Compare revisions

65049a56 · 65049a56 · 65049a56 · 65049a56 · 65049a56 · 65049a56
--- a/public/imperial.svg
+++ b/public/imperial.svg
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Generator: Adobe Illustrator 22.0.1, SVG Export Plug-In . SVG Version: 6.00 Build 0)  -->
+<svg version="1.1" id="Layer_1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px"
+	 viewBox="0 0 417.7 150.7" style="enable-background:new 0 0 417.7 150.7;" xml:space="preserve">
+<style type="text/css">
+	.st0{fill:#003C70;}
+</style>
+<path class="st0" d="M28.4,68.2V30.3h7.4v37.9H28.4z"/>
+<path class="st0" d="M46.7,44.3h0.1c1.8-2.4,5.2-3.8,8.3-3.8c3.3,0,6.2,1.4,7.8,3.8c2.2-2.2,5.6-3.8,8.8-3.8c6-0.1,9.1,3.7,9.2,9.9
+	v17.8h-7V51.7c0-3.1-1.1-6.4-4.5-6.4c-3.4,0-5.5,2.1-5.5,6.8v16.2h-7V51.7c0-3.8-1.6-6.4-4.6-6.4c-3.3,0-5.4,2.3-5.4,6.9v16h-7V41.1
+	h7V44.3z"/>
+<path class="st0" d="M98.5,44.8c4,0,6,4.7,6,9.3c0,4.8-1.6,10.4-6.3,10.4c-3.8,0-6.5-3.8-6.5-9.5C91.8,48.7,94.1,44.8,98.5,44.8z
+	 M91.8,41.1h-7v40.7h7V64.8c2,2.4,4.7,4,7.9,4c7.5,0,12.3-7.6,12.3-14.8c0-6-3.4-13.6-11.7-13.6c-3.2,0-6.6,1.6-8.4,4.4h-0.1V41.1z"
+	/>
+<path class="st0" d="M122,51.4c-0.1-3.6,1.7-6.9,5.8-6.9c3.5,0,4.9,2.8,4.6,6.9H122z M139,55.3c0.5-8.1-2.9-14.8-11.1-14.8
+	c-7.5,0-13.5,5.3-13.5,13.7c0,8.9,6,14.7,13.9,14.7c3,0,6.8-0.9,10.3-3l-2-3.8c-1.7,1.2-4.5,2.2-7.1,2.2c-4.4,0-7.9-3.8-7.7-8.9H139
+	z"/>
+<path class="st0" d="M149.4,45.9h0.1l1.4-2.1c0.8-1.1,2.4-3.3,4.5-3.3c1.6,0,3.3,0.9,4.8,2.4l-2.6,5c-1.2-0.6-1.9-0.9-3.3-0.9
+	c-2.4,0-4.8,2-4.8,7.9v13.4h-7V41.1h7V45.9z"/>
+<path class="st0" d="M169.4,41.1v27.1h-7V41.1H169.4z M161.7,33c0-2.1,1.7-4.2,4.1-4.2c2.4,0,4.3,2.1,4.3,4.2c0,2.3-1.6,4.5-4.2,4.5
+	C163.4,37.5,161.7,35.3,161.7,33z"/>
+<path class="st0" d="M188.5,52.5c0.5,8-3.1,11.5-5.9,11.5c-1.7,0-3.2-1.6-3.2-4c0-3.1,1.7-5.1,5.2-6.2L188.5,52.5z M188.4,64.2
+	c0,1.5,0.2,3,0.7,4h7.4c-0.8-1.9-1.1-4.4-1.1-6.6V50.5c0-8.5-6-10.1-10.8-10.1c-3.6,0-6.9,0.9-10.1,3.7l2.3,3.4c1.8-1.6,4-2.8,7-2.8
+	c2.3,0,4.4,1.6,4.8,4.1l-6.2,1.9c-6.1,1.8-9.8,4.7-9.8,9.9c0,5,3.4,8.2,7.5,8.2c2.4,0,4.8-1.7,6.8-3.3L188.4,64.2z"/>
+<path class="st0" d="M199.8,68.2V28.4h7v39.8H199.8z"/>
+<path class="st0" d="M253.1,37.1c-1.8-1-4.8-2.1-7.7-2.1c-7.6,0-13.1,5.5-13.1,14.1c0,9,6.1,14.3,13.3,14.3c2.9,0,5.5-0.8,7.4-1.9
+	l2.1,4.7c-2.3,1.4-6.2,2.6-9.8,2.6c-12.8,0-20.9-8.7-20.9-19.8c0-10.4,8-19.4,21-19.4c3.9,0,7.4,1.4,10,2.9L253.1,37.1z"/>
+<path class="st0" d="M269.1,64.8c-5,0-6.4-5.7-6.4-10.5c0-4.5,1.6-9.9,6.4-9.9c4.9,0,6.4,5.4,6.4,9.9
+	C275.5,59.1,274.2,64.8,269.1,64.8z M269.1,68.9c8.3,0,13.9-6.1,13.9-14.5c0-8.8-6.7-13.9-13.9-13.9c-7.1,0-13.8,5.1-13.8,13.9
+	C255.3,62.7,260.8,68.9,269.1,68.9z"/>
+<path class="st0" d="M286,68.2V28.4h7v39.8H286z"/>
+<path class="st0" d="M297.4,68.2V28.4h7v39.8H297.4z"/>
+<path class="st0" d="M314.9,51.4c-0.1-3.6,1.7-6.9,5.7-6.9c3.5,0,4.9,2.8,4.6,6.9H314.9z M331.9,55.3c0.5-8.1-2.9-14.8-11.1-14.8
+	c-7.5,0-13.5,5.3-13.5,13.7c0,8.9,6,14.7,13.9,14.7c3,0,6.8-0.9,10.3-3l-2-3.8c-1.7,1.2-4.5,2.2-7.1,2.2c-4.4,0-7.9-3.8-7.7-8.9
+	H331.9z"/>
+<path class="st0" d="M372.2,51.4c-0.1-3.6,1.7-6.9,5.8-6.9c3.5,0,4.9,2.8,4.6,6.9H372.2z M389.2,55.3c0.5-8.1-2.9-14.8-11.1-14.8
+	c-7.5,0-13.5,5.3-13.5,13.7c0,8.9,6,14.7,13.9,14.7c3,0,6.8-0.9,10.3-3l-2-3.8c-1.7,1.2-4.5,2.2-7.1,2.2c-4.4,0-7.9-3.8-7.7-8.9
+	H389.2z"/>
+<path class="st0" d="M348.3,44.8c4.2,0,6.4,4.4,6.4,9.1c0,5.4-2,10.6-6.7,10.6c-4.1,0-6.1-5.1-6.1-10.4
+	C342,48.9,343.8,44.8,348.3,44.8z M361.7,41.1h-7v3.3h-0.1c-1.5-2.4-4.6-4-7.9-4c-7.2,0-12.2,6.8-12.2,13.9
+	c0,8.7,4.6,14.5,11.6,14.5c4,0,6.8-2.3,8.5-4.6h0.1v3.6c0,6.3-3.6,9.2-8.2,9.2c-3.6,0-6.6-0.7-9.2-2.3l-1.4,4.4
+	c3.1,1.6,7.1,2.6,11.1,2.6c7.9,0,14.7-4,14.7-16V41.1z"/>
+<path class="st0" d="M28.4,84.5h7.5v32.8h15.8v5.1H28.4V84.5z"/>
+<path class="st0" d="M92.8,98.5c2.5-2.6,6-3.8,9.5-3.8c6.5,0,9.6,3.5,9.6,10.3v17.5h-7.1v-16.6c0-3.8-1.7-6.3-5.6-6.3
+	c-3.6,0-6.4,2.3-6.4,6.8v16.2h-7.1V95.3h7V98.5z"/>
+<path class="st0" d="M130.2,99c4.4,0,6.7,4.4,6.7,9.1c0,5.4-2.1,10.6-7.1,10.6c-4.3,0-6.4-5.1-6.4-10.4S125.4,99,130.2,99z
+	 M136.9,122.4h7.1V82.6h-7.1v15.9h-0.1c-1.7-2.4-4.9-3.8-8.5-3.8c-7.4,0-12.7,6.8-12.7,13.9c0,8.7,4.8,14.5,12.1,14.5
+	c4.3,0,7.2-2.3,9-4.6h0.1V122.4z"/>
+<path class="st0" d="M162.3,119c-5.3,0-6.7-5.7-6.7-10.5c0-4.5,1.7-9.9,6.7-9.9c5.2,0,6.8,5.4,6.8,9.9
+	C169,113.3,167.6,119,162.3,119z M162.3,123.1c8.7,0,14.6-6.1,14.6-14.5c0-8.8-7.1-13.9-14.6-13.9c-7.4,0-14.5,5.1-14.5,13.9
+	C147.7,116.9,153.6,123.1,162.3,123.1z"/>
+<path class="st0" d="M187.7,98.5c2.5-2.6,6-3.8,9.5-3.8c6.5,0,9.6,3.5,9.6,10.3v17.5h-7.1v-16.6c0-3.8-1.7-6.3-5.6-6.3
+	c-3.6,0-6.4,2.3-6.4,6.8v16.2h-7.1V95.3h7V98.5z"/>
