Create geometry_docs.rb

Added description of Geometry module and scale_rect method

1 files changed, 51 insertions, 0 deletions

diff --git a/dragon/geometry_docs.rb b/dragon/geometry_docs.rb
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+# coding: utf-8
+# Copyright 2019 DragonRuby LLC
+# MIT License
+# geometry_docs.rb has been released under MIT (*only this file*).
+
+module GeometryDocs
+  def docs_method_sort_order
+    [:docs_class, :docs_scale_rect]
+  end
+
+  def docs_class
+    <<-S
+* DOCS: ~Geometry~
+
+The Geometry module contains methods for calculations that are frequently used in game development.
+
+S
+  end
+
+  def docs_scale_rect
+    <<-S
+* DOCS: ~GTK::Geometry#scale_rect~
+
+Given an array with 4 elements representing a rect [x, y, w, h], this function returns a scaled rect. It accepts three arguments:
+
+~ratio~: the ratio by which to scale the sprite. A ratio of 2 will double the dimensions of the sprite while a ratio of 0.5 will halve its dimensions. 
+
+~anchor_x~ and ~anchor_y~ specify the point within the rect from which to resize it. Setting both to 0 will affect the width and height of the rect, leaving x and y unchanged. Setting both to 0.5 will scale all sides of the rect proportionally from the center.
+
+The ~scale_rect~ method can be applied directly to a sprite or other primitives. See CHEATSHEET: How to Scale a Sprite.
+
+#+begin_src ruby
+  def tick args
+    #       x,   y,   w,   h
+    my_rect = [100, 100, 200, 200]
+
+    # halve the dimensions of the rect: 
+    #                             ratio, anchor_x, anchor_y
+    new_rect = my_rect.scale_rect(0.5,   0.5,      0.5)
+  
+    puts new_rect # => [150.0, 150.0, 100.0, 100.0]
+  end
+#+end_src
+
+S
+  end
+
+module Geometry
+  extend Docs
+  extend GeometryDocs
+end