Overview

DragCanvas is a built-in behavior in G6 for implementing canvas dragging functionality, supporting panning the entire canvas by dragging with a mouse or touching the screen. This is the most basic and commonly used navigation behavior in graph visualization, allowing users to freely explore graph content beyond the current viewport.

Usage Scenarios

This behavior is mainly used for:

• Navigating and browsing large charts to view content outside the current viewport
• Adjusting the view focus to move areas of interest to the center of the viewport
• Combining with zoom interactions to achieve a complete canvas navigation experience

Online Experience

createGraph(
  {
    data: { nodes: [{ id: 'node-1' }] },
    layout: { type: 'force' },
    behaviors: [
      {
        type: 'drag-canvas',
        key: 'drag-canvas',
      },
    ],
    node: { style: { fill: '#7e3feb' } },
    edge: { style: { stroke: '#8b9baf' } },
    plugins: [{ type: 'grid-line', size: 30 }],
  },
  { width: 600, height: 300 },
  (gui, graph) => {
    const options = {
      key: 'drag-canvas',
      type: 'drag-canvas',
      enable: true,
      sensitivity: 1,
      trigger: 'Use cursor by default',
    };
    const optionFolder = gui.addFolder('ZoomCanvas Options');
    optionFolder.add(options, 'type').disable(true);
    optionFolder.add(options, 'enable');
    optionFolder.add(options, 'sensitivity', 0, 10, 1);
    optionFolder.add(options, 'trigger', {
      'Use cursor by default': [],
      'Shift+Arrow Key': {
        up: ['Shift', 'ArrowUp'],
        down: ['Shift', 'ArrowDown'],
        left: ['Shift', 'ArrowLeft'],
        right: ['Shift', 'ArrowRight'],
      },
    });
    optionFolder.onChange(({ property, value }) => {
      graph.updateBehavior({
        key: 'drag-canvas',
        [property]: value,
      });
      graph.render();
    });
  },
);

Basic Usage

Add this behavior in the graph configuration:

1. Quick Configuration (Static)

Declare directly using a string form. This method is simple but only supports default configuration and cannot be dynamically modified after configuration:

const graph = new Graph({
  // Other configurations...
  behaviors: ['drag-canvas'],
});

2. Object Configuration (Recommended)

Configure using an object form, supporting custom parameters, and can dynamically update the configuration at runtime:

const graph = new Graph({
  // Other configurations...
  behaviors: [
    {
      type: 'drag-canvas',
      key: 'drag-canvas-1',
      direction: 'x', // Only allow horizontal dragging
      key: 'drag-behavior', // Specify an identifier for the behavior for dynamic updates
    },
  ],
});

Configuration Options

range

range is used to control the draggable range of the canvas:

• Set as a single number: Use the same value for all four directions
• Set as an array: Specify the range for [top, right, bottom, left] directions respectively

For example:

range: 2; // Can drag 2 viewport distances in any direction
range: [1, 2, 1, 2]; // Can drag 1 viewport up and down, 2 viewports left and right

The value range for each direction is [0, Infinity], 0 means no dragging, Infinity means unlimited dragging.

trigger

trigger allows you to configure keyboard keys to control canvas movement:

{
  trigger: {
    up: ['ArrowUp'],     // Shortcut key for moving up
    down: ['ArrowDown'], // Shortcut key for moving down
    left: ['ArrowLeft'], // Shortcut key for moving left
    right: ['ArrowRight'] // Shortcut key for moving right
  }
}

You can also configure combination keys:

{
  trigger: {
    up: ['Control', 'ArrowUp'],     // Ctrl + Up Arrow
    down: ['Control', 'ArrowDown'], // Ctrl + Down Arrow
    left: ['Control', 'ArrowLeft'], // Ctrl + Left Arrow
    right: ['Control', 'ArrowRight'] // Ctrl + Right Arrow
  }
}

Code Examples

Basic Dragging Function

const graph = new Graph({
  container: 'container',
  width: 800,
  height: 600,
  behaviors: ['drag-canvas'],
});

Only Allow Horizontal Dragging

const graph = new Graph({
  // Other configurations...
  behaviors: [
    {
      type: 'drag-canvas',
      direction: 'x', // Only allow horizontal dragging
    },
  ],
});

Limit Dragging Range

const graph = new Graph({
  // Other configurations...
  behaviors: [
    {
      type: 'drag-canvas',
      range: 1.5, // Limit dragging range to 1.5 viewport sizes
    },
  ],
});

Control Movement with Keyboard Arrow Keys

const graph = new Graph({
  // Other configurations...
  behaviors: [
    {
      type: 'drag-canvas',
      trigger: {
        up: ['ArrowUp'],
        down: ['ArrowDown'],
        left: ['ArrowLeft'],
        right: ['ArrowRight'],
      },
      animation: {
        duration: 100, // Add smooth animation effect
      },
    },
  ],
});

FAQ

1. Difference between DragCanvas and other behaviors

• DragCanvas is used for dragging the entire canvas view
• DragElement is used for dragging individual graph elements (nodes/edges/combinations)
• ScrollCanvas is used for scrolling the canvas with the mouse wheel without changing the zoom ratio

Practical Example