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lightbox: Replace lightbox_canvas with PanZoom library. 

This PR changes how the Pan & Zoom feature of images displayed in the
attachment lightbox are handled.

The existing method of using a canvas element is replaced by the Panzoom
library (timmywil/panzoom). This library is lightweight and has 0
transitive dependencies.

This fixes #20759 where the issue is that the viewport of a zoomed image
was not expanding to fill the available space on the page. Switching to
this new library also solves several other UX issues:

    * Images are no longer blurred when in Pan & Zoom mode.
    * The zoom behavior itself uses focal point zooming: zooming occurs
      where the cursor is on the image instead of at the center of the
      image, reducing the need for extra panning.
    * CSS transitions are used for a more visually pleasing experience
      when switching images, toggling zoom off, etc.
    * The library has the potential to open other file types which
      leaves that option open for us in the future.
This commit is contained in:
Austin Riba 2022-01-13 15:46:54 -08:00 committed by Tim Abbott
parent 97ffe2b123
commit 5f83bc5cfe
8 changed files with 95 additions and 308 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
package.json
View File

@ -14,6 +14,7 @@
"@formatjs/intl": "^1.9.7",
"@giphy/js-components": "^5.0.5",
"@giphy/js-fetch-api": "^4.0.1",
"@panzoom/panzoom": "^4.4.3",
"@uppy/core": "^1.7.1",
"@uppy/progress-bar": "^1.3.4",
"@uppy/xhr-upload": "^1.4.2",

97
static/js/lightbox.js
View File

@ -1,9 +1,9 @@
import panzoom from "@panzoom/panzoom";
import $ from "jquery";
import render_lightbox_overlay from "../templates/lightbox_overlay.hbs";
import * as blueslip from "./blueslip";
import {LightboxCanvas} from "./lightbox_canvas";
import * as message_store from "./message_store";
import * as overlays from "./overlays";
import * as people from "./people";
@ -15,6 +15,64 @@ let is_open = false;
// memoized instead of being looked up multiple times.
const asset_map = new Map();
export class PanZoomControl {
// Class for both initializing and controlling the
// the pan/zoom functionality.
constructor(container) {
this.container = container;
this.panzoom = panzoom(this.container, {
disablePan: true,
disableZoom: true,
cursor: "auto",
});
// keybinds
document.addEventListener("keydown", (e) => {
if (!overlays.lightbox_open()) {
return;
}
switch (e.key) {
case "Z":
case "+":
this.zoomIn();
break;
case "z":
case "-":
this.zoomOut();
break;
case "v":
overlays.close_overlay("lightbox");
break;
}
e.preventDefault();
e.stopPropagation();
});
}
reset() {
this.panzoom.reset();
}
disablePanZoom() {
this.container.removeEventListener("wheel", this.panzoom.zoomWithWheel);
this.panzoom.setOptions({disableZoom: true, disablePan: true, cursor: "auto"});
this.reset();
}
enablePanZoom() {
this.panzoom.setOptions({disableZoom: false, disablePan: false, cursor: "move"});
this.container.addEventListener("wheel", this.panzoom.zoomWithWheel);
}
zoomIn() {
this.panzoom.zoomIn();
}
zoomOut() {
this.panzoom.zoomOut();
}
}
export function clear_for_testing() {
is_open = false;
asset_map.clear();
@ -51,21 +109,10 @@ function display_image(payload) {
$(".player-container").hide();
$(".image-actions, .image-description, .download, .lightbox-canvas-trigger").show();
const lightbox_canvas = $(".lightbox-canvas-trigger").hasClass("enabled");
if (lightbox_canvas === true) {
const canvas = document.createElement("canvas");
canvas.dataset.src = payload.source;
$("#lightbox_overlay .image-preview").html(canvas).show();
const photo = new LightboxCanvas(canvas);
photo.speed(2.3);
} else {
const img_container = $("#lightbox_overlay .image-preview > .zoom-element");
const img = new Image();
img.src = payload.source;
$("#lightbox_overlay .image-preview").html(img).show();
}
img_container.html(img).show();
$(".image-description .title").text(payload.title || "N/A");
$(".image-description .user").text(payload.user);
@ -282,9 +329,15 @@ export function next() {
// this is a block of events that are required for the lightbox to work.
export function initialize() {
// Renders the DOM for the lightbox.
const rendered_lightbox_overlay = render_lightbox_overlay();
$("body").append(rendered_lightbox_overlay);
// Bind the pan/zoom control the newly created element.
const pan_zoom_control = new PanZoomControl(
$("#lightbox_overlay .image-preview > .zoom-element")[0],
);
$("#main_div, #compose .preview_content").on("click", ".message_inline_image a", function (e) {
// prevent the link from opening in a new page.
e.preventDefault();
@ -308,6 +361,7 @@ export function initialize() {
$(".image-list .image.selected").removeClass("selected");
$(this).addClass("selected");
pan_zoom_control.reset();
const parentOffset = this.parentNode.clientWidth + this.parentNode.scrollLeft;
// this is the left and right of the image compared to its parent.
@ -341,18 +395,15 @@ export function initialize() {
});
$("#lightbox_overlay").on("click", ".lightbox-canvas-trigger", function () {
let $img = $("#lightbox_overlay").find(".image-preview img");
if ($img.length) {
$(this).addClass("enabled");
// the `lightbox.open` function will see the enabled class and
// enable the `LightboxCanvas` class.
const $img = $("#lightbox_overlay").find(".image-preview img");
open($img);
} else {
$img = $($("#lightbox_overlay").find(".image-preview canvas")[0].image);
if ($(this).hasClass("enabled")) {
pan_zoom_control.disablePanZoom();
$(this).removeClass("enabled");
open($img);
} else {
pan_zoom_control.enablePanZoom();
$(this).addClass("enabled");
}
});

