Glimmer DSL for GTK Tetris + Cairo Tutorial
Tags: ruby, gtk, desktop, gui
Published: 2022-01-30 22:47:36

[Glimmer DSL for GTK](https://github.com/AndyObtiva/glimmer-dsl-gtk) ([Ruby GNOME](https://github.com/ruby-gnome/ruby-gnome) Desktop Development GUI Library) had a few releases in response to [an issue requesting a Tetris sample](https://github.com/AndyObtiva/glimmer-dsl-gtk/issues/2). The project now includes brand new [declarative support for Cairo graphics](https://github.com/AndyObtiva/glimmer-dsl-gtk#declarative-cairo-graphics) and an [implementation of the Tetris game as a sample](https://github.com/AndyObtiva/glimmer-dsl-gtk#tetris). Additionally, the majority of [Cairo samples](https://www.cairographics.org/samples/) mentioned in this [Cairo Tutorial blog post by Mohit Sindhwani ("Cairo with Ruby - Samples using RCairo")](https://notepad.onghu.com/2021/cairo-samples-in-ruby/) have been included too. 

Below is a [Glimmer DSL for GTK rewriting of Mohit's tutorial](https://github.com/AndyObtiva/glimmer-dsl-gtk#declarative-cairo-graphics) using the much simpler and more maintainable [Glimmer DSL for GTK declarative Cairo syntax](https://github.com/AndyObtiva/glimmer-dsl-gtk#declarative-cairo-graphics) (instead of the default [RCairo](https://github.com/rcairo/rcairo) imperative syntax).

## [Tutorial of using Cairo in Ruby with Glimmer DSL for GTK:](https://github.com/AndyObtiva/glimmer-dsl-gtk#declarative-cairo-graphics)

[Cairo](https://www.cairographics.org/) is the engine behind drawing arbitrary 2D geometric shapes in [GTK](https://www.gtk.org/).

In [Glimmer DSL for GTK](https://github.com/AndyObtiva/glimmer-dsl-gtk), you can draw Cairo shapes declaratively in a way similar to how SVG works, but using one language; Ruby, thus being able to utilize Ruby logic (e.g. if statement or each loop) with it effortlessly when needed. Declarative syntax also yields less code that is simpler, not dependent on ordering of nested properties, and more understandable/maintainable.

Below is a quick tutorial consisting of samples inspired and ported from [Mohit Sindhwani's blog post "Cairo with Ruby - Samples using RCairo"](https://notepad.onghu.com/2021/cairo-samples-in-ruby/).

#### Arc

[samples/cairo/arc.rb](/samples/cairo/arc.rb)

```ruby
require 'glimmer-dsl-gtk'

include Glimmer

window {
  title 'Hello, Drawing Area!'
  default_size 256, 256
  
  drawing_area {
    # Surface Paint
    paint 242.25, 242.25, 242.25
    
    # Set up the parameters
    xc = 128.0
    yc = 128.0
    radius = 100.0
    angle1 = 45.0  * (Math::PI/180.0) # angles are specified
    angle2 = 180.0  * (Math::PI/180.0) # in radians
    
    # The main arc
    arc(xc, yc, radius, angle1, angle2) {
      stroke 0, 0, 0
      line_width 10
    }
    
    # Draw helping lines
    
    # First, the circle at the centre
    arc(xc, yc, 10.0, 0, 2*Math::PI) {
      fill 255, 51, 51, 0.6
    }
    
    # Then, the lines reaching out
    path {
      arc xc, yc, radius, angle1, angle1
      line_to xc, yc
      arc xc, yc, radius, angle2, angle2
      line_to xc, yc
      
      stroke 255, 51, 51, 0.6
      line_width 6
    }
  }
}.show
```

![Arc](https://raw.githubusercontent.com/AndyObtiva/glimmer-dsl-gtk/master/screenshots/glimmer-dsl-gtk-mac-cairo-arc.png)

