bmp "disappearing" ?

[iza]

i copy a bmp into memory, then from memory to a window
this goes fine almost all the time, but from time to time, under certain platform (win9x - win2000 is always fine), instead of copying the bmp to the window, i get a grey screen - nothing was copied. but no error raises tho ... f someone could help !!
some code :
HDC hdcScreen = CreateDC("DISPLAY", NULL, NULL, NULL); // normal DC, provides a "snapshot" of the screen contents.
hdcCompatible = CreateCompatibleDC(hdcScreen); // memory DC keeps a copy of this "snapshot" in the associated bmp
botx=GetDeviceCaps(hdcScreen, HORZRES);
boty=GetDeviceCaps(hdcScreen, VERTRES);

// Create a compatible bitmap for hdcScreen.
hbmScreen = CreateCompatibleBitmap(hdcScreen,botx,boty);
if (hbmScreen==NULL)
raise error

// Select the bitmaps into the compatible DC.
if (SelectObject(hdcCompatible, hbmScreen)==NULL)
raise error

// won't capture the window
ShowWindow(SW_HIDE);

//Copy color data for the entire display into a bitmap that is selected into a compatible DC.
if (BitBlt(hdcCompatible,topx,topy,botx, boty,hdcScreen, 0,0,SRCCOPY))
....
else
raise error

 

[TGM]

Here is some other code that works:

pdc is the CDC* received from the framework

CBitmap bitmap;
CDC memDC;
CRect rect;
int nWidth;
int nHeigth;

... init nWidth and nHeight

memDC.CreateCompatibleDC( pdc);

bitmap.CreateCompatibleBitmap( pdc, nWidth, nHeight);

CBitmap* pOldBitmap = memDC.SelectObject(&bitmap);
memDC.BitBlt(0, 0, nWidth, nHeight, pdc, 0, 0, SRCCOPY);

memDC.SelectObject(pOldBitmap);


Thierry

 

[iza]

thanks thierry
- but actually, my code DO work - only from time to time the bmp is not here ... sounds like memory flaw, but i can't figure out where/how ...
- btw your code and my code are the same, except that you don't catch errors - i do but they are never raised, and except that you select twice the bmp into memory (i'll try this anyway !) ...