The bottom &quot;frame details panel&quot; sometimes hides the &quot;frames list&quot; panel, unless you hover your mouse under a column header and drag down.

![wonderful websockets ux design][1]


Update 1: As Sylvain Girard pointed out, this is Chromium issue [895548][2]

Update 4: It&#39;s been fixed in Chrome 72, available in stable channel


  [1]: https://i.stack.imgur.com/Sizcr.gif
  [2]: https://bugs.chromium.org/p/chromium/issues/detail?id=895548

Ugh, the UI was pulling the wool over my eyes.  The pane that shows new frames was pulled all the way up so I could not see them.  

It&#39;s a split pane with the frame summary on top, and individual frame inspector on bottom -- but the split divider was pulled all the way to the top.  Was tough to see that.  Google UI team: would be great to provide a better visual indicator on this :)

[![enter image description here][1]][1]


  [1]: https://i.stack.imgur.com/xrGi2.png

I&#39;m looking through the Apple&#39;s [Vision API documentation](https://developer.apple.com/documentation/vision) and I see a couple of classes that relate to text detection in `UIImages`:

1) [`class VNDetectTextRectanglesRequest`](https://developer.apple.com/documentation/vision/vndetecttextrectanglesrequest)

2) [`class VNTextObservation`](https://developer.apple.com/documentation/vision/vntextobservation)

It looks like they can detect characters, but I don&#39;t see a means to do anything with the characters. Once you&#39;ve got characters detected, how would you go about turning them into something that can be interpreted by [`NSLinguisticTagger`](https://developer.apple.com/documentation/foundation/nslinguistictagger)?

Here&#39;s a post that is a brief overview of [`Vision`](https://medium.com/compileswift/swift-world-whats-new-in-ios-11-vision-456ba4156bad).

Thank you for reading. 

Converting a Vision VNTextObservation to a String

Is it possible to use ES6&#39;s `Set` data structure in React?

For example, if I have a checklist composed of distinct items, and I&#39;d like to maintain each item&#39;s checked state. I&#39;d like to write something like this:

    export default class Checklist extends React.Component {
      constructor(props) {
        super(props);
        
        this.state = {
          checkedItems: new Set()
        }
      }
      
      addItem(item) {
        //...?
      }
      
      removeItem(item) {
        //...?
      }
      
      getItemCheckedStatus(item) {
        return this.state.checkedItems.has(item);
      }

      // More code...
    }

I understand there may be a problem with the fact that a Set is mutable by nature, and React performs a shallow comparison when updating the component, so it expects immutable objects to be passed and held in the state. However, is there a way to hold and maintain a Set object in the state?

Using a Set data structure in React&#39;s state

Ever since I upgrade from Chrome 58 =&gt; 59 on Mac OS El Capitan, when I use Dev Tools Network inspector to view WebSocket frames, the frames no longer are visible.  We build an app that makes heavy use of WS, so I rely heavily on this capability.

I thought perhaps it was something maybe we changed in our app -- encoding or protocol that maybe causes it to not show up, so I tried this simple test here: https://websocket.org/echo.html

1. Open DevTools
2. Go to https://websocket.org/echo.html
3. Go to Network tab, filter on WS, go to Frames tab
4. Click Connect in echo app followed by Send Message

This results in no frames showing up in DevTools, but the socket messages work fine with the app.  I&#39;ve asked a few other people and some of them do not have this problem.

I&#39;m wondering if I either have an extension that is causing this issue, or if I have some other arcane setting that might be blocking the frames from displaying?

