Meteor observeChanges runs before screen reactivity - javascript

I'm using Collections.observe in my chat app. After submitted one message, all the users needs to be scrolled down to appear the new message.
I am trying:
Messages.find().observe({
added: function() {
$('.messages').scrollTop($('.messages')[0].scrollHeight); // scroll to bottom
}
});
However, this function execute before the message appears in the screen.
But I need the observe function to execute AFTER the message appears on the screen, to scroll down. How can I do that?

Maybe you should use this.autorun() in an onRendered event in template with .messages elem. I mean something like:
Template.myTemplate.onRendered(function () {
this.autorun(function () {
if (Messages.find().count() /*or some more specific reactive dep*/) {
this.$('.messages').scrollTop(this.$('.messages')[0].scrollHeight);
}
}.bind(this))
})

You could wrap it in a Meteor.defer or a Tracker.afterflush. But those are a slippery slope.
Ideally, observe should be reserved for 3rd party APIs (like maps, d3js, etc). By having an observe out there for something simple like a scroll, and then your template + helpers handling the same thing, your code is gonna be a hot mess in terms of MVC.
What I'd do instead, is put an index in your helper. When the index === collection.cursor.count(), you know you're at the most recent message, and then you can scroll to that template instance. (I'm assuming each message has it's own template here).

Related

DOM elements manipulation with javascript persists after reload or going to next page in pagination

I am trying to toggle a view between grid and list view mode on my frontend HTML page. I am able to do this fine with dom and HTML classes manipulation by toggling "display: none" between two containers. However, when I go to the next product page(through pagination) or when I reload the page, the default view is the one that appears and not the one that was last toggled. Is there a way to persist the view in case a page reload or product pagination changes? thank you.
here is the dom code that achieves this :
viewList.addEventListener('click', function() {
this.classList.add('view__active');
viewGrid.classList.remove('view__active');
gridItem.classList.add('hidden');
listItem.classList.remove('hidden');
});
viewGrid.addEventListener('click', function() {
this.classList.add('view__active');
viewList.classList.remove('view__active');
gridItem.classList.remove('hidden');
listItem.classList.add('hidden');
});
So far I found that I have to use localStorage to achieve this. but is there a better way to do this?
Essentially what is happening is when you request something from the server, the server responds with an HTML document, and whichever scripts associated with that document is run, So whatever JS executed in the first request is not in context when the second request(paginate or reload) is made.
So you need a way to persist information across these page loads, For that, you have 3 options.
Use sessionStorage.
Use localStorage
Use Cookies.
Of the 3 above the easiest would be to use either option 1 or 2.
Replying to your comment,
Also, If I am using localStorage, What am I using to store the view state?
I'm not quite clear as to what you mean by "What you are using to store the state" If your question is about where your data is stored, you need not worry about it as this is handled by the browser. If your question is about "How" to store it you can go through the MDN docs attached in option 1 or 2. This is simply storing a key-value pair as shown in the docs
localStorage.setItem('preferedView', 'grid'); You can add this to your on click handlers as follows,
viewList.addEventListener('click', function() {
this.classList.add('view__active');
viewGrid.classList.remove('view__active');
gridItem.classList.add('hidden');
listItem.classList.remove('hidden');
localStorage.setItem('preferedView', 'grid');
});
viewGrid.addEventListener('click', function() {
this.classList.add('view__active');
viewList.classList.remove('view__active');
gridItem.classList.remove('hidden');
listItem.classList.add('hidden');
localStorage.setItem('preferedView', 'list');
});
Then when loading a new page at the top of your script you can get the users preferedView(if existing) via const preferedView = localStorage.getItem('preferedView');
Here is a complete example from MDN
In order for anyone to find an answer for a similar task, thanks to #Umendra insight, I was able to solve this by using this :
function viewToggeler(viewBtn1, viewBtn2, view1, view2, viewStord) {
viewBtn2.classList.add('view__active');
viewBtn1.classList.remove('view__active');
view1.classList.add('hidden');
view2.classList.remove('hidden');
sessionStorage.setItem('preferedView', viewStord);
}
viewList.addEventListener('click', () => {
viewToggeler(viewGrid, viewList, gridItem, listItem, 'list');
});
viewGrid.addEventListener('click', () => {
viewToggeler(viewList, viewGrid, listItem, gridItem, 'grid');
});
if (sessionStorage.getItem('preferedView') === 'grid') {
viewToggeler(viewList, viewGrid, listItem, gridItem, 'grid');
} else if (sessionStorage.getItem('preferedView') === 'list') {
viewToggeler(viewGrid, viewList, gridItem, listItem, 'list');
}
I ended up using sessionStorage over localStorage because it empties itself on window/tab closing which might be the most desirable result. localStorage persists even after exiting the browser and opening it back.
Also, at any point someone wants to empty the sessionStorage on exit, I used :
window.addEventListener('onbeforeunload', () => {
sessionStorage.removeItem('preferedView');
});

