# Glimmer (The Original One And Only)
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Glimmer is a cross-platform Ruby desktop development library. Glimmer's main innovation is a JRuby DSL that enables easy and efficient authoring of desktop application user-interfaces while relying on the robust platform-independent Eclipse SWT library. Glimmer additionally innovates by having built-in desktop UI data-binding support to greatly facilitate synchronizing the UI with domain models. As a result, that achieves true decoupling of object oriented components, enabling developers to solve business problems without worrying about UI concerns, or alternatively drive development UI-first, and then write clean business components test-first afterward.

You may learn more by reading this article: [Eclipse Zone Tutorial](http://eclipse.dzone.com/articles/an-introduction-glimmer)

## Examples

### Hello World

Glimmer code (from `samples/hello_world.rb`):
```ruby
include Glimmer

shell {
  text "Glimmer"
  label {
    text "Hello World!"
  }
}.open
```

Run:
```
glimmer samples/hello_world.rb
```

Glimmer app:

![Hello World](https://github.com/AndyObtiva/glimmer/raw/master/images/glimmer-hello-world.png)

### Tic Tac Toe

Glimmer code (from `samples/tictactoe/tic_tac_toe.rb`):

```ruby
shell {
  text "Tic-Tac-Toe"
  composite {
    layout GridLayout.new(3,true)
    (1..3).each { |row|
      (1..3).each { |column|
        button {
          layout_data GridData.new(GSWT[:fill], GSWT[:fill], true, true)
          text        bind(@tic_tac_toe_board.box(row, column), :sign)
          enabled     bind(@tic_tac_toe_board.box(row, column), :empty)
          on_widget_selected {
            @tic_tac_toe_board.mark_box(row, column)
          }
        }
      }
    }
  }
}
```

Run:

```
glimmer samples/tictactoe/tic_tac_toe.rb
```

Glimmer app:

![Tic Tac Toe](https://github.com/AndyObtiva/glimmer/raw/master/images/glimmer-tic-tac-toe.png)

## Resources

* [Eclipse Zone Tutorial](http://eclipse.dzone.com/articles/an-introduction-glimmer)
* [InfoQ Article](http://www.infoq.com/news/2008/02/glimmer-jruby-swt)
* [RubyConf 2008 Video](https://confreaks.tv/videos/rubyconf2008-desktop-development-with-glimmer)
* [Code Blog](http://andymaleh.blogspot.com/search/label/Glimmer)

## Background

Ruby is a dynamically-typed object-oriented language, which provides great productivity gains due to its powerful expressive syntax and dynamic nature. While it is proven by the Ruby on Rails framework for web development, it currently lacks a robust platform-independent framework for building desktop applications. Given that Java libraries can now be utilized in Ruby code through JRuby, Eclipse technologies, such as SWT, JFace, and RCP can help fill the gap of desktop application development with Ruby.

## Platform Support

Glimmer runs on the following platforms:
- Mac
- Windows
- Linux

## Pre-requisites

* Java SE Runtime Environment 7 or higher (find at https://www.oracle.com/java/technologies/javase-downloads.html)
* JRuby 9.2.10.0 (supporting Ruby 2.5.x syntax) (find at https://www.jruby.org/download)

On **Mac** and **Linux**, an easy way to obtain JRuby is through [RVM](http://rvm.io) by running:

```bash
rvm install jruby-9.2.10.0
```

## Setup

Please follow these instructions to make the `glimmer` command available on your system.

### Option 1: Direct Install

Run this command to install directly:
```
jgem install glimmer -v 0.4.1
```

### Option 2: Bundler

Add the following to `Gemfile`:
```
gem 'glimmer', '~> 0.4.1'
```

And, then run:
```
bundle install
```

## Glimmer command

Usage:
```
glimmer application.rb
```

Runs a Glimmer application using JRuby, automatically preloading
the glimmer ruby gem and SWT jar dependency.

Example:
```
glimmer hello_world.rb
```
This runs the Glimmer application hello_world.rb

## Glimmer DSL Syntax

### Widgets

Glimmer UIs (user interfaces) are modeled with widgets (wrappers around the SWT library widgets found here: https://help.eclipse.org/2019-12/topic/org.eclipse.platform.doc.isv/guide/swt_widgets_controls.htm?cp=2_0_7_0_0).