+<path class="st0" d="M67.2,119c-5.3,0-6.7-5.7-6.7-10.5c0-4.5,1.7-9.9,6.7-9.9c5.2,0,6.8,5.4,6.8,9.9C74,113.3,72.6,119,67.2,119z
+	 M67.2,123.1c8.7,0,14.6-6.1,14.6-14.5c0-8.8-7.1-13.9-14.6-13.9c-7.4,0-14.5,5.1-14.5,13.9C52.7,116.9,58.6,123.1,67.2,123.1z"/>
+</svg>
--- a/public/index.html
+++ b/public/index.html
@@ -4,39 +4,26 @@
    <meta charset="UTF-8" />
    <link rel="manifest" href="manifest.json" />
    <link rel="shortcut icon" href="logo.png" />
+    <link rel="apple-touch-icon" href="logo.png" />
    <link rel="stylesheet" href="styles.css" />
-
-    <link
-      rel="stylesheet"
-      href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css"
-    />
    <script>
      if (navigator.serviceWorker) {
-        navigator.serviceWorker
-          .register("service-worker.js")
-          .then(
-            (registration) =>
-              console.log(
-                `Service worker registered on scope ${registration.scope}`,
-              ),
-            (reason) =>
-              console.log(`Service worker failed to register ~ ${reason}`),
-          )
+        navigator.serviceWorker.register("service-worker.js").then(
+          (registration) =>
+            console.log(
+              `Service worker registered on scope ${registration.scope}`,
+            ),
+          (reason) =>
+            console.log(`Service worker failed to register ~ ${reason}`),
+        )
      }
    </script>
  </head>
  <body>
-    <div style="display:none">
-      Your client ID: <input id="user-id" type="text" value="" readonly="" />
-    </div>
-    <div style="display:none">
-      Enter peer ID: <input id="peer-id" type="text" value="" />
-      <button id="peer-connect">Connect</button>
-    </div>
    <div id="top-panel">
      <div class="top-bar">
        <div class="dropdown">
-          <button class="dropdown-peers"><i class="fa fa-bars"></i></button>
+          <button class="dropdown-peers"><i class="fas fa-bars"></i></button>
          <div class="peers">
            <ul id="connected-peers">
              No peers are connected
@@ -58,11 +45,11 @@
          size="25"
          color="gray"
        />
-        <button id="room-connect">Connect <i class="fa fa-link"></i></button>
+        <button id="room-connect">Connect <i class="fas fa-link"></i></button>
      </div>
      <div id="tools-panel">
-        <button id="pen-tool" class="selected">
-          <i class="fa fa-paint-brush"></i>
+        <button id="pen-tool" class="selectable-tool selected">
+          <i class="fas fa-paint-brush"></i>
        </button>
        <div id="pen-properties" class="properties">
          <div class="pen-contents">
@@ -87,8 +74,7 @@
                <input
                  type="range"
                  min="1"
-                  max="100"
-                  value="10"
+                  max="10"
                  class="slider"
                  id="range"
                />
@@ -193,19 +179,51 @@
                <b>Other colours</b>
              </div>
              <label id="colours">
-                <input id="other-colours" type="color" value="#0000ff" />
+                <input id="other-colours" type="color" />
              </label>
            </div>
          </div>
        </div>
-        <button id="eraser-tool"><i class="fa fa-eraser"></i></button>
-        <div id="connected-room-info">
-          You are connected to a room: <span id="connected-room-id"></span>
+        <button id="eraser-tool" class="selectable-tool">
+          <i class="fas fa-eraser"></i>
+        </button>
+        <button id="dragging-tool" class="selectable-tool">
+          <i class="far fa-hand-paper"></i>
+        </button>
+        <button id="canvas-center" class="selectable-tool">
+          <i class="fas fa-crosshairs"></i>
+        </button>
+        <button id="recognition-mode" class="selectable-tool">
+          <i class="fas fa-square"></i>
+        </button>
+        <div class="spacer"></div>
+
+        <div id="status-info">
+          <button id="fast-undo-tool" class="disabled selectable-tool">
+            <i class="fas fa-fast-backward"></i>
+          </button>
+          <button id="undo-tool" class="disabled selectable-tool">
+            <i class="fas fa-step-backward"></i>
+          </button>
+          <div id="connected-room-info">
+            Room:&nbsp;
+            <span id="connected-room-id"></span>
+          </div>
+          <div id="user-avatar"></div>
+          <div id="imperial-logo">
+            <img
+              src="imperial.svg"
+              alt="Imperial College London Logo"
+              height="42px"
+            />
+          </div>
        </div>
      </div>
    </div>

