1 files changed, 138 insertions, 0 deletions
diff --git a/frontend/app/views/graph/components/graph.canvas.js b/frontend/app/views/graph/components/graph.canvas.js
new file mode 100644
index 0000000..2896c6b
--- /dev/null
+++ b/frontend/app/views/graph/components/graph.canvas.js
@@ -0,0 +1,138 @@
+import React, { Component } from 'react'
+
+import { mod, angle } from 'app/utils'
+
+const DEFAULT_MEASUREMENT = { width: 16, height: 16 }
+const BACKLINK_SPACING = 10
+const ARROWHEAD_LENGTH = 10
+const GRAPH_LINK_COLOR = "#ff88ff"
+const GRAPH_BACKLINK_COLOR = "#88ffff"
+const GRAPH_UNHOVER_LINK_COLOR = "#884488"
+const GRAPH_UNHOVER_BACKLINK_COLOR = "#448888"
+
+export default 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, measurements, highlightedPageId } = 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]
+        const isHighlightedPage = !highlightedPageId || highlightedPageId === page.id || highlightedPageId === tile.page_id
+        let tile_measurement = measurements[tile.page_id] || DEFAULT_MEASUREMENT
+        let target_measurement = measurements[tile.target_page_id] || DEFAULT_MEASUREMENT
+        let theta = angle(targetCoord.x, targetCoord.y, sourceCoord.x, sourceCoord.y)
+        let x1_offset = tile_measurement.width / 2 // * (0.5 - Math.cos(theta))
+        let y1_offset = tile_measurement.height / 2
+        let x2_offset = target_measurement.width / 2 // (0.5 - Math.cos(theta))
+        let y2_offset = target_measurement.height / 2
+        // skip duplicate links
+        if (sourceCoord.backlinks.has(tile.page_id)) {
+          return
+        }
+        /*
+          if it's pointing right, cos(t) is 1
+          if it's pointing left,  cos(t) is -1
+        */
+        // if (Math.abs(Math.cos(theta)) > 0.5) {
+        // x1_offset += target_measurement.width / 3 * (- Math.cos(theta))
+        // x1_offset += target_measurement.height / 4 * (- Math.sin(theta))
+        x2_offset += target_measurement.width / 3 * (- Math.cos(theta))
+        y2_offset += target_measurement.height / 6 * (- Math.sin(theta))
+        // }
+        // if this is the first time encountering this link...
+        if (!targetCoord.backlinks.has(tile.target_page_id)) {
+          sourceCoord.backlinks.add(tile.page_id)
+          ctx.strokeStyle = isHighlightedPage
+            ? GRAPH_LINK_COLOR
+            : GRAPH_UNHOVER_LINK_COLOR
+        } else { // otherwise this is a two-way link
+          x1_offset += BACKLINK_SPACING * Math.sin(theta)
+          y1_offset += BACKLINK_SPACING * Math.cos(theta)
+          x2_offset += BACKLINK_SPACING * Math.sin(theta)
+          y2_offset += BACKLINK_SPACING * Math.cos(theta)
+          // x1_offset += BACKLINK_SPACING * Math.cos(theta + Math.PI /2)
+          // y1_offset += BACKLINK_SPACING * Math.sin(theta + Math.PI /2)
+          // x2_offset += BACKLINK_SPACING * Math.cos(theta + Math.PI /2)
+          // y2_offset += BACKLINK_SPACING * Math.sin(theta + Math.PI /2)
+          ctx.strokeStyle = isHighlightedPage
+            ? GRAPH_BACKLINK_COLOR
+            : GRAPH_UNHOVER_BACKLINK_COLOR
+        }
+        ctx.beginPath()
+        const x1 = targetCoord.x * width + x1_offset
+        const y1 = targetCoord.y * height + y1_offset
+        const x2 = sourceCoord.x * width + x2_offset
+        const y2 = sourceCoord.y * height + y2_offset
+        this.arrow(ctx, x1, y1, x2, y2)
+        ctx.stroke()
+      })
+    })
+  }
+  
+  arrow(ctx, x1, y1, x2, y2) {
+    const farOffset = 20
+    const endOffset = 1
+    const theta = angle(x1, y1, x2, y2)
+    x1 += Math.cos(theta) * 0
+    x2 -= Math.cos(theta) * farOffset
+    y1 += Math.sin(theta) * 0
+    y2 -= Math.sin(theta) * farOffset
+    const xEnd = x2 - Math.cos(theta) * endOffset
+    const yEnd = y2 - Math.sin(theta) * endOffset
+    const leftAngle = mod(theta - Math.PI / 6, Math.PI * 2)
+    const rightAngle = mod(theta + Math.PI / 6, Math.PI * 2)
+    ctx.moveTo(x1, y1)
+    ctx.lineTo(xEnd, yEnd)
+    ctx.moveTo(x2, y2)
+    ctx.lineTo(x2 - ARROWHEAD_LENGTH * Math.cos(leftAngle), y2 - ARROWHEAD_LENGTH * Math.sin(leftAngle))
+    ctx.moveTo(x2, y2)
+    ctx.lineTo(x2 - ARROWHEAD_LENGTH * Math.cos(rightAngle), y2 - ARROWHEAD_LENGTH * Math.sin(rightAngle))
+  }
+
+  render() {
+    return (
+      <canvas ref={this.canvasRef} />
+    )
+  }
+}