From 65187cd5126227778146ec33c2857a391fbab620 Mon Sep 17 00:00:00 2001
From: lstrzebinczyk <lukasz.strzebinczyk@ac-project.net>
Date: Sun, 21 May 2017 21:26:12 +0200
Subject: Implement #contains? for all renderables

---
 lib/ruby2d/image.rb      |  4 ++++
 lib/ruby2d/line.rb       | 17 +++++++++++++++++
 lib/ruby2d/quad.rb       | 18 ++++++++++++++++++
 lib/ruby2d/rectangle.rb  |  4 ++++
 lib/ruby2d/renderable.rb |  4 ++++
 lib/ruby2d/text.rb       |  4 ++++
 lib/ruby2d/triangle.rb   | 17 +++++++++++++++++
 7 files changed, 68 insertions(+)

(limited to 'lib')

diff --git a/lib/ruby2d/image.rb b/lib/ruby2d/image.rb
index 6660a4d..2691f78 100644
--- a/lib/ruby2d/image.rb
+++ b/lib/ruby2d/image.rb
@@ -26,5 +26,9 @@ module Ruby2D
     def color=(c)
       @color = Color.new(c)
     end
+
+    def contains?(x, y)
+      @x < x and @x + @width > x and @y < y and @y + @height > y
+    end
   end
 end
diff --git a/lib/ruby2d/line.rb b/lib/ruby2d/line.rb
index 9ef534e..769c37f 100644
--- a/lib/ruby2d/line.rb
+++ b/lib/ruby2d/line.rb
@@ -19,8 +19,25 @@ module Ruby2D
       update_color(@color)
     end
 
+    def length
+      points_distance(@x1, @y1, @x2, @y2)
+    end
+
+    # Line contains a point if the point is closer than the length of line from both ends
+    # and if the distance from point to line is smaller than half of the width.
+    # Check https://en.wikipedia.org/wiki/Distance_from_a_point_to_a_line for reference
+    def contains?(x, y)
+      points_distance(x1, y1, x, y) < length and
+      points_distance(x2, y2, x, y) < length and
+      (((@y2 - @y1) * x - (@x2 - @x1) * y + @x2 * @y1 - @y2 * @x1).abs / length) < 0.5 * @width
+    end
+
     private
 
+    def points_distance(x1, y1, x2, y2)
+      Math.sqrt((x1 - x2) ** 2 + (y1 - y2) ** 2)
+    end
+
     def update_color(c)
       if c.is_a? Color::Set
         if c.length == 4
diff --git a/lib/ruby2d/quad.rb b/lib/ruby2d/quad.rb
index e3906c0..4fac328 100644
--- a/lib/ruby2d/quad.rb
+++ b/lib/ruby2d/quad.rb
@@ -29,8 +29,26 @@ module Ruby2D
       update_color(@color)
     end
 
+    # The logic is the same as for a triangle
+    # See triangle.rb for reference
+    def contains?(x, y)
+      self_area = triangle_area(@x1, @y1, @x2, @y2, @x3, @y3) +
+                  triangle_area(@x1, @y1, @x3, @y3, @x4, @y4)
+
+      questioned_area = triangle_area(@x1, @y1, @x2, @y2, x, y) +
+                        triangle_area(@x2, @y2, @x3, @y3, x, y) +
+                        triangle_area(@x3, @y3, @x4, @y4, x, y) +
+                        triangle_area(@x4, @y4, @x1, @y1, x, y)
+
+      questioned_area <= self_area
+    end
+
     private
 
+    def triangle_area(x1, y1, x2, y2, x3, y3)
+      (x1*y2 + x2*y3 + x3*y1 - x3*y2 - x1*y3 - x2*y1).abs / 2
+    end
+
     def update_color(c)
       if c.is_a? Color::Set
         if c.length == 4
diff --git a/lib/ruby2d/rectangle.rb b/lib/ruby2d/rectangle.rb
index 569b8b5..db54b46 100644
--- a/lib/ruby2d/rectangle.rb
+++ b/lib/ruby2d/rectangle.rb
@@ -39,6 +39,10 @@ module Ruby2D
       update_coords(@x, @y, @width, h)
     end
 
+    def contains?(x, y)
+      @x < x and @x + @width > x and @y < y and @y + @height > y
+    end
+
     private
 
     def update_coords(x, y, w, h)
diff --git a/lib/ruby2d/renderable.rb b/lib/ruby2d/renderable.rb
index d80482a..8a581ae 100644
--- a/lib/ruby2d/renderable.rb
+++ b/lib/ruby2d/renderable.rb
@@ -27,5 +27,9 @@ module Ruby2D
     def opacity=(val)
       self.color.opacity = val
     end
+
+    def contains?(x, y)
+      raise "Not implemented yet"
+    end
   end
 end
diff --git a/lib/ruby2d/text.rb b/lib/ruby2d/text.rb
index d3c525f..c036a92 100644
--- a/lib/ruby2d/text.rb
+++ b/lib/ruby2d/text.rb
@@ -33,6 +33,10 @@ module Ruby2D
       @color = Color.new(c)
     end
 
+    def contains?(x, y)
+      @x < x and @x + @width > x and @y < y and @y + @height > y
+    end
+
     private
 
     def resolve_path(font)
diff --git a/lib/ruby2d/triangle.rb b/lib/ruby2d/triangle.rb
index eb6b07f..e3b091b 100644
--- a/lib/ruby2d/triangle.rb
+++ b/lib/ruby2d/triangle.rb
@@ -25,8 +25,25 @@ module Ruby2D
       update_color(@color)
     end
 
+    # Point is inside a triangle if
+    # the area of 3 triangles, constructed from triangle sides and that point
+    # is equal to the area of triangle.
+    def contains?(x, y)
+      self_area = triangle_area(@x1, @y1, @x2, @y2, @x3, @y3)
+      questioned_area =
+        triangle_area(@x1, @y1, @x2, @y2, x, y) +
+        triangle_area(@x2, @y2, @x3, @y3, x, y) +
+        triangle_area(@x3, @y3, @x1, @y1, x, y)
+
+      questioned_area <= self_area
+    end
+
     private
 
+    def triangle_area(x1, y1, x2, y2, x3, y3)
+      (x1*y2 + x2*y3 + x3*y1 - x3*y2 - x1*y3 - x2*y1).abs / 2
+    end
+
     def update_color(c)
       if c.is_a? Color::Set
         if c.length == 3
-- 
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