From 84f5954ad52e82b795b1e493a9111355ddaa0f07 Mon Sep 17 00:00:00 2001
From: Alex Yatskov <alex@foosoft.net>
Date: Sun, 21 May 2017 22:44:22 -0700
Subject: [PATCH] handle scanning text for janky websites better #23

---
 ext/fg/js/source-range.js | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/ext/fg/js/source-range.js b/ext/fg/js/source-range.js
index 58b6a415..95177f0b 100644
--- a/ext/fg/js/source-range.js
+++ b/ext/fg/js/source-range.js
@@ -84,8 +84,22 @@ class TextSourceRange {
     }
 
     static shouldEnter(node) {
+        if (node.nodeType !== 1) {
+            return false;
+        }
+
         const skip = ['RT', 'SCRIPT', 'STYLE'];
-        return !skip.includes(node.nodeName);
+        if (skip.includes(node.nodeName)) {
+            return false;
+        }
+
+        const style = window.getComputedStyle(node);
+        const hidden =
+            style.visibility === 'hidden' ||
+            style.display === 'none' ||
+            parseFloat(style.fontSize) === 0;
+
+        return !hidden;
     }
 
     static seekForward(node, offset, length) {
@@ -106,7 +120,7 @@ class TextSourceRange {
     }
 
     static seekForwardHelper(node, state) {
-        if (node.nodeType === 3) {
+        if (node.nodeType === 3 && node.parentElement && TextSourceRange.shouldEnter(node.parentElement)) {
             const offset = state.node === node ? state.offset : 0;
             const remaining = node.length - offset;
             const consumed = Math.min(remaining, state.remainder);
@@ -143,7 +157,7 @@ class TextSourceRange {
     }
 
     static seekBackwardHelper(node, state) {
-        if (node.nodeType === 3) {
+        if (node.nodeType === 3 && node.parentElement && TextSourceRange.shouldEnter(node.parentElement)) {
             const offset = state.node === node ? state.offset : node.length;
             const remaining = offset;
             const consumed = Math.min(remaining, state.remainder);