-    <svg id="canvas"></svg>
+    <div id="canvas-container">
+      <svg id="canvas"></svg>
+    </div>

    <script src="js/app.js"></script>
  </body>

--- a/public/styles.css
+++ b/public/styles.css
@@ -3,6 +3,10 @@ body {
  height: 100%;
 }

+#console {
+  color: white;
+}
+
 body {
  background-color: black;
  margin: 0;
@@ -10,11 +14,21 @@ body {
  flex-direction: column;
 }

-#canvas {
+#canvas-container {
  width: calc(100vw - 8px);
  background-color: white;
  border: 4px solid red;
  flex-grow: 1;
+  position: relative;
+  overflow: hidden;
+}
+
+#canvas {
+  position: absolute;
+  left: -5000px;
+  top: -5000px;
+  width: 10000px;
+  height: 10000px;
 }

 #tools-panel {
@@ -23,11 +37,18 @@ body {
  align-items: center;
 }

+.spacer {
+  flex: 1;
+}
+
 #connected-room-info {
-  display: none;
  color: white;
-  flex: 1;
-  text-align: right;
+  display: flex;
+  align-items: center;
+  background-color: #4f4f4fb7;
+  border-radius: 4px;
+  justify-content: center;
+  padding: 0.75em;
 }

 button.selected {
@@ -60,7 +81,7 @@ button.selected {
  cursor: pointer;
  border-radius: 4px;
  transition-duration: 0.4s;
-  height: 100%;
+  height: 36px;
  width: 36px;
 }

@@ -71,7 +92,7 @@ button.selected {
  min-width: 160px;
  box-shadow: 0px 8px 16px 0px rgba(0, 0, 0, 0.2);
  z-index: 999;
-  padding: 16px;
+  padding: 8px;
 }

 .peers a {
@@ -254,9 +275,13 @@ button.selected {
  border: none;
  cursor: pointer;
  border-radius: 4px;
+  width: 78px;
+  height: 36px;
+  white-space: nowrap;
+  overflow: hidden;
 }

-#pen-tool {
+.selectable-tool {
  background-color: #2f2f2f;
  color: white;
  padding: 10px;
@@ -264,27 +289,89 @@ button.selected {
  border: none;
  cursor: pointer;
  border-radius: 50%;
-  margin-right: 8px;
 }

-#pen-tool:hover {
+.selectable-tool:hover {
  background-color: #4f4f4f !important;
  transition-duration: 0.4s;
 }

+#pen-tool {
+  width: 39px;
+  height: 39px;
+  margin-right: 8px;
+}
+
+#pen-tool > i {
+  padding: 0 1.5px;
+}
+
 #eraser-tool {
-  background-color: #2f2f2f;
-  color: white;
-  padding: 10px;
-  font-size: 16px;
-  border: none;
-  cursor: pointer;
-  border-radius: 50%;
+  width: 39px;
+  height: 39px;
+  margin-right: 8px;
 }

