Feat/font autoscale (#288)

* PoC font autosize feature

* Take enumerables or 'auto' keyword for autoscaling

* Allo enumerables of font_size per card, where the largest font size that does not ellipsize is chosen

* Use ellipsize: :autoscale keyword to determine font autosizing

* Use binary search to find the correct font size

* Consider new ellipsize option in testcase

* Document ellipsize: :autoscale option

* Add ellipsize: :autoscale sample to text sample

* Fix double multiplication with Pango::SCALE

* Scale embedded images with text when autoscaling

* Remove stray semicolon

* Return dummy value for FontDescription.size in mock_cairo

* Update regression test data for autoscale feature.

* Add ellipsize: :autoscale example to existing font_autoscale sample

* Add missing :autoscale to list of options in documentation

samples/autoscale_font/_autoscale_font.rb

@@ -16,14 +16,20 @@ def autoscale(str_array)
   end
 end
 
-Squib::Deck.new(width: 300, height: 100, cards: 3) do
+Squib::Deck.new(width: 300, height: 200, cards: 3) do
   background color: :white
   rect
   title = ['Short & Big',
            'Medium Length & Size',
            'Super duper long string here, therefore a smaller font.']
+  
+  # Scale text based on the string length
   text str: title, font: 'Arial', font_size: autoscale(title),
        x: 10, y:10, align: :center, width: 280, ellipsize: false, hint: :red
+  
+  # Automatically scale the text down from the specified font_size to the largest size that fits
+  text str: title, font: 'Arial', font_size: 10,
+       x: 10, y:100, align: :center, width: 280, height: 50, ellipsize: :autoscale, hint: :red
 
   save_sheet columns: 3
 end

samples/text/_text.rb

@@ -1,7 +1,7 @@
 require 'squib'
 require 'squib/sample_helpers'
 
-Squib::Deck.new(width: 1000, height: 1250) do
+Squib::Deck.new(width: 1000, height: 1450) do
   draw_graph_paper width, height
 
   sample 'Font strings are quite expressive. Specify family, modifiers, then size. Font names with spaces in them should end with a comma to help with parsing.' do |x, y|
@@ -21,6 +21,11 @@ Squib::Deck.new(width: 1000, height: 1250) do
          hint: :red, width: 350, font: 'Serif bold 7'
   end
 
+  sample 'If you specify ellipsize: :autosize, the font size will autoscale.' do |x, y|
+    text str: 'This text doeas not fit with font size 7. It is autoscaled to the largest size that fits instead.', x: x - 50, y: y,
+         hint: :red, width: 350, height: 100, ellipsize: :autoscale, font: 'Serif bold 7'
+  end
+
   sample 'If you specify the width only, and turn off ellipsize, the height will auto-stretch.' do |x, y|
     text str: 'This has fixed width, but not fixed height.', x: x, y: y,
          hint: :red, width: 300, ellipsize: false, font: 'Serif bold 8'