make shorthands more intuitive

docs/shorthands.rst

@@ -5,17 +5,20 @@ For the arguments ``x``, ``y``, ``width``, and ``height``, a few convenient shor
 
 * ``middle`` for ``x`` and ``width`` refer to the deck's width / 2
 * ``middle`` for ``y`` and ``height`` refer to the deck's height / 2
+* The word ``center`` behaves the same way
 * ``deck`` refers to the deck's width for ``x`` and ``width``
 * ``deck`` refers to the deck's height for ``y`` and ``height``
-* You can offset from the middle by using +, -, and /, e.g. ``middle + 1in``
-* You can offset from the width or height using, e.g. ``width - 1in`` or ``height - 2mm``
-* Works with the ``cell`` unit as well, e.g. `middle + 1 cell`. See :doc:`units`.
+* You can offset from the middle by using + or - operators, e.g. ``middle + 1in``
+* You can offset from the deck width or height using the + or - operators, e.g. ``deck - 1in`` or ``deck - 2mm``
+* You can offset from the deck width or height using, e.g. ``deck / 3``
+* Works with all unit conversion too, e.g. `middle + 1 cell`. See :doc:`units`.
 
 These are all passed as strings. So you will need to quote them in Ruby, or just plain in your layout YAML.
 
 Note that the following are NOT supported:
 
 * The `+=` operator when using `extends` in a layout file
+* Complicated formulas. We're not evaluating this as code, we're looking for these specific patterns and applying them. Anything more complicated you'll have to handle with Ruby code.
 
 Samples
 -------

lib/squib/args/xywh_shorthands.rb

@@ -3,49 +3,44 @@ require_relative 'unit_conversion'
 module Squib
   module Args
     module XYWHShorthands
-      WIDTH_MINUS_REGEX = /^width\s*\-\s*/
-      HEIGHT_MINUS_REGEX = /^height\s*\-\s*/
-      WIDTH_DIV_REGEX = /^width\s*\/\s*/
-      HEIGHT_DIV_REGEX = /^height\s*\/\s*/
-      MIDDLE_PLUS_REGEX = /^middle\s*\+\s*/
-      MIDDLE_MINUS_REGEX = /^middle\s*\-\s*/
 
+      MIDDLE_ONLY = /^(middle|center)\s*$/
+      DECK_ONLY = /^deck\s*$/
+      MIDDLE_MINUS_REGEX = /^(middle|center)\s*\-\s*/
+      MIDDLE_PLUS_REGEX = /^(middle|center)\s*\+\s*/
+      DECK_MINUS_REGEX = /^deck\s*\-\s*/
+      DECK_PLUS_REGEX = /^deck\s*\+\s*/
+      DECK_DIV_REGEX = /^deck\s*\/\s*/
 
       # dimension is usually either deck_width or deck_height
       def apply_shorthands(arg, deck, axis: :x)
         dimension = (axis == :x) ? deck.width : deck.height
         arg_s = arg.to_s
         case arg_s
-        when 'middle'
+        when MIDDLE_ONLY
           dimension / 2.0
-        when 'center'
-          dimension / 2.0
-        when 'deck'
+        when DECK_ONLY
           dimension
-        when WIDTH_MINUS_REGEX # e.g. width - 1.5in
-          n = arg_s.sub WIDTH_MINUS_REGEX, ''
-          n = UnitConversion.parse(n, deck.dpi, deck.cell_px)
-          deck.width - n
-        when HEIGHT_MINUS_REGEX # e.g. height - 1.5in
-          n = arg_s.sub HEIGHT_MINUS_REGEX, ''
-          n = UnitConversion.parse(n, deck.dpi, deck.cell_px)
-          deck.height - n
-        when WIDTH_DIV_REGEX # e.g. width / 3
-          n = arg_s.sub WIDTH_DIV_REGEX, ''
-          n = UnitConversion.parse(n, deck.dpi, deck.cell_px).to_f
-          deck.width / n
-        when HEIGHT_DIV_REGEX # e.g. height / 3
-          n = arg_s.sub HEIGHT_DIV_REGEX, ''
+        when MIDDLE_MINUS_REGEX # e.g. width: middle - 3
+          n = arg_s.sub MIDDLE_MINUS_REGEX, ''
           n = UnitConversion.parse(n, deck.dpi, deck.cell_px).to_f
-          deck.height / n
+          dimension / 2.0 - n
         when MIDDLE_PLUS_REGEX # e.g. middle + 1.5in
           n = arg_s.sub MIDDLE_PLUS_REGEX, ''
-          n = UnitConversion.parse(n, deck.dpi, deck.cell_px)
+          n = UnitConversion.parse(n, deck.dpi, deck.cell_px).to_f
           dimension / 2.0 + n
-        when MIDDLE_MINUS_REGEX # e.g. middle - 1.5in
-          n = arg_s.sub MIDDLE_MINUS_REGEX, ''
-          n = UnitConversion.parse(n, deck.dpi, deck.cell_px)
-          dimension / 2.0 - n
+        when DECK_MINUS_REGEX # e.g. width: deck - 1.5in
+          n = arg_s.sub DECK_MINUS_REGEX, ''
+          n = UnitConversion.parse(n, deck.dpi, deck.cell_px).to_f
+          dimension - n
+        when DECK_PLUS_REGEX # e.g. deck + 1.5in (which is weird but ok)
+          n = arg_s.sub DECK_PLUS_REGEX, ''
+          n = UnitConversion.parse(n, deck.dpi, deck.cell_px).to_f
+          dimension + n
+        when DECK_DIV_REGEX # e.g. width: deck/3
+          n = arg_s.sub DECK_DIV_REGEX, ''
+          n = UnitConversion.parse(n, deck.dpi, deck.cell_px).to_f
+          dimension / n
         else
           arg
         end