#### Arc Negative

[samples/cairo/arc_negative.rb](/samples/cairo/arc_negative.rb)

```ruby
require 'glimmer-dsl-gtk'

include Glimmer

window {
  title 'Arc Negative'
  default_size 256, 256
  
  drawing_area {
    # Surface Paint
    paint 255, 255, 255
    
    # Set up the parameters
    xc = 128.0
    yc = 128.0
    radius = 100.0
    angle1 = 45.0  * (Math::PI/180.0) # angles are specified
    angle2 = 180.0  * (Math::PI/180.0) # in radians
    
    # The main negative arc
    arc_negative(xc, yc, radius, angle1, angle2) {
      stroke 0, 0, 0
      line_width 10
    }
    
    # Draw helping lines
    
    # First, the circle at the centre
    arc(xc, yc, 10.0, 0, 2*Math::PI) {
      fill 255, 51, 51, 0.6
    }
    
    # Then, the lines reaching out
    path {
      arc(xc, yc, radius, angle1, angle1)
      line_to(xc, yc)
      arc(xc, yc, radius, angle2, angle2)
      line_to(xc, yc)
      
      stroke 255, 51, 51, 0.6
      line_width 6
    }
  }
}.show
```

![Arc Negative](https://raw.githubusercontent.com/AndyObtiva/glimmer-dsl-gtk/master/screenshots/glimmer-dsl-gtk-mac-cairo-arc-negative.png)

#### Clip

[samples/cairo/clip.rb](/samples/cairo/clip.rb)

```ruby
require 'glimmer-dsl-gtk'

include Glimmer

window {
  title 'Clip'
  default_size 256, 256
  
  drawing_area {
    # Surface Paint
    paint 255, 255, 255
    
    # Designate arc as the clipping area
    arc(128.0, 128.0, 76.8, 0, 2 * Math::PI) {
      clip true
    }
    
    # Rectangle will get clipped by arc
    rectangle(0, 0, 256, 256) {
      fill 0, 0, 0
    }
    
    # Path will get clipped by arc
    path {
      move_to 0, 0
      line_to 256, 256
      move_to 256, 0
      line_to 0, 256
      
      stroke 0, 255, 0
      line_width 10
    }
  }
}.show
```

![Clip](https://raw.githubusercontent.com/AndyObtiva/glimmer-dsl-gtk/master/screenshots/glimmer-dsl-gtk-mac-cairo-clip.png)

#### Clip Image

[samples/cairo/clip_image.rb](/samples/cairo/clip_image.rb)

```ruby
require 'glimmer-dsl-gtk'
require 'net/http'

image_content = Net::HTTP.get(URI('https://raw.githubusercontent.com/AndyObtiva/glimmer-dsl-gtk/master/images/breaking-blue-wave.png'))
image_file = File.join(Dir.home, 'breaking-blue-wave.png')
File.write(image_file, image_content)

include Glimmer

window {
  title 'Clip Image'
  default_size 256, 256
  
  drawing_area {
    paint 242.25, 242.25, 242.25

    arc(128.0, 128.0, 76.8, 0, 2 * Math::PI) {
      clip true # designate arc as the clipping area
    }

    rectangle(0, 0, 256, 256) {
      # Source image is from:
      # - https://www.publicdomainpictures.net/en/view-image.php?image=7683&picture=breaking-blue-wave
      # Converted to PNG before using it
      image = Cairo::ImageSurface.from_png(image_file)
      w = image.width
      h = image.height
  
      scale 256.0/w, 256.0/h, exclude: :shape # applies scale to fill source image only
      fill image, 0, 0
    }
  }
}.show
```

![Clip Image](https://raw.githubusercontent.com/AndyObtiva/glimmer-dsl-gtk/master/screenshots/glimmer-dsl-gtk-mac-cairo-clip-image.png)

#### Curve to

[samples/cairo/curve_to.rb](/samples/cairo/curve_to.rb)

```ruby
require 'glimmer-dsl-gtk'

include Glimmer

window {
  title 'Curve to'
  default_size 256, 256
  
  drawing_area {
    paint 242.25, 242.25, 242.25
    
    x=25.6
    y=128.0
    x1=102.4
    y1=230.4
    x2=153.6
    y2=25.6
    x3=230.4
    y3=128.0
    
    path {
      move_to x, y
      curve_to x1, y1, x2, y2, x3, y3
      
      line_width 10
      stroke 0, 0, 0
    }
    
    path {
      move_to x,y
      line_to x1,y1
      move_to x2,y2
      line_to x3,y3
      
      line_width 6
      stroke 255, 51, 51, 0.6
    }
  }
}.show
```

