@@ -15,6 +15,7 @@ import { DartHoverProvider } from "./dart_hover_provider";
 import { DartIndentFixer } from "./dart_indent_fixer";
 import { DartWorkspaceSymbolProvider } from "./dart_workspace_symbol_provider";
 import { FileChangeHandler } from "./file_change_handler";
+import { OpenFileTracker } from "./open_file_tracker";
 import { ServerStatusNotification } from "./analysis_server_types";
 
 const DART_MODE: vscode.DocumentFilter = { language: "dart", scheme: "file" };
@@ -80,6 +81,13 @@ export function activate(context: vscode.ExtensionContext) {
 	context.subscriptions.push(vscode.workspace.onDidCloseTextDocument(td => fileChangeHandler.onDidCloseTextDocument(td)));
 	vscode.workspace.textDocuments.forEach(td => fileChangeHandler.onDidOpenTextDocument(td)); // Handle already-open files.
 
+	// Hook open/active file changes so we can set priority files with the analyzer.
+	let openFileTracker = new OpenFileTracker(analyzer);
+	context.subscriptions.push(vscode.workspace.onDidOpenTextDocument(td => openFileTracker.trackFile(td)));
+	context.subscriptions.push(vscode.workspace.onDidCloseTextDocument(td => openFileTracker.untrackFile(td)));
+	context.subscriptions.push(vscode.window.onDidChangeActiveTextEditor(e => openFileTracker.updatePriorityFiles()));
+	openFileTracker.trackFile(vscode.window.activeTextEditor.document); // Handle already-open files.
+
 	// Hook active editor change to reset Dart indenting.
 	let dartIndentFixer = new DartIndentFixer();
 	context.subscriptions.push(vscode.window.onDidChangeActiveTextEditor(td => dartIndentFixer.onDidChangeActiveTextEditor(td)));
 
@@ -0,0 +1,43 @@
+"use strict";
+
+import { window, workspace, TextDocument } from "vscode";
+import { Analyzer } from "./analyzer";
+import * as util from "./utils";
+
+export class OpenFileTracker {
+	private analyzer: Analyzer;
+	private openDocuments: TextDocument[] = []; // Don't store filenames, can be renamed!
+	constructor(analyzer: Analyzer) {
+		this.analyzer = analyzer;
+	}
+
+	trackFile(doc: TextDocument) {
+		this.openDocuments.push(doc);
+		this.updatePriorityFiles();
+	}
+
+	untrackFile(doc: TextDocument) {
+		let index = this.openDocuments.indexOf(doc);
+		if (index >= 0) {
+			this.openDocuments.splice(index, 1);
+			// TODO: When a document is closed this actually fires before the visibleTextEditor
+			// is removed, so we will still send the file until the next go. This isn't a big deal
+			// but maybe can be improved later.
+			this.updatePriorityFiles();
+		}
+	}
+
+	updatePriorityFiles() {
+		let visibleDocuments = window.visibleTextEditors.map(e => e.document);
+		let otherOpenDocuments = this.openDocuments.filter(doc => visibleDocuments.indexOf(doc) == -1);
+
+		let priorityDocuments = visibleDocuments.concat(otherOpenDocuments).filter(d => util.isDartLike(d));
+		let priorityFiles = priorityDocuments.map(doc => doc.fileName);
+
+		console.log("Sending: " + priorityFiles.join(", "));
+
+		this.analyzer.analysisSetPriorityFiles({
+			files: priorityFiles
+		})
+	}
+}