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CSS font metrics in detail

Line-height and vertical-align are simple CSS properties. So simple that most of us are convinced to fully understand how they work and how to use them. But it’s not. They really are complex, maybe the hardest ones, as they have a major role in the creation of one of the less-known feature of CSS: inline formatting context.

For example, line-height can be set as a length or a unitless value 1, but the default is normal. OK, but what normal is? We often read that it is (or should be) 1, or maybe 1.2, even the CSS spec is unclear on that…

Repeats

Ruby and Rails deprecation warnings and how to fix them

Add deprecation warnings and their solution or link to available solutions.

Global access to Rake DSL methods is deprecated. Please include Rake::DSL into classes and modules which use the Rake DSL methods.

Open your Rakefile and add the following line above YourApp::Application.load_tasks:

YourApp::Application.class_eval do
  include Rake::DSL
end

Use of ole/file_system is deprecated. Use ole/storage (the file_system api is recommended and enabled by default)…

Repeats

Simple database lock for MySQL

Note: For PostgreSQL you should use an alternative that doesn't require a database table. For MySQL we still recommend the solution in this card.


If you need to synchronize multiple rails processes, you need some shared resource that can be used as a mutex. One option is to simply use your existing (MySQL) database.

The attached code provides a database-based mutex for MySQL. You use it by simply calling

Lock....

Some useful vim settings

Below is a list of some VIM settings I find useful. You can add them to your .vimrc.

```plain
source $VIMRUNTIME/mswin.vim " adds Ctrl-X, Ctrl-C, Ctrl-V; block visual mode is now Ctrl-Q
behave mswin

set autowriteall " autosave all files when a buffer is closed

set backupdir=~/.temp " dont pollute local directory with swap file, backup files etc
set dir=~/.temp

set undofile " enable persistent undo
set undodir=~/.temp

set encoding=utf-8

How to get the currently selected text in Javascript

Simple:

window.getSelection().toString();

Browser support: IE9+, Android 4.3+, Safari 5+

Bug in Chrome 56 prevents filling in fields with slashes using selenium-webdriver/Capybara

There seems to be a nasty bug in Chrome 56 when testing with Selenium and Capybara: Slashes are not written to input fields with fill_in. A workaround is to use javascript / jquery to change the contents of an input field.

Use the following code or add the attached file to your features/support/-directory to overwrite fill_in.

```
module ChromedriverWorkarounds

def fill_in(locator, options = {})
text = options[:with].to_s
if Capybara.current_driver == :selenium && text.include?('/')
# There is a nasty Bug in Chrome …

Repeats

Beware of "nil" values in params

Recent rails security updates have shown that people make incorrect assumptions about the possible contents of the params hash.

Just don't make any! Treat it as what it is: potentially unsafe user input. For example:

/pages/edit?foo    --> params == {:foo => nil}
/pages/edit?foo[]  --> params == {:foo => [nil]} # at least in older rails 3 and in rails 2.x

Be especially wary about stuff like

User.find_by_password_reset_token(params[:password_reset_token])

If params[:password_reset_token] is nil, you'll retriev…

Getting error Bundler::Plugin::API::Source

Error: /home/.../ruby/gems/2.1.0/gems/bundler-1.14.3/lib/bundler/rubygems_ext.rb:45:in `full_gem_path': uninitialized constant Bundler::Plugin::API::Source (NameError)

Solution: Upgrade Rubygems beyond 2.6.9.

Repeats

sessionStorage: Per-window browser storage

All major browsers (IE8+, FF3.5+, Safari 4+, any Chrome) support sessionStorage, a JavaScript storage object that

  • survives page reloads and browser restores,
  • but is different per new tab/window (in contrast to localStorage which is shared across all tabs).

MDN says:

The sessionStorage object is most useful for hanging on to temporary data that should be saved and restored if the browser is accidentally refreshed

Demo

Example usage:

``` …

RubyMine: Better soft wraps

Sometimes your code has long lines:

describe 'foo' do
  describe 'bar' do
    really_long_line_really_long_line_really_long_line
    another_line

When you're working with multiple editor panes, such code will often be wider than the pane area:

describe 'foo' do                |
  describe 'bar' do              |
    really_long_line_really_long_|
    another_line                 |

To help with this you can activate Soft wraps in the RubyMine options under General → Editor .

Your code will now look like this:

```
des…

JavaScript: Hash/Object with default value

You can easily have a JavaScript hash/object that returns a default value for unset keys/properties – as long as you need to support only recent browsers.

The key are JavaScript proxies from ECMAScript 6 that allow implementing a custom getter method. They work like this:

var hash = new Proxy({}, {
  get: function(object, property) {
    return object.hasOwnProperty(property) ? object[property] : 'hello';
  }
});

When you set a key,…

Linux: Quickly create large files for testing

To create a 10 GB file:

fallocate -l 10G huge_file.dat
Repeats

Finding a method name on a Ruby object

Wondering how a specific method on an object is exactly named? You can use Enumerable#grep to detect it in the array of methods.

@user.methods.grep /name/ # => [:name, :first_name, :last_name]

You can also call #private_methods or #public_methods. To find only relevant methods, it is suggested to subtract generic methods like this:

User.methods - Object.methods
User.methods - ActiveRecord::Base.methods

If you call #methods(false) you only get methods defined on the object's class directly, but not methods inherite…

Auto-destruct in 48 days

Updated: sessionStorage: Per-window browser storage

Added that sessionStorage and localStorage can only store string keys and values.

If you need to store structured data you need to use JSON.stringify(object) and JSON.parse(string).

Deprecated

Properly require your "spec_helper"

Always use simply

require 'spec_helper'

If you mix it up like

require 'spec_helper'
require File.dirname(__FILE__) + '/../spec_helper'
require File.dirname(__FILE__) + '/../../spec_helper'
require File.expand_path('spec/spec_helper')

the file will be executed each time, since Ruby (at least 1.8) identifies it simply by the string you passed to "require".

External content

JavaScript Start-up Performance

As web developers, we know how easy it is to end up with web page bloat. But loading a webpage is much more than shipping bytes down the wire. Once the browser has downloaded our page’s scripts it then has to parse, interpret & run them. In this post, we’ll dive into this phase for JavaScript, why it might be slowing down your app’s start-up & how you can fix it.

The article author also tested 6000+ production sites for load times. Apps became interactive in 8 seconds on desktop (using cable) and 16 seconds on mobile (Moto G4 over 3G).

Ruby: Return boolean for regex comparison

A collection of code snippets which return a boolean value for a regex comparison.

regexp.match?(string) # Recommended for Ruby >= 2.4

!!(string =~ regexp)  # Recommended for older Rubies

regexp === string

!(regexp !~ string)

The Ruby 2.4 method Regexp#match? does not set globals like $~ or $1, so it should be more performant.

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