Problem with my Rich Edit print preview

[Charles Dietz]

This code demonstrates a problem I am having running it on my Vista laptop. The code runs properly on my two other computers with XP. The problem is with the StretchBlt() function under %WM_PAINT of the PrintPreview callback. It returns a result of 0 for my Vista laptop, but 1 for my other two computers... same printers, same code, same compiler. I though that over the last year, I must have used the print preview feature on this laptop, but maybe not.

Although this technique is slow, it does give very accurate previews, even showing the slight differences for different printers due to their differing dead spaces. So I would like to keep the algorithm, but for the life of me, I can't detect what's wrong... so I am hoping that one of you GUI experts can spot what is going on. The code is attached as PrnPreview.bas, and any text or rtf file can be opened.

[Chris Holbrook]

Charles, just searched for "vista stretchblt" and found this - does it help?

[Charles Dietz]

Thanks Chris. You may very well have the answer. I googled with only "stretchblt", and did not find what you did... I should have searched with "Vista stretchblt", as you did.

Anyway, now I have to figure out how to implement the stretchDIBits function. It looks kind of complicated. I'll report back what the results are. Thanks, again.

[Charles Dietz]

Problem solved

As Chris surmised, 'StretchDIBits' is required for Vista. I had to change only the following callback function to incorporate that API. I'm embarrassed to admit how many hours I required getting there, even making heavy use of Poffs2, and for that reason, I thought others might benefit from the code.

TYPE MyBITMAPINFO
  bmiHeader AS BITMAPINFOHEADER
  bmiColors(0 TO 1) AS RGBQUAD
END TYPE

CALLBACK FUNCTION printPreviewProc()
   LOCAL hdc AS DWORD, xppi, yppi, hPrnDC, hOldBmp, result AS LONG
   LOCAL ps AS PAINTSTRUCT, s AS STRING, wi, ht AS SINGLE
   STATIC bm AS BITMAP                  'bitmap of rich edit page
   STATIC bmBits AS STRING             'string serving as memory for DIB bits
   STATIC bmSize AS LONG               'space needed by bitmap bits
   STATIC bmInfo AS myBITMAPINFO       'structure defining properties of a DIB
   STATIC bitsPtr AS STRING PTR        'pointer to string memory
   STATIC nWi, nHt, nx, ny, xp, yp, x, y, kx, ky AS DWORD
   STATIC nPage, numPages, dPages, lastPage, hVScroll, hHScroll AS LONG
   STATIC memdc, hBmp AS DWORD, zoom AS SINGLE, si, ssi AS SCROLLINFO, r AS rect
   SELECT CASE CBMSG
      CASE %WM_INITDIALOG
         'create window that proportionally matches printed paper 
         'with hidden scrollbars for zoom feature
         IF PRINTERCOUNT = 0 THEN
            MSGBOX "No windows printers are connected", %MB_ICONERROR, "Initialize Print Preview"
            DIALOG END CBHNDL: EXIT FUNCTION
         END IF
         XPRINT ATTACH DEFAULT
         XPRINT GET CLIENT TO wi, ht
         XPRINT GET DC TO hPrnDC
         hdc = GetDC(CBHNDL)
         xppi = GetDeviceCaps(hdc, %LOGPIXELSX)
         yppi = GetDeviceCaps(hdc, %LOGPIXELSY)
         nHt = .90 * GetDeviceCaps(hdc, %VERTRES) - 90
         nWi = (wi/ht) * (xppi / yppi) * nHt
         x = MAX(460, nWi + 60)
         DIALOG SET CLIENT CBHNDL, x, nHt + 60
         DIALOG SET LOC CBHNDL, 100, 10
         nx = (x - nWi - 9)/2: ny = 30
         CONTROL SET SIZE CBHNDL, %IDC_VScroll, 18, nHt
         CONTROL SET LOC CBHNDL, %IDC_VScroll, nx + nWi, ny
         CONTROL SET SIZE CBHNDL, %IDC_HScroll, nWi, 18
         CONTROL SET LOC CBHNDL, %IDC_HScroll, nx, nHt + ny
         CONTROL SHOW STATE CBHNDL, %IDC_VScroll, %SW_HIDE
         CONTROL SHOW STATE CBHNDL, %IDC_HScroll, %SW_HIDE
         CONTROL HANDLE CBHNDL, %IDC_VScroll TO hVScroll
         CONTROL HANDLE CBHNDL, %IDC_HScroll TO hHScroll

         memdc = CreateCompatibleDC(hPrnDC)
         hBmp = CreateCompatibleBitmap(hPrnDC, wi, ht)
         SelectObject memdc, hBmp
         