In Glimmer DSL, widgets are declared with lowercase underscored naming (you may look at usage examples in the `samples` directory).

The `shell` widget is always the outermost widget containing all others in a desktop windowed application.

Other widget examples:
- `button`: wrapper for `org.eclipse.swt.widgets.Button`
- `label`: wrapper for `org.eclipse.swt.widgets.Label`
- `tab_folder`: wrapper for `org.eclipse.swt.widgets.TabFolder`
- `tab_item`: wrapper for `org.eclipse.swt.widgets.TabItem`
- `table`: wrapper for `org.eclipse.swt.widgets.Table`
- `table_column`: wrapper for `org.eclipse.swt.widgets.TableColumn`
- `tree`: wrapper for `org.eclipse.swt.widgets.Tree`

### Widget Styles

SWT widgets receive `SWT` styles in their constructor as per this guide:

https://wiki.eclipse.org/SWT_Widget_Style_Bits

Glimmer DSL facilitates that by passing symbols representing `SWT` constants as widget method arguments (i.e. inside widget `()` parentheses. See example below) in lower case version (e.g. `SWT::MULTI` becomes `:multi`).

These styles customize widget look, feel, and behavior.

Example:
```ruby
list(:multi) { # SWT styles go inside ()
  # ...
}
```

Passing `:multi` to `list` widget enables list element multi-selection.

```ruby
composite(:border) { # SWT styles go inside ()
  # ...
}
```

Passing `:border` to `composite` widget ensures it has a border.

When you need to pass in **multiple SWT styles**, simply separate by commas.

Example:
```ruby
text(:center, :border) { # Multiple SWT styles separated by comma
  # ...
}
```

Glimmer ships with SWT style **smart defaults** so you wouldn't have to set them yourself most of the time (albeit you can always override them):

- `text(:border)`
- `table(:border)`
- `spinner(:border)`
- `list(:border, :v_scroll)`
- `button(:push)`

You may check out all available `SWT` styles here:

https://help.eclipse.org/2019-12/nftopic/org.eclipse.platform.doc.isv/reference/api/org/eclipse/swt/SWT.html

**Final Note** (advanced case outside of standard Glimmer DSL):

When building a widget-related SWT object manually (e.g. `GridData.new(...)`), you are expected to use `SWT::CONSTANT` directly or BIT-OR a few SWT constants together like `SWT::BORDER | SWT::V_SCROLL`.

Glimmer facilitates that with `GSWT` class by allowing you to pass multiple styles as an argument array of symbols instead of dealing with BIT-OR. For example: `GSWT[:border, :v_scroll]`

### Widget Properties

Widget properties such as value, enablement, and layout details are set within the widget block using methods matching SWT widget property names in lower snakecase. You may refer to SWT widget guide for details on available widget properties:

https://help.eclipse.org/2019-12/topic/org.eclipse.platform.doc.isv/guide/swt_widgets_controls.htm?cp=2_0_7_0_0


Code examples:

```ruby
label {
  text "Hello World!" # SWT properties go inside {} block
}
```

In the above example, the `label` widget `text` property was set to "Hello World!".

```ruby
button {
  enabled bind(@tic_tac_toe_board.box(row, column), :empty)
}
```

In the above example, the `text` widget `enabled` property was data-bound to `#empty` method on `@tic_tac_toe_board.box(row, column)` (learn more about data-binding below)

### Layouts

Glimmer lays widgets out visually using SWT layouts, which can only be set on composite widget and subclasses.

The most common SWT layouts are:
- `FillLayout`: lays widgets out in equal proportion horizontally or vertically with spacing/margin options
- `RowLayout`: lays widgets out horizontally or vertically in varying proportions with advanced spacing/margin/justify options
- `GridLayout`(**default**): lays widgets out in a grid with advanced spacing/margin/alignment/indentation options. This is the **default** layout in Glimmer. It is important to master.

In Glimmer DSL, just like widgets, layouts can be specified with lowercase underscored names followed by a block containing properties (e.g. `RowLayout` is `row_layout`).