[![enter image description here][1]][1]


  [1]: https://i.stack.imgur.com/dUrZQ.png

Chrome 59+ websocket frames no longer visible in DevTools

Ever since I upgrade from Chrome 58 => 59 on Mac OS El Capitan, when I use Dev Tools Network inspector to view WebSocket frames, the frames no longer are visible. We build an app that makes heavy use of WS, so I rely heavily on this capability.
I thought perhaps it was something maybe we changed in our app -- encoding or protocol that maybe causes it to not show up, so I tried this simple test here: <a href="https://websocket.org/echo.html" target="_blank" rel="noopener noreferrer">https://websocket.org/echo.html</a>
<ol>
<li>Open DevTools</li>
<li>Go to <a href="https://websocket.org/echo.html" target="_blank" rel="noopener noreferrer">https://websocket.org/echo.html</a></li>
<li>Go to Network tab, filter on WS, go to Frames tab</li>
<li>Click Connect in echo app followed by Send Message</li>
</ol>
This results in no frames showing up in DevTools, but the socket messages work fine with the app. I've asked a few other people and some of them do not have this problem.
I'm wondering if I either have an extension that is causing this issue, or if I have some other arcane setting that might be blocking the frames from displaying?
<a href="https://i.stack.imgur.com/dUrZQ.png" target="_blank" rel="noopener noreferrer"><img src="https://i.stack.imgur.com/dUrZQ.png" alt="enter image description here"></a>

I am interested in chrome memory cache vs disk cache? I use webpack, common chunks plugin and generate all my files with chunkhash. 

How does memory differ from disk cache. When I reload my page some files are loaded from memory cache and some from disk cache (bundle.js and image.jpg from memory cache and css from disk cache). Sometimes it&#39;s different. Can we control that, choose what gets loaded from where? Memory cache seems to be faster than disk cache.


Chrome memory cache vs disk cache

I am in the developer view in Chrome &lt;kbd&gt;⌘&lt;/kbd&gt; + &lt;kbd&gt;shift&lt;/kbd&gt;+&lt;kbd&gt;c&lt;/kbd&gt;. Under the console tab, it shows this message

&gt; 7 items hidden by filters 

But the issue is I have no filters set. I tried right clicking and selecting &#39;Filter&#39; but the unhide all is greyed out. And tried reseting the developer console.But it didnt work, how do i fix this ? 



How to unhide filtered messages in Chrome developer Tools on a MAC

I&#39;m facing this strange issue that looks like a bug on Chrome mobile.

I have a div with position:fixed; aligned to the top right corner of the screen. On desktop, it works fine (it stays in place), in mobile, however, the div is moving when I scroll up or down. I made a video to explain it better:

https://www.youtube.com/watch?v=gCgN6ULkcMg

[![scroll up][1]][1]

*On scroll up works fine*

[![scroll down][2]][2]

*on scroll down, a piece of the div with position:fixed disappears outside the viewport*



I tried to isolate the problem on a fiddle, but couldn&#39;t reproduce it. So I encapsulated the entire website in a fiddle, and the issue stopped ocurring. I still didn&#39;t understand why.

Website isolated in a fiddle:
Removed*

Live website:
Removed*

Furthermore, I performed some tests on different devices, on the live website:

 - Chrome mobile: **Bugs**
 - Chrome desktop: **Works fine**
 - Firefox mobile: **Works fine**
 - Safari mobile: **Works fine**

Can someone explain me why Chrome Mobile have this issue, while the others don&#39;t?

My position:fixed div looks something like this:

    div {
      position:fixed;
      top:10px;
      left:0;
      width:100%;
      text-align:right;
    }

*Removed the links because it&#39;s a client&#39;s website. The solution is in the answer below.


  [1]: https://i.stack.imgur.com/QigMC.jpg
  [2]: https://i.stack.imgur.com/96vqu.jpg

Position fixed on chrome mobile causing element to move on scroll up/down

I made a browser action, but I just tried testing a page action. The button is put in the same place, but the page action button can&#39;t be clicked (the icon is greyed-out). I thought page action buttons were located on the address bar, not in the toolbar. Why is it located in the same place?

My browser action button:  
[![browser_action][1]][1]

My page action button:  
[![page_action][2]][2]


  [1]: https://i.stack.imgur.com/9dQc2.jpg
  [2]: https://i.stack.imgur.com/tUe8t.jpg

What are the differences between page action and browser action?

