2 files changed, 109 insertions, 4 deletions
diff --git a/frontend/views/graph/components/graph.editor.js b/frontend/views/graph/components/graph.editor.js
index 5093327..c21c624 100644
--- a/frontend/views/graph/components/graph.editor.js
+++ b/frontend/views/graph/components/graph.editor.js
@@ -9,7 +9,7 @@ import actions from '../../../actions'
 import * as graphActions from '../graph.actions'
 
 import { Loader } from '../../../common'
-import { clamp, dist } from '../../../util'
+import { clamp, dist, mod } from '../../../util'
 
 const defaultState = {
   dragging: false,
@@ -144,19 +144,24 @@ class GraphEditor extends Component {
 
   render(){
     // console.log(this.props.graph.show.res)
-    const currentPage = this.state.page
-    const currentBox = this.state.box
+    const { page: currentPage, box } = this.state
     const { res: graph } = this.props.graph.show
     // console.log(res.pages)
     return (    
       <div className='graph' ref={this.graphRef}>
+        <GraphCanvas
+          bounds={this.state.bounds}
+          pages={graph.pages}
+          currentPage={currentPage}
+          box={box}
+        />
         {this.state.bounds && graph.pages.map(page => (
           <PageHandle
             key={page.id}
             graph={graph}
             page={page}
             bounds={this.state.bounds}
-            box={currentPage && page.id === currentPage.id && currentBox}
+            box={currentPage && page.id === currentPage.id && box}
             onMouseDown={e => this.handleMouseDown(e, page)}
           />
         ))}
@@ -165,6 +170,101 @@ class GraphEditor extends Component {
   }
 }
 
+class GraphCanvas extends Component {
+  constructor(props) {
+    super(props)
+    this.canvasRef = React.createRef()
+  }
+  
+  componentDidMount() {
+    if (this.props.bounds) {
+      this.draw({})      
+    }
+  }
+  
+  componentDidUpdate(prevProps) {
+    this.draw(prevProps)
+  }
+
+  draw(prevProps) {
+    const { current: canvas } = this.canvasRef
+    const { bounds, pages, currentPage, box } = this.props
+    const { width, height } = bounds
+    if (prevProps.bounds !== bounds) {
+      canvas.width = width
+      canvas.height = height
+    }
+    const ctx = canvas.getContext('2d')
+    ctx.clearRect(0, 0, width, height)
+    ctx.lineWidth = 2
+    const coordsLookup = pages.reduce((a,b) => {
+      if (currentPage && box && b.id === currentPage.id) {
+        a[b.id] = {
+          x: box.x,
+          y: box.y,
+          backlinks: new Set([]),
+        }
+      } else {
+        a[b.id] = {
+          x: b.settings.x,
+          y: b.settings.y,
+          backlinks: new Set([]),
+        }
+      }
+      return a
+    }, {})
+    pages.map(page => {
+      const sourceCoord = coordsLookup[page.id]
+      page.backlinks.map(tile => {
+        if (tile.target_page_id <= 0) return
+        const targetCoord = coordsLookup[tile.page_id]
+        let xOffset = 16
+        let yOffset = 16
+        // console.log(tile.page_id, tile.target_page_id, sourceCoord.backlinks, targetCoord.backlinks)
+        if (targetCoord.backlinks.has(tile.target_page_id)) {
+          xOffset += 10
+          ctx.strokeStyle = "#88ffff"
+        } else {
+          sourceCoord.backlinks.add(tile.page_id)
+          ctx.strokeStyle = "#ff88ff"
+        }
+        ctx.beginPath()
+        const x1 = targetCoord.x * width + xOffset
+        const y1 = targetCoord.y * height + yOffset
+        const x2 = sourceCoord.x * width + xOffset
+        const y2 = sourceCoord.y * height + yOffset
+        this.arrow(ctx, x1, y1, x2, y2)
+        ctx.stroke()
+      })
+    })
+  }
+  
+  arrow(ctx, x1, y1, x2, y2) {
+    const headlen = 10 // length of head in pixels
+    const dx = x2 - x1
+    const dy = y2 - y1
+    const angle = Math.atan2(dy, dx)
+    const farOffset = 20
+    x1 += Math.cos(angle) * 0
+    x2 -= Math.cos(angle) * farOffset
+    y1 += Math.sin(angle) * 0
+    y2 -= Math.sin(angle) * farOffset
+    const leftAngle = mod(angle - Math.PI / 6, Math.PI * 2)
+    const rightAngle = mod(angle + Math.PI / 6, Math.PI * 2)
+    ctx.moveTo(x1, y1)
+    ctx.lineTo(x2, y2)
+    ctx.lineTo(x2 - headlen * Math.cos(leftAngle), y2 - headlen * Math.sin(leftAngle))
+    ctx.moveTo(x2, y2)
+    ctx.lineTo(x2 - headlen * Math.cos(rightAngle), y2 - headlen * Math.sin(rightAngle))
+  }
+
+  render() {
+    return (
+      <canvas ref={this.canvasRef} />
+    )
+  }
+}
+
 const PageHandle = ({ graph, page, bounds, box, onMouseDown }) => {
   let style;
   if (box) {
diff --git a/frontend/views/graph/graph.css b/frontend/views/graph/graph.css
index 511d15e..52f1a7e 100644
--- a/frontend/views/graph/graph.css
+++ b/frontend/views/graph/graph.css
@@ -12,6 +12,11 @@
       rgba(128, 0, 64, 0.2)
     );
 }
+.graph canvas {
+  position: absolute;
+  top: 0;
+  left: 0;
+}
 
 /* Sidebar boxes */