279
static/js/lightbox_canvas.js
View File

@ -1,279 +0,0 @@
import * as blueslip from "./blueslip";
import * as overlays from "./overlays";
const funcs = {
setZoom(meta, zoom) {
// condition to handle zooming event by zoom hotkeys
if (zoom === "+") {
zoom = meta.zoom * 1.2;
} else if (zoom === "-") {
zoom = meta.zoom / 1.2;
}
// make sure the zoom is above 1 and below the maxZoom.
meta.zoom = Math.min(Math.max(zoom, 1), meta.maxZoom);
},
// this is a function given a canvas that attaches all of the events
// required to pan and zoom.
attachEvents(canvas, context, meta) {
let mousedown = false;
// wheelEvent.deltaMode is a value that describes what the unit is
// for the `deltaX`, `deltaY`, and `deltaZ` properties.
const DELTA_MODE = {
PIXEL: 0,
LINE: 1,
PAGE: 2,
};
// 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
// worrying about scrollable content.
canvas.addEventListener("wheel", (e) => {
e.preventDefault();
// this is to reverse scrolling directions for the image.
let delta = meta.direction * e.deltaY;
if (e.deltaMode === DELTA_MODE.LINE) {
// the vertical height in pixels of an approximate line.
delta *= 15;
}
if (e.deltaMode === DELTA_MODE.PAGE) {
// the vertical height in pixels of an approximate page.
delta *= 300;
}
// this is calculated as the user defined speed times the normalizer
// (which just is what it takes to take the raw delta and transform
// it to a normal speed), multiply it against the current zoom.
// Example:
// delta = 8
// normalizedDelta = delta * (1 / 20) * 1 = 0.4
// zoom = zoom * (0.4 / 100) + 1
const zoom =
meta.zoom * ((meta.speed * meta.internalSpeedMultiplier * delta) / 100 + 1);
funcs.setZoom(meta, zoom);
funcs.displayImage(canvas, context, meta);
return false;
});
// the only valid mousedown events should originate inside of the
// canvas.
canvas.addEventListener("mousedown", () => {
mousedown = true;
});
// on mousemove, actually run the pan events.
canvas.addEventListener("mousemove", (e) => {
// to pan, there must be mousedown and mousemove, check if valid.
if (mousedown === true) {
// find the percent of movement relative to the canvas width
// since e.movementX, e.movementY are in px.
const percentMovement = {
x: e.movementX / canvas.width,
y: e.movementY / canvas.height,
};
// add the percentMovement to the meta coordinates but divide
// out by the zoom ratio because when zoomed in 10x for example
// moving the photo by 1% will appear like 10% on the <canvas>.
meta.coords.x += (percentMovement.x * 2) / meta.zoom;
meta.coords.y += (percentMovement.y * 2) / meta.zoom;
// redraw the image.
funcs.displayImage(canvas, context, meta);
}
});
// event listener to handle zoom in and out from using keyboard keys z/Z and +/-
// in the canvas
// these hotkeys are not implemented in static/js/hotkey.js as the code in
// static/js/lightbox_canvas.js and static/js/lightbox.js isn't written a way
// that the LightboxCanvas instance created in lightbox.js can be
// accessed from hotkey.js. Major code refactoring is required in lightbox.js
// to implement these keyboard shortcuts in hotkey.js
document.addEventListener("keydown", (e) => {
if (!overlays.lightbox_open()) {
return;
}
switch (e.key) {
case "Z":
case "+":
funcs.setZoom(meta, "+");
funcs.displayImage(canvas, context, meta);
break;
case "z":
case "-":
funcs.setZoom(meta, "-");
funcs.displayImage(canvas, context, meta);
break;
case "v":
overlays.close_overlay("lightbox");
break;
}
e.preventDefault();
e.stopPropagation();
});
// make sure that when the mousedown is lifted on <canvas>to prevent
// panning events.
canvas.addEventListener("mouseup", () => {
mousedown = false;
});
// do so on the document.body as well, though depending on the infra,
// these are less reliable as preventDefault may prevent these events
// from propagating all the way to the <body>.
