✨ hardware cursor positioning via text() caret - #103
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Adds a normative paragraph to §7.6 stating that a `caret` declaration on empty content places the cursor at the text element's origin — the cell where the first code point of `content` would be drawn if it were a single space. Frames the empty-content case as a rendering commitment the renderer must honor, without prescribing mechanism.
Substitute a single-space slice for empty text nodes carrying a caret declaration so the layout engine emits one cell of geometry at the text element's origin. Replaces the v1-limitation test with one asserting the spec's outcome (CUP to row 1, col 1 + DECTCEM-show).
The `value || " "` fallback previously worked around the renderer's inability to attach a caret to an empty text node. That case is now handled directly by the renderer, so the example can pass the raw value through and let the caret resolve at the input box's origin.
Precompute the caret's byte offset within its text node at OP_TEXT decode time, then place the caret cell as a side effect of render_text's existing walk: at the top of each iteration, if the current pointer matches the target byte offset, record the cell. Two edge cases fall out of the same mechanism. A slice whose first byte is already past the target (Clay dropped whitespace at the wrap seam) snaps the caret to the slice's origin — the start of the next wrapped line — rather than orphaning it off the end of the previous line. And the trailing cell of the last walked caret slice is remembered as the end-of-content fallback for offset == content-length. Deletes locate_caret, which walked slices with a code-point accumulator that diverged from the caller's original offset whenever the layout engine's wrap pass either dropped or retained-off-screen the seam whitespace. Adds tests covering both wrap-boundary cases and tightens the previously-lax "correct wrapped line" assertion to an exact cell.
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What does this PR do?
Adds a
caret?: numberproperty to thetext()directive. When declared, the renderer positions the terminal's native cursor at the code-point offset within the text and manages cursor visibility automatically across frames.Motivation: building a text input on top of the renderer requires the terminal cursor to track the insertion point and disappear when no input is focused. The cell where the caret sits depends on the text's layout and wrapping — information the renderer already has and the caller does not.
While painting a synthetic caret is always a possibility, the native caret is almost always going to be preferable.