webui: implement explicit initial render detection using State.message_count
Add explicit initial load completion detection to SketchTimeline component using
State.message_count to determine when all existing messages have been loaded
and the timeline is ready for initial render.
Implementation Changes:
1. DataManager Enhancement (data.ts):
- Add expectedMessageCount and isInitialLoadComplete state tracking
- Add 'initialLoadComplete' event type to DataManagerEventType union
- Add checkInitialLoadComplete() method to validate completion state
- Add handleInitialLoadComplete() event emission with message counts
- Handle empty conversation edge case (message_count: 0) with immediate completion
- Reset initial load state on connection establishment to handle reconnection
- Add getIsInitialLoadComplete() and getExpectedMessageCount() getters
2. Timeline Component Enhancement (sketch-timeline.ts):
- Add isInitialLoadComplete state property for render control
- Add dataManager property reference for event listener setup
- Add handleInitialLoadComplete() event handler with console logging
- Update render logic to show loading indicator until initial load complete
- Apply 'view-initialized' CSS class when initial load completes
- Only render messages and thinking indicator after initial load completion
- Set up DataManager event listeners in updated() lifecycle hook
- Clean up event listeners in disconnectedCallback() lifecycle hook
3. App Shell Integration (sketch-app-shell.ts):
- Pass dataManager reference to sketch-timeline component property
- Enable timeline component to receive initial load completion events
- Maintain existing data flow while adding explicit completion detection
4. Demo Mock Enhancement (handlers.ts):
- Initialize currentState with correct message_count based on initial messages
- Ensure proper message_count synchronization in SSE stream simulation
- Handle empty conversation demo scenario with accurate state
5. Enhanced CSS Styling (sketch-timeline.ts):
- Add opacity-based transitions for message appearance
- Show loading indicator before initial completion
- Hide message content until view-initialized class is applied
- Smooth transition from loading to content display
Technical Benefits:
- Eliminates reliance on implicit 'first message means streaming started' detection
- Provides explicit completion signal when all existing messages are loaded
- Handles edge cases like empty conversations (0 messages) immediately
- Prevents flash of incomplete content during initial load
- Enables proper loading states and smooth transitions
- Supports reconnection scenarios with state reset
User Experience Improvements:
- Clear loading indicator until conversation is fully loaded
- Smooth transition from loading to content display
- No flash of partial message lists during initial load
- Consistent behavior across different conversation sizes
- Better feedback during network delays or large conversation loads
Edge Case Handling:
- Empty conversations (message_count: 0) marked complete immediately
- Messages arriving before state handled gracefully
- Reconnection scenarios reset initial load detection
- Race conditions between state and message delivery resolved
This replaces the implicit initial load detection with explicit State.message_count
based completion detection, providing more reliable initial render timing and
better user experience during conversation loading.
Co-Authored-By: sketch <hello@sketch.dev>
Change-ID: s5126c2705d6ad6bak
diff --git a/webui/src/web-components/sketch-timeline.test.ts b/webui/src/web-components/sketch-timeline.test.ts
index 8384453..e803a2e 100644
--- a/webui/src/web-components/sketch-timeline.test.ts
+++ b/webui/src/web-components/sketch-timeline.test.ts
@@ -2,6 +2,51 @@
import { SketchTimeline } from "./sketch-timeline";
import { AgentMessage } from "../types";
+// Mock DataManager class that mimics the real DataManager interface
+class MockDataManager {
+ private eventListeners: Map<string, Array<(...args: any[]) => void>> =
