HTMLCanvasElement: contextlost event
Limited availability
This feature is not Baseline because it does not work in some of the most widely-used browsers.
The contextlost
event of the Canvas API is fired if the user agent detects that the backing storage associated with a CanvasRenderingContext2D
context is lost.
Contexts can be lost for several reasons like driver crashes or the application runs out of memory, etc.
By default the user agent will attempt to restore the context and then fire the contextrestored
event.
User code can prevent the context from being restored by calling Event.preventDefault()
during event handling.
Syntax
Use the event name in methods like addEventListener()
, or set an event handler property.
addEventListener("contextlost", (event) => {});
oncontextlost = (event) => {};
Event type
A generic Event
.
Example
The code fragment below detects the contextlost
event.
const canvas = document.getElementById("canvas");
canvas.addEventListener("contextlost", (event) => {
console.log(event);
});
To prevent the context from being restored the code might instead look like this:
const canvas = document.getElementById("canvas");
canvas.addEventListener("contextlost", (event) => {
event.preventDefault();
});
Specifications
Specification |
---|
HTML Standard # event-contextlost |
Browser compatibility
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