Online Presentation Editor Development

Online Presentation Editor Development

Online presentation editor is a rich interface for creating slideshows with text, images, shapes, animations. Canvas-based rendering, drag-and-drop, collaborative editing. Building full Google Slides equivalent requires large-scale engineering; specialized editor for specific context (marketing materials, data presentations) is realistic project.

Rendering Architecture

Two approaches to slide rendering:

DOM-based: each slide element is HTML element with absolute positioning. Simpler to implement, accessible for screen readers. Hard to achieve pixel-perfect rendering on export.

Canvas-based: slide drawn on <canvas>. Precise pixel output control, easy PNG export. Harder interactivity (events, text selection).

Fabric.js — Canvas library with object model (rectangles, ellipses, text, images), drag-and-drop, scaling, grouping:

const canvas = new fabric.Canvas('editor-canvas', { width: 1280, height: 720 });

const text = new fabric.Textbox('Slide Title', {
  left: 100, top: 50, width: 600,
  fontSize: 48, fontFamily: 'Inter',
  fill: '#1a1a2e',
});
canvas.add(text);
canvas.setActiveObject(text);

Konva.js — Fabric alternative, focused on React with react-konva.

Slide Data Model

Presentation → Slides → Elements. Each element is JSON object:

{
  "id": "el_abc123",
  "type": "text",
  "x": 100, "y": 50,
  "width": 600, "height": 80,
  "rotation": 0,
  "content": "Title",
  "styles": {
    "fontSize": 48,
    "fontFamily": "Inter",
    "bold": true,
    "color": "#1a1a2e",
    "align": "center"
  }
}

Slide stored as JSON. Change history is immutable list of operations (Command pattern).

Drag & Drop and Alignment

When moving object: smart guides (alignment lines appear when coordinates match other objects or slide center/edges). Grid snapping optional.

Implementing smart guides: on drag compute distance to anchor points of all objects, at distance < threshold (5–8px) show line and "snap".

Collaborative Editing

Yjs with Y.Array for slides and Y.Map for each element:

const ydoc = new Y.Doc();
const slides = ydoc.getArray('slides');
const provider = new WebsocketProvider('wss://server', `pres_${id}`, ydoc);

// Update element position
ydoc.transact(() => {
  const slideMap = slides.get(slideIndex);
  const elements = slideMap.get('elements');
  const el = elements.get(elementId);
  el.set('x', newX);
  el.set('y', newY);
});

Each user sees other participants' cursors (Yjs awareness API).

Templates

Template library — set of ready slides and full presentations. Template stored as JSON structure, on creation from template — cloned to new presentation.

Export

• PPTX: via pptxgenjs (Node.js). Convert JSON model to PPTX objects.
• PDF: render each slide to PNG via Canvas → combine into PDF via pdf-lib.
• PNG/JPG: canvas.toDataURL('image/png') for each slide.

import pptxgen from 'pptxgenjs';
const pptx = new pptxgen();
const slide = pptx.addSlide();
slide.addText('Hello World', { x: 1, y: 1, fontSize: 36, bold: true });
pptx.writeFile({ fileName: 'presentation.pptx' });

Animations

Slide animations (fade, fly-in, scale) in browser via CSS animations or Web Animations API. For PPTX export map to built-in PowerPoint animations via pptxgenjs.

Timeline

Specialized editor (fixed element types, basic manipulations, PNG/PDF export): 3–4 months. Full editor with collaborative editing, templates, PPTX export and animations: 6–10 months.