събитие OnMouseDown

Fired when the user presses a mouse button 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: begin a custom selection box, start panning, or capture coordinates for a "go to this annotation" feature. 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 that 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.OnMouseDown := MyHandler.
• Combine with the matching Set Cursor / Set Caret calls on TPdfView to keep visual feedback synchronized.