From 4c1b586dd24d499e0a7f7b47ef5c70d049b8a67f Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Sun, 5 Sep 2021 12:12:34 +0200
Subject: [PATCH] Reduce the size of `TextLayerRenderTask._textDivProperties`
 in "regular" text-selection mode

While these changes will obviously not have a significant effect on overall memory usage, it cannot hurt as far as I'm concerned. This patch makes the following changes:
 - Clear out `_textDivProperties` once rendering is done, since those properties are only necessary to keep alive when *enhanced* text-selection is being used.

 - Reduce the size of the `_textDivProperties`-entries by default, since a majority of the properties are only relevant when *enhanced* text-selection is being used.
---
 src/display/text_layer.js | 43 ++++++++++++++++++++++++++-------------
 1 file changed, 29 insertions(+), 14 deletions(-)

diff --git a/src/display/text_layer.js b/src/display/text_layer.js
index b1b22ec1afb00..5ba09adbedcd6 100644
--- a/src/display/text_layer.js
+++ b/src/display/text_layer.js
@@ -118,18 +118,25 @@ function getAscent(fontFamily, ctx) {
 function appendText(task, geom, styles, ctx) {
   // Initialize all used properties to keep the caches monomorphic.
   const textDiv = document.createElement("span");
-  const textDivProperties = {
-    angle: 0,
-    canvasWidth: 0,
-    hasText: geom.str !== "",
-    hasEOL: geom.hasEOL,
-    originalTransform: null,
-    paddingBottom: 0,
-    paddingLeft: 0,
-    paddingRight: 0,
-    paddingTop: 0,
-    scale: 1,
-  };
+  const textDivProperties = task._enhanceTextSelection
+    ? {
+        angle: 0,
+        canvasWidth: 0,
+        hasText: geom.str !== "",
+        hasEOL: geom.hasEOL,
+        originalTransform: null,
+        paddingBottom: 0,
+        paddingLeft: 0,
+        paddingRight: 0,
+        paddingTop: 0,
+        scale: 1,
+      }
+    : {
+        angle: 0,
+        canvasWidth: 0,
+        hasText: geom.str !== "",
+        hasEOL: geom.hasEOL,
+      };
 
   task._textDivs.push(textDiv);
 
@@ -588,6 +595,11 @@ class TextLayerRenderTask {
     // Always clean-up the temporary canvas once rendering is no longer pending.
     this._capability.promise
       .finally(() => {
+        if (!this._enhanceTextSelection) {
+          // The `textDiv` properties are no longer needed.
+          this._textDivProperties = null;
+        }
+
         if (this._layoutTextCtx) {
           // Zeroing the width and height cause Firefox to release graphics
           // resources immediately, which can greatly reduce memory consumption.
@@ -679,8 +691,11 @@ class TextLayerRenderTask {
       const { width } = this._layoutTextCtx.measureText(textDiv.textContent);
 
       if (width > 0) {
-        textDivProperties.scale = textDivProperties.canvasWidth / width;
-        transform = `scaleX(${textDivProperties.scale})`;
+        const scale = textDivProperties.canvasWidth / width;
+        if (this._enhanceTextSelection) {
+          textDivProperties.scale = scale;
+        }
+        transform = `scaleX(${scale})`;
       }
     }
     if (textDivProperties.angle !== 0) {