lib/squib/version.rb

@@ -6,5 +6,6 @@ module Squib
   # Most of the time this is in the alpha of the next release.
   # e.g. v0.0.5a is on its way to becoming v0.0.5
   #
-  VERSION = '0.16.0-preview1'
+  VERSION = '0.16.0-preview2a'
 end
+

samples/units/_shorthands.rb

@@ -20,14 +20,13 @@ Squib::Deck.new(width: '0.5in', height: '0.25in') do
 
   # We can also do width-, height-, width/, height/
   rect x: 20, y: 5, stroke_color: :green,
-  width: 'width - 0.1in', height: 10
+  width: 'deck - 0.1in', height: 10
 
-  rect x: 10, y: 50, width: 10, height: 'height / 3',
+  rect x: 10, y: 50, width: 10, height: 'deck / 3',
        stroke_color: :purple
 
   # And middle+/-
-
-  rect x: 'middle + 0.1in', y: 'middle - 0.1in',
+  rect x: 'middle + 0.1in', y: 'center - 0.1in',
        width: '0.1in', height: '0.1in', fill_color: :blue
 
   # Layouts apply this too.

spec/args/box_spec.rb

@@ -152,14 +152,14 @@ describe Squib::Args::Box do
       expect(box).to have_attributes(width: [61.5], height: [228.0])
     end
 
-    it 'listens to height/2' do
-      args = { width: 'height / 2', height: :deck }
+    it 'listens to deck/2' do
+      args = { width: 'deck / 2', height: :deck }
       box = Squib::Args.extract_box args, deck
-      expect(box).to have_attributes(width: [228.0], height: [456])
+      expect(box).to have_attributes(width: [61.5], height: [456])
     end
 
-    it 'listens to width - 0.5in' do
-      args = { x: 'width - 0.5in'}
+    it 'listens to deck - 0.5in' do
+      args = { x: 'deck - 0.5in'}
       box = Squib::Args.extract_box args, deck
       expect(box).to have_attributes(x: [ 123 - 150 ])
     end
@@ -172,8 +172,8 @@ describe Squib::Args::Box do
       args = {
         x: 'middle + 1c',
         y: 'middle',
-        width: 'width - 2c',
-        height: 'height / 3'
+        width: 'deck - 2c',
+        height: 'deck / 3'
       }
       box = Squib::Args.extract_box args, deck
       expect(box).to have_attributes(

spec/args/xywh_shorthands_spec.rb

@@ -9,8 +9,8 @@ describe Squib::Args::XYWHShorthands do
     args = {
       x: 'middle',
       y: 'middle + 1in',
-      width: 'width / 2',
-      height: 'height - 1in',
+      width: 'deck / 2',
+      height: 'deck - 1in',
     }
     box = Squib::Args.extract_box args, deck
     expect(box).to have_attributes({