Fix TAB failing to re-expand collapsed tool blocks (#166)#168
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When a user expands a collapsed tool block, reads the output, then presses TAB to collapse it again, the next TAB to re-expand silently does nothing. Instead of toggling, Emacs jumps to an unrelated heading somewhere else in the buffer. The problem is that collapsing places the cursor at the exact end position of the tool overlay. Emacs overlays use half-open intervals: overlays-at considers a position inside [start, end) but not at end itself. So the subsequent TAB finds no tool overlay at point and falls through to outline-cycle, which navigates to the nearest markdown heading---appearing to the user as a random jump. The trigger condition is that original-pos (where TAB was pressed in the expanded view) exceeds the collapsed overlay's end, so the clamping expression (min original-pos (cdr new-bounds)) yields exactly the overlay boundary. This happens reliably when collapsing from the [-] button or from any line in the lower portion of the expanded output. Fix this by clamping to (1- end) rather than end, keeping the cursor on the last character inside the overlay. One character of difference, but it preserves the invariant that point remains inside the tool block after every toggle.
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Fixes #166.
When a user expands a collapsed tool block, reads the output, then presses TAB to collapse it again, the next TAB to re-expand silently does nothing — Emacs jumps to an unrelated heading instead.
Root cause: Collapsing places the cursor at the exact end position of the tool overlay. Emacs overlays use half-open intervals:
overlays-atconsiders a position inside[start, end)but not atenditself. The subsequent TAB finds no tool overlay at point and falls through tooutline-cycle, which navigates to the nearest markdown heading.Trigger: Collapsing from the
[-]button or any line in the lower portion of the expanded output. The clamping expression(min original-pos (cdr new-bounds))yields exactly the overlay boundary when the cursor was deep in the expanded content.Fix: Clamp to
(1- end)rather thanend, keeping the cursor on the last character inside the overlay.Tests: Unit test for the exact boundary condition, plus a GUI test exercising the full expand → collapse → re-expand cycle with tree-sitter and font-lock active.