# Migrating pre-release applications

YASL 0.1 has no stable source or binary compatibility promise. Rebuild all
consumers against the matching installed headers and library after updating.
The following changes replace backend-specific input fields with a common
contract. See the [application guide](guide.md) for the full input workflow.

## Keyboard events

| Previous use | Replacement |
| --- | --- |
| Linux keysym or Cocoa virtual keycode in `key.key` | Portable physical `YASL_KEY_*` identity |
| `key.base` | `key.native_code`, with explicit backend-specific encoding |
| `key.keypad` | Distinct `YASL_KEY_KP_*` identities |
| Advisory `key.text` character | `YASL_INPUT_TEXT` UTF-8 payload for insertion |
| Layout label from a keysym | Optional `key.codepoint` and `key.shifted` Unicode scalars |

Replace magic numbers and X11 symbols with named keys. For example, a quit
command checks `key.key == YASL_KEY_ESCAPE` on a press. `YASL_KEY_A` means the
US A position on every layout; use layout labels when a command should follow
the printed letter instead. Do not cast key identities to characters. Keypad
Enter and ordinary Enter now have distinct identities without a separate flag.

Text comes only from `YASL_INPUT_TEXT`. Handle its byte length, copy it when
retaining it after the next successful poll, and allow multiple characters per
commit. Cocoa sends key events through its text input manager; Wayland emits
ordinary XKB text and locale compose results in addition to IME commits.

## Scroll events

Replace `scroll_lines`, `scroll_delta`, and scroll button numbers with
`mouse.scroll.x` and `.y` when `mouse.kind == YASL_PTR_SCROLL`. These double
values are fractional line offsets, positive right/down on every backend.
Do not infer scroll direction from `button`. One event may include both axes.
Remove backend-specific sign inversions and whole-line casts; multiply the
offset by your application's preferred pixels per line instead.

X11 still supplies whole wheel steps. Wayland high-resolution wheels and smooth
offsets, and Cocoa precise scrolling, preserve fractions. Device acceleration
and system preferences still affect the native offsets.