adding source highlighting class

Author: omarArm

src/desktop/extension.ts

@@ -27,6 +27,7 @@ import { GenericCommands } from '../features/generic-commands';
 import { ComponentViewer } from '../views/component-viewer/component-viewer';
 import { ComponentViewerTreeDataProvider } from '../views/component-viewer/component-viewer-tree-view';
 import { CorePeripherals } from '../views/core-peripherals/core-peripherals';
+import {SourceFileHighlighting} from '../features/source-file-highlighting/source-file-highlighting';
 
 const BUILTIN_TOOLS_PATHS = [
     'tools/pyocd/pyocd',
@@ -58,6 +59,7 @@ export const activate = async (context: vscode.ExtensionContext): Promise<void>
     corePeripheralsTreeDataProvider = new ComponentViewerTreeDataProvider();
     const componentViewer = new ComponentViewer(context, componentViewerTreeDataProvider);
     const corePeripherals = new CorePeripherals(context, corePeripheralsTreeDataProvider);
+    const sourceFileHighlighting = new SourceFileHighlighting(context);
 
     addToolsToPath(context, BUILTIN_TOOLS_PATHS);
     // Activate generic commands
@@ -69,6 +71,7 @@ export const activate = async (context: vscode.ExtensionContext): Promise<void>
     cpuStates.activate(gdbtargetDebugTracker);
     cpuStatesCommands.activate(context, cpuStates);
     cpuStatesStatusBarItem.activate(context, cpuStates);
+    sourceFileHighlighting.activate();
     // Live Watch view
     logger.debug('Activating Live Watch Tree Data Provider');
     if (!await liveWatchTreeDataProvider.activate(gdbtargetDebugTracker)) {

src/features/source-file-highlighting/source-file-highlighting.ts

@@ -0,0 +1,79 @@
+/**
+ * Copyright 2026 Arm Limited
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import * as vscode from 'vscode';
+import { DebugProtocol } from '@vscode/debugprotocol';
+
+export class SourceFileHighlighting {
+    private activeDebugSession: vscode.DebugSession | undefined;
+    private context: vscode.ExtensionContext;
+    private executableLineDecorator = vscode.window.createTextEditorDecorationType({
+        // turn it red for testing
+        backgroundColor: 'rgba(255, 0, 0, 0.3)',
+        // only highlight the margin of the line to avoid obscuring code
+        isWholeLine: true,
+    });
+
+    constructor(context: vscode.ExtensionContext) {
+        this.context = context;
+    }
+
+    public activate(): void {
+        this.registerToTrackerEvents();
+        vscode.window.onDidChangeActiveTextEditor(editor => {
+            this.handleOnDidChangeActiveTextEditor(editor);
+        });
+    }
+
+    private registerToTrackerEvents(): void {
+        const onDidChangeActiveDebugSessionDisposable = vscode.debug.onDidChangeActiveDebugSession(session => {
+            this.activeDebugSession = session;
+        });
+        this.context.subscriptions.push(onDidChangeActiveDebugSessionDisposable);
+    }
+
+    private async handleOnDidChangeActiveTextEditor(editor: vscode.TextEditor | undefined): Promise<void> {
+        if (!editor || !this.activeDebugSession) {
+            return;
+        }
+        const breakpointLocations = await this.getBreakpointLocations(editor);
+        if (!breakpointLocations) {
+            return;
+        }
+        const executableLines = new Set(breakpointLocations.breakpoints.map((bp: DebugProtocol.BreakpointLocation) => bp.line));
+        const decorations: vscode.DecorationOptions[] = Array.from(executableLines).map((exeline: number) => {
+            const line = exeline - 1; // Convert to 0-based index
+            return {
+                range: new vscode.Range(line, 0, line, 0),
+            };
+        });
+        editor.setDecorations(this.executableLineDecorator, decorations);
+    }
+
+    private async getBreakpointLocations(editor: vscode.TextEditor): Promise<DebugProtocol.BreakpointLocationsResponse['body'] | void> {
+        if(editor.document.uri.scheme !== 'file') {
+            return;
+        }
+        const currentSourceFile = editor.document.fileName;
+        const args : DebugProtocol.BreakpointLocationsArguments = {
+            source: { path: currentSourceFile },
+            line: 1,
+            endLine: editor.document.lineCount, // Requesting breakpoint locations for the whole file
+        };
+        const breakpointLocations = await this.activeDebugSession?.customRequest('breakpointLocations', args);
+        return breakpointLocations;
+    }
+}