Can't find element using UI hash in Marionette Layout

I'm not sure why I can't get the button element using my UI hash. This is what my Layout looks like:
Layout: App.Base.Objects.BaseLayout.extend({
// Rest of the code left out for brevity
ui: {
btnSave: "#btnSave"
},
events: {
"click #ui.btnSave": "onSave"
},
onInitialize: function () {
this.listenTo(App.vent, "DisableSaveButton", function(val) {
this.disableSaveButton(val);
},this);
},
disableSaveButton: function () {
this.ui.btnSave.prop("disabled",val).toggleClass("ui-state-disabled",val);
},
onSave: function () {
alert("saved!");
}
})
In VS2013, when my breakpoint hits the line inside disableSaveButton method, I entered $("#btnSave") into the Watch window and I was able to get the element back. I could tell because it had a length of 1. From this, I know the button is rendered. However, if I enter this.ui.btnSave into the Watch window, I would get an element with length of 0.
My BaseLayout object is basically a custom object extended from Marionette.Layout
Marionette version: 1.8.8
Any ideas why I can't find the button element using this.ui.btnSave?
Thanks in advance!
Got some help from a coworker and the issue might be because the element is out of scope. Basically, inside the Layout object, 'this' does not contain the element. We were able replace 'this.ui.btnSave' with '$("#btnSave",this.buttonset.el)' and that works fine. buttonset is the region that actually contains the html element.
This seems like an inconsistency because even though the ui hash didn't work, the click event utilizing the ui hash did work.
UPDATE 6/3/2015:
Another coworker of mine provided a better solution. Basically, in my Layout I use a display function to display my view. It looks something like this:
Layout: App.Base.Objects.BaseLayout.extend({
// Rest of the code left out for brevity
display: function() {
$(this.buttonset.el).html(_.template($("#buttonset-view").html(), {"viewType": viewType}));
}
})
Basically, I'm saying to set the html of my region, which is this.buttonset.el, to my template's html. As of now, my layout doesn't know any of the elements inside the region. It just contains a region which displays the elements. So there is some sort of disconnect between my layout and the elements in my region.
The correct solution, as opposed to my earlier workaround, is to simply add the following line of code at the end:
this.bindUIElements();
From Marionette Annotated Source:
This method binds the elements specified in the “ui” hash inside the
view’s code with the associated jQuery selectors.
So this final code looks like this:
Layout: App.Base.Objects.BaseLayout.extend({
// Rest of the code left out for brevity
display: function() {
$(this.buttonset.el).html(_.template($("#buttonset-view").html(), {"viewType": viewType}));
this.bindUIElements();
}
})
With this, I was able to finally able to retrieve my element using this.ui.btnSave.

