
      MessageBox(hWnd, szMsg, TEXT("Error"), MB_ICONEXCLAMATION | MB_OK); 
      return; 
   }

   nRet = L_ShowMagGlass(hWnd, TRUE); 
   if (nRet != SUCCESS) 
   {
      wsprintf(szMsg, TEXT("Error Displaying Magnifying Glass, Error: %d"), nRet); 
      MessageBox(hWnd, szMsg, TEXT("Error"), MB_ICONEXCLAMATION | MB_OK); 
      return; 
   }

   bLeftButton = TRUE; 
}

L_VOID Child_OnMouseMove(L_HWND    hWnd,
                         L_INT   x,
                         L_INT   y,
                         L_UINT keyFlags) 
{
   UNREFERENCED_PARAMETER(x);
   UNREFERENCED_PARAMETER(y);
   UNREFERENCED_PARAMETER(keyFlags);
   L_INT    nRet; 
   L_TCHAR   szMsg[256]=TEXT(""); 

   if (!L_WindowHasMagGlass(hWnd) || !bLeftButton) 
      return; 

   nRet = L_SetMagGlassPos (hWnd, x, y); 
   if (nRet != SUCCESS) 
   {
      wsprintf(szMsg, TEXT("Error Moving Magnifying Glass, Error: %d"), nRet); 
      MessageBox(hWnd, szMsg, TEXT("Error"), MB_ICONEXCLAMATION | MB_OK); 
   }
}

L_VOID Child_OnLButtonUp(L_HWND    hWnd,
                         L_INT   x,
                         L_INT   y,
                         L_UINT  keyFlags) 
{
   UNREFERENCED_PARAMETER(x);
   UNREFERENCED_PARAMETER(y);
   UNREFERENCED_PARAMETER(keyFlags);
   L_INT    nRet; 
   L_TCHAR   szMsg[256]=TEXT(""); 

   if (!L_WindowHasMagGlass(hWnd) || !bLeftButton) 
      return; 

   ReleaseCapture();

   nRet = L_ShowMagGlass(hWnd, FALSE); 
   if (nRet != SUCCESS) 
   {
      wsprintf(szMsg, TEXT("Error Hiding Magnifying Glass, Error: %d"), nRet); 
      MessageBox(hWnd, szMsg, TEXT("Error"), MB_ICONEXCLAMATION | MB_OK); 
   }

   ShowCursor(TRUE); 

   bLeftButton = FALSE; 
}