-#eraser-tool:hover {
-  background-color: #4f4f4f !important;
-  transition-duration: 0.4s;
+#eraser-tool > i {
+  padding: 0 1.5px;
+}
+
+#dragging-tool {
+  width: 39px;
+  height: 39px;
+  margin-right: 8px;
+}
+
+#dragging-tool > i {
+  padding: 0 2.5px;
+}
+
+#canvas-center {
+  width: 39px;
+  height: 39px;
+  margin-right: 8px;
+}
+
+#canvas-center > i {
+  padding: 0 1.5px;
+}
+
+#recognition-mode {
+  width: 39px;
+  height: 39px;
+  margin-right: 8px;
+}
+
+#recognition-mode > i {
+  padding: 0 2.5px;
+}
+
+#undo-tool {
+  width: 39px;
+  height: 39px;
+  margin-right: 8px;
+}
+
+#undo-tool.disabled {
+  display: none;
+}
+
+#undo-tool > i {
+  padding: 0 2.5px;
+}
+
+#fast-undo-tool {
+  width: 39px;
+  height: 39px;
+  margin-right: 8px;
+}
+
+#fast-undo-tool.disabled {
+  display: none;
+}
+
+#fast-undo-tool > i {
+  padding: 0 1.5px;
 }

 .properties {
@@ -523,3 +610,32 @@ button.selected {
    url("./assets/fonts/martel-v4-latin/martel-v4-latin-regular.svg#Martel")
      format("svg");
 }
+
+.avatar {
+  margin-right: 5px;
+}
+
+#user-avatar {
+  color: white;
+  display: flex;
+  align-items: center;
+  background-color: #4f4f4fb7;
+  border-radius: 4px;
+  margin-left: 0.75em;
+  padding: 0 0.75em 0 0;
+}
+
+#status-info {
+  display: flex;
+  align-items: center;
+  justify-content: right;
+}
+
+#imperial-logo {
+    background-color: white;
+    display: flex;
+    align-items: center;
+    border-radius: 4px;
+    margin-left: 0.75em;
+    padding: 0;
+}
--- a/report/report.pdf
+++ b/report/report.pdf
--- a/src/app.js
+++ b/src/app.js
--- a/src/canvas.js
+++ b/src/canvas.js
+import "array-flat-polyfill"
+
 // Local canvas rendering.
 // Emit input events and receive draw calls seperately - these must be piped
 // together externally if desired.

-import { line, curveBasis } from "d3-shape"
+import { line, curveCatmullRom, curveLinear } from "d3-shape"

 import { canvas } from "./elements.js"

 const SVG_URL = "http://www.w3.org/2000/svg"

-// TODO: switch to curve interpolation that respects mouse points based on velocity
-const lineFn = line()
+import * as HTML from "./elements.js"
+
+export const LAST_RECOGNIZED_PATH_ID = "LSP"
+
+const curve = curveCatmullRom.alpha(1.0)
+const smoothLine = line()
  .x((d) => d[0])
  .y((d) => d[1])
-  .curve(curveBasis)
+  .curve(curve)
+const straightLine = line()
+  .x((d) => d[0])
+  .y((d) => d[1])
+  .curve(curveLinear)

 const pathGroupElems = new Map()

-let strokeColour = "#0000ff"
-let strokeRadius = 5
-
-const MAX_POINT_DISTANCE = 5
 const MAX_RADIUS_DELTA = 0.05

 // Interpolate a path so that:
-// - The distance between two adjacent points is capped at MAX_POINT_DISTANCE.
 // - The radius delta between two adjacent points is capped at
-//   MAX_RADIUS_DELTA
+//   MAX_RADIUS_DELTA.
 // If paths are too choppy, try decreasing these constants.
 const smoothPath = ([...path]) => {
-  // Apply MAX_POINT_DISTANCE.
-  for (let i = 1; i < path.length; i++) {
-    const dx = path[i][0] - path[i - 1][0]
-    const dy = path[i][1] - path[i - 1][1]
-    const dw = path[i][2] - path[i - 1][2]
-    const distance = Math.hypot(dx, dy)
-    const segmentsToSplit = Math.ceil(distance / MAX_POINT_DISTANCE)
-    const newPoints = []
-    for (let j = 1; j < segmentsToSplit; j++) {
-      newPoints.push([
-        path[i - 1][0] + (dx / segmentsToSplit) * j,
-        path[i - 1][1] + (dy / segmentsToSplit) * j,
-        path[i - 1][2] + (dw / segmentsToSplit) * j,
-        path[i - 1][3],
-        path[i - 1][4],
-      ])
-    }
-    path.splice(i, 0, ...newPoints)
-    i += newPoints.length
-  }
-
  // Apply MAX_RADIUS_DELTA.
  for (let i = 1; i < path.length; i++) {
    const dx = path[i][0] - path[i - 1][0]
@@ -62,7 +46,6 @@ const smoothPath = ([...path]) => {
        path[i - 1][1] + (dy / segmentsToSplit) * j,
        path[i - 1][2] + (dw / segmentsToSplit) * j,
        path[i - 1][3],
-        path[i - 1][4],
      ])
    }
    path.splice(i, 0, ...newPoints)
@@ -73,76 +56,197 @@ const smoothPath = ([...path]) => {

 export const input = new EventTarget()