Example:

```ruby
composite {
  row_layout {
    wrap true
    pack false
    justify true
    type :vertical
    margin_left 1
    margin_top 2
    margin_right 3
    margin_bottom 4
    spacing 5
  }
  # ... widgets follow
}
```

Alternatively, a layout may be constructed by following the SWT API for the layout object. For example, a `RowLayout` can be constructed by passing it an SWT style constant.

```ruby
composite {
  row_layout(:horizontal)
  # ... widgets follow
}
```

Check out the samples directory for more advanced examples of layouts in Glimmer.

**Defaults**:

Glimmer composites always come with grid_layout by default, but you can still specify explicitly if you'd like to set specific properties on it.

Glimmer shell always comes containing one composite by default that wraps around specified shell content. That specific composite (the one directly under shell) has fill_layout with :horizontal type.

This is a great guide for learning more about SWT layouts:

https://www.eclipse.org/articles/Article-Understanding-Layouts/Understanding-Layouts.htm

Also, for a reference, check the SWT API:

https://help.eclipse.org/2019-12/nftopic/org.eclipse.platform.doc.isv/reference/api/index.html

### Layout Data

Layouts organize widgets following common rules for all widgets directly under a composite. But, what if a specific widget needs its own rules. That's where layout data comes into play.

By convention, SWT layouts expect widgets to set layout data with a class matching their class name with the word "Data" replacing "Layout":
- `GridLayout` on a composite demands `GridData` on contained widgets
- `RowLayout` on a composite demands `RowData` on contained widgets

Not all layouts support layout data to further customize widget layouts. For example, `FillLayout` supports no layout data.

Unlike widgets and layouts in Glimmer DSL, layout data is simply specified with `layout_data` keyword nested inside a widget block body, and followed by arguments and/or a block of its own properties. Glimmer automatically deduces layout data class name by convention as per rule above, with the assumption that the layout data class lives under the same exact Java package as the layout (one can set custom layout data that breaks convention if needed in rare cases. See code below for an example)

Examples:

```ruby
composite {
  row_layout(:horizontal)
  label {
    layout_data { # followed by properties
      width 50
      height 30
    }
  }
  # ... more widgets follow
}
```

```ruby
composite {
  grid_layout(3, false) # grid layout with 3 columns not of equal width
  label {
    # layout data followed by arguments passed to SWT constructor
    layout_data(GSWT[:fill], GSWT[:end], true, false)
  }
}
```

```ruby
composite {
  grid_layout(3, false) # grid layout with 3 columns not of equal width
  label {
    # layout data set explicitly via an object (helps in rare cases that break convention)
    layout_data GridData.new(GSWT[:fill], GSWT[:end], true, false)
  }
}
```

**NOTE**: Layout data must never be reused between widgets. Always specify or clone again for every widget.

This is a great guide for learning more about SWT layouts:

https://www.eclipse.org/articles/Article-Understanding-Layouts/Understanding-Layouts.htm

Also, for a reference, check the SWT API:

https://help.eclipse.org/2019-12/nftopic/org.eclipse.platform.doc.isv/reference/api/index.html

### Colors

Colors make up a subset of widget properties. SWT accepts color objects created with RGB (Red Green Blue) or RGBA (Red Green Blue Alpha). Glimmer supports constructing color objects using the `rgb` and `rgba` DSL methods.

Example:

```ruby
label {
  background rgb(144, 240, 244)
  foreground rgba(38, 92, 232, 255)
}
```

SWT also supports all standard colors available as constants under the `SWT` namespace (e.g. `SWT::COLOR_BLUE`)

Glimmer accepts these constants as Ruby symbols prefixed by `color_`.

Example:

```ruby
label {
  background :color_white
  foreground :color_black
}
```

You may check out all available standard colors in `SWT` over here (having `COLOR_` prefix):

https://help.eclipse.org/2019-12/nftopic/org.eclipse.platform.doc.isv/reference/api/org/eclipse/swt/SWT.html

### Fonts

Fonts are represented in Glimmer as a hash of name, height, and style keys.