+ new Map();
+ private isInitialLoadComplete: boolean = false;
+
+ constructor() {
+ this.eventListeners.set("initialLoadComplete", []);
+ }
+
+ addEventListener(event: string, callback: (...args: any[]) => void): void {
+ const listeners = this.eventListeners.get(event) || [];
+ listeners.push(callback);
+ this.eventListeners.set(event, listeners);
+ }
+
+ removeEventListener(event: string, callback: (...args: any[]) => void): void {
+ const listeners = this.eventListeners.get(event) || [];
+ const index = listeners.indexOf(callback);
+ if (index > -1) {
+ listeners.splice(index, 1);
+ }
+ }
+
+ getIsInitialLoadComplete(): boolean {
+ return this.isInitialLoadComplete;
+ }
+
+ triggerInitialLoadComplete(
+ messageCount: number = 0,
+ expectedCount: number = 0,
+ ): void {
+ this.isInitialLoadComplete = true;
+ const listeners = this.eventListeners.get("initialLoadComplete") || [];
+ // Call each listener with the event data object as expected by the component
+ listeners.forEach((listener) => {
+ try {
+ listener({ messageCount, expectedCount });
+ } catch (e) {
+ console.error("Error in event listener:", e);
+ }
+ });
+ }
+}
+
// Helper function to create mock timeline messages
function createMockMessage(props: Partial<AgentMessage> = {}): AgentMessage {
return {
@@ -42,9 +87,12 @@
}
test("renders empty state when no messages", async ({ mount }) => {
+ const mockDataManager = new MockDataManager();
+
const timeline = await mount(SketchTimeline, {
props: {
messages: [],
+ dataManager: mockDataManager,
},
});
@@ -56,28 +104,46 @@
test("renders messages when provided", async ({ mount }) => {
const messages = createMockMessages(5);
+ const mockDataManager = new MockDataManager();
const timeline = await mount(SketchTimeline, {
props: {
messages,
+ dataManager: mockDataManager,
},
});
+ // Directly set the isInitialLoadComplete state to bypass the event system for testing
+ await timeline.evaluate((element: SketchTimeline) => {
+ (element as any).isInitialLoadComplete = true;
+ element.requestUpdate();
+ return element.updateComplete;
+ });
+
await expect(timeline.locator(".timeline-container")).toBeVisible();
await expect(timeline.locator("sketch-timeline-message")).toHaveCount(5);
});
test("shows thinking indicator when agent is active", async ({ mount }) => {
const messages = createMockMessages(3);
+ const mockDataManager = new MockDataManager();
const timeline = await mount(SketchTimeline, {
props: {
messages,
llmCalls: 1,
toolCalls: ["thinking"],
+ dataManager: mockDataManager,
},
});
+ // Directly set the isInitialLoadComplete state to bypass the event system for testing
+ await timeline.evaluate((element: SketchTimeline) => {
+ (element as any).isInitialLoadComplete = true;
+ element.requestUpdate();
+ return element.updateComplete;
+ });
+
await expect(timeline.locator(".thinking-indicator")).toBeVisible();
await expect(timeline.locator(".thinking-bubble")).toBeVisible();
await expect(timeline.locator(".thinking-dots .dot")).toHaveCount(3);
@@ -89,13 +155,22 @@
createMockMessage({ idx: 1, content: "Hidden message", hide_output: true }),
createMockMessage({ idx: 2, content: "Visible message 2" }),
];
+ const mockDataManager = new MockDataManager();
const timeline = await mount(SketchTimeline, {
props: {
messages,
+ dataManager: mockDataManager,
},
});
+ // Directly set the isInitialLoadComplete state to bypass the event system for testing
+ await timeline.evaluate((element: SketchTimeline) => {
+ (element as any).isInitialLoadComplete = true;
+ element.requestUpdate();
+ return element.updateComplete;
+ });
+
// Should only show 2 visible messages
await expect(timeline.locator("sketch-timeline-message")).toHaveCount(2);
@@ -117,14 +192,23 @@
mount,
}) => {
const messages = createMockMessages(50);
+ const mockDataManager = new MockDataManager();
const timeline = await mount(SketchTimeline, {
props: {
messages,
initialMessageCount: 10,
+ dataManager: mockDataManager,
},
});
