OnMouseWheel event

Fired when the wheel is rotated over the view. 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: implement Ctrl+wheel zoom or replace the default page scroll. 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.OnMouseWheel := MyHandler
• Combine it with the matching Set Cursor / Set Caret calls on TPdfView to keep visual feedback in sync