fix: factor out dispatchers and lambda

Author: aminya

lib/mixins/canvas-drawer.js

@@ -144,6 +144,10 @@ export default class CanvasDrawer extends Mixin {
       orders: Main.getPluginsOrder()
     }
 
+    const drawCustomDecorationLambda = (decoration, data, decorationColor) => drawCustomDecoration(decoration, data, decorationColor, editorElement)
+    backgroundDecorationDispatcher['background-custom'] = drawCustomDecorationLambda
+    frontDecorationDispatcher['foreground-custom'] = drawCustomDecorationLambda
+
     this.updateBackDecorationsLayer(firstRow, lastRow, renderData, lineHeight, editorElement, decorations)
 
     renderData.context = this.frontLayer.context
@@ -485,9 +489,6 @@ export default class CanvasDrawer extends Mixin {
   drawBackDecorationsForLines (firstRow, lastRow, offsetRow, renderData, lineHeight, editorElement, decorations) {
     if (firstRow > lastRow) { return }
 
-    const drawCustomDecorationLambda = (decoration, data, decorationColor) => drawCustomDecoration(decoration, data, decorationColor, editorElement)
-    backgroundDecorationDispatcher['background-custom'] = drawCustomDecorationLambda
-
     for (let screenRow = firstRow; screenRow <= lastRow; screenRow++) {
       renderData.row = offsetRow + (screenRow - firstRow)
       renderData.yRow = renderData.row * lineHeight
@@ -519,9 +520,6 @@ export default class CanvasDrawer extends Mixin {
   drawFrontDecorationsForLines (firstRow, lastRow, offsetRow, renderData, lineHeight, editorElement, decorations) {
     if (firstRow > lastRow) { return }
 
-    const drawCustomDecorationLambda = (decoration, data, decorationColor) => drawCustomDecoration(decoration, data, decorationColor, editorElement)
-    frontDecorationDispatcher['foreground-custom'] = drawCustomDecorationLambda
-
     for (let screenRow = firstRow; screenRow <= lastRow; screenRow++) {
       renderData.row = offsetRow + (screenRow - firstRow)
       renderData.yRow = renderData.row * lineHeight
@@ -747,13 +745,21 @@ function getInvisibleRegExp (editor) {
   }
 }
 
-// dispatchers for decoration drawing (custom decoration drawer added dynamically)
-
+/**
+ * dispatchers for decoration drawing (custom decoration drawer added dynamically)
+ * @param {Object} backgroundDecorationDispatcher an object with the type to render as key and the
+ *                        render method as value
+*/
 const backgroundDecorationDispatcher = {
   line: drawLineDecoration,
   'highlight-under': drawHighlightDecoration
 }
 
+/**
+ * dispatchers for decoration drawing (custom decoration drawer added dynamically)
+ * @param {Object} frontDecorationDispatcher an object with the type to render as key and the
+ *                        render method as value
+*/
 const frontDecorationDispatcher = {
   gutter: drawGutterDecoration,
   'highlight-over': drawHighlightDecoration,