![Curve to](https://raw.githubusercontent.com/AndyObtiva/glimmer-dsl-gtk/master/screenshots/glimmer-dsl-gtk-mac-cairo-curve-to.png)

#### Dashes

[samples/cairo/dashes.rb](/samples/cairo/dashes.rb)

```ruby
require 'glimmer-dsl-gtk'

include Glimmer

window {
  title 'Dashes'
  default_size 256, 256
  
  drawing_area {
    paint 242.25, 242.25, 242.25

    dashes = [ 50.0, # ink
                       10.0,  # skip
                       10.0,  # ink
                       10.0   # skip
            ]
    offset = -50.0
    
    path {
      move_to 128.0, 25.6
      line_to 230.4, 230.4
      rel_line_to -102.4, 0.0
      curve_to 51.2, 230.4, 51.2, 128.0, 128.0, 128.0
      
      line_width 10
      dash dashes, offset
      stroke 0, 0, 0
    }
  }
}.show
```

![Dashes](https://raw.githubusercontent.com/AndyObtiva/glimmer-dsl-gtk/master/screenshots/glimmer-dsl-gtk-mac-cairo-dashes.png)

#### Fill and Stroke 2

(note: there is no Fill and Stroke 1; this was adopted from [Mohit's blog post](https://notepad.onghu.com/2021/cairo-samples-in-ruby/), which only mentioned Fill and Stroke 2)

[samples/cairo/fill_and_stroke2.rb](/samples/cairo/fill_and_stroke2.rb)

```ruby
require 'glimmer-dsl-gtk'

include Glimmer

window {
  title 'Fill and Stroke 2'
  default_size 256, 256
  
  drawing_area {
    paint 242.25, 242.25, 242.25
    
    path {
      move_to 128.0, 25.6
      line_to 230.4, 230.4
      rel_line_to -102.4, 0.0
      curve_to 51.2, 230.4, 51.2, 128.0, 128.0, 128.0
      close_path

      fill 0, 0, 255
      stroke 0, 0, 0
      line_width 10
    }
    
    path {
      move_to 64.0, 25.6
      rel_line_to 51.2, 51.2
      rel_line_to -51.2, 51.2
      rel_line_to -51.2, -51.2
      close_path

      fill 0, 0, 255
      stroke 0, 0, 0
      line_width 10
    }
  }
}.show
```

![Fill and Stroke 2](https://raw.githubusercontent.com/AndyObtiva/glimmer-dsl-gtk/master/screenshots/glimmer-dsl-gtk-mac-cairo-fill-and-stroke2.png)

#### Fill Style

[samples/cairo/fill_style.rb](/samples/cairo/fill_style.rb)

```ruby
require 'glimmer-dsl-gtk'

include Glimmer

window {
  title 'Fill Style'
  default_size 256, 256
  
  drawing_area {
    paint 242.25, 242.25, 242.25
    
    path {
      rectangle 12, 12, 232, 70
      path { # sub-path
        arc 64, 64, 40, 0, 2*Math::PI
      }
      path { # sub-path
        arc_negative 192, 64, 40, 0, -2*Math::PI
      }
      
      fill_rule Cairo::FILL_RULE_EVEN_ODD
      line_width 6
      fill 0, 178.5, 0
      stroke 0, 0, 0
    }
    
    path {
      rectangle 12, 12, 232, 70
      path { # sub-path
        arc 64, 64, 40, 0, 2*Math::PI
      }
      path { # sub-path
        arc_negative 192, 64, 40, 0, -2*Math::PI
      }
      
      translate 0, 128
      fill_rule Cairo::FILL_RULE_WINDING
      line_width 6
      fill 0, 0, 229.5
      stroke 0, 0, 0
    }
  }
}.show
```

![Fill Style](https://raw.githubusercontent.com/AndyObtiva/glimmer-dsl-gtk/master/screenshots/glimmer-dsl-gtk-mac-cairo-fill-style.png)

