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TypeScript

/*---------------------------------------------------------------------------------------------
* Copyright (c) Microsoft Corporation. All rights reserved.
* Licensed under the MIT License. See License.txt in the project root for license information.
*--------------------------------------------------------------------------------------------*/
import mermaid, { MermaidConfig } from 'mermaid';
import { VsCodeApi } from './vscodeApi';
interface PanZoomState {
readonly scale: number;
readonly translateX: number;
readonly translateY: number;
}
export class PanZoomHandler {
private scale = 1;
private translateX = 0;
private translateY = 0;
private isPanning = false;
private hasDragged = false;
private hasInteracted = false;
private startX = 0;
private startY = 0;
private readonly minScale = 0.1;
private readonly maxScale = 5;
private readonly zoomFactor = 0.002;
constructor(
private readonly container: HTMLElement,
private readonly content: HTMLElement,
private readonly vscode: VsCodeApi
) {
this.container = container;
this.content = content;
this.content.style.transformOrigin = '0 0';
this.container.style.overflow = 'hidden';
this.container.style.cursor = 'default';
this.setupEventListeners();
}
/**
* Initializes the pan/zoom state - either restores from saved state or centers the content.
*/
public initialize(): void {
if (!this.restoreState()) {
// Use requestAnimationFrame to ensure layout is updated before centering
requestAnimationFrame(() => {
this.centerContent();
});
}
}
private setupEventListeners(): void {
// Pan with mouse drag
this.container.addEventListener('mousedown', e => this.handleMouseDown(e));
document.addEventListener('mousemove', e => this.handleMouseMove(e));
document.addEventListener('mouseup', () => this.handleMouseUp());
// Click to zoom (Alt+click = zoom in, Alt+Shift+click = zoom out)
this.container.addEventListener('click', e => this.handleClick(e));
// Trackpad: pinch = zoom, Alt + two-finger scroll = zoom
this.container.addEventListener('wheel', e => this.handleWheel(e), { passive: false });
// Update cursor when Alt/Option key is pressed
this.container.addEventListener('mousemove', e => this.updateCursorFromModifier(e));
this.container.addEventListener('mouseenter', e => this.updateCursorFromModifier(e));
window.addEventListener('keydown', e => this.handleKeyChange(e));
window.addEventListener('keyup', e => this.handleKeyChange(e));
// Re-center on resize if user hasn't interacted yet
window.addEventListener('resize', () => this.handleResize());
}
private handleKeyChange(e: KeyboardEvent): void {
if ((e.key === 'Alt' || e.key === 'Shift') && !this.isPanning) {
e.preventDefault();
if (e.altKey && !e.shiftKey) {
this.container.style.cursor = 'grab';
} else if (e.altKey && e.shiftKey) {
this.container.style.cursor = 'zoom-out';
} else {
this.container.style.cursor = 'default';
}
}
}
private updateCursorFromModifier(e: MouseEvent): void {
if (this.isPanning) {
return;
}
if (e.altKey && !e.shiftKey) {
this.container.style.cursor = 'grab';
} else if (e.altKey && e.shiftKey) {
this.container.style.cursor = 'zoom-out';
} else {
this.container.style.cursor = 'default';
}
}
private handleClick(e: MouseEvent): void {
// Only zoom on click if Alt is held and we didn't drag