         'initialize info for DIB (device independent bitmap)
         bmInfo.bmiHeader.biSize = SIZEOF(bmInfo.bmiHeader)
         bmInfo.bmiHeader.biWidth = wi
         bmInfo.bmiHeader.biHeight = ht
         bmInfo.bmiHeader.biPlanes = 1
         bmInfo.bmiHeader.biBitCount = 1 'monochrome
         bmInfo.bmiHeader.biCompression = %BI_RGB
         bmInfo.bmiColors(0).rgbBlue = 255
         bmInfo.bmiColors(0).rgbGreen = 255
         bmInfo.bmiColors(0).rgbRed = 255
         bmInfo.bmiColors(1).rgbBlue = 0
         bmInfo.bmiColors(1).rgbGreen = 0
         bmInfo.bmiColors(1).rgbRed = 0
         
         'create string for DIB memory space [bmBits]
         'and calculate size needed it [bmSize]
         bmBits = STRING$(SIZEOF(BITMAPINFOHEADER), 0)
         bmSize = wi  
         bmSize = (bmSize + 1) / 8
         bmSize = ((bmSize + 3) / 4) * 4
         bmSize = bmSize * ht
         bmBits = bmBits + STRING$(bmSize, 0)
         bitsPtr = STRPTR(bmbits) + SIZEOF(BITMAPINFOHEADER)
         