#### Gradient

[samples/cairo/gradient.rb](/samples/cairo/gradient.rb)

```ruby
require 'glimmer-dsl-gtk'

include Glimmer

window {
  title 'Gradient'
  default_size 256, 256
  
  drawing_area {
    paint 242.25, 242.25, 242.25
        
    # Create the Linear Pattern
    rectangle(0, 0, 256, 256) {
      pat = Cairo::LinearPattern.new(0.0, 0.0,  0.0, 256.0)
      pat.add_color_stop_rgba(1, 0, 0, 0, 1)
      pat.add_color_stop_rgba(0, 1, 1, 1, 1)
      
      fill pat
    }
    
    # Create the radial pattern
    arc(128.0, 128.0, 76.8, 0, 2 * Math::PI) {
      pat = Cairo::RadialPattern.new(115.2, 102.4, 25.6,
                                         102.4,  102.4, 128.0)
      pat.add_color_stop_rgba(0, 1, 1, 1, 1)
      pat.add_color_stop_rgba(1, 0, 0, 0, 1)
      
      fill pat
    }
  }
}.show
```

![Gradient](https://raw.githubusercontent.com/AndyObtiva/glimmer-dsl-gtk/master/screenshots/glimmer-dsl-gtk-mac-cairo-gradient.png)

#### Image

[samples/cairo/image.rb](/samples/cairo/image.rb)

```ruby
require 'glimmer-dsl-gtk'
require 'net/http'

image_content = Net::HTTP.get(URI('https://raw.githubusercontent.com/AndyObtiva/glimmer-dsl-gtk/master/images/breaking-blue-wave.png'))
image_file = File.join(Dir.home, 'breaking-blue-wave.png')
File.write(image_file, image_content)

include Glimmer

window {
  title 'Image'
  default_size 256, 256
  
  drawing_area {
    paint 242.25, 242.25, 242.25
        
    image = Cairo::ImageSurface.from_png(image_file)
    w = image.width
    h = image.height
    
    translate 128.0, 128.0
    rotate 45*Math::PI/180
    scale 256.0/w, 256.0/h
    translate -0.5*w, -0.5*h
    
    paint image, 0, 0
  }
}.show
```

![Image](https://raw.githubusercontent.com/AndyObtiva/glimmer-dsl-gtk/master/screenshots/glimmer-dsl-gtk-mac-cairo-image.png)

#### Image Gradient

[samples/cairo/image_gradient.rb](/samples/cairo/image_gradient.rb)

```ruby
require 'glimmer-dsl-gtk'
require 'net/http'

image_content = Net::HTTP.get(URI('https://raw.githubusercontent.com/AndyObtiva/glimmer-dsl-gtk/master/images/breaking-blue-wave.png'))
image_file = File.join(Dir.home, 'breaking-blue-wave.png')
File.write(image_file, image_content)

include Glimmer

window {
  title 'Image Gradient'
  default_size 256, 256
  
  drawing_area {
    paint 242.25, 242.25, 242.25
    
    image = Cairo::ImageSurface.from_png(image_file)
    w = image.width
    h = image.height
    
    # Load the image as a surface pattern
    pattern = Cairo::SurfacePattern.new(image)
    pattern.extend = Cairo::EXTEND_REPEAT
    
    # Set up the scale matrix
    pattern.matrix = Cairo::Matrix.scale(w/256.0 * 5.0, h/256.0 * 5.0)
    
    rectangle(0, 0, 256, 256) {
      translate 128.0, 128.0
      rotate Math::PI / 4
      scale 1/Math.sqrt(2), 1/Math.sqrt(2)
      translate -128.0, -128.0
        
      fill pattern
    }
  }
}.show
```

![Image Gradient](https://raw.githubusercontent.com/AndyObtiva/glimmer-dsl-gtk/master/screenshots/glimmer-dsl-gtk-mac-cairo-image-gradient.png)

#### Multi Segment Caps

[samples/cairo/multi_segment_caps.rb](/samples/cairo/multi_segment_caps.rb)

```ruby
require 'glimmer-dsl-gtk'

include Glimmer

window {
  title 'Multi Segment Caps'
  default_size 256, 256
  
  drawing_area {
    paint 242.25, 242.25, 242.25
    
    path {
      move_to 50.0, 75.0
      line_to 200.0, 75.0
      
      move_to 50.0, 125.0
      line_to 200.0, 125.0
      
      move_to 50.0, 175.0
      line_to 200.0, 175.0
      
      line_width 30
      line_cap Cairo::LINE_CAP_ROUND
      stroke 0, 0, 0
    }
  }
}.show
```