-const createPathElem = (d, width) => {
-  const pathGroupElem = document.createElementNS(SVG_URL, "path")
-  pathGroupElem.setAttribute("stroke-width", width)
-  pathGroupElem.setAttribute("d", d)
-  return pathGroupElem
+const createSvgElem = (tagName) => document.createElementNS(SVG_URL, tagName)
+
+const interpolate = (point0, point1, fraction) => [
+  point0[0] + fraction * (point1[0] - point0[0]),
+  point0[1] + fraction * (point1[1] - point0[1]),
+  point0[2] + fraction * (point1[2] - point0[2]),
+  point0[3],
+]
+
+const ensurePathGroupElem = (id) => {
+  let groupElem = pathGroupElems.get(id)
+
+  if (groupElem == null) {
+    groupElem = createSvgElem("g")
+
+    groupElem.setAttribute("fill", "none")
+    groupElem.setAttribute("stroke-linecap", "round")
+    groupElem.setAttribute("pointer-events", "none")
+
+    HTML.canvas.appendChild(groupElem)
+    pathGroupElems.set(id, groupElem)
+  }
+
+  groupElem.innerHTML = ""
+
+  return groupElem
 }

-export const renderPath = (id, points) => {
-  points = points.filter(([x]) => x != null)
-  let colour = ""
-
-  // Split up points into completely non-erased segments.
-  let segments = [[]]
-  for (const point of points) {
-    colour = point[3]
-    if (point[4] != false) {
-      segments[segments.length - 1].push(point)
-    } else {
-      segments.push([])
-    }
+const renderSubpath = (subpath, pathSmooth) => {
+  const pathElem = createSvgElem("path")
+  pathElem.setAttribute("stroke", subpath[0][3])
+  pathElem.setAttribute("stroke-width", subpath[0][2] * 2)
+  pathElem.setAttribute(
+    "d",
+    pathSmooth ? smoothLine(subpath) : straightLine(subpath),
+  )
+  return pathElem
+}
+
+const isValidPoint = (point) => {
+  return point != null && point[0] != null
+}
+
+const POINT_ERASE_LIMIT = 0.0001
+
+const pointWasErased = (pointEraseIntervals) => {
+  return (
+    pointEraseIntervals.length > 0 &&
+    pointEraseIntervals[0][0] <= POINT_ERASE_LIMIT
+  )
+}
+
+const needToDrawLastPoint = (points, pathEraseIntervals) => {
+  if (points.length < 2) return true
+  const penultimatePointIndex = points.length - 2
+  const pointEraseIntervals = pathEraseIntervals[penultimatePointIndex] || null
+
+  if (
+    pointEraseIntervals != null &&
+    pointEraseIntervals.length > 0 &&
+    pointEraseIntervals.some((interval) => interval[1] >= 1 - POINT_ERASE_LIMIT)
+  ) {
+    return false
  }
-  segments = segments.filter((a) => a.length > 0)
+  return true
+}

-  let pathGroupElem = pathGroupElems.get(id)
+const applyErasureIntervals = (points, pathEraseIntervals) => {
+  if (points.length == 0) {
+    return []
+  }

-  if (segments.length == 0) {
-    if (pathGroupElem != null) {
-      canvas.removeChild(pathGroupElem)
-      pathGroupElems.delete(id)
+  const subpaths = []
+
+  let subpath = []
+  for (let i = 0; i < points.length; i++) {
+    const point = points[i]
+    if (!isValidPoint(point)) {
+      continue
+    }
+
+    const nextPoint = points[i + 1]
+    const pointEraseIntervals = pathEraseIntervals[i] || null
+
+    if (pointEraseIntervals == null) {
+      subpath.push(point)
+      continue
+    } else if (nextPoint == null) {
+      if (JSON.stringify(pointEraseIntervals) != "[[0,0]]") subpath.push(point)
+      continue
+    }
+
+    if (!pointWasErased(pointEraseIntervals) || subpath.length) {
+      subpath.push(point)
+    }
+
+    for (const pointEraseInterval of pointEraseIntervals) {
+      const eraseIntervalBounds = pointEraseInterval.map((f) =>
+        interpolate(point, nextPoint, f),
+      )
+      const [endOfDrawnSegment, startOfNewSegment] = eraseIntervalBounds
+
+      if (pointEraseInterval[0] > POINT_ERASE_LIMIT) {
+        subpath.push(endOfDrawnSegment)
+      }
+
+      subpaths.push(subpath.slice())
+
+      if (pointEraseInterval[1] < 1 - POINT_ERASE_LIMIT) {
+        subpath = [startOfNewSegment]
+      } else {
+        subpath = []
+      }
    }
-    return
  }

-  if (pathGroupElem == null) {
-    pathGroupElem = document.createElementNS(SVG_URL, "g")
-    pathGroupElem.setAttribute("stroke", colour)
-    pathGroupElem.setAttribute("fill", "none")
-    pathGroupElem.setAttribute("stroke-linecap", "round")
-    pathGroupElem.setAttribute("pointer-events", "none")
-    canvas.appendChild(pathGroupElem)
-    pathGroupElems.set(id, pathGroupElem)
+  if (needToDrawLastPoint(points, pathEraseIntervals)) {
+    subpaths.push(subpath.slice())
  }

