How does $timeout cause the afterSelectionChange function to be called? - angularjs

Question

I'm trying here to get enough info to go fix this problem, just wanting some help understanding what is going on inside angular.
ng-grid has issues, lots of them, but I've found a "fix" to this one that I don't understand.
I have a grid with enough rows that it fills the visible area. If I click on the different rows, the afterSelectionChange method is called. If after clicking in the grid I move the focus with the arrow keys, it only calls that callback if the grid scrolls.
So I put in a $timeout to print out the selected row every half second to see if it was changing the selected row and just not calling the callback, and THAT fixed the problem. Now every time I move the cursor with the keyboard, the callback fires, even though the only thing happening in the callback is $log.debug().
Is this because $timeout is causing something to happen within the framework like a $apply or a $digest?
If that's the case, why isn't the keyboard causing that to happen?
Edit: Options for #tasseKATT
$scope.callGridOptions = {
data: 'callRecords',
multiSelect: false,
sortInfo: {fields:['startOn'], directions:['asc']},
columnDefs: [ ...
],
afterSelectionChange: $scope.onCallChange,
selectedItems: $scope.selectedCalls
};
In the end, I could reduce the timeout code to this:
function ngGridFixer() {
// Presence of this timer causes the ngGrid to correctly react to up/down arrow and call the
// afterSelectionChange callback like it is supposed to.
$timeout(ngGridFixer, 500);
}
ngGridFixer();
I put this in the rootscope because the problem happens on all the pages of the app.

Answer 1

$log is part of the Angular framework, anything processed by it is might execute watches laid down earlier. In other words by calling $log.debug() to print out the structure, you might be basically running scope.$digest every half second, which cause the callback(s) to fire. If you take out everything inside the $timeout function, or use console.log instead, the callback(s) probably won't fire
A way to do this semi-properly would be to use something like ngKeydown.
EDIT:
$timeout execute the function in scope.$apply by default. https://docs.angularjs.org/api/ng/service/$timeout (invokeApply). I was not aware of this. So essentially your code is calling scope.$apply every half second.