Visible property

Setting Visible := False removes the viewer from the screen without destroying it; the underlying PDFium document, current page, zoom factor and selection state are all preserved. When the property is set back to True the cached state is re-displayed immediately and a repaint is queued automatically.

Hiding the viewer is the canonical way to swap between alternative document views (for example a thumbnail-only mode and the full reader) without recreating the component. Because PDFium page handles are kept open while hidden, the user can toggle quickly between views with no reload delay.

Visibility also propagates through container controls: if the parent panel is invisible, the viewer is invisible regardless of its own setting. The framework still raises OnShow / OnHide notifications on the form so application code can synchronise toolbars accordingly.

• Persistent property — saved to the form file. Defaults to True on a published TWinControl.
• VCL and LCL share the same semantics; LCL additionally pushes the visibility state to the underlying widget-set handle.
• Hiding the viewer does not close the document. To free the PDF and reclaim memory call PdfView1.Active := False or Pdf1.Close.
• If you also want to skip background rendering while hidden, set AsyncRendering := False beforehand — otherwise queued rendering may continue briefly.