Omzetting naar stdio.

STDIO-PROTOCOL.md

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+# racket-webview stdio protocol
+
+The Qt backend is a child process of the Racket process. Communication uses
+UTF-8 JSON records, one compact JSON object per line.
+
+- stdin of `rktwebview_prg`: commands from Racket
+- stdout of `rktwebview_prg`: handshake, results, and events
+- stderr of `rktwebview_prg`: diagnostics only
+
+No diagnostic text may be written to stdout.
+
+## Compatibility
+
+The existing numeric command identifiers in `rkt_protocol.h` and their JSON
+payload objects are retained. The stdio transport adds only an envelope and a
+request identifier. The request identifier allows replies to be matched even
+when several Racket threads issue commands concurrently.
+
+## Handshake
+
+The backend writes this record after Qt has been initialized and the command
+reader has started:
+
+```json
+{"type":"ready","protocol":1}
+```
+
+Racket must not send application commands until this record has been received.
+
+## Command
+
+```json
+{"type":"command","id":17,"command":6,"data":{"wv":1,"url":"https://example.test"}}
+```
+
+Fields:
+
+- `id`: positive request identifier chosen by Racket
+- `command`: existing numeric command from `rkt_protocol.h`
+- `data`: existing command payload object
+
+## Result
+
+```json
+{"type":"result","id":17,"result":0,"data":null}
+```
+
+`result` has the same meaning as before. Depending on the command it can be a
+`result_t`, a handle, a context identifier, a window-state value, or a metric.
+For `CMD_CALL_JS`, `data` contains the JavaScript result string.
+
+Every command now receives a result record, including commands that previously
+returned `void`, such as close and setting the OU token. Their public Racket
+return values remain unchanged.
+
+## Event
+
+```json
+{"type":"event","wv":1,"data":"{\"event\":\"page-loaded\",...}"}
+```
+
+The `data` field is the original event JSON string. It is deliberately not
+restructured by the transport, so existing event parsing remains unchanged.
+Events are independent of command results.
+
+## Shutdown
+
+A normal shutdown sends `CMD_QUIT`, waits for its result, closes the child's
+stdin, and waits for the child process. If the Racket process terminates
+unexpectedly, the operating system closes the pipe; EOF on stdin makes the Qt
+backend close all windows and quit.