Implement canvas-based mistake highlighting in BesService

- There's still a work to be done, but IMO it is a step inthe right direction

service.js

@@ -331,25 +331,76 @@ class BesService {
    * @returns {Array} Grammar mistake highlight elements
    */
   addMistakeMarkup(range, ruleId) {
-    const scrollPanelRect = this.scrollPanel.getBoundingClientRect()
+    const canvasPanelRect = this.canvasPanel.getBoundingClientRect()
-    let highlights = []
+    console.log(canvasPanelRect)
-    for (let rect of range.getClientRects()) {
+    const highlights = []
-      const highlight = document.createElement('div')
+    this.canvasPanel.classList.add('bes-canvas')
-      highlight.classList.add(
+    const ctx = this.canvasPanel.getContext('2d')
-        ruleId.startsWith('MORFOLOGIK_RULE')
+    ctx.lineWidth = 2
-          ? 'bes-spelling-mistake'
+    ctx.strokeStyle = ruleId.startsWith('MORFOLOGIK_RULE')
-          : 'bes-grammar-mistake'
+      ? '#e91313'
-      )
+      : '#269b26'
-      highlight.style.left = `${rect.left - scrollPanelRect.left}px`
+
-      highlight.style.top = `${rect.top - scrollPanelRect.top}px`
+    // Set the canvas dimensions and scale the context only once
-      highlight.style.width = `${rect.width}px`
+    if (!this.canvasInitialized) {
-      highlight.style.height = `${rect.height}px`
+      const dpr = window.devicePixelRatio || 1
-      this.scrollPanel.appendChild(highlight)
+      this.canvasPanel.width = canvasPanelRect.width * dpr
-      highlights.push(highlight)
+      this.canvasPanel.height = canvasPanelRect.height * dpr
+      this.canvasPanel.style.width = `${canvasPanelRect.width}px`
+      this.canvasPanel.style.height = `${canvasPanelRect.height}px`
+      const ctx = this.canvasPanel.getContext('2d')
+      ctx.scale(dpr, dpr)
+      this.canvasInitialized = true
     }
+
+    for (let rect of range.getClientRects()) {
+      console.log(rect)
+      const x = rect.left - canvasPanelRect.left
+      const y = rect.top - canvasPanelRect.top + rect.height
+      const width = rect.width
+
+      console.log('rect.left: ', rect.left)
+      console.log('canvasPanelRect.left: ', canvasPanelRect.left)
+      console.log('x: ', x)
+      console.log('y: ', y)
+      console.log('width: ', width)
+
+      // Draw the underline
+      ctx.beginPath()
+      ctx.moveTo(x, y)
+      ctx.lineTo(x + width, y)
+      ctx.stroke()
+    }
+
     return highlights
   }
 
+  // addMistakeMarkup(range, ruleId) {
+  //   const scrollPanelRect = this.scrollPanel.getBoundingClientRect()
+  //   let highlights = []
+  //   for (let rect of range.getClientRects()) {
+  //     const highlight = document.createElement('div')
+  //     highlight.classList.add(
+  //       ruleId.startsWith('MORFOLOGIK_RULE')
+  //         ? 'bes-spelling-mistake'
+  //         : 'bes-grammar-mistake'
+  //     )
+  //     highlight.style.left = `${rect.left - scrollPanelRect.left}px`
+  //     highlight.style.top = `${rect.top - scrollPanelRect.top}px`
+  //     highlight.style.width = `${rect.width}px`
+  //     highlight.style.height = `${rect.height}px`
+  //     this.scrollPanel.appendChild(highlight)
+  //     highlights.push(highlight)
+  //   }
+  //   return highlights
+  // }
+  // highlight.style.left = `${rect.left - scrollPanelRect.left}px`
+  // highlight.style.top = `${rect.top - scrollPanelRect.top}px`
+  // highlight.style.width = `${rect.width}px`
+  // highlight.style.height = `${rect.height}px`
+  // this.scrollPanel.appendChild(highlight)
+  // highlights.push(highlight)
+
   /**
    * Tests if given coordinate is inside of a rectangle.
    *
@@ -375,8 +426,11 @@ class BesService {
     this.scrollPanel = document.createElement('div')
     this.scrollPanel.classList.add('bes-correction-panel-scroll')
 
+    this.canvasPanel = document.createElement('canvas')
+
     panelParent.appendChild(this.correctionPanel)
     this.correctionPanel.appendChild(this.scrollPanel)
+    this.scrollPanel.appendChild(this.canvasPanel)
     this.textElement.parentElement.insertBefore(panelParent, this.textElement)
     this.setCorrectionPanelSize()
   }
@@ -404,6 +458,8 @@ class BesService {
     this.correctionPanel.style.paddingBottom = styles.paddingBottom
     this.scrollPanel.style.width = `${this.hostElement.scrollWidth}px`
     this.scrollPanel.style.height = `${this.hostElement.scrollHeight}px`
+    this.canvasPanel.style.width = `${this.hostElement.scrollWidth}px`
+    this.canvasPanel.style.height = `${this.hostElement.scrollHeight}px`
     if (this.isHostElementInline()) {
       const totalWidth =
         parseFloat(styles.paddingLeft) +

styles.css

@@ -15,6 +15,12 @@
   cursor: text;
 }
 
+.bes-canvas {
+  position: relative;
+  z-index: 3;
+  cursor: text;
+}
+
 .bes-spelling-mistake.bes-mistake-highlight-selected {
   background: #cc7024;
   opacity: 0.5;