Using highlight.js in ember

My ember app is set up with a list of posts on the left and a view for an individual post on the right. When one of the posts on the left is clicked it's content is rendered in the view on the right.
This is the code I'm using to add syntax highlighting to a post.
App.PostView = Ember.View.extend({
didInsertElement: function() {
$('pre code').each(function(i, e) {hljs.highlightBlock(e)});
}
});
When the first post view is rendered, it has the syntax highlighting, but when I click on a different post and it's content gets loaded into the post view the syntax highlighting does not get applied. How can I make it so that the highlighting applied every time a post is rendered?
I can only guess without a more comprehensive example. Is PostView what gets created in the right panel? If so, then you need to constrain your view rendering to the stuff inside the view.
In your example, $('pre code') will target all pre code elements inside the document. Try this.$('pre code'), or whatever element/selector needs to be highlighted within the view.
This may be not the cleanest way to do the job, but you could try adding observer to the controller's model, and make required changes. But this will only work, if the model itself changes.
Like this:
postHasChanged: function() {
if (this.get('state') === 'inDOM') {
$('pre code').each(function(i, e) {
hljs.highlightBlock(e)
});
}
}.observes('controller.model')

Releasing OrbitControls in threejs

I have a Single Page Application with a lot of stuff in it, using durandal. On one page I have a link that leads to a different page where 3d model is rendered. OrbitControls are used to make model turn etc. That takes away my default left click and right click. After leaving that page, it still keeps mouse bindings and my left click and right click become useless for some uses like - selecting an tag meaning that input tags cannot be accessed again.
I could release bindings and reset them if I knew how. There is a deactivate function which is called when that 3d window is closed, but I have no idea what piece of code to write there. Any help would be extremely useful. I doubt any code will be of any use so I won't put any.
Thank you!
Due to request, here is simplified viewmodel:
define(['services/logger'], function (logger) {
var vm = {
attached: attached
};
return vm;
function attached(view) {
var camera, cameraTarget, scene, renderer, controls;
init();
animate();
function init() {
...
controls = new THREE.OrbitControls(camera);
...
}
function animate(){...}
function render(){...}
}
}
View is extremely complicated, but pasted here in full:
<div id="canvasDiv" style="overflow: hidden; width:100%; height:100%">
</div>
Actually, it would probably be helpful to include your code to setup OrbitControls (I'm not familiar with it).
The best approach to this whole issue would probably be to write a Knockout custom binding (google if you don't know them). A custom binding is a great place to abstract away DOM manipulation, in your case for setting up OrbitControls.
Let's assume that you have a div on which you set up OrbitControls. You could then do something like the following:
HTML:
<div data-bind="myOrbitControlsBinding: { someSetting: true; someOtherSetting: false }"></div>
JavaScript:
ko.bindingHandlers.myOrbitControlsBinding = {
init: function (element, valueAccessor) {
var settings = ko.utils.unwrapObservable(valueAccessor());
setupOrbitControlsOnElement(element, settings); // This should be your setup code for OrbitControls
ko.utils.domNodeDisposal.addDisposeCallback(element, function () {
// Here, you should unbind the event handlers for mouse clicks. How you do this depends on how OrbitControls sets them up. Please refer to their documentation for this. Maybe there is a generic dispose function?
disposeOrbitControls(element);
});
}
}
Edit:
Ah, I didn't realize you use Three. I've quickly scanned their documentation to see if they use some sort of input module that captures the events. They don't seem to. Which probably means that some where in your code, there is the keyword 'addEventListener' (search for it). This will be where the events are caught.
Your view probably has a viewmodel attached to it since you're using durandal. Inside the viewmodel, add a 'deactivate' method (and return it). In this method, you need to remove the event listener again. You probably already guessed it, but the method is called removeEventListener (see https://developer.mozilla.org/en-US/docs/Web/API/EventTarget.removeEventListener for an explanation)
I still highly recommend that you create a custom binding to setup Three. This will give you much more control over creation/deletion than you might have now. If you don't want to, make sure that Three is initialized inside the viewmodel as well, in the activate method.
Let me know if that helped, otherwise some viewmodel / three init code would be helpful.