if (!e.altKey || this.hasDragged) {
return;
}
e.preventDefault();
e.stopPropagation();
const rect = this.container.getBoundingClientRect();
const x = e.clientX - rect.left;
const y = e.clientY - rect.top;
// Alt+Shift+click = zoom out, Alt+click = zoom in
const factor = e.shiftKey ? 0.8 : 1.25;
this.zoomAtPoint(factor, x, y);
}
private handleWheel(e: WheelEvent): void {
// Only zoom when Alt is held (or ctrlKey for pinch-to-zoom gestures)
// ctrlKey is set by browsers for pinch-to-zoom gestures
const isPinchZoom = e.ctrlKey;
if (!e.altKey && !isPinchZoom) {
// Allow normal scrolling when Alt is not held
return;
}
if (isPinchZoom || e.altKey) {
// Pinch gesture or Alt + two-finger drag = zoom
e.preventDefault();
e.stopPropagation();
const rect = this.container.getBoundingClientRect();
const mouseX = e.clientX - rect.left;
const mouseY = e.clientY - rect.top;
// Calculate zoom (scroll up = zoom in, scroll down = zoom out)
// Pinch gestures have smaller deltaY values, so use a higher factor
const effectiveZoomFactor = isPinchZoom ? this.zoomFactor * 5 : this.zoomFactor;
const delta = -e.deltaY * effectiveZoomFactor;
const newScale = Math.min(this.maxScale, Math.max(this.minScale, this.scale * (1 + delta)));
// Zoom toward mouse position
const scaleFactor = newScale / this.scale;
this.translateX = mouseX - (mouseX - this.translateX) * scaleFactor;
this.translateY = mouseY - (mouseY - this.translateY) * scaleFactor;
this.scale = newScale;
this.applyTransform();
this.saveState();
}
}
private handleMouseDown(e: MouseEvent): void {
if (e.button !== 0 || !e.altKey) {
return;
}
e.preventDefault();
e.stopPropagation();
this.isPanning = true;
this.hasDragged = false;
this.startX = e.clientX - this.translateX;
this.startY = e.clientY - this.translateY;
this.container.style.cursor = 'grabbing';
}
private handleMouseMove(e: MouseEvent): void {
if (!this.isPanning) {
return;
}
// Handle case where mouse was released outside the webview
if (e.buttons === 0) {
this.handleMouseUp();
return;
}
const dx = e.clientX - this.startX - this.translateX;
const dy = e.clientY - this.startY - this.translateY;
if (Math.abs(dx) > 3 || Math.abs(dy) > 3) {
this.hasDragged = true;
}
this.translateX = e.clientX - this.startX;
this.translateY = e.clientY - this.startY;
this.applyTransform();
}
private handleMouseUp(): void {
if (this.isPanning) {
this.isPanning = false;
this.container.style.cursor = 'default';
this.saveState();
}
}
private applyTransform(): void {
this.content.style.transform = `translate(${this.translateX}px, ${this.translateY}px) scale(${this.scale})`;
}
private saveState(): void {
this.hasInteracted = true;
const currentState = this.vscode.getState() || {};
this.vscode.setState({
...currentState,
panZoom: {
scale: this.scale,
translateX: this.translateX,
translateY: this.translateY
}
});
}
private restoreState(): boolean {
const state = this.vscode.getState();
if (state?.panZoom) {
const panZoom = state.panZoom as PanZoomState;
this.scale = panZoom.scale ?? 1;
this.translateX = panZoom.translateX ?? 0;
this.translateY = panZoom.translateY ?? 0;
this.hasInteracted = true;
this.applyTransform();
return true;
}
return false;
}
private handleResize(): void {
if (!this.hasInteracted) {
this.centerContent();
}
}
/**
* Centers the content within the container.
