Logout from HTTP auth using Apache

Since there is no mechanism defined to log the user out of a HTTP authenticated session you have to use a workaround. Most browsers forget their login data once they received a 403 response. The problem is, that the user have to return to the normal starting page manually.

Update 2017-02-22: It seems that this technique doesn't work anymore in recent Firefox and Chrome browsers.

The following code, which can be embedded into an Apache VHost declaration, uses a cookie to send a 403 response to the browser the first time he requests "/logout", and redirects it to "/" on the second time. So the user can immediately login again if he want to.

Please note that the order of the declarations does matter! The Location-Block must be the last block which requires a user or group.

RewriteCond %{HTTP_COOKIE} ^.*logout=1.*$
RewriteRule ^/logout$ / [R,L,co=logout:0:%{HTTP_HOST}:0:/logout]                                                                                                         
RewriteRule ^/logout$ - [R,L,co=logout:1:%{HTTP_HOST}:0:/logout]
<Location /logout>
    Require user nonexistinguser
</Location>

• #javascript
• #http
• #howto

Introducing: Nested Scroll

Nested Scroll is a Javascript library that allows you to scroll
selected elements into the viewport. You can define if the element should be aligned to the upper, lower, left or right
boundary, or let Nested Scroll automatically decide depending on the shortest path.

Additionally, it is possible to define some animation methods, respect the element's border and margin
and add extra margins on each side when scrolling.

But what makes this library unique compared to other libraries I've looked into is that it that it
not only works with vertical but also with horizontal scrollbars, with nested scrollable DIVs
and with fixed elements!

Usage

  // Scroll with default options
  var target = document.getElementById('target-element');
  nestedScroll(target);

  // Scroll with additional parameters
  var options = {
    // See section options
    animationMethod: 'easeInOut',
    animationTimeout: 500,
    force: true,
    align: 'auto',
    withCssMargins: true,
    marginTop: 10,
    marginLeft: 10,
    marginRight: 10,
    marginBottom: 10
  };
  nestedScroll(target, options);

  // Define a global option
  nestesScroll.defaultOptions['animationMethod'] = 'easeIn';

Download

Download the library on github.

Disclamer: This is tested on Vivaldi 1.10, Firefox 52 and Chromium 59. Edge should also work, but I had some problems using the example file with IE11. Maybe I'll fix this later, or somebody as does ;-)

• #javascript
• #github

QtWebEngine: Be careful when doing periodic WebChannel requests

Today I had to resolve a mysterious bug in a PyQt5 / QtWebEngine application. After the user unlocked his session, the application hangs for a while before resuming to normal activity. I've added an JavaScript interval that prints the current time once a second onto the console, but even through the timestamps were OK it seems that something had freezed the application while the screen was locked.

To make it short, the application requested a status update via WebChannel once a second. While the Javascript kept active, the event loop of QApplication was blocked, so that the WebChannel events were put into a queue. (The reason for the block was the change to a new VT by the light-locker lock screen - I was able emulate it by manually switching to VT1 after the application has been started). When the application got active again, Qt started to empty the queue before any new events were processed.

My solution was to omit the periodic status updates when the webchannel isn't idle.

• #python
• #qt
• #javascript
• #webchannel
• #qtwebengine