OnPageChange event

Fired when the current page changes for any reason. The Sender parameter references the TPdfView instance that raised the event, so a single handler can serve multiple views by inspecting Sender

Typical uses include: update an external "Page X of Y" label or sync a side-by-side thumbnail panel. Because the handler runs on the VCL main thread, you can update form controls and call other VCL APIs directly

Handlers must return quickly — PDFium rendering and form filling occur on the same thread, and any delay here postpones the next page repaint

• Set TabStop to True if you want this control to participate in tab-key focus traversal so keyboard events are delivered
• When you assign this event at design time, the IDE generates a stub procedure on the form; you can also assign it at run time with PdfView1.OnPageChange := MyHandler
• Combine it with the matching Set Cursor / Set Caret calls on TPdfView to keep visual feedback in sync