-  pathGroupElem.innerHTML = ""
-
-  for (const subpath of segments) {
-    if (subpath.length == 1) {
-      const circleElem = document.createElementNS(SVG_URL, "circle")
-      circleElem.setAttribute("stroke", "none")
-      circleElem.setAttribute("fill", colour)
-      circleElem.setAttribute("cx", subpath[0][0])
-      circleElem.setAttribute("cy", subpath[0][1])
-      circleElem.setAttribute("r", subpath[0][2])
-      pathGroupElem.appendChild(circleElem)
-    } else {
-      // Further split up segments based on thickness.
-      const subpath_ = smoothPath(subpath)
-      let w = subpath_[0][2]
-      for (let i = 1; i < subpath_.length; i++) {
-        if (subpath_[i][2] != w) {
-          const d = lineFn([...subpath_.splice(0, i), subpath_[0]])
-          pathGroupElem.appendChild(createPathElem(d, w * 2))
-          w = subpath_[0][2]
-          i = 1
-        }
+  return subpaths.filter((subpath) => subpath.length > 0)
+}
+
+export const splitOnPressures = ([...path]) => {
+  const subpaths = []
+  let w = path[0][2]
+  for (let i = 1; i < path.length; i++) {
+    if (path[i][2] != w) {
+      subpaths.push([...path.splice(0, i), path[0]])
+      w = path[0][2]
+      i = 1
+    }
+  }
+  subpaths.push(path)
+  return subpaths
+}
+
+export const renderPath = (id, points, pathEraseIntervals) => {
+  let rectShapeStartIndex = -1
+  const pointsWithIntervals = Object.keys(pathEraseIntervals).length
+
+  // Rect recognition hint shape: pure rect with no erasure
+  if (pointsWithIntervals == 0 && points.length == 5) {
+    rectShapeStartIndex = 0
+    // Recognised rect shape: rect after completely erased raw data
+  } else if (pointsWithIntervals > 0 && points.length > 5) {
+    // Check that the preceding raw data is completely erased
+    for (let i = 0; i < points.length - 5; i++) {
+      if (
+        !pathEraseIntervals[i] ||
+        pathEraseIntervals[i].length != 1 ||
+        pathEraseIntervals[i][0][0] != 0 ||
+        pathEraseIntervals[i][0][1] != 1
+      ) {
+        break
      }
-      const d = lineFn(subpath_)
-      pathGroupElem.appendChild(createPathElem(d, w * 2))
    }
+
+    rectShapeStartIndex = points.length - 5
  }
+
+  // Only draw the path smooth if it is not a recognised rect shape, i.e. the last five points form a cycle
+  const pathSmooth = !(
+    rectShapeStartIndex >= 0 &&
+    points[rectShapeStartIndex][0] == points[rectShapeStartIndex + 4][0] &&
+    points[rectShapeStartIndex][1] == points[rectShapeStartIndex + 4][1] &&
+    points[rectShapeStartIndex][2] == points[rectShapeStartIndex + 4][2] &&
+    points[rectShapeStartIndex][3] == points[rectShapeStartIndex + 4][3]
+  )
+
+  let subpaths = applyErasureIntervals(points, pathEraseIntervals)
+
+  if (subpaths.length < 1 && id != LAST_RECOGNIZED_PATH_ID) {
+    const pathGroupElem = pathGroupElems.get(id)
+
+    if (pathGroupElem) {
+      pathGroupElems.delete(id)
+      HTML.canvas.removeChild(pathGroupElem)
+    }
+
+    return
+  }
+
+  subpaths = subpaths.map(smoothPath)
+  subpaths = subpaths.flatMap(splitOnPressures)
+  const subpathElems = subpaths.map((subpath) =>
+    renderSubpath(subpath, pathSmooth),
+  )
+
+  const pathGroupElem = ensurePathGroupElem(id)
+  subpathElems.forEach((subpathElem) => pathGroupElem.appendChild(subpathElem))
 }

 export const clear = () => {
@@ -151,12 +255,13 @@ export const clear = () => {
 }

 // Necessary since buttons property is non standard on iOS versions < 13.2
-function checkValidPointerEvent(e) {
+const isValidPointerEvent = (e, name) => {
+  if (name === "strokeend") return true
  return e.buttons & 1 || e.pointerType === "touch"
 }

