L_SetStatusCallBack
#include "l_bitmap.h"
L_VOID EXT_FUNCTION L_SetStatusCallBack(pfnCallback, pUserData)
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STATUSCALLBACK pfnCallback; |
/* pointer to your callback function */ |
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/* pointer to more parameters for the callback */ | |
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STATUSCALLBACK L_FAR * pfnOldCallback; |
/* pointer to old callback function */ |
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/* pointer to more parameters for the old callback */ |
Sets the new status callback function and gets the old status callback.
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Parameter |
Description |
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pfnCallback |
Pointer to your callback function. The callback function must adhere to the function syntax specified in STATUSCALLBACK Function. |
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This callback function must return SUCCESS if the operation was successfully done, or any error if the function call was a failure. If the callback function returns a failure, the current function will terminate and return the same error that the callback returned. |
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pUserData |
Void pointer that you can use to pass one or more additional parameters that the callback function needs. |
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To use this feature, assign a value to a variable or create a structure that contains as many fields as you need. Then, in this parameter, pass the address of the variable or structure, casting it to L_VOID L_FAR *. The callback function, which receives the address in its own pUserData parameter, can cast it to a pointer of the appropriate data type to access your variable or structure. |
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If the additional parameters are not needed, you can pass NULL in this parameter. |
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pfnOldCallback |
Pointer to a variable which will be updated with the old status callback function |
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ppOldUserData |
Pointer to a variable which will be updated with the user data for the old status callback function |
Returns
None.
Comments
The status callback is returned through a parameter. You used to have to call L_GetStatusCallBack to get the user data prior to calling L_SetStatusCallback. Now you can get the old callback and set the new callback in one function call.
You can use this function to specify a callback for any of the following functions:
L_AddBitmapNoise
L_AverageFilterBitmap
L_BinaryFilterBitmap
L_ChangeBitmapContrast
L_ChangeBitmapHue
L_ChangeBitmapIntensity
L_ChangeBitmapSaturation
L_ClearBitmap
L_ColorMergeBitmap
L_ColorSeparateBitmap
L_CombineBitmap
L_DeskewBitmap
L_DespeckleBitmap
L_EmbossBitmap
L_FillBitmap
L_FlipBitmap
L_GammaCorrectBitmap
L_GetBitmapHistogram
L_GrayScaleBitmap
L_HalfToneBitmap
L_HistoEqualizeBitmap
L_IntensityDetectBitmap
L_InvertBitmap
L_MedianFilterBitmap
L_MMConvertFromBitmapList(Video Module only)
L_MMSaveFile(Video Module only)
L_MosaicBitmap
L_PaintDCEffect
L_PosterizeBitmap
L_PrintBitmap
L_RemapBitmapIntensity
L_ResampleBitmap
L_ResizeBitmap
L_ReverseBitmap
L_RotateBitmap
L_RotateBitmapFine
L_SharpenBitmap
L_ShearBitmap
L_SizeBitmap
L_SpatialFilterBitmap
L_StretchBitmapIntensity
L_UnderlayBitmap
Both the old status callback function and the user data required for the old status callback function are updated in the pfnOldCallbaclk and ppOldUserData parameters, respectively.
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1. |
Call the L_SetStatusCallBack function, assigning its return value to a STATUSCALLBACK variable, and passing the pointer to your callback as the new value. |
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2. |
Call the function that uses the callback (for example L_AverageFilterBitmap). |
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3. |
Call the L_SetStatusCallBack function again, restoring the original value by passing the variable that you saved in Step 1. |
Required DLLs and Libraries
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LTKRN For a listing of the exact DLLs and Libraries needed, based on the toolkit version, refer to Files To Be Included With Your Application. |
Platforms
Windows 95 / 98 / Me, Windows 2000 / XP, Windows CE.
See Also
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Functions: |
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Topics: |
Example
For complete sample code, refer to the CHILD.C module of the DEMO example.
/**************** Global declarations
***********************************************/
HINSTANCE hInst; /* Current instance of the application, set by the
InitInstance function */
BITMAPHANDLE LeadBitmap; /* Bitmap handle for the loaded image */
L_BOOL KillProgress; /* Boolean flag to test for a user interrupt */
L_BOOL InterruptActive; /* Boolean flag to enable use of an interrupt key
*/
/* Prototype for the STATUSCALLBACK function */
L_INT L_EXPORT EXT_CALLBACK StatusCallBack (L_INT nPercent, L_VOID L_FAR*
pUserData);
/* This function uses L_SetStatusCallBack to implement the STATUSCALLBACK
function when applying a median filter. */
void TestFunction(HWND hWnd)
{
STATUSCALLBACK lpfnOldStatusCB; /* Pointer to the previous
STATUSCALLBACK function */
L_VOID L_FAR* pOldData; /* Pointer to the user data for the previous status callback function */
/* Set the STATUSCALLBACK function, saving the pointer to the previous
one */
L_SetStatusCallBack(StatusCallBack, NULL, &lpfnOldStatusCB, &pOldData );
/* Initialize global variables for detecting a user interrupt */
InterruptActive = TRUE;
KillProgress = FALSE;
/* Apply an intentionally slow median filter with a neighborhood of 7x7
pixels */
L_MedianFilterBitmap(&LeadBitmap, 7 );
/* Disable the user interrupt key */
InterruptActive = FALSE;
/* Restore the previous STATUSCALLBACK function */
L_SetStatusCallBack (lpfnOldStatusCB, pOldData, NULL, NULL);
/* Force a repaint */
InvalidateRect(hWnd,NULL,FALSE);
return;
}
/* This is the STATUSCALLBACK function, which stops the process
if the user has pressed the interrupt key. */
L_INT L_EXPORT EXT_CALLBACK StatusCallBack (L_INT nPercent, L_VOID L_FAR
*pUserData)
{
HWND hWnd=NULL;
L_TCHAR achMsg[80]; /* MessageBox string */
MSG msg;
hWnd = (HWND)pUserData;
/* Let the application detect a WM_KEYDOWN event */
while (PeekMessage (&msg, NULL, 0, 0, PM_REMOVE))
{
TranslateMessage (&msg);
DispatchMessage (&msg);
}
/* Check the global variable and return an error if necessary */
if (KillProgress)
{
wsprintf (achMsg, TEXT("Interrupted by the user with %d percent finished"),
nPercent);
MessageBox (hWnd, achMsg, TEXT("Notice"), MB_OK);
return (ERROR_USER_ABORT);
}
return SUCCESS;
}
/* This is the main window processing function, where the interrupt key is
detected */
L_INT32 EXT_FUNCTION MainWndProc (HWND hWnd, L_UINT Message, WPARAM wParam,
LPARAM lParam)
{
switch (Message)
{
case WM_KEYDOWN:
/* Use the Esc key as the user interrupt key */
if (((int) wParam == VK_ESCAPE) && (InterruptActive == TRUE))
KillProgress = TRUE;
/* Use the Insert key to run the test function */
if ((int) wParam == VK_INSERT)
TestFunction (hWnd);
}
return (0);
}