property TabStop: Boolean; // published, inherited from TWinControl
When TabStop is True the PDF viewer joins the form's tab cycle. Pressing Tab while another control on the form has focus eventually moves focus into the viewer, after which keyboard shortcuts such as Page Up / Page Down, the arrow keys for scrolling and the find-shortcut handler defined in OnKeyDown all become active.
Keeping the viewer focusable is important for accessibility: screen readers and keyboard-only users need to reach the document area to step through pages or trigger text selection by holding Shift with the arrow keys. The default value for a published TabStop on a TScrollingWinControl descendant is True.
Setting TabStop := False removes the viewer from the tab order; the user can still click into it to scroll with the mouse, but the keyboard cannot focus it without an explicit PdfView1.SetFocus call. This is sometimes useful when the viewer is purely decorative — for example a preview pane next to a list of search results.
TabStop and TabOrder are saved to the form file.AllowUserTextSelection only reacts to mouse drags and to keyboard input once the viewer has focus, so disabling TabStop effectively forces users to click before they can select text by keyboard.OnEnter / OnExit in combination with TabStop to update toolbars (for example enabling a Copy button only when the viewer is the active control).
// Make the viewer fully keyboard-accessible and the first tab stop
procedure TForm1.FormCreate(Sender: TObject);
begin
PdfView1.TabStop := True;
PdfView1.TabOrder := 0;
PdfView1.OnKeyDown := PdfView1KeyDown;
end;
procedure TForm1.PdfView1KeyDown(Sender: TObject;
var Key: Word; Shift: TShiftState);
begin
if (Key = VK_F3) then PdfView1.FindNext
else if (Key = Ord('C')) and (ssCtrl in Shift) then
Clipboard.AsText := PdfView1.SelectedText;
end;