document.body.addEventListener("mouseup", function body_mouseup() {
if (document.body.contains(canvas)) {
mousedown = false;
} else {
document.body.removeEventListener("mouseup", body_mouseup);
}
});
window.addEventListener("resize", function window_resize() {
if (document.body.contains(canvas)) {
funcs.sizeCanvas(canvas, meta);
funcs.displayImage(canvas, context, meta);
} else {
window.removeEventListener("resize", window_resize);
}
});
},
imageRatio(image) {
return image.naturalWidth / image.naturalHeight;
},
displayImage(canvas, context, meta) {
meta.coords.x = Math.max(1 / (meta.zoom * 2), meta.coords.x);
meta.coords.x = Math.min(1 - 1 / (meta.zoom * 2), meta.coords.x);
meta.coords.y = Math.max(1 / (meta.zoom * 2), meta.coords.y);
meta.coords.y = Math.min(1 - 1 / (meta.zoom * 2), meta.coords.y);
const c = {
x: meta.coords.x - 1,
y: meta.coords.y - 1,
};
const x = meta.zoom * c.x * canvas.width + canvas.width / 2;
const y = meta.zoom * c.y * canvas.height + canvas.height / 2;
const w = canvas.width * meta.zoom;
const h = canvas.height * meta.zoom;
context.clearRect(0, 0, canvas.width, canvas.height);
context.imageSmoothingEnabled = false;
context.drawImage(meta.image, x, y, w, h);
},
// the `sizeCanvas` method figures out the appropriate bounding box for
// the canvas given a parent that has constraints.
// for example, if a photo has a ration of 1.5:1 (w:h), and the parent
// box is 1:1 respectively, we want to stretch the photo to be as large
// as we can, which means that we check if having the photo width = 100%
// means that the height is less than 100% of the parent height. If so,
// then we size the photo as w = 100%, h = 100% / 1.5.
sizeCanvas(canvas, meta) {
if (canvas.parentNode === null) {
return;
}
if (typeof meta.resize_handler === "function") {
meta.resize_handler(canvas);
}
const parent = {
width: canvas.parentNode.clientWidth,
height: canvas.parentNode.clientHeight,
};
if (parent.height * meta.ratio > parent.width) {
canvas.width = parent.width * 2;
canvas.style.width = parent.width + "px";
canvas.height = (parent.width / meta.ratio) * 2;
canvas.style.height = parent.width / meta.ratio + "px";
} else {
canvas.height = parent.height * 2;
canvas.style.height = parent.height + "px";
canvas.width = parent.height * meta.ratio * 2;
canvas.style.width = parent.height * meta.ratio + "px";
}
blueslip.warn("Please specify a 'data-width' or 'data-height' argument for canvas.");
},
};
export class LightboxCanvas {
meta = {
direction: -1,
zoom: 1,
image: null,
coords: {
x: 0.5,
y: 0.5,
},
speed: 1,
// this is to normalize the speed to what I would consider to be
// "standard" zoom speed.
internalSpeedMultiplier: 0.05,
maxZoom: 10,
};
constructor(el) {
if (el instanceof Node) {
this.canvas = el;
} else if (typeof el === "string") {
this.canvas = document.querySelector(el);
} else {
throw new TypeError("'LightboxCanvas' accepts either string selector or node.");
}
this.context = this.canvas.getContext("2d");
this.meta.image = new Image();
this.meta.image.src = this.canvas.dataset.src;
this.meta.image.addEventListener("load", () => {
this.meta.ratio = funcs.imageRatio(this.meta.image);
funcs.sizeCanvas(this.canvas, this.meta);
funcs.displayImage(this.canvas, this.context, this.meta);
});
this.canvas.image = this.meta.image;
funcs.attachEvents(this.canvas, this.context, this.meta);
}
// set the speed at which scrolling zooms in on a photo.
speed(speed) {
this.meta.speed = speed;
}
// set the max zoom of the `LightboxCanvas` canvas as a mult of the total width.
maxZoom(maxZoom) {
this.meta.maxZoom = maxZoom;
}
reverseScrollDirection() {
this.meta.direction = 1;
}
setZoom(zoom) {
funcs.setZoom(this.meta, zoom);
funcs.displayImage(this.canvas, this.context, this.meta);
}
resize(callback) {
this.meta.resize_handler = callback;
}
}