*/
private centerContent(): void {
const containerRect = this.container.getBoundingClientRect();
// Get the SVG element inside the content - mermaid renders to an SVG
const svg = this.content.querySelector('svg');
if (!svg) {
return;
}
const svgRect = svg.getBoundingClientRect();
// Calculate the center position based on the SVG dimensions
this.translateX = (containerRect.width - svgRect.width) / 2;
this.translateY = (containerRect.height - svgRect.height) / 2;
this.applyTransform();
}
public reset(): void {
this.scale = 1;
this.translateX = 0;
this.translateY = 0;
this.hasInteracted = false;
this.applyTransform(); // Apply scale first so content size is correct
// Clear the saved pan/zoom state
const currentState = this.vscode.getState() || {};
delete currentState.panZoom;
this.vscode.setState(currentState);
// Use requestAnimationFrame to ensure layout is updated before centering
requestAnimationFrame(() => {
this.centerContent();
});
}
public zoomIn(): void {
const rect = this.container.getBoundingClientRect();
this.zoomAtPoint(1.25, rect.width / 2, rect.height / 2);
}
public zoomOut(): void {
const rect = this.container.getBoundingClientRect();
this.zoomAtPoint(0.8, rect.width / 2, rect.height / 2);
}
private zoomAtPoint(factor: number, x: number, y: number): void {
const newScale = Math.min(this.maxScale, Math.max(this.minScale, this.scale * factor));
const scaleFactor = newScale / this.scale;
this.translateX = x - (x - this.translateX) * scaleFactor;
this.translateY = y - (y - this.translateY) * scaleFactor;
this.scale = newScale;
this.applyTransform();
this.saveState();
}
}
export function getMermaidTheme(): 'dark' | 'default' {
return document.body.classList.contains('vscode-dark') || (document.body.classList.contains('vscode-high-contrast') && !document.body.classList.contains('vscode-high-contrast-light'))
? 'dark'
: 'default';
}
/**
* Unpersisted state
*/
interface LocalState {
readonly mermaidSource: string;
readonly theme: 'dark' | 'default';
}
interface PersistedState {
readonly mermaidSource: string;
readonly panZoom?: PanZoomState;
}
/**
* Re-renders the mermaid diagram when theme changes
*/
async function rerenderMermaidDiagram(
diagramElement: HTMLElement,
diagramText: string,
newTheme: 'dark' | 'default'
): Promise<void> {
diagramElement.textContent = diagramText;
delete diagramElement.dataset.processed;
mermaid.initialize({
theme: newTheme,
});
await mermaid.run({
nodes: [diagramElement]
});
}
export async function initializeMermaidWebview(vscode: VsCodeApi): Promise<PanZoomHandler | undefined> {
const diagram = document.querySelector<HTMLElement>('.mermaid');
if (!diagram) {
return;
}
// Capture diagram state
const theme = getMermaidTheme();
const diagramText = diagram.textContent ?? '';
let state: LocalState = {
mermaidSource: diagramText,
theme
};
// Save the mermaid source in the webview state
const currentState: PersistedState = vscode.getState() || {};
vscode.setState({
...currentState,
mermaidSource: diagramText
});
// Wrap the diagram for pan/zoom support
const wrapper = document.createElement('div');
wrapper.className = 'mermaid-wrapper';
wrapper.style.cssText = 'position: relative; width: 100%; height: 100%; overflow: hidden;';
const content = document.createElement('div');
content.className = 'mermaid-content';
// Move the diagram into the content wrapper
diagram.parentNode?.insertBefore(wrapper, diagram);
content.appendChild(diagram);
wrapper.appendChild(content);
// Run mermaid
const config: MermaidConfig = {
startOnLoad: false,
theme,
};
mermaid.initialize(config);
await mermaid.run({ nodes: [diagram] });
// Show the diagram now that it's rendered
diagram.classList.add('rendered');
const panZoomHandler = new PanZoomHandler(wrapper, content, vscode);
panZoomHandler.initialize();
// Listen for messages from the extension
window.addEventListener('message', event => {
const message = event.data;
if (message.type === 'resetPanZoom') {
panZoomHandler.reset();
}
});
// Re-render when theme changes
new MutationObserver(() => {
const newTheme = getMermaidTheme();
if (state?.theme === newTheme) {
return;
}
const diagramNode = document.querySelector('.mermaid');
if (!diagramNode || !(diagramNode instanceof HTMLElement)) {
return;
}
state = {
mermaidSource: state?.mermaidSource ?? '',
theme: newTheme
};
rerenderMermaidDiagram(diagramNode, state.mermaidSource, newTheme);
}).observe(document.body, { attributes: true, attributeFilter: ['class'] });
return panZoomHandler;
}