+ // Directly set the isInitialLoadComplete state to bypass the event system for testing
+ await timeline.evaluate((element: SketchTimeline) => {
+ (element as any).isInitialLoadComplete = true;
+ element.requestUpdate();
+ return element.updateComplete;
+ });
+
// Should only render the most recent 10 messages initially
await expect(timeline.locator("sketch-timeline-message")).toHaveCount(10);
@@ -139,15 +223,24 @@
test("handles viewport expansion correctly", async ({ mount }) => {
const messages = createMockMessages(50);
+ const mockDataManager = new MockDataManager();
const timeline = await mount(SketchTimeline, {
props: {
messages,
initialMessageCount: 10,
loadChunkSize: 5,
+ dataManager: mockDataManager,
},
});
+ // Directly set the isInitialLoadComplete state to bypass the event system for testing
+ await timeline.evaluate((element: SketchTimeline) => {
+ (element as any).isInitialLoadComplete = true;
+ element.requestUpdate();
+ return element.updateComplete;
+ });
+
// Initially shows 10 messages
await expect(timeline.locator("sketch-timeline-message")).toHaveCount(10);
@@ -174,14 +267,23 @@
mount,
}) => {
const messages = createMockMessages(50);
+ const mockDataManager = new MockDataManager();
const timeline = await mount(SketchTimeline, {
props: {
messages,
initialMessageCount: 10,
+ dataManager: mockDataManager,
},
});
+ // Directly set the isInitialLoadComplete state to bypass the event system for testing
+ await timeline.evaluate((element: SketchTimeline) => {
+ (element as any).isInitialLoadComplete = true;
+ element.requestUpdate();
+ return element.updateComplete;
+ });
+
// Expand viewport
await timeline.evaluate((element: SketchTimeline) => {
(element as any).visibleMessageStartIndex = 10;
@@ -210,13 +312,22 @@
mount,
}) => {
const messages = createMockMessages(10);
+ const mockDataManager = new MockDataManager();
const timeline = await mount(SketchTimeline, {
props: {
messages,
+ dataManager: mockDataManager,
},
});
+ // Directly set the isInitialLoadComplete state to bypass the event system for testing
+ await timeline.evaluate((element: SketchTimeline) => {
+ (element as any).isInitialLoadComplete = true;
+ element.requestUpdate();
+ return element.updateComplete;
+ });
+
// Initially should be pinned to latest (button hidden)
await expect(timeline.locator("#jump-to-latest.floating")).not.toBeVisible();
@@ -233,13 +344,22 @@
test("jump-to-latest button calls scroll method", async ({ mount }) => {
const messages = createMockMessages(10);
+ const mockDataManager = new MockDataManager();
const timeline = await mount(SketchTimeline, {
props: {
messages,
+ dataManager: mockDataManager,
},
});
+ // Directly set the isInitialLoadComplete state to bypass the event system for testing
+ await timeline.evaluate((element: SketchTimeline) => {
+ (element as any).isInitialLoadComplete = true;
+ element.requestUpdate();
+ return element.updateComplete;
+ });
+
// Initialize the scroll tracking flag and set to floating state to show button
await timeline.evaluate((element: SketchTimeline) => {
// Initialize tracking flag
@@ -277,15 +397,18 @@
mount,
}) => {
const messages = createMockMessages(10);
+ const mockDataManager = new MockDataManager();
const timeline = await mount(SketchTimeline, {
props: {
messages,
+ dataManager: mockDataManager,
},
});
- // Simulate loading state
+ // Set initial load complete first, then simulate loading older messages
await timeline.evaluate((element: SketchTimeline) => {
+ (element as any).isInitialLoadComplete = true;
(element as any).isLoadingOlderMessages = true;
element.requestUpdate();
return element.updateComplete;
@@ -300,13 +423,22 @@
test("hides loading indicator when not loading", async ({ mount }) => {
const messages = createMockMessages(10);
+ const mockDataManager = new MockDataManager();
const timeline = await mount(SketchTimeline, {
props: {
messages,
+ dataManager: mockDataManager,
},
});
+ // Set initial load complete so no loading indicator is shown
+ await timeline.evaluate((element: SketchTimeline) => {