ExtJS: starting HtmlEditor defaulting to source

I'm using ExtJS 3.2.1 and I need a component almost identical to the bundled HtmlEditor, with one exception: it must start editing the HTML source code directly. The reason I don't use a normal TextArea is that the user should be able to preview the result of his actions before submitting.
I've tried calling toggleSourceEdit(), as per ExtJS documentation, with no success. Debugging, I see that the editor object has the sourceEditMode property set to true, and the Source Edit button seems as if it was "pressed", but clicking on it does not render the typed HTML, and clicking it again goes to the Source Mode.
I've tried calling toggleSourceEdit() after the container show() method, on the container afterLayout listener and on the editor afterRender listener. I've tried also calling it on another button that I added to the container. The result is the same on every try.
The only other option I see is updating ExtJS to 3.3.0, but I haven't seem anything related on the changelogs. Either way, it's going to be my next step. EDIT: The app had another problems when updating, we'll make a bigger effort to update later. As of right now, we are using the HtmlEditor in its original setting.
Thanks!
ran into the same problem (using 3.3.0 by the way)
stumbled upon a fix by dumb luck. i have no idea why this works, but second time is the charm. call it twice in a row to achieve the desired effect..
HTMLEditor.toggleSourceEdit(true);
HTMLEditor.toggleSourceEdit(true);
hope that helps!
Rather calling toggleSourceEdit(), try to setup the configuration while you create HtmlEditor Object
Using toggleSourceEdit() caused some problems for me. One was that this seemed to put the editor somewhere in limbo between source edit and WYSIWYG mode unless I used a timeout of 250ms or so. It also puts the focus in that editor, and I don't want to start the form's focus in the editor, especially since it's below the fold and the browser scrolls to the focused html editor when it opens.
The only thing that worked for me was to extend Ext.form.HtmlEditor and then overwrite toggleSourceEdit, removing the focus command. Then adding a listener for toggling to the source editor when the component is initialized. This is for Ext 4.1 and up. For older versions, replace me.updateLayout() with me.doComponentLayout().
var Namespace = {
SourceEditor: Ext.define('Namespace.SourceEditor', {
extend: 'Ext.form.HtmlEditor',
alias: 'widget.sourceeditor',
initComponent: function() {
this.callParent(arguments);
},
toggleSourceEdit: function (sourceEditMode) {
var me = this,
iframe = me.iframeEl,
textarea = me.textareaEl,
hiddenCls = Ext.baseCSSPrefix + 'hidden',
btn = me.getToolbar().getComponent('sourceedit');
if (!Ext.isBoolean(sourceEditMode)) {
sourceEditMode = !me.sourceEditMode;
}
me.sourceEditMode = sourceEditMode;
if (btn.pressed !== sourceEditMode) {
btn.toggle(sourceEditMode);
}
if (sourceEditMode) {
me.disableItems(true);
me.syncValue();
iframe.addCls(hiddenCls);
textarea.removeCls(hiddenCls);
textarea.dom.removeAttribute('tabindex');
//textarea.focus();
me.inputEl = textarea;
} else {
if (me.initialized) {
me.disableItems(me.readOnly);
}
me.pushValue();
iframe.removeCls(hiddenCls);
textarea.addCls(hiddenCls);
textarea.dom.setAttribute('tabindex', -1);
me.deferFocus();
me.inputEl = iframe;
}
me.fireEvent('editmodechange', me, sourceEditMode);
me.updateLayout();
}
})
}
Then to use it:
Ext.create('Namespace.SourceEditor', {
/*regular options*/
listeners: {
initialize: function(thisEditor) {
thisEditor.toggleSourceEdit();
}
}
});
htmlEditor.toggleSourceEdit(true);
one time should be enough if you do this listening to the afterrender event of the editor.

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