The style can be one (or more) of 3 values: `:normal`, `:bold`, and `:italic`

Example:

```ruby
label {
  font name: 'Arial', height: 36, style: :normal
}
```

Keys are optional, so some of them may be left off.
When passing multiple styles, they are included in an array.

Example:

```ruby
label {
  font style: [:bold, :italic]
}
```

### Data-Binding

Data-binding is done with `bind` command following widget property to bind and taking model and bindable attribute as arguments.

Data-binding examples:
- `text bind(contact, :first_name)`
- `text bind(contact, 'address.street')`
- `text bind(contact, 'addresses[1].street')`
- `text bind(contact, :name, computed_by: [:first_name, :last_name])`
- `text bind(contact, 'profiles[0].name', computed_by: ['profiles[0].first_name', 'profiles[0].last_name'])`

The first example binds the text property of a widget like `label` to the first name of a contact model.

The second example binds the text property of a widget like `label` to the nested street of
the address of a contact. This is called nested property data binding.

The third example binds the text property of a widget like `label` to the nested indexed address street of a contact. This is called nested indexed property data binding.

The fourth example demonstrates computed value data binding whereby the value of `name` depends on changes to both `first_name` and `last_name`.

The fifth example demonstrates nested indexed computed value data binding whereby the value of `profiles[0].name` depends on changes to both nested `profiles[0].first_name` and `profiles[0].last_name`.

You may learn more about Glimmer's syntax by reading the Eclipse Zone Tutorial mentioned in resources and opening up the samples under the `samples` folder.

### Observer

Glimmer comes with `Observer` module, which is used internally for data-binding, but can also be used externally for custom use of the Observer Pattern.

In summary, the class that needs to observe an object, must include Observer and implement `#call(new_value)` method. The class to be observed doesn't need to do anything. It will automatically be enhanced by Glimmer for observation.

To register observer, one has to call the `#observe` method and pass in the observable and the property(ies) to observe.

```ruby
class TicTacToe
  include Glimmer
  include Observer

  def initialize
    # ...
    observe(@tic_tac_toe_board, "game_status")
  end

  def call(game_status)
    display_win_message if game_status == TicTacToeBoard::WIN
    display_draw_message if game_status == TicTacToeBoard::DRAW
  end
  # ...
end
```

Alternatively, one can use a default Observer::Proc implementation via Observer#proc method:
```ruby
observer = Observer.proc { |new_value| puts new_value }
observer.observe(@tic_tac_toe_board, "game_status")
```

Observers can be a good mechanism for displaying dialog messages with Glimmer (using SWT's `MessageBox`).

Look at `samples/tictactoe/tic_tac_toe.rb` for an `Observer` dialog message example (sample below).

```ruby
class TicTacToe
  include Glimmer
  include Observer

  def initialize
    # ...
    observe(@tic_tac_toe_board, "game_status")
  end

  def call(game_status)
    display_win_message if game_status == TicTacToeBoard::WIN
    display_draw_message if game_status == TicTacToeBoard::DRAW
  end

  def display_win_message
    display_game_over_message("Player #{@tic_tac_toe_board.winning_sign} has won!")
  end

  def display_draw_message
    display_game_over_message("Draw!")
  end

  def display_game_over_message(message)
    message_box = MessageBox.new(@shell.widget)
    message_box.setText("Game Over")
    message_box.setMessage(message)
    message_box.open
    @tic_tac_toe_board.reset
  end
  # ...
end
```

## Samples

Check the "samples" folder for examples on how to write Glimmer applications. To run them, make sure to install the `glimmer` gem first and then use the `glimmer` command.

Example:

```
glimmer samples/hello_world.rb
```

## SWT Reference

https://www.eclipse.org/swt/docs.php

Here is the SWT API:

https://help.eclipse.org/2019-12/nftopic/org.eclipse.platform.doc.isv/reference/api/index.html

Here is a list of SWT widgets:

https://help.eclipse.org/2019-12/topic/org.eclipse.platform.doc.isv/guide/swt_widgets_controls.htm?cp=2_0_7_0_0

Here is a list of SWT style bits:

https://wiki.eclipse.org/SWT_Widget_Style_Bits

## SWT Packages

Glimmer automatically imports all SWT Java packages upon adding `include Glimmer` to a class or module.

