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lightbox_canvas: Remove movementX, movementY polyfill. 

This isn’t necessary in modern browsers and throws errors with "use
strict".

Signed-off-by: Anders Kaseorg <anders@zulipchat.com>
This commit is contained in:
Anders Kaseorg 2020-08-12 14:02:31 -07:00 committed by Tim Abbott
parent 7a1002af96
commit 4e7eda0539
1 changed files with 0 additions and 22 deletions
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22
static/js/lightbox_canvas.js
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@ -25,24 +25,6 @@ const funcs = {
PAGE: 2,
};
// give object structure in `mousedown`, because its props are only
// ever set once `mousedown` + `mousemove` is triggered.
let lastPosition = {};
// in browsers such as Safari, the `e.movementX` and `e.movementY`
// props don't exist, so we need to create them as a difference of
// where the last `layerX` and `layerY` movements since the last
// `mousemove` event in this `mousedown` event were registered.
const polyfillMouseMovement = (e) => {
e.movementX = e.layerX - lastPosition.x || 0;
e.movementY = e.layerY - lastPosition.y || 0;
lastPosition = {
x: e.layerX,
y: e.layerY,
};
};
// use the wheel event rather than scroll because this isn't
// actually an element that can scroll. The wheel event will
// detect the *gesture* of scrolling over an element, without actually
@ -89,7 +71,6 @@ const funcs = {
canvas.addEventListener("mousemove", (e) => {
// to pan, there must be mousedown and mousemove, check if valid.
if (mousedown === true) {
polyfillMouseMovement(e);
// find the percent of movement relative to the canvas width
// since e.movementX, e.movementY are in px.
const percentMovement = {
@ -136,9 +117,6 @@ const funcs = {
// panning events.
canvas.addEventListener("mouseup", () => {
mousedown = false;
// reset this to be empty so that the values will `NaN` on first
// mousemove and default to a change of (0, 0).
lastPosition = {};
});
// do so on the document.body as well, though depending on the infra,