client/home: show post notes (read-only)

client/css/colors.styl

@@ -32,3 +32,8 @@ $new-tag-text-color = black
 $default-tag-category-background-color = $active-tab-background-color
 $duplicate-tag-background-color = #FDC
 $duplicate-tag-text-color = black
+$note-overlay-background-color = rgba(255, 255, 255, 0.3)
+$note-overlay-border-color = rgba(0, 0, 0, 0.3)
+$note-text-background-color = lemonchiffon
+$note-text-border-color = black
+$note-text-text-color = black

client/css/posts.styl

@@ -27,3 +27,27 @@
             bottom: 0
             width: 100%
             height: 100%
+
+        .notes
+            stroke-width: 1px
+            polygon
+                fill: $note-overlay-background-color
+                stroke: $note-overlay-border-color
+
+.note-text
+    position: absolute
+    max-width: 22.5em
+    margin-top: -0.5em
+    display: none
+
+    &>.wrapper
+        background: $note-text-background-color
+        padding: 0.5em
+        border: 1px solid $note-text-border-color
+        color: $note-text-text-color
+        margin-top: 1em
+
+        p:last-of-type
+            margin-bottom: 0
+        p:first-of-type
+            margin-top: 0

client/js/controls/post_notes_overlay_control.js

@@ -0,0 +1,79 @@
+'use strict';
+
+const views = require('../util/views.js');
+const misc = require('../util/misc.js');
+const svgNS = 'http://www.w3.org/2000/svg';
+
+class PostNotesOverlayControl {
+    constructor(postOverlayNode, post) {
+        this._post = post;
+        this._postOverlayNode = postOverlayNode;
+        this._install();
+    }
+
+    _evtMouseEnter(e) {
+        const bodyRect = document.body.getBoundingClientRect();
+        const svgRect = this._svgNode.getBoundingClientRect();
+        const polygonRect = e.target.getBBox();
+        this._textNode.querySelector('.wrapper').innerHTML
+            = misc.formatMarkdown(e.target.getAttribute('data-text'));
+        this._textNode.style.left = (
+            svgRect.left + svgRect.width * polygonRect.x) + 'px';
+        this._textNode.style.top = (
+            svgRect.top + svgRect.height * (
+                polygonRect.y + polygonRect.height)) + 'px';
+        this._textNode.style.display = 'block';
+    }
+
+    _evtMouseLeave(e) {
+        const newElement = e.relatedTarget;
+        if (newElement === this._svgNode ||
+                (!this._svgNode.contains(newElement)
+                    && !this._textNode.contains(newElement)
+                    && newElement !== this._textNode)) {
+            this._textNode.style.display = 'none';
+        }
+    }
+
+    _install() {
+        this._svgNode = document.createElementNS(svgNS, 'svg');
+        this._svgNode.classList.add('notes');
+        this._svgNode.setAttribute('preserveAspectRatio', 'none');
+        this._svgNode.setAttribute('viewBox', '0 0 1 1');
+        for (let note of this._post.notes) {
+            const polygonNode = document.createElementNS(svgNS, 'polygon');
+            polygonNode.setAttribute(
+                'vector-effect', 'non-scaling-stroke');
+            polygonNode.setAttribute(
+                'stroke-alignment', 'inside');
+            polygonNode.setAttribute(
+                'points', note.polygon.map(point => point.join(',')).join(' '));
+            polygonNode.setAttribute('data-text', note.text);
+            polygonNode.addEventListener(
+                'mouseenter', e => this._evtMouseEnter(e));
+            polygonNode.addEventListener(
+                'mouseleave', e => this._evtMouseLeave(e));
+            this._svgNode.appendChild(polygonNode);
+        }
+        this._postOverlayNode.appendChild(this._svgNode);
+
+        const wrapperNode = document.createElement('div');
+        wrapperNode.classList.add('wrapper');
+        this._textNode = document.createElement('div');
+        this._textNode.classList.add('note-text');
+        this._textNode.appendChild(wrapperNode);
+        this._textNode.addEventListener(
+            'mouseleave', e => this._evtMouseLeave(e));
+        document.body.appendChild(this._textNode);
+
+        views.monitorNodeRemoval(
+            this._postOverlayNode, () => { this._uninstall(); });
+    }
+
+    _uninstall() {
+        this._postOverlayNode.removeChild(this._svgNode);
+        document.body.removeChild(this._textNode);
+    }
+};
+
+module.exports = PostNotesOverlayControl;

client/js/views/home_view.js

@@ -5,6 +5,8 @@ const config = require('../config.js');
 const misc = require('../util/misc.js');
 const views = require('../util/views.js');
 const PostContentControl = require('../controls/post_content_control.js');
+const PostNotesOverlayControl
+    = require('../controls/post_notes_overlay_control.js');
 const TagAutoCompleteControl =
     require('../controls/tag_auto_complete_control.js');
 
@@ -49,6 +51,10 @@ class HomeView {
                         window.innerHeight * 0.7,
                     ];
                 });
+
+            new PostNotesOverlayControl(
+                postContainerNode.querySelector('.post-overlay'),
+                ctx.featuredPost);
         }
     }
 }