![Multi Segment Caps](https://raw.githubusercontent.com/AndyObtiva/glimmer-dsl-gtk/master/screenshots/glimmer-dsl-gtk-mac-cairo-multi-segment-caps.png)

#### Rounded Rectangle

[samples/cairo/rounded_rectangle.rb](/samples/cairo/rounded_rectangle.rb)

```ruby
require 'glimmer-dsl-gtk'

include Glimmer

window {
  title 'Rounded Rectangle'
  default_size 256, 256
  
  drawing_area {
    paint 242.25, 242.25, 242.25
    
    path {
      rounded_rectangle(25.6, 25.6, 204.8, 204.8, 20)
    
      fill 127.5, 127.5, 255
      line_width 10.0
      stroke 127.5, 0, 0, 0.5
    }
  }
}.show
```

![Rounded Rectangle](https://raw.githubusercontent.com/AndyObtiva/glimmer-dsl-gtk/master/screenshots/glimmer-dsl-gtk-mac-cairo-rounded-rectangle.png)

#### Set line cap

[samples/cairo/set_line_cap.rb](/samples/cairo/set_line_cap.rb)

```ruby
require 'glimmer-dsl-gtk'

include Glimmer

window {
  title 'Set line cap'
  default_size 256, 256
  
  drawing_area {
    paint 242.25, 242.25, 242.25
    
    # The main code
    path {
      move_to 64.0, 50.0
      line_to 64.0, 200.0
      
      line_cap Cairo::LINE_CAP_BUTT #  default
      line_width 30
      stroke 0, 0, 0
    }
    
    path {
      move_to 128.0, 50.0
      line_to 128.0, 200.0
      
      line_cap Cairo::LINE_CAP_ROUND
      line_width 30
      stroke 0, 0, 0
    }
    
    path {
      move_to 192.0, 50.0
      line_to 192.0, 200.0
      
      line_cap Cairo::LINE_CAP_SQUARE
      line_width 30
      stroke 0, 0, 0
    }
    
    #  draw helping lines */
    path {
      move_to 64.0, 50.0
      line_to 64.0, 200.0
      move_to 128.0, 50.0
      line_to 128.0, 200.0
      move_to 192.0, 50.0
      line_to 192.0, 200.0
      
      line_width 2.56
      stroke 255, 51, 51
    }
  }
}.show
```

![Set line cap](https://raw.githubusercontent.com/AndyObtiva/glimmer-dsl-gtk/master/screenshots/glimmer-dsl-gtk-mac-cairo-set-line-cap.png)

#### Set line join

[samples/cairo/set_line_join.rb](/samples/cairo/set_line_join.rb)

```ruby
require 'glimmer-dsl-gtk'

include Glimmer

window {
  title 'Set line join'
  default_size 256, 256
  
  drawing_area {
    paint 242.25, 242.25, 242.25
    
    # The main code
    path {
      move_to 76.8, 84.48
      rel_line_to 51.2, -51.2
      rel_line_to 51.2, 51.2
      
      line_join Cairo::LINE_JOIN_MITER # default
      line_width 40.96
      stroke 0, 0, 0
    }
    
    path {
      move_to 76.8, 161.28
      rel_line_to 51.2, -51.2
      rel_line_to 51.2, 51.2
      
      line_join Cairo::LINE_JOIN_BEVEL
      line_width 40.96
      stroke 0, 0, 0
    }
    
    path {
      move_to 76.8, 238.08
      rel_line_to 51.2, -51.2
      rel_line_to 51.2, 51.2
      
      line_join Cairo::LINE_JOIN_ROUND
      line_width 40.96
      stroke 0, 0, 0
    }
  }
}.show
```

![Set line join](https://raw.githubusercontent.com/AndyObtiva/glimmer-dsl-gtk/master/screenshots/glimmer-dsl-gtk-mac-cairo-set-line-join.png)

