InkPresenter
Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.
The InkPresenter
interface of the Ink API provides the ability to instruct the OS-level compositor to render ink strokes between pointer event dispatches.
Instance properties
expectedImprovement
Experimental Read only-
Returns a value, in milliseconds, indicating the latency improvement that can be expected using this presenter.
presentationArea
Experimental Read only-
Returns the
Element
inside which rendering of ink strokes is confined.
Instance methods
updateInkTrailStartPoint()
Experimental-
Passes the
PointerEvent
that was used as the last rendering point for the current frame, allowing the OS-level compositor to render a delegated ink trail ahead of the next pointer event being dispatched.
Example
In this example, we draw a trail onto a 2D canvas. Near the start of the code, we call Ink.requestPresenter()
, passing it the canvas as the presentation area for it to take care of and storing the promise it returns in the presenter
variable.
Later on, in the pointermove
event listener, the new position of the trailhead is drawn onto the canvas each time the event fires. In addition, the InkPresenter
object returned when the presenter
promise fulfills has its updateInkTrailStartPoint()
method invoked; this is passed:
- The last trusted pointer event representing the rendering point for the current frame.
- A
style
object containing color and diameter settings.
The result is that a delegated ink trail is drawn ahead of the default browser rendering on the app's behalf, in the specified style, until the next time it receives a pointermove
event.
js
const ctx = canvas.getContext("2d");
let presenter = navigator.ink.requestPresenter({ presentationArea: canvas });
let move_cnt = 0;
let style = { color: "rgba(0, 0, 255, 1)", diameter: 10 };
function getRandomInt(min, max) {
min = Math.ceil(min);
max = Math.floor(max);
return Math.floor(Math.random() * (max - min + 1)) + min;
}
canvas.addEventListener("pointermove", (evt) => {
const pointSize = 10;
ctx.fillStyle = "#000000";
ctx.fillRect(evt.pageX, evt.pageY, pointSize, pointSize);
if (move_cnt == 50) {
let r = getRandomInt(0, 255);
let g = getRandomInt(0, 255);
let b = getRandomInt(0, 255);
style = { color: "rgba(" + r + ", " + g + ", " + b + ", 1)", diameter: 10 };
move_cnt = 0;
document.getElementById("div").style.backgroundColor =
"rgba(" + r + ", " + g + ", " + b + ", 1)";
}
move_cnt += 1;
presenter.then(function (v) {
v.updateInkTrailStartPoint(evt, style);
});
});
window.addEventListener("pointerdown", (evt) => {
evt.pointerId;
ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height);
});
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
Note: See this example running live — Delegated ink trail.
Specifications
Specification |
---|
Ink API # ink-presenter |
Browser compatibility
BCD tables only load in the browser