isSelectionActive

True while text selection owns the pointer, and while the selection it produced is still on screen.

PdfView yields to it: one-finger pan and the list/pager's own scrolling are both suppressed while this is set, so a drag that began as a selection never slides the page out from under the finger, and the page stays put afterwards while the user acts on the selected text. Two-finger pinch zoom is unaffected.

It goes true the instant the long press fires, which is BEFORE selection exists (the hit test and the text extraction still have to run), and it stays true after the finger lifts. clearSelection turns it off, and so does a long press that never anchored anything (an empty page region), which releases the lock when that drag ends.