Updated highlighting algorithm

background.js

@@ -1,10 +1,3 @@
-function doInCurrentTab(tabCallback) {
-    chrome.tabs.query(
-        { currentWindow: true, active: true },
-        function (tabArray) { tabCallback(tabArray[0]); }
-    );
-}
-
 chrome.commands.onCommand.addListener(function(command) {
     if (command === "start") {
         chrome.tabs.query({active: true, currentWindow: true}, function(tabs){

keyhinter.js

@@ -1,12 +1,31 @@
-var isVisible = function(node) {
-    // From: http://stackoverflow.com/questions/123999/how-to-tell-if-a-dom-element-is-visible-in-the-current-viewport/7557433#7557433
-    var rect = node.getBoundingClientRect();
-    return (
-        rect.top >= 0 &&
-            rect.left >= 0 &&
-            rect.bottom <= (window.innerHeight || document.documentElement.clientHeight) && /*or $(window).height() */
-        rect.right <= (window.innerWidth || document.documentElement.clientWidth) /*or $(window).width() */
-    );
+// Checks if the provided child is descendant of the parent (any level)
+function is_descendant(parent, child) {
+    var node = child.parentNode;
+    while (node !== null) {
+        console.log(node)
+        if (node === parent) return true;
+        node = node.parentNode;
+    }
+    return false;
+}
+
+function isVisible(element) {
+    // Element is obviously not visible
+    if (element.offsetWidth === 0 || element.offsetHeight === 0) return false;
+    let rect = element.getClientRects()[0];
+    if (!rect) return false;
+
+    // Get the element clicked in the center of the element rect
+    var element_in_position = document.elementFromPoint((rect.left + rect.right) / 2, (rect.top + rect.bottom) / 2);
+
+    // If there's no result, assume not visible
+    if (!element_in_position) return false;
+
+    // If the element clicked is the same as provided, the element is clearly visible
+    if (element_in_position === element) return true;
+
+    // If the element is not in the position we clicked, check if it's at least a child node
+    return is_descendant(element, element_in_position);
 }
 
 class KeyHinter {