ViewerPreferences Complete Reference

ViewerPreferences allow you to control how PDF documents are presented in supporting viewers and how some default print settings are initialized. The current HotPDF library supports 14 ViewerPreferences values plus the related InitialZoom property.

Current Data Types

THPDFDirection = (LeftToRight, RightToLeft);
THPDFNonFullScreenPageMode = (
  nfpmUseNone, nfpmUseOutlines, nfpmUseThumbs, nfpmUseOC, nfpmUseAttachments
);
THPDFPrintScaling = (psNone, psAppDefault);
THPDFDuplex = (dupSimplex, dupDuplexFlipShortEdge, dupDuplexFlipLongEdge);
THPDFPageBoundary = (pbMediaBox, pbCropBox, pbBleedBox, pbTrimBox, pbArtBox);
THPDFInitialZoom = (
  FitNone, FitPage, FitWidth, FitHeight, FitBox, FitBoxWidth, FitBoxHeight,
  Zoom50, Zoom75, Zoom100, Zoom125, Zoom150, Zoom200
);

THPDFViewerPreference = (
  vpHideToolbar, vpHideMenubar, vpHideWindowUI, vpFitWindow, vpCenterWindow,
  vpDisplayDocTitle, vpDirection, vpNonFullScreenPageMode, vpPrintScaling,
  vpDuplex, vpPickTrayByPDFSize, vpNumCopies, vpPrintArea, vpPrintClip,
  vpViewArea, vpViewClip
);

THPDFViewerPreferences = set of THPDFViewerPreference;

Supported ViewerPreferences

Option	Companion Property	Description
vpHideToolbar	None	Hide the viewer toolbar.
vpHideMenubar	None	Hide the viewer menu bar.
vpHideWindowUI	None	Hide UI elements such as scroll bars and navigation controls.
vpFitWindow	None	Resize the document window to fit the first displayed page.
vpCenterWindow	None	Center the document window on the screen.
vpDisplayDocTitle	Title	Display the document title instead of the file name in the viewer caption.
vpDirection	Direction	Store the predominant reading order using `LeftToRight` or `RightToLeft`.
vpNonFullScreenPageMode	NonFullScreenPageMode	Choose the page mode to use after leaving full-screen mode.
vpPrintScaling	PrintScaling	Choose `psNone` or `psAppDefault` for default print scaling.
vpDuplex	Duplex	Choose simplex or duplex printing behavior.
vpPickTrayByPDFSize	None	Request printer tray selection based on the PDF page size.
vpNumCopies	NumCopies	Store the suggested print copy count.
vpPrintArea	PrintArea	Select the page boundary used for print rendering.
vpPrintClip	PrintClip	Select the page boundary used for print clipping.
vpViewArea	ViewArea	Page boundary used for the on-screen view area (PDF 1.4 12.2). Available since HotPDF v2.29.0.
vpViewClip	ViewClip	Page boundary used for the on-screen view clipping (PDF 1.4 12.2). Available since HotPDF v2.29.0.

Companion Property Values

These properties are written only when the matching ViewerPreferences flag is enabled.

Property	Values
Direction	LeftToRight, RightToLeft
NonFullScreenPageMode	nfpmUseNone, nfpmUseOutlines, nfpmUseThumbs, nfpmUseOC, nfpmUseAttachments
PrintScaling	psNone, psAppDefault
Duplex	dupSimplex, dupDuplexFlipShortEdge, dupDuplexFlipLongEdge
PrintArea / PrintClip / ViewArea / ViewClip	pbMediaBox, pbCropBox, pbBleedBox, pbTrimBox, pbArtBox

InitialZoom Integration

InitialZoom complements ViewerPreferences by controlling the initial page display mode when the document is opened.

Default: Since HotPDF v2.3.11 the default value is FitHeight (PDF /FitV destination), so generated documents open with each page fitted to the viewer's window height. Set InitialZoom to FitNone to omit the OpenAction and let the viewer fall back to its own default zoom.

// Complete document presentation setup
HotPDF.ViewerPreferences := [vpFitWindow, vpCenterWindow, vpDisplayDocTitle];
HotPDF.InitialZoom := FitWidth;

// Technical document setup
HotPDF.ViewerPreferences := [vpDisplayDocTitle, vpPrintScaling];
HotPDF.InitialZoom := Zoom125;

// Presentation mode
HotPDF.ViewerPreferences := [vpFitWindow, vpHideToolbar, vpHideMenubar];
HotPDF.InitialZoom := FitPage;

Implementation Example

var
  VPref: THPDFViewerPreferences;
begin
  VPref := [vpFitWindow, vpCenterWindow, vpDisplayDocTitle];

  if EnableDirection then
  begin
    Include(VPref, vpDirection);
    HotPDF.Direction := RightToLeft;
  end;

  if EnablePrintScaling then
  begin
    Include(VPref, vpPrintScaling);
    HotPDF.PrintScaling := psNone;
  end;

  HotPDF.ViewerPreferences := VPref;
  HotPDF.InitialZoom := FitWidth;
end;

Compatibility Notes

Adobe Reader/Acrobat: Usually provides the most complete ViewerPreferences support.
Other Viewers: Support varies because these values are preferences, not hard requirements.
Graceful Degradation: Unsupported settings should be ignored safely by conforming viewers.

Demo Applications

The following demos are synchronized with the current library support:

Demo\Delphi\ViewerPref
Demo\CBuilder\ViewerPref