#### Text

[samples/cairo/text.rb](/samples/cairo/text.rb)

```ruby
require 'glimmer-dsl-gtk'

include Glimmer

window {
  title 'Text'
  default_size 256, 256
  
  drawing_area {
    paint 242.25, 242.25, 242.25
    
    font_family = OS.linux? ? 'Sans' : (OS.mac? ? 'Helvetica' : 'Arial')
    
    # The main code
    path {
      move_to 10.0, 135.0
      show_text 'Hello'
      
      font_face font_family, Cairo::FONT_SLANT_NORMAL, Cairo::FONT_WEIGHT_BOLD
      font_size 90.0
      line_width 2.56
      fill 0, 0, 0
      stroke 0, 0, 0
    }
    
    path {
      move_to 70.0, 165.0
      text_path 'void'
      
      font_face font_family, Cairo::FONT_SLANT_NORMAL, Cairo::FONT_WEIGHT_BOLD
      font_size 90.0
      line_width 2.56
      fill 127.5, 127.5, 255
      stroke 0, 0, 0
    }
    
    # draw helping lines
    path {
      arc 10.0, 135.0, 5.12, 0, 2*Math::PI
      close_path
      arc 70.0, 165.0, 5.12, 0, 2*Math::PI
      
      fill 255, 51, 51, 0.6
    }
  }
}.show
```

![Text](https://raw.githubusercontent.com/AndyObtiva/glimmer-dsl-gtk/master/screenshots/glimmer-dsl-gtk-mac-cairo-text.png)

## Tetris Screenshot:

Here is a screenshot of [Tetris](https://github.com/AndyObtiva/glimmer-dsl-gtk#tetris), written with [declarative Cairo code using Glimmer DSL for GTK](https://github.com/AndyObtiva/glimmer-dsl-gtk#declarative-cairo-graphics).

![Tetris](https://github.com/AndyObtiva/glimmer-dsl-gtk/raw/master/screenshots/glimmer-dsl-gtk-linux-tetris.png)