 const dispatchPointerEvent = (name) => (e) => {
-  if (checkValidPointerEvent(e)) {
+  if (isValidPointerEvent(e, name)) {
    input.dispatchEvent(new CustomEvent(name, { detail: e }))
  }
 }
@@ -165,41 +270,8 @@ const dispatchPointerEvent = (name) => (e) => {
 canvas.addEventListener("pointerdown", dispatchPointerEvent("strokestart"))
 canvas.addEventListener("pointerenter", dispatchPointerEvent("strokestart"))
 canvas.addEventListener("pointerup", dispatchPointerEvent("strokeend"))
+canvas.addEventListener("onmouseup", dispatchPointerEvent("strokeend"))
+canvas.addEventListener("mouseup", dispatchPointerEvent("strokeend"))
 canvas.addEventListener("pointerleave", dispatchPointerEvent("strokeend"))
 canvas.addEventListener("pointermove", dispatchPointerEvent("strokemove"))
 canvas.addEventListener("touchmove", (e) => e.preventDefault())
-
-export function setStrokeColour(colour) {
-  strokeColour = colour
-}
-
-export function getStrokeColour() {
-  return strokeColour
-}
-
-const MIN_PRESSURE_FACTOR = 0.1
-const MAX_PRESSURE_FACTOR = 1.5
-
-// This is a quadratic such that:
-// - getPressureFactor(0.0) = MIN_PRESSURE_FACTOR
-// - getPressureFactor(0.5) = 1.0
-// - getPressureFactor(1.0) = MAX_PRESSURE_FACTOR
-// For sensible results, maintain that:
-// - 0.0 <= MIN_PRESSURE_FACTOR <= 1.0
-// - 1.0 <= MAX_PRESSURE_FACTOR
-// For intuitive results, maintain that:
-// - MAX_PRESSURE_FACTOR <= ~2.0
-const getPressureFactor = (pressure) => {
-  const a = 2 * (MAX_PRESSURE_FACTOR + MIN_PRESSURE_FACTOR) - 4
-  const b = -MAX_PRESSURE_FACTOR - 3 * MIN_PRESSURE_FACTOR + 4
-  const c = MIN_PRESSURE_FACTOR
-  return a * pressure ** 2 + b * pressure + c
-}
-
-export function getStrokeRadius(pressure) {
-  return strokeRadius * getPressureFactor(pressure)
-}
-
-export function setStrokeRadius(radius) {
-  strokeRadius = radius
-}
--- a/src/connection/Connection.js
+++ b/src/connection/Connection.js
+export default class AbstractConnection extends EventTarget {
+  constructor(options) {
+    super()
+
+    this.options = options
+  }
+
+  /*
+    Supported events:
+     - roomJoined => ()
+     - roomLeft => ()
+     - channelOpened => ({detail: uid})
+     - channelError => ({detail: uid})
+     - channelClosed => ({detail: uid})
+     - messageReceived => ({detail: {uid, channel, message}})
+    */
+
+  getUserID() {
+    // => int
+  }
+
+  getPeerHandle(/*uid*/) {
+    // => opaque
+  }
+
+  getPeerFootprint(/*uid*/) {
+    // => Promise => int
+  }
+
+  send(/*uid, channel, message*/) {
+    // => void
+  }
+
+  broadcast(/*channel, message*/) {
+    // => void
+  }
+
+  terminatePeer(/*uid*/) {
+    // => void
+  }
+
+  destructor() {
+    // => void
+  }
+}
--- a/src/connection/MockConnection.js
+++ b/src/connection/MockConnection.js
+export const userID = { uuid: null }
+
+export const sendListener = { callback: null }
+export const broadcastListener = { callback: null }
+
+const eventListeners = new Map()
+export const getEventListener = (room, event) =>
+  eventListeners.get(`${room}:${event}`)
+
+class MockConnection {
+  constructor({ room }) {
+    this.room = room
+
+    setTimeout(
+      () =>
+        getEventListener(room, "roomJoined") &&
+        getEventListener(room, "roomJoined")(),
+      0,
+    )
+  }
+
+  getUserID() {
+    return userID.uuid
+  }
+
+  getPeerHandle(/*uid*/) {
+    return undefined
+  }
+
+  getPeerFootprint(/*uid*/) {
+    return Promise.resolve(Date.now())
+  }
+
+  send(uid, channel, message) {
+    if (sendListener.callback) {
+      sendListener.callback(uid, channel, message)
+    }
+  }
+
+  broadcast(channel, message) {
+    if (broadcastListener.callback) {
+      broadcastListener.callback(channel, message)
+    }
+  }
+
+  terminatePeer() {
+    // Twiddle thumbs
+  }
+
+  destructor() {
+    sendListener.callback = null
+    broadcastListener.callback = null
+
+    eventListeners.clear()
+  }
+
+  addEventListener(event, callback) {
+    eventListeners.set(`${this.room}:${event}`, callback)
+  }
+}
+
+export default MockConnection
--- a/src/connection/WebRTC.js
+++ b/src/connection/WebRTC.js
+import AbstractConnection from "./Connection.js"
+
+import LioWebRTC from "liowebrtc"
+
+export default class WebRTCConnection extends AbstractConnection {
+  constructor(options) {
+    super(options)
+
+    this.webrtc = new LioWebRTC({
+      url: this.options.url,
+      dataOnly: true,
+      constraints: {
+        minPeers: this.options.mesh.minPeers,
+        maxPeers: this.options.mesh.maxPeers,
+      },
+    })
+
+    this.webrtc.on("ready", () => {
+      this.webrtc.joinRoom(this.options.room)
+    })
+
+    this.webrtc.on("joinedRoom", () => {
+      this.dispatchEvent(new CustomEvent("roomJoined"))
+    })
+
+    this.webrtc.on("leftRoom", () => {
+      this.dispatchEvent(new CustomEvent("roomLeft"))
+    })
+
+    this.webrtc.on("channelOpen", (dataChannel, peer) => {
+      this.dispatchEvent(new CustomEvent("channelOpened", { detail: peer.id }))
+    })
+
+    this.webrtc.on("channelError", (dataChannel, peer) => {
+      this.dispatchEvent(new CustomEvent("channelError", { detail: peer.id }))
+    })
+
+    this.webrtc.on("channelClose", (dataChannel, peer) => {
+      this.dispatchEvent(new CustomEvent("channelClosed", { detail: peer.id }))
+    })
+
+    this.webrtc.on("receivedPeerData", (channel, message, peer) => {
+      // Message could have been forwarded but interface only needs to know about directly connected peers
+      this.dispatchEvent(
+        new CustomEvent("messageReceived", {
+          detail: {
+            uid: peer.forwardedBy ? peer.forwardedBy.id : peer.id,
+            channel,
+            message,
+          },
+        }),
+      )
+    })
+  }
+
+  getUserID() {
+    return this.webrtc.getMyId()
+  }
+
+  getPeerHandle(uid) {
+    return this.webrtc.getPeerById(uid)
+  }
+
+  getPeerFootprint(uid) {
+    const peer = this.webrtc.getPeerById(uid)
+
+    if (!peer) return Promise.reject()
+
+    return new Promise(function(resolve, reject) {
+      peer.getStats(null).then((stats) => {
+        let footprint = -1
+
+        stats.forEach((report) => {
+          if (
+            report.type == "candidate-pair" &&
+            report.bytesSent > 0 &&
+            report.bytesReceived > 0 &&
+            report.writable
+          ) {
+            footprint = Math.max(footprint, report.bytesReceived)
+          }
+        })
+
+        if (footprint != -1) {
+          resolve(footprint)
+        } else {
+          reject()
+        }
+      })
+    })
+  }
+
+  send(uid, channel, message) {
+    const peer = this.webrtc.getPeerById(uid)
+
+    if (!peer) return
+
+    this.webrtc.whisper(peer, channel, message)
+  }
+
+  broadcast(channel, message) {
+    this.webrtc.shout(channel, message)
+  }
+
+  terminatePeer(uid) {
+    const peer = this.webrtc.getPeerById(uid)
+
+    if (!peer) return
+
+    peer.end()
+  }
+
+  destructor() {
+    this.webrtc.quit()
+  }
+}
--- a/src/connection/XMPP.js
+++ b/src/connection/XMPP.js
--- a/drawing-crdt @ 139ab6e2
+++ b/drawing-crdt @ 139ab6e2
+Subproject commit 139ab6e2cc9d6f0501fa958f3c813df0fcc81310
--- a/src/elements.js
+++ b/src/elements.js
-export const userIDElem = document.getElementById("user-id")
-
-export const peerIDElem = document.getElementById("peer-id")
-export const peerButton = document.getElementById("peer-connect")
 export const connectedPeers = document.getElementById("connected-peers")