Recently I&#39;ve been working on building a tree-view component library for Angular, as [ngx-tree](https://github.com/e-cloud/ngx-tree).

## Problem
Soon after I figured out how to implement a **virtual-scroll feature** for this library for performance with large data set, and got it to run properly in Firefox, I am trapped by a weird scrolling behavior in **[Blink](https://en.wikipedia.org/wiki/Blink_(web_engine))-included browsers**(like Chromium, Chrome, Opera).

## Demo link

&gt; Here is the demo plunkr -- &lt;del&gt;https://embed.plnkr.co/xMpmK5EBC46tDKpYFpw8&lt;/del&gt; see Update #1 below

## Situation

* In Firefox, Edge and IE 11, my library with virtual scroll feature works in expectation with smooth scrolling.
* However, in Chrome and Opera, when I scroll to some positions inside the tree-view, the position of the scrollbar(which is the `scrollTop` property of scroll area) jump up and down, causes a **flickering** tree-view and break down the virtual-scroll feature.

### browser detail version

* Chrome - 59.0.3071.115
* Firefox - 54.0
* Edge - 40.15063.0.0

### other browsers

In China, there are some **shelled** browsers derived from Chromium project(like 360se, QQ browser, Sogou browser, UC browser) with **older version of V8 and blink**. And they don&#39;t have that weird scroll behavior.

### Some Assumption

Is it caused by some optimization on the scroll implementation(like smooth scrolling) by the Chromium team?

Hope to get some guides!!! (≧﹏ ≦)

---

**Update #1**

&gt; Demo link update with event log: https://embed.plnkr.co/GpQBZsguhZZOQWWbZnqI/   

**One must test the scrolling before opening devtool to see the logs**

I have to explain a little more how the virtual-scrolling works and what&#39;s causing the flickering.

First, see the [design of Virtual Scrolling](https://github.com/e-cloud/ngx-tree/blob/feature/virtual-scroll/src/lib/services/virtual-scroll.md).

A key point of virtual scrolling is， we create a fake scroll area the same size as that area without virtual scrolling instrumented. So in an optimal situation, the scrollbar position of the scroll area ought not to change until some expected events trigger its changes. For scroll event, we update the view for every animation frame.

Within a height-fixed scrolling area, we assume a truth that the scrollTop property will not change **with a large percentage**, if we simulate the those unrendered elements&#39; height properly(there could be **a bit of deviation for the calculation accuracy**) within an animation frame.

However, based on my observed results, the blink-series browsers seems to perform a different strategy to update the scrollTop of the scrollable element. Its timing to update the scrollTop is different than none-blink-series browsers. That all I&#39;ve figured out so far.


---

## Sample gifs
Here I made some gifs to show the output of Chrome, Firefox, and Edge.

### Chrome

[![Chrome gif][1]][1]

### Firefox

[![Firefox gif][2]][2]

### Edge

[![Edge gif][3]][3]


  [1]: https://i.stack.imgur.com/i48Er.gif
  [2]: https://i.stack.imgur.com/asEQb.gif
  [3]: https://i.stack.imgur.com/fSa19.gif

Weird scroll behavior in latest Blink-included browsers (like Chrome, Opera)

I&#39;ve been struggling a lot to properly implement Stomp (websocket) **Authentication** and **Authorization** with Spring-Security. *For posterity i&#39;ll answer my own question to provide a guide.*

&lt;br /&gt;

### The Problem
Spring WebSocket documentation (for Authentication) looks unclear ATM (IMHO). And i couldn&#39;t understand how to properly handle **Authentication** and **Authorization**.

&lt;br /&gt;

### What i want
- Authenticate users with login/password.
- Prevent anonymous users to CONNECT though WebSocket.
- Add authorization layer (user, admin, ...).
- Having `Principal` available in controllers.