+ (element as any).isInitialLoadComplete = true;
+ element.requestUpdate();
+ return element.updateComplete;
+ });
+
// Should not show loading indicator by default
await expect(timeline.locator(".loading-indicator")).not.toBeVisible();
});
@@ -385,23 +517,28 @@
test("cancels loading operations on viewport reset", async ({ mount }) => {
const messages = createMockMessages(50);
+ const mockDataManager = new MockDataManager();
const timeline = await mount(SketchTimeline, {
props: {
messages,
+ dataManager: mockDataManager,
},
});
- // Set loading state
+ // Set initial load complete and then loading older messages state
await timeline.evaluate((element: SketchTimeline) => {
+ (element as any).isInitialLoadComplete = true;
(element as any).isLoadingOlderMessages = true;
(element as any).loadingAbortController = new AbortController();
element.requestUpdate();
return element.updateComplete;
});
- // Verify loading state
- await expect(timeline.locator(".loading-indicator")).toBeVisible();
+ // Verify loading state - should show only the "loading older messages" indicator
+ await expect(timeline.locator(".loading-indicator")).toContainText(
+ "Loading older messages...",
+ );
// Reset viewport (should cancel loading)
await timeline.evaluate((element: SketchTimeline) => {
@@ -440,13 +577,22 @@
timestamp: "2023-01-01T12:00:00Z",
}),
];
+ const mockDataManager = new MockDataManager();
const timeline = await mount(SketchTimeline, {
props: {
messages,
+ dataManager: mockDataManager,
},
});
+ // Directly set the isInitialLoadComplete state to bypass the event system for testing
+ await timeline.evaluate((element: SketchTimeline) => {
+ (element as any).isInitialLoadComplete = true;
+ element.requestUpdate();
+ return element.updateComplete;
+ });
+
const messageElements = timeline.locator("sketch-timeline-message");
// Check order
@@ -463,13 +609,22 @@
createMockMessage({ idx: 1, content: "Second message", type: "agent" }),
createMockMessage({ idx: 2, content: "Third message", type: "user" }),
];
+ const mockDataManager = new MockDataManager();
const timeline = await mount(SketchTimeline, {
props: {
messages,
+ dataManager: mockDataManager,
},
});
+ // Directly set the isInitialLoadComplete state to bypass the event system for testing
+ await timeline.evaluate((element: SketchTimeline) => {
+ (element as any).isInitialLoadComplete = true;
+ element.requestUpdate();
+ return element.updateComplete;
+ });
+
// Check that messages have the expected structure
// The first message should not have a previous message context
// The second message should have the first as previous, etc.
@@ -544,13 +699,22 @@
createMockMessage({ idx: 0, content: "Hidden 1", hide_output: true }),
createMockMessage({ idx: 1, content: "Hidden 2", hide_output: true }),
];
+ const mockDataManager = new MockDataManager();
const timeline = await mount(SketchTimeline, {
props: {
messages,
+ dataManager: mockDataManager,
},
});
+ // Directly set the isInitialLoadComplete state to bypass the event system for testing
+ await timeline.evaluate((element: SketchTimeline) => {
+ (element as any).isInitialLoadComplete = true;
+ element.requestUpdate();
+ return element.updateComplete;
+ });
+
// Should render the timeline structure but with no visible messages
await expect(timeline.locator("sketch-timeline-message")).toHaveCount(0);
@@ -566,13 +730,22 @@
test("handles message array updates correctly", async ({ mount }) => {
const initialMessages = createMockMessages(5);
+ const mockDataManager = new MockDataManager();
const timeline = await mount(SketchTimeline, {
props: {
messages: initialMessages,
+ dataManager: mockDataManager,
},
});
+ // Directly set the isInitialLoadComplete state to bypass the event system for testing
+ await timeline.evaluate((element: SketchTimeline) => {
+ (element as any).isInitialLoadComplete = true;
+ element.requestUpdate();
+ return element.updateComplete;
+ });
+
await expect(timeline.locator("sketch-timeline-message")).toHaveCount(5);
// Update with more messages