## Tetris Glimmer DSL for GTK Code:

Cairo usage is mostly the [Glimmer-only](https://github.com/AndyObtiva/glimmer-dsl-gtk#hello-drawing-area) `square` and `polygon` shape constructions (not available in standard [RCairo](https://github.com/rcairo/rcairo)).

```ruby
# From: https://github.com/AndyObtiva/glimmer-dsl-gtk#tetris

require 'glimmer-dsl-gtk'

require_relative 'tetris/model/game'

class Tetris
  include Glimmer
  
  BLOCK_SIZE = 25
  BEVEL_CONSTANT = 20
  COLOR_GRAY = [192, 192, 192]
    
  def initialize
    @game = Model::Game.new
  end
  
  def launch
    create_gui
    register_observers
    @game.start!
    @main_window.show
  end
  
  def create_gui
    @main_window = window {
      title 'Glimmer Tetris'
      default_size Model::Game::PLAYFIELD_WIDTH * BLOCK_SIZE, Model::Game::PLAYFIELD_HEIGHT * BLOCK_SIZE # + 98
      
      box(:vertical) {
        tetris_menu_bar

        box(:horizontal) {
          @playfield_blocks = playfield(playfield_width: @game.playfield_width, playfield_height: @game.playfield_height, block_size: BLOCK_SIZE)
          
          score_board
        }
        
      }
      
      on(:key_press_event) do |widget, key_event|
        case key_event.keyval
        when 65364 # down arrow
          @game.down!
        when 32 # space
          @game.down!(instant: true)
        when 65362 # up arrow
          case @game.up_arrow_action
          when :instant_down
            @game.down!(instant: true)
          when :rotate_right
            @game.rotate!(:right)
          when :rotate_left
            @game.rotate!(:left)
          end
        when 65361 # left arrow
          @game.left!
        when 65363 # right arrow
          @game.right!
        when 65506 # right shift
          @game.rotate!(:right)
        when 65505 # left shift
          @game.rotate!(:left)
        else
          # Do Nothing
        end
      end
    }
  end
  
  def register_observers
    observe(@game, :game_over) do |game_over|
      if game_over
        show_game_over_dialog
      else
        start_moving_tetrominos_down
      end
    end
    
    @game.playfield_height.times do |row|
      @game.playfield_width.times do |column|
        observe(@game.playfield[row][column], :color) do |new_color|
          color = new_color
          block = @playfield_blocks[row][column]
          block[:background_square].fill = color
          block[:top_bevel_edge].fill = [color[0] + 4*BEVEL_CONSTANT, color[1] + 4*BEVEL_CONSTANT, color[2] + 4*BEVEL_CONSTANT]
          block[:right_bevel_edge].fill = [color[0] - BEVEL_CONSTANT, color[1] - BEVEL_CONSTANT, color[2] - BEVEL_CONSTANT]
          block[:bottom_bevel_edge].fill = [color[0] - BEVEL_CONSTANT, color[1] - BEVEL_CONSTANT, color[2] - BEVEL_CONSTANT]
          block[:left_bevel_edge].fill = [color[0] - BEVEL_CONSTANT, color[1] - BEVEL_CONSTANT, color[2] - BEVEL_CONSTANT]
          block[:border_square].stroke = new_color == Model::Block::COLOR_CLEAR ? COLOR_GRAY : color
          block[:drawing_area].queue_draw
          false
        end
      end
    end
    
    Model::Game::PREVIEW_PLAYFIELD_HEIGHT.times do |row|
      Model::Game::PREVIEW_PLAYFIELD_WIDTH.times do |column|
        observe(@game.preview_playfield[row][column], :color) do |new_color|
          color = new_color
          block = @preview_playfield_blocks[row][column]
          block[:background_square].fill = color
          block[:top_bevel_edge].fill = [color[0] + 4*BEVEL_CONSTANT, color[1] + 4*BEVEL_CONSTANT, color[2] + 4*BEVEL_CONSTANT]
          block[:right_bevel_edge].fill = [color[0] - BEVEL_CONSTANT, color[1] - BEVEL_CONSTANT, color[2] - BEVEL_CONSTANT]
          block[:bottom_bevel_edge].fill = [color[0] - BEVEL_CONSTANT, color[1] - BEVEL_CONSTANT, color[2] - BEVEL_CONSTANT]
          block[:left_bevel_edge].fill = [color[0] - BEVEL_CONSTANT, color[1] - BEVEL_CONSTANT, color[2] - BEVEL_CONSTANT]
          block[:border_square].stroke = new_color == Model::Block::COLOR_CLEAR ? COLOR_GRAY : color
          block[:drawing_area].queue_draw
        end
      end
    end
    
    observe(@game, :score) do |new_score|
      @score_label.text = new_score.to_s
    end

    observe(@game, :lines) do |new_lines|
      @lines_label.text = new_lines.to_s
    end

    observe(@game, :level) do |new_level|
      @level_label.text = new_level.to_s
    end
  end
  
  def tetris_menu_bar
    menu_bar {
      menu_item(label: 'Game') { |mi|
        m = menu {
          check_menu_item(label: 'Pause') {
            on(:activate) do
              @game.paused = !@game.paused?
            end
          }
          
          menu_item(label: 'Restart') {
            on(:activate) do
              @game.restart!
            end
          }
          
          separator_menu_item
          
          menu_item(label: 'Exit') {
            on(:activate) do
              @main_window.close
            end
          }
        }
        mi.submenu = m.gtk
      }
      
      menu_item(label: 'View') { |mi|
        m = menu {
          menu_item(label: 'Show High Scores') {
            on(:activate) do
              show_high_score_dialog
            end
          }
          