8
static/styles/lightbox.css
View File

@ -36,6 +36,14 @@
canvas {
cursor: pointer;
}
.zoom-element {
width: 100%;
height: 100%;
display: flex;
align-items: center;
justify-content: center;
}
}
.exit {

4
static/templates/lightbox_overlay.hbs
View File

@ -16,7 +16,9 @@
<div class="clear-float"></div>
</div>
<div class="image-preview overlay-content no-select"></div>
<div class="image-preview overlay-content no-select">
<div class="zoom-element"></div>
</div>
<div class="player-container"></div>
<div class="center">
<div class="arrow no-select" data-direction="prev">&lt;</div>

1
tools/test-js-with-node
View File

@ -93,7 +93,6 @@ EXEMPT_FILES = make_set(
"static/js/info_overlay.js",
"static/js/invite.js",
"static/js/lightbox.js",
"static/js/lightbox_canvas.js",
"static/js/list_util.ts",
"static/js/loading.ts",
"static/js/local_message.js",

2
version.py
View File

@ -48,4 +48,4 @@ API_FEATURE_LEVEL = 115
# historical commits sharing the same major version, in which case a
# minor version bump suffices.
PROVISION_VERSION = "173.3"
PROVISION_VERSION = "173.4"

5
yarn.lock
View File

@ -1377,6 +1377,11 @@
mkdirp "^1.0.4"
rimraf "^3.0.2"
"@panzoom/panzoom@^4.4.3":
version "4.4.3"
resolved "https://registry.yarnpkg.com/@panzoom/panzoom/-/panzoom-4.4.3.tgz#439ef0c3eba1cba0ad9b661fda5961aa2e2eec64"
integrity sha512-fTAr7/bc9ukvWKxxqdoAuIhKhvu6TwuNiGcA0N3lrSj5OZGlISGLXcSZZyN7kgqH/6icYS7b18UT/Iq/W2rTOA==
"@plotly/d3-sankey-circular@0.33.1":
version "0.33.1"
resolved "https://registry.yarnpkg.com/@plotly/d3-sankey-circular/-/d3-sankey-circular-0.33.1.tgz#15d1e0337e0e4b1135bdf0e2195c88adacace1a7"