 export const overallStatusIcon = document.getElementById("overall-status-icon")
@@ -12,6 +8,12 @@ export const overallStatusIconImage = document.getElementById(
 export const canvas = document.getElementById("canvas")
 export const penButton = document.getElementById("pen-tool")
 export const eraserButton = document.getElementById("eraser-tool")
+export const recognitionModeButton = document.getElementById("recognition-mode")
+export const draggingToolButton = document.getElementById("dragging-tool")
+export const canvasCenterToolButton = document.getElementById("canvas-center")
+
+export const fastUndoButton = document.getElementById("fast-undo-tool")
+export const undoButton = document.getElementById("undo-tool")

 export const roomIDElem = document.getElementById("room-id")
 export const roomConnectButton = document.getElementById("room-connect")
@@ -25,7 +27,9 @@ export const closeButton = document.querySelectorAll(".close")
 export const palette = document.getElementById("palette")
 export const rectangle = document.getElementById("rectangle")
 export const wheel = document.getElementById("wheel")
-export const picker = document.getElementById("other-colours")
-export const slider = document.getElementById("range")
+export const strokeColorPicker = document.getElementById("other-colours")
+export const strokeRadiusSlider = document.getElementById("range")
 export const output = document.getElementById("value")
 export const labelColours = document.getElementById("colours")
+export const userInfo = document.getElementById("user-avatar")
+export const topPanel = document.getElementById("top-panel")
--- a/src/erasure.js
+++ b/src/erasure.js
--- a/src/intelligence-exfiltrator.js
+++ b/src/intelligence-exfiltrator.js
--- a/src/p2p-mesh.js
+++ b/src/p2p-mesh.js
--- a/src/queue.js
+++ b/src/queue.js
--- a/src/room.js
+++ b/src/room.js
--- a/src/server.js
+++ b/src/server.js
@@ -45,6 +45,17 @@ app.use((request, response, next) => {
  next()
 })

+app.get("/", (request, response, next) => {
+  if (request.query.room == null) {
+    const url = new URL(
+      `${request.protocol}://${request.get("host")}${request.originalUrl}`,
+    )
+    url.searchParams.set("room", "imperial")
+    return response.redirect(url)
+  }
+  next()
+})
+
 app.use("/", express.static("public"))

 server.listen(port, host, () => {

--- a/public/service-worker.js
+++ b/public/service-worker.js
@@ -7,24 +7,7 @@ self.addEventListener("activate", (event) => {
 })

 const CACHE_NAME = "APP-V0"
-const FILES_TO_CACHE = [
-  "/index.html",
-  "/styles.css",
-  "/js/app.js",
-  "/js/queue.js",
-  "/logo.png",
-  "/manifest.json",
-  "/assets/fonts/martel-v4-latin/martel-v4-latin-regular.eot",
-  "/assets/fonts/martel-v4-latin/martel-v4-latin-regular.svg",
-  "/assets/fonts/martel-v4-latin/martel-v4-latin-regular.ttf",
-  "/assets/fonts/martel-v4-latin/martel-v4-latin-regular.woff",
-  "/assets/fonts/martel-v4-latin/martel-v4-latin-regular.woff2",
-  "/synchronising.svg",
-  "/synchronised.svg",
-  "/quality-high.svg",
-  "/quality-medium.svg",
-  "/quality-low.svg",
-]
+const FILES_TO_CACHE = [FILES_TO_CACHE_LIST] // eslint-disable-line no-undef
 const FILE_ALIASES = new Map([["/", "/index.html"]])

 self.addEventListener("install", async () => {
@@ -40,7 +23,11 @@ self.addEventListener("activate", async () => {
 })

 const normalizePath = (path) => {
-  let normalizedPath = path.replace(/\/+/g, "/").replace(/$(?<!^)\/$/, "")
+  let normalizedPath = path.replace(/\/+/g, "/")
+  // TODO: Is this a correct replacement for replace(/$(?<!^)\/$/, "") (compatible with Safari)?
+  if (normalizedPath != "/" && normalizedPath.endsWith("/")) {
+    normalizedPath = normalizedPath.slice(0, -1)
+  }
  normalizedPath = FILE_ALIASES.get(normalizedPath) || normalizedPath
  return normalizedPath
 }

--- a/src/shapes.js
+++ b/src/shapes.js
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