&lt;br /&gt;

### What i don&#39;t want
- Authenticate on HTTP negotiation endpoints (since most of JavaScript libraries don&#39;t sends authentication headers along with the HTTP negotiation call).

Websocket Authentication and Authorization in Spring

What is the procedure to change ws into wss?

Whether wss is make upgrade over normal HTTP or wss works only HTTPS?

    webSocket = new WebSocket(&quot;ws://localhost:port/Esv/ocp&quot;);

works fine, when I changed ws to wss

    webSocket = new WebSocket(&quot;wss://localhost:port/Esv/ocp&quot;);

it shows this error:

&gt; Error in connection establishment: net::ERR_SSL_PROTOCOL_ERROR

Difference between ws and wss?

I want to develop a client-server application in a bi-directional streaming manner.

what is more suitable technology for this, grpc or websocket?

What is difference between grpc and websocket? Which one is more suitable for bidirectional streaming connection?

Writing a bash script to connect to [GDAX&#39;s Websocket Feed](https://docs.gdax.com/#websocket-feed) at wss://ws-feed.gdax.com but curl doesn&#39;t seem to support this as I get 

    curl &quot;wss://ws-feed.gdax.com&quot;
    curl: (1) Protocol &quot;wss&quot; not supported or disabled in libcurl

How to read websocket response in linux shell

**Background:**

I am building an application and the proposed architecture is Event/Message Driven on a microservice architecture. 

The monolithic way of doing thing is that I&#39;ve a `User/HTTP request` and that actions some commands that have a direct `synchronous response`. Thus, to respond to the same User/HTTP request is &#39;hassle free&#39;.


[![enter image description here][1]][1]

**The problem:**

The user sends an `HTTP request` to the **UI Service** (there are multiple UI Services) that fires some events to a queue (Kafka/RabbitMQ/any). a N of services picks up that Event/Message do some magic along the way and **then at some point that same UI Service should pick that up a response and give that back to the user that originated HTTP request.** Request processing is `ASYNC` but the `User/HTTP REQUEST-&gt;RESPONSE` is `SYNC` as per your typical HTTP interaction.

**Question:**
How do I send a response to the same UI Service that originated the action (The service thats interacting with the user over HTTP) in this Agnostic/Event driven world?

**My research so far** 
I&#39;ve been looking around and it seems that some people are solving that problem using WebSockets.

But the layer of complexity is that there needs to be some table that maps `(RequestId-&gt;Websocket(Client-Server))` which is used to ‘discover’ which node in the gateway has the websocket connection for some particular response. But even if I understand the problem and complexity I&#39;m stuck that I can&#39;t find any articles that would give me info on how to solve this problem at the implementation layer. **AND** this still is not a viable option because of 3rd party integrations such as payments providers(WorldPay) that expect `REQUEST-&gt;RESPONSE` - specially on the 3DS validation.


So I am somehow reluctant to think that WebSockets is an option. But even if WebSockets are ok for Webfacing apps, for API that connects to external systems is not a great architecture.


** ** ** **Update:** ** ** ** 

Even if long polling is an possible solution for a WebService API with a `202 Accepted` a `Location header` and a `retry-after header` it wouldn&#39;t be performant for a high concurrency &amp; high ability website. 
Imagine a huge number of people trying to get the transaction status update on EVERY request they make and you have to invalidate CDN cache (go and play with that problem now! ha).

But most important and relatable to my case I&#39;ve 3rd party APIs such as payment systems where the 3DS systems have automatic redirects that are handled by the payment provider system and they expect a typical `REQUEST/RESPONSE flow`, thus this model would not work for me nor the sockets model would work. 

Because of this use-case the `HTTP REQUEST/RESPONSE` should be handled in the typical fashion where i have a dumb client that expect that the complexity of the precessing is handled in back-end.

**So i am looking for a solution where externally I have a typical `Request-&gt;Response`(SYNC) and the complexity of the status(ASYNCrony of the system) is handled internally** 

 
An example of the long polling, but this model wouldn&#39;t work for 3rd party API such as payments provider on `3DS Redirects` that are not within my control.