          menu_item(label: 'Clear High Scores') {
            on(:activate) do
              @game.clear_high_scores!
            end
          }
        }
        mi.submenu = m.gtk
      }
      
      menu_item(label: 'Options') { |mi|
        m = menu {
          rmi = radio_menu_item(nil, 'Instant Down on Up') {
            on(:activate) do
              @game.instant_down_on_up!
            end
          }
          
          default_rmi = radio_menu_item(rmi.group, 'Rotate Right on Up') {
            on(:activate) do
              @game.rotate_right_on_up!
            end
          }
          default_rmi.activate
          
          radio_menu_item(rmi.group, 'Rotate Left on Up') {
            on(:activate) do
              @game.rotate_left_on_up!
            end
          }
        }
        mi.submenu = m.gtk
      }
      
      menu_item(label: 'Options') { |mi|
        m = menu {
          menu_item(label: 'About') {
            on(:activate) do
              show_about_dialog
            end
          }
        }
        mi.submenu = m.gtk
      }
    }
  end
  
  def score_board
    box(:vertical) {
      label
      @preview_playfield_blocks = playfield(playfield_width: Model::Game::PREVIEW_PLAYFIELD_WIDTH, playfield_height: Model::Game::PREVIEW_PLAYFIELD_HEIGHT, block_size: BLOCK_SIZE)
      
      label
      label('Score')
      @score_label = label

      label
      label('Lines')
      @lines_label = label

      label
      label('Level')
      @level_label = label
      label
    }
  end
  
  def playfield(playfield_width: , playfield_height: , block_size: , &extra_content)
    blocks = []
    box(:vertical) {
      playfield_height.times.map do |row|
        blocks << []
        box(:horizontal) {
          playfield_width.times.map do |column|
            blocks.last << block(row: row, column: column, block_size: block_size)
          end
        }
      end
      
      extra_content&.call
    }
    blocks
  end
  
  def block(row: , column: , block_size: , &extra_content)
    block = {}
    bevel_pixel_size = 0.16 * block_size.to_f
    color = Model::Block::COLOR_CLEAR
    block[:drawing_area] = drawing_area {
      size_request block_size, block_size
      
      block[:background_square] = square(0, 0, block_size) {
        fill *color
      }
      
      block[:top_bevel_edge] = polygon(0, 0, block_size, 0, block_size - bevel_pixel_size, bevel_pixel_size, bevel_pixel_size, bevel_pixel_size) {
        fill color[0] + 4*BEVEL_CONSTANT, color[1] + 4*BEVEL_CONSTANT, color[2] + 4*BEVEL_CONSTANT
      }
       
      block[:right_bevel_edge] = polygon(block_size, 0, block_size - bevel_pixel_size, bevel_pixel_size, block_size - bevel_pixel_size, block_size - bevel_pixel_size, block_size, block_size) {
        fill color[0] - BEVEL_CONSTANT, color[1] - BEVEL_CONSTANT, color[2] - BEVEL_CONSTANT
      }
       
      block[:bottom_bevel_edge] = polygon(block_size, block_size, 0, block_size, bevel_pixel_size, block_size - bevel_pixel_size, block_size - bevel_pixel_size, block_size - bevel_pixel_size) {
        fill color[0] - BEVEL_CONSTANT, color[1] - BEVEL_CONSTANT, color[2] - BEVEL_CONSTANT
      }
      
      block[:left_bevel_edge] = polygon(0, 0, 0, block_size, bevel_pixel_size, block_size - bevel_pixel_size, bevel_pixel_size, bevel_pixel_size) {
        fill color[0] - BEVEL_CONSTANT, color[1] - BEVEL_CONSTANT, color[2] - BEVEL_CONSTANT
      }
      
      block[:border_square] = square(0, 0, block_size) {
        stroke *COLOR_GRAY
      }
      
      extra_content&.call
    }
    block
  end
  
  def start_moving_tetrominos_down
    unless @tetrominos_start_moving_down
      @tetrominos_start_moving_down = true
      GLib::Timeout.add(@game.delay*1000) do
        @game.down! if !@game.game_over? && !@game.paused?
        true
      end
    end
  end
  
  def show_game_over_dialog
    message_dialog(@main_window) { |md|
      title 'Game Over!'
      text "Score: #{@game.high_scores.first.score}\nLines: #{@game.high_scores.first.lines}\nLevel: #{@game.high_scores.first.level}"
      
      on(:response) do
        md.destroy
      end
    }.show
    
    @game.restart!
    false
  end
  
  def show_high_score_dialog
    game_paused = !!@game.paused
    @game.paused = true
    
    if @game.high_scores.empty?
      high_scores_string = "No games have been scored yet."
    else
      high_scores_string = @game.high_scores.map do |high_score|
        "#{high_score.name} | Score: #{high_score.score} | Lines: #{high_score.lines} | Level: #{high_score.level}"
      end.join("\n")
    end
    
    message_dialog(@main_window) { |md|
      title 'High Scores'
      text high_scores_string
      
      on(:response) do
        md.destroy
      end
    }.show
    
    @game.paused = game_paused
  end
  
  def show_about_dialog
    message_dialog(@main_window) { |md|
      title 'About'
      text "Glimmer Tetris\n\nGlimmer DSL for GTK\n\nElaborate Sample\n\nCopyright (c) 2021-2022 Andy Maleh"
      
      on(:response) do
        md.destroy
      end
    }.show
  end
end

Tetris.new.launch
```

Happy [Glimmering](https://github.com/AndyObtiva/glimmer-dsl-gtk)!