slintpad: Fix showDocument sent from LSP

The latest version of the monaco LS integration has changed how
to show documents in an editor again. We would need to include even more
services to make it automatically handle the `showDocument` the LS sends.

Instead just handle the request going around the "official" API.

tools/slintpad/src/editor_widget.ts

@@ -247,6 +247,11 @@ class EditorPaneWidget extends Widget {
         monaco.editor.onDidCreateModel((model: monaco.editor.ITextModel) =>
             this.add_model_listener(model),
         );
+
+        lsp.show_document_callback = (uri, position) => {
+            this.goto_position(uri, position);
+            return true;
+        };
     }
 
     async map_url(url_: string): Promise<string | undefined> {

tools/slintpad/src/lsp.ts

@@ -10,6 +10,7 @@ import {
     NotificationMessage,
     RequestMessage,
     ResponseMessage,
+    ShowDocumentParams,
 } from "vscode-languageclient";
 import { MonacoLanguageClient } from "monaco-languageclient";
 
@@ -19,12 +20,18 @@ import {
     MessageReader,
     MessageWriter,
 } from "vscode-languageserver-protocol/browser";
+import { LspPosition } from "./lsp_integration";
 
 import slint_init, * as slint_preview from "@lsp/slint_lsp_wasm.js";
 
 import type { ResourceUrlMapperFunction } from "@lsp/slint_lsp_wasm.js";
 export { ResourceUrlMapperFunction };
 
+export type ShowDocumentCallback = (
+    _uri: string,
+    _posiiton: LspPosition,
+) => boolean;
+
 function createLanguageClient(
     transports: MessageTransports,
 ): MonacoLanguageClient {
@@ -107,6 +114,8 @@ export class Lsp {
     #lsp_client: MonacoLanguageClient | null = null;
     #file_reader: FileReader | null = null;
 
+    #show_document_callback: ShowDocumentCallback;
+
     readonly #lsp_worker: Worker;
     readonly #lsp_reader: MessageReader;
     readonly #lsp_writer: MessageWriter;
@@ -115,6 +124,8 @@ export class Lsp {
 
     constructor(worker: Worker) {
         this.#lsp_worker = worker;
+        this.#show_document_callback = (_uri, _pos) => true;
+
         const reader = new FilterProxyReader(
             new BrowserMessageReader(this.#lsp_worker),
             (data: Message) => {
@@ -156,6 +167,29 @@ export class Lsp {
 
                     return true;
                 }
+                if ((data as RequestMessage).method == "window/showDocument") {
+                    const request = data as RequestMessage;
+                    const params = request.params as ShowDocumentParams;
+
+                    const selection = params.selection?.start || {
+                        line: 1,
+                        character: 1,
+                    };
+
+                    const success = this.#show_document_callback(
+                        params.uri,
+                        selection,
+                    );
+
+                    writer.write({
+                        jsonrpc: request.jsonrpc,
+                        id: request.id,
+                        result: { success: success },
+                        error: undefined,
+                    } as ResponseMessage);
+
+                    return true;
+                }
                 return false;
             },
         );
@@ -181,6 +215,10 @@ export class Lsp {
         this.#file_reader = fr;
     }
 
+    set show_document_callback(cb: ShowDocumentCallback) {
+        this.#show_document_callback = cb;
+    }
+
     private read_url(url: string): Promise<string> {
         try {
             return this.#file_reader?.(url) ?? Promise.reject();