     POST /user
        Payload {userdata}
        RETURNs: 
            HTTP/1.1 202 Accepted
            Content-Type: application/json; charset=utf-8
            Date: Mon, 27 Nov 2018 17:25:55 GMT
            Location: https://mydomain/user/transaction/status/:transaction_id
            Retry-After: 10
    
    GET 
       https://mydomain/user/transaction/status/:transaction_id



[![enter image description here][2]][2]




  [1]: https://i.stack.imgur.com/rP5nf.png
  [2]: https://i.stack.imgur.com/rznNC.png


How to handle HTTP requests in a Microservice / Event Driven Architecture?

The Coverage tool is good at finding used and unused code.  However, there doesn&#39;t appear to be a way to save or export only the used code.  Even hiding unused code would be helpful.

I&#39;m attempting to reduce the amount of Bootstrap CSS in my application; the file is more than 7000 lines.  The only way to get just the used code is to carefully scroll thru the file, look for green sections, then copy that code to a new file.  It&#39;s time-consuming and unreliable.

Is there a different way?  Chrome 60 does not seem to have added this functionality.

Chrome Devtools Coverage: how to save or capture code used code?

I would like to know if I can tell puppeteer to wait until an element is displayed.

```javascript
const inputValidate = await page.$(&#39;input[value=validate]&#39;);
await inputValidate.click()
        
// I want to do something like that 
waitElemenentVisble(&#39;.btnNext &#39;)

const btnNext = await page.$(&#39;.btnNext&#39;);
await btnNext.click();
```

Is there any way I can accomplish this?

puppeteer: how to wait until an element is visible?

I&#39;m using [Puppeteer][1] for E2E test, and I am now trying to fill an input field with the code below:

    await page.type(&#39;#email&#39;, &#39;test@example.com&#39;);

It worked, but I found the email address was typed into the field one character by one character as if a real human being was typing.

Is it possible to fill the input field with the email address all at one time?

  [1]: https://github.com/GoogleChrome/puppeteer

How to fill an input field using Puppeteer?

Chrome DevTools previously offered a setting to show rulers when inspecting elements. It had a pixel ruler at the sides of the view, and boundary lines for each element extending the full view of the page. 

It used to be found (as I recall) in &quot;DevTools Settings / General&quot;. There no longer is a General section, and I don&#39;t see it in &quot;DevTools Settings / Appearance&quot;. Has this been moved, or removed? I&#39;m not finding documentation or discussion of it. 

How to enable view of rulers in Chrome DevTools?

In the Chrome browser&#39;s developer tools, there are various ways to throttle your network connection to emulate different connection types.

Those menus for selecting a connection type used to show the speeds and latency that would be used to simulate each connection type.  
[![Throttling menu with informative labels][1]][1]

Now, as of at least Chrome 64, the useful information about speed and latency has been removed.  
[![Throttling menu with uninformative labels][2]][2]

  [1]: https://i.stack.imgur.com/aHe7X.png
  [2]: https://i.stack.imgur.com/U6QuC.png

I tried duplicating the numbers from the first image for Regular 3G and Good 3G in my own custom profiles to see if they matched the Slow 3G and Fast 3G presets from the first image but I got significantly different results for the DOMContentLoaded and Load event times between the presets and my custom profiles.

Content Type	Original Author	Original Content on Stackoverflow
Question	zenocon	View Question on Stackoverflow
Solution 1 - Google Chrome	Ray Foss	View Answer on Stackoverflow
Solution 2 - Google Chrome	zenocon	View Answer on Stackoverflow

Chrome 59+ websocket frames no longer visible in DevTools

Google Chrome Problem Overview

Google Chrome Solutions

Solution 1 - Google Chrome

Solution 2 - Google Chrome

Using a Set data structure in React's state

Converting a Vision VNTextObservation to a String

Attributions