Smart Paste for Links and Images

January 17, 2026 · View on GitHub

Overview

Task 5 implements intelligent paste behavior that automatically creates markdown links and images when pasting URLs.

Features

When text is selected and a URL is pasted:

  • Select "Click here", paste https://example.com
  • Result: [Click here](https://example.com)
  • Cursor lands after the closing parenthesis

2. Image Insertion without Selection

When an image URL is pasted with no selection:

  • Paste https://example.com/pic.png
  • Result: ![](https://example.com/pic.png)
  • Cursor lands after the inserted image markdown

3. Regular URL Paste

When a regular URL (non-image) is pasted with no selection:

  • Normal paste behavior (URL inserted as-is)

4. Non-URL Paste

When non-URL text is pasted:

  • Normal paste behavior

Implementation

Key Files

  • src/app.rs - Core smart paste logic

Helper Functions

/// Check if a string looks like a URL
fn is_url(s: &str) -> bool

/// Check if a URL points to an image based on file extension
fn is_image_url(s: &str) -> bool

URL Detection

URLs are detected by checking for:

  • http:// or https:// prefix
  • General scheme pattern: [a-zA-Z][a-zA-Z0-9+.-]*://

Image URL Detection

Image URLs are detected by checking file extensions (case-insensitive):

  • .png, .jpg, .jpeg, .gif, .webp, .svg, .bmp, .ico, .tiff, .tif
  • Query strings and fragments are stripped before extension check

Architecture

The implementation uses a pre-render event consumption pattern:

Pre-render Phase (consume_smart_paste):

  1. Scan egui input events for Event::Paste(text)
  2. Check if pasted text is a URL
  3. If URL + selection → create markdown link, consume event
  4. If image URL + no selection → create markdown image, consume event
  5. Otherwise → let normal paste proceed

This approach:

  • Intercepts paste events before TextEdit processes them
  • Only consumes events when smart behavior applies
  • Falls through to default paste for normal cases

Integration Points

The consume_smart_paste function is called in update():

// IMPORTANT: Handle smart paste BEFORE rendering to intercept paste events
// and transform them into markdown links/images when appropriate.
self.consume_smart_paste(ctx);

Testing

ScenarioExpected Behavior
Select "Click here", paste URL[Click here](https://example.com)
No selection, paste image URL![](https://example.com/pic.png)
No selection, paste regular URLPlain URL inserted
Paste non-URL textNormal paste behavior
Undo after smart pasteRestores to before
URLs with query stringsDetection still works
URLs with fragmentsDetection still works

Supported Image Extensions

  • PNG: .png
  • JPEG: .jpg, .jpeg
  • GIF: .gif
  • WebP: .webp
  • SVG: .svg
  • BMP: .bmp
  • ICO: .ico
  • TIFF: .tiff, .tif

Edge Cases

  • URLs with query strings: https://example.com/pic.png?v=1 → detects as image
  • URLs with fragments: https://example.com/pic.png#section → detects as image
  • Mixed case extensions: https://example.com/pic.PNG → detects as image
  • Non-standard schemes: ftp://, file:// → detected as URLs

Undo Behavior

  • Smart link creation: Undo removes the entire link and restores selection
  • Smart image insertion: Undo removes the image markdown
  • Both operations are recorded as single edits for clean undo

Future Enhancements

  • Auto-fetch image titles for alt text
  • Smart paste for other URL types (YouTube → embedded video placeholder)
  • Configurable behavior per URL pattern
  • Clipboard image detection (paste image data as file)