         'initialize top controls for specifying pages to preview
         xp = wi: yp = ht: zoom = 1: x = 0: y = 0
         numPages = printRTF(hPrnDC, -1, 0, -1)
         IF numPages THEN
            nPage = 1: CONTROL SET TEXT CBHNDL, %IDC_PageNo, " 1": GOSUB previewPage
         END IF
         dPages = MAX(numPages / 10, 5)
         r.nLeft = nx: r.nTop = ny
         r.nRight = r.nLeft + nWi: r.nBottom = r.nTop + nHt
         CONTROL SET TEXT CBHNDL, %IDC_NumPages, "of" + STR$(numPages) + " pages"
         CONTROL SEND CBHNDL, %IDC_PageNo, %EM_SETSEL, -1, 0
         CONTROL SET FOCUS CBHNDL, %IDC_PageNo
      CASE %WM_PAINT
         hdc = BeginPaint(CBHNDL, ps)
         result = StretchDIBits(hdc, nx, ny, nWi, nHt, x, y, xp/zoom, yp/zoom, _
                  BYVAL bitsPtr, BYVAL VARPTR(bmInfo), %DIB_RGB_COLORS, %SRCCOPY)
         EndPaint CBHNDL, ps
      CASE %WM_COMMAND
         IF CBCTL = %IDC_Fwd THEN
            IF nPage < numPages THEN INCR nPage: GOSUB previewPage
         ELSEIF CBCTL = %IDC_Bwd THEN
            IF nPage > 1 THEN DECR nPage: GOSUB previewPage
         ELSEIF CBCTL = %IDC_FastFwd THEN
            nPage = MIN(nPage + dPages, numPages)
            IF nPage <> lastPage THEN GOSUB previewPage
         ELSEIF CBCTL = %IDC_FastBwd THEN
            nPage = MAX(nPage - dPages, 1)
            IF nPage <> lastPage THEN GOSUB previewPage
         ELSEIF CBCTL = %IDOK THEN 'clicked ENTER key
            CONTROL GET TEXT CBHNDL, %IDC_PageNo TO s
            IF VAL(s) THEN
               nPage = MAX(1, MIN(VAL(s), numPages))
               CONTROL SET TEXT CBHNDL, %IDC_PageNo, STR$(nPage)
               IF nPage <> lastPage THEN
                  lastPage = nPage: zoom = 2.25
                  GOSUB previewPage
               END IF
            END IF
         ELSEIF CBCTL = %IDCANCEL THEN 'clicked ESC key
            DIALOG END CBHNDL
         ELSEIF CBCTL = %IDC_Zoom THEN
            zoom = 1.5 * zoom: IF zoom > 2.25 THEN zoom = 1
            IF zoom > 1 THEN
               CONTROL SHOW STATE CBHNDL, %IDC_VScroll, %SW_SHOW
               CONTROL SHOW STATE CBHNDL, %IDC_HScroll, %SW_SHOW
               si.cbSize = LEN(si)
               si.fMask  = %SIF_ALL
               si.nPage = (1 - 1/zoom)*yp/4
               si.nMax  = 5 * si.nPage
               si.nPos   = 0   'ky * si.nPage
               SetScrollInfo hVScroll, %SB_CTL, si, 1
               ssi.cbSize = LEN(ssi)
               ssi.fMask  = %SIF_ALL
               ssi.nPage = (1 - 1/zoom)*xp/4
               ssi.nMax  = 5 * ssi.nPage
               ssi.nPos   = 0   'kx * ssi.nPage
               SetScrollInfo hHScroll, %SB_CTL, ssi, 1
               x = ssi.nPos: y = 4 * si.nPage  'y = si.nPos
            ELSE
               x = 0: y = 0
               CONTROL SHOW STATE CBHNDL, %IDC_VScroll, %SW_HIDE
               CONTROL SHOW STATE CBHNDL, %IDC_HScroll, %SW_HIDE
            END IF
            InvalidateRect CBHNDL, r, 0
         ELSEIF CBCTL = %IDC_Print THEN
            printFile
         ELSE
            EXIT FUNCTION
         END IF
         IF zoom > 1 AND CBCTL < %IDC_Zoom THEN
            zoom = 2.25: DIALOG SEND CBHNDL, %WM_COMMAND, %IDC_Zoom, 0
         END IF
         IF CBCTL < %IDC_Print THEN 'clear visible focus of buttons pressed
            CONTROL SEND CBHNDL, CBCTL, %BM_SETSTYLE, %BS_PUSHBUTTON, %TRUE
         END IF
      CASE %WM_VSCROLL
         SELECT CASE LOWRD(CBWPARAM)
            CASE %SB_LINEDOWN, %SB_PAGEDOWN 
               si.nPos = MAX(si.nPos + si.nPage, si.nMin): y = y - si.nPage
            CASE %SB_LINEUP, %SB_PAGEUP
               si.nPos = MIN(si.nPos - si.nPage, si.nMax - si.nPage): y = y + si.nPage
            CASE %SB_THUMBTRACK
               si.nPos = MIN(HIWRD(CBWPARAM), si.nMax - si.nPage): y = 4 * si.nPage - si.nPos
            CASE ELSE
               EXIT FUNCTION
         END SELECT
         InvalidateRect CBHNDL, r, 0
         si.cbSize = SIZEOF(si)
         si.fMask = %SIF_POS OR %SIF_PAGE
         SetScrollInfo hVScroll, %SB_CTL, si, 1
      CASE %WM_HSCROLL
         SELECT CASE LOWRD(CBWPARAM)
            CASE %SB_LINEDOWN, %SB_PAGEDOWN
               ssi.nPos = MIN(ssi.nPos + ssi.nPage, ssi.nMax - ssi.nPage): x = x + ssi.nPage
            CASE %SB_LINEUP, %SB_PAGEUP
               ssi.nPos = MAX(ssi.nPos - ssi.nPage, ssi.nMin): x = x - ssi.nPage
            CASE %SB_THUMBTRACK
               ssi.nPos = MIN(HIWRD(CBWPARAM), ssi.nMax - ssi.nPage): x = ssi.nPos
            CASE ELSE
               EXIT FUNCTION
         END SELECT
         InvalidateRect CBHNDL, r, 0 
         ssi.cbSize = SIZEOF(ssi)
         ssi.fMask = %SIF_POS OR %SIF_PAGE
         SetScrollInfo hHScroll, %SB_CTL, ssi, 1
      CASE %WM_DESTROY
         DeleteDC memdc
         DeleteObject hBmp
         XPRINT CANCEL
   END SELECT
   EXIT FUNCTION
previewPage:
   IF nPage THEN
      PatBlt memdc, 0, 0, xp, yp, %PATCOPY
      printRTF memdc, 0, pageEnd(nPage-1) + 1, pageEnd(nPage)
      GetDIBits(memDC, hBmp, 0, yp, BYVAL bitsPtr, BYVAL VARPTR(bmInfo), %DIB_RGB_COLORS)
      InvalidateRect CBHNDL, r, 0: lastPage = nPage
      CONTROL SET TEXT CBHNDL, %IDC_PageNo, STR$(MIN(nPage, numPages))
   END IF
   RETURN
END FUNCTION