Resolve a left-click at pos to the tool that selects whatever is under it: a
route, a child-block pin, or a shape (block / port / area / image / text).
Returns None when nothing selectable is there — empty canvas, or a route
label (left for the double-click rename). Shared by every selecting tool so a
click always lands on the clicked object, even when something else is already
selected.
Resolve a drag started at pos to the tool that moves/edits whatever is under
it: a title, block tag, port, child-block pin, route label, route edge, or a
shape body — falling back to a marquee on empty canvas. Always returns an
action. Shared by every selecting tool so a drag begins on the grabbed object
immediately, even when something else is already selected.
The text editor a double-click at pos should open, if it landed on an
editable label: a title, block tag, pin name/type/tag, route label, or a text
box. Shared by every selecting tool so a double-click always opens the right
editor regardless of what is currently selected — including committing one
in-place edit and handing straight off to another thing double-clicked.
Whether pos lands on any in-place-editor target — an editable label or a
text box — regardless of whether that target is currently editable. Used to
tell an uneditable target (e.g. a locked block’s type) from empty canvas so a
double-click on it is consumed rather than treated as a fit-to-view.
Toggle shape into the shape selection base (shift-click): add it if absent,
remove it if present. Resolves to the right tool for the resulting size —
nothing → select tool, one → block-style single selection, many → multi-select.