Canvas Component

Defines the RevCanvas class, which encapsulates a grid's HTML canvas element and manages its rendering and user interaction. It is the central component for rendering and handling all user interactions with the grid's canvas surface.

Main responsibilities

• Canvas Management: Creates, configures, and attaches the canvas element to the DOM, handling sizing, DPI scaling, and resizing logic.
• Rendering Context: Wraps the 2D rendering context for efficient drawing operations.
• Event Handling: Registers and manages a wide range of event listeners for pointer, mouse, keyboard, touch, clipboard, drag-and-drop, and focus events.
• Pointer and Drag State: Tracks pointer and drag states to support complex interactions like dragging and selection.
• Resizing Logic: Observes host element size changes and debounces resize events to optimize performance.
• Utility Methods: Provides methods for focus management, cursor and title updates, and event dispatching.
• External Integration: Allows external code to add or remove event listeners on the canvas element.

Rendering context

Creates a CanvasRenderingContext2D for the canvas and then wraps it in a RevCachedCanvasRenderingContext2D object. The RevCachedCanvasRenderingContext2D object caches the context's properties and will not update them unless they are changed. All drawing related operations on the canvas use RevCachedCanvasRenderingContext2D.

Resizing

Ensures that the canvas element is always resized to match the size of its parent element (hostElement). Resize related events are debounced to minimise the number of renders when resizing.

Drag events

Drag events are simulated by:

• listening for dragstart events from canvas element
• capturing the mouse
• firing simulated drag events when canvas mousemove events occur while dragging is active
• firing simulated dragEnd events when canvas mouseup of mousecancel events occur while dragging is active
• releasing the mouse.

Settings used

• useHiDPI
• resizedEventDebounceExtendedWhenPossible
• resizedEventDebounceInterval