Still, if you'd like to import manually elsewhere, you may add the following lines to your code (in the class or module body) to import SWT Java packages using `include_package`:

```ruby
include_package 'org.eclipse.swt'
include_package 'org.eclipse.swt.widgets'
include_package 'org.eclipse.swt.layout'
include_package 'org.eclipse.swt.graphics'
```

To import a specific SWT Java class using `java_import`, add the following:

```ruby
java_import 'org.eclipse.swt.SWT'
```

This allows you to call SWT Java classes from Ruby without mentioning package namespaces.

For example, after imports, `org.eclipse.swt.graphics.Color` can be referenced by just `Color`

## Girb (Glimmer irb)

With Glimmer installed, you may run want to run `girb` instead of standard `irb` to have SWT preloaded and the Glimmer library required and included for quick Glimmer coding/testing.

## Logging

Glimmer comes with a Ruby Logger accessible via `Glimmer.logger`
Its level of logging defaults to `Logger::WARN`
It may be configured to show a different level of logging as follows:
```ruby
Glimmer.logger.level = Logger::DEBUG
```
This results in more verbose debugging log to `STDOUT`, which is helpful in troubleshooting Glimmer DSL syntax when needed.

Example log:
```
D, [2017-07-21T19:23:12.587870 #35707] DEBUG -- : method: shell and args: []
D, [2017-07-21T19:23:12.594405 #35707] DEBUG -- : ShellCommandHandler will handle command: shell with arguments []
D, [2017-07-21T19:23:12.844775 #35707] DEBUG -- : method: composite and args: []
D, [2017-07-21T19:23:12.845388 #35707] DEBUG -- : parent is a widget: true
D, [2017-07-21T19:23:12.845833 #35707] DEBUG -- : on listener?: false
D, [2017-07-21T19:23:12.864395 #35707] DEBUG -- : WidgetCommandHandler will handle command: composite with arguments []
D, [2017-07-21T19:23:12.864893 #35707] DEBUG -- : widget styles are: []
D, [2017-07-21T19:23:12.874296 #35707] DEBUG -- : method: list and args: [:multi]
D, [2017-07-21T19:23:12.874969 #35707] DEBUG -- : parent is a widget: true
D, [2017-07-21T19:23:12.875452 #35707] DEBUG -- : on listener?: false
D, [2017-07-21T19:23:12.878434 #35707] DEBUG -- : WidgetCommandHandler will handle command: list with arguments [:multi]
D, [2017-07-21T19:23:12.878798 #35707] DEBUG -- : widget styles are: [:multi]
```

## Raw JRuby Command

If there is a need to run Glimmer directly via the `jruby` command, you
may run the following:

```
jruby -J-classpath "path_to/swt.jar" -r glimmer -S application.rb
```

The `-J-classpath` option specifies the `swt.jar` file path, which can be a
manually downloaded version of SWT, or otherwise the one included in the gem. You can lookup the one included in the gem by running `jgem which glimmer` to find the gem path and then look through the `vendor` directory.

The `-r` option preloads (requires) the `glimmer` library in Ruby.

The `-S` option specifies a script to run.

### Mac Support

Mac is well supported with the `glimmer` command. However, if there is a reason to use the raw jruby command, you need to pass an extra option (`-J-XstartOnFirstThread`) to JRuby on the Mac.

Example:
```
jruby -J-XstartOnFirstThread -J-classpath "path_to/swt.jar" -r glimmer -S application.rb
```

## Feature Suggestions

These features have been suggested. You might see them in a future version of Glimmer. You are welcome to contribute more feature suggestions.

[TODO.md](https://github.com/AndyObtiva/glimmer/blob/master/TODO.md)

## Change Log

[CHANGELOG.md](https://github.com/AndyObtiva/glimmer/blob/master/CHANGELOG.md)

## Contributing

[CONTRIBUTING.md](https://github.com/AndyObtiva/glimmer/blob/master/CONTRIBUTING.md)

## Contributors

* Andy Maleh (Founder)
* Dennis Theisen

## License

Copyright (c) 2007-2020 Andy Maleh.
See LICENSE.txt for further details.