fix: make updateBackDecorationsLayer a free function

Author: aminya

lib/mixins/canvas-drawer.js

@@ -156,7 +156,7 @@ export default class CanvasDrawer extends Mixin {
     backgroundDecorationDispatcher['background-custom'] = drawCustomDecorationLambda
     frontDecorationDispatcher['foreground-custom'] = drawCustomDecorationLambda
 
-    this.updateBackDecorationsLayer(firstRow, lastRow, renderData, lineHeight, editorElement, decorations)
+    updateBackDecorationsLayer(this.backLayer, firstRow, lastRow, this.offscreenFirstRow, this.offscreenLastRow, this.pendingBackDecorationChanges, renderData, lineHeight, editorElement, decorations)
 
     renderData.context = this.frontLayer.context
 
@@ -180,58 +180,6 @@ export default class CanvasDrawer extends Mixin {
     this.offscreenLastRow = lastRow
   }
 
-  /**
-   * Performs an update of the back decorations layer using the pending back
-   * decorations changes arrays.
-   *
-   * @param  {number} firstRow firstRow the first row of the range to update
-   * @param  {number} lastRow lastRow the last row of the range to update
-   *
-   * @param {Object} renderData
-   * @param {number} lineHeight  this.minimap.getLineHeight() * devicePixelRatio
-   * @param {TextEditorElement} editorElement  this.minimap.getTextEditorElement()
-   * @param {Array<Decoration>} decorations
-   * @access private
-   */
-  updateBackDecorationsLayer (firstRow, lastRow, renderData, lineHeight, editorElement, decorations) {
-    const intactRanges = computeIntactRanges(firstRow, lastRow, this.pendingBackDecorationChanges, this.offscreenFirstRow, this.offscreenLastRow)
-
-    // NOTE: this method is the hot function of Minimap. Do not refactor. The code is inlined delibarately.
-
-    // redrawRangesOnLayer
-
-    this.backLayer.clearCanvas()
-
-    if (intactRanges.length === 0) {
-      drawBackDecorationsForLines(firstRow, lastRow, 0, renderData, lineHeight, editorElement, decorations)
-    } else {
-      for (let j = 0, len = intactRanges.length; j < len; j++) {
-        const intact = intactRanges[j]
-
-        this.backLayer.copyPartFromOffscreen(
-          intact.offscreenRow * lineHeight,
-          (intact.start - firstRow) * lineHeight,
-          (intact.end - intact.start) * lineHeight
-        )
-      }
-      // drawLinesForRanges
-      let currentRow = firstRow
-      for (let i = 0, len = intactRanges.length; i < len; i++) {
-        const range = intactRanges[i]
-
-        drawBackDecorationsForLines(currentRow, range.start, currentRow - firstRow, renderData, lineHeight, editorElement, decorations)
-
-        currentRow = range.end
-      }
-      if (currentRow <= lastRow) {
-        drawBackDecorationsForLines(currentRow, lastRow, currentRow - firstRow, renderData, lineHeight, editorElement, decorations)
-      }
-    }
-
-    this.backLayer.resetOffscreenSize()
-    this.backLayer.copyToOffscreen()
-  }
-
   /**
    * Performs an update of the front decorations layer using the pending front
    * decorations changes arrays.
@@ -421,6 +369,61 @@ function updateTokensLayer (tokensLayer, firstRow, lastRow, offscreenFirstRow, o
   tokensLayer.copyToOffscreen()
 }
 
+/**
+ * Performs an update of the back decorations layer using the pending back
+ * decorations changes arrays.
+ * @param {CanvasLayer} backLayer
+ * @param  {number} firstRow firstRow the first row of the range to update
+ * @param  {number} lastRow lastRow the last row of the range to update
+ *
+ * @param {number} offscreenFirstRow
+ * @param {number} offscreenLastRow
+ * @param {Array<>} pendingBackDecorationChanges
+ * @param {Object} renderData
+ * @param {number} lineHeight  this.minimap.getLineHeight() * devicePixelRatio
+ * @param {TextEditorElement} editorElement  this.minimap.getTextEditorElement()
+ * @param {Array<Decoration>} decorations
+ * @access private
+ */
+function updateBackDecorationsLayer (backLayer, firstRow, lastRow, offscreenFirstRow, offscreenLastRow, pendingBackDecorationChanges, renderData, lineHeight, editorElement, decorations) {
+  const intactRanges = computeIntactRanges(firstRow, lastRow, pendingBackDecorationChanges, offscreenFirstRow, offscreenLastRow)
+
+  // NOTE: this method is the hot function of Minimap. Do not refactor. The code is inlined delibarately.
+
+  // redrawRangesOnLayer
+
+  backLayer.clearCanvas()
+
+  if (intactRanges.length === 0) {
+    drawBackDecorationsForLines(firstRow, lastRow, 0, renderData, lineHeight, editorElement, decorations)
+  } else {
+    for (let j = 0, len = intactRanges.length; j < len; j++) {
+      const intact = intactRanges[j]
+
+      backLayer.copyPartFromOffscreen(
+        intact.offscreenRow * lineHeight,
+        (intact.start - firstRow) * lineHeight,
+        (intact.end - intact.start) * lineHeight
+      )
+    }
+    // drawLinesForRanges
+    let currentRow = firstRow
+    for (let i = 0, len = intactRanges.length; i < len; i++) {
+      const range = intactRanges[i]
+
+      drawBackDecorationsForLines(currentRow, range.start, currentRow - firstRow, renderData, lineHeight, editorElement, decorations)
+
+      currentRow = range.end
+    }
+    if (currentRow <= lastRow) {
+      drawBackDecorationsForLines(currentRow, lastRow, currentRow - firstRow, renderData, lineHeight, editorElement, decorations)
+    }
+  }
+
+  backLayer.resetOffscreenSize()
+  backLayer.copyToOffscreen()
+}
+
 const whitespaceTokenRegex = /^\s+$/
 const oneOrMoreWhiteSpaceRegexp = /\s+/