From 58e4d59aa83f0bd39d87418d2e3a43021200d4b9 Mon Sep 17 00:00:00 2001
From: Alex Clink <alexclink@gmail.com>
Date: Fri, 25 Feb 2022 00:38:53 -0500
Subject: [PATCH] Add rect / bounding_box to cubic bezier

---
 examples/cubic_bezier.cr | 29 +++++++++++++----------------
 src/bezier/cubic.cr      | 35 ++++++++++++++++++++++++++---------
 2 files changed, 39 insertions(+), 25 deletions(-)

diff --git a/examples/cubic_bezier.cr b/examples/cubic_bezier.cr
index 9e50c1c..d688e31 100644
--- a/examples/cubic_bezier.cr
+++ b/examples/cubic_bezier.cr
@@ -31,12 +31,12 @@ module PF
     def update(dt, event)
       case event
       when SDL::Event::MouseButton
-        if event.pressed? && event.button == 1
-          @selected_point = @hover_point
-        end
-
-        if event.released? && event.button == 1
-          @selected_point = nil
+        if event.button == 1
+          if event.pressed?
+            @selected_point = @hover_point
+          else
+            @selected_point = nil
+          end
         end
       when SDL::Event::MouseMotion
         @mouse_pos = Vector[event.x, event.y] // scale
@@ -44,8 +44,7 @@ module PF
         unless point = @selected_point
           @hover_point = @curve.points.find { |p| @mouse_pos.distance(p.value) < 4 }
         else
-          point.value.x = @mouse_pos.x.to_f
-          point.value.y = @mouse_pos.y.to_f
+          point.value = @mouse_pos.to_f
         end
       end
     end
@@ -57,16 +56,14 @@ module PF
       draw_line(@curve.p3, @curve.p2, CTL_COLOR)
 
       draw_string("Length: " + @curve.length.round(2).to_s, 5, 5, FONT_COLOR)
+
+      draw_rect(*@curve.rect.map(&.to_i), CTL_COLOR)
       draw_curve(@curve, CURVE_COLOR)
 
-      ext_x, ext_y = @curve.extremeties
-
-      ext_x.each do |point|
-        draw_circle(point.to_i, 3, EXT_X_COLOR)
-      end
-
-      ext_y.each do |point|
-        draw_circle(point.to_i, 3, EXT_Y_COLOR)
+      @curve.extremeties.each do |point|
+        point.try do |p|
+          draw_circle(p.to_i, 3, EXT_Y_COLOR)
+        end
       end
 
       fill_circle(@curve.p0.to_i, 2, POINT_COLOR)
diff --git a/src/bezier/cubic.cr b/src/bezier/cubic.cr
index 34494a7..58524f0 100644
--- a/src/bezier/cubic.cr
+++ b/src/bezier/cubic.cr
@@ -24,7 +24,7 @@ module PF
 
         disc = b * b - 4 * a * c
 
-        return Tuple.new unless disc >= 0
+        return {nil, nil} unless disc >= 0
 
         t1 = (-b + Math.sqrt(disc)) / (2 * a)
         t2 = (-b - Math.sqrt(disc)) / (2 * a)
@@ -35,11 +35,11 @@ module PF
         if accept_1 && accept_2
           {t1, t2}
         elsif accept_1
-          {t1}
+          {t1, nil}
         elsif accept_2
-          {t2}
+          {nil, t2}
         else
-          {0.5}
+          {0.5, nil}
         end
       end
 
@@ -80,14 +80,31 @@ module PF
       end
 
       # Get the points at the extremeties of this curve
+      # note: Will return 4 values which are either Float64 | nil
       def extremeties
-        txs = self.class.extremeties(@p0.x, @p1.x, @p2.x, @p3.x)
-        tys = self.class.extremeties(@p0.y, @p1.y, @p2.y, @p3.y)
+        exts = self.class.extremeties(@p0.x, @p1.x, @p2.x, @p3.x) +
+               self.class.extremeties(@p0.y, @p1.y, @p2.y, @p3.y)
+        exts.map { |e| e ? at(e) : e }
+      end
 
-        txs = txs.map { |t| at(t) }
-        tys = tys.map { |t| at(t) }
+      def rect
+        tl, br = @p0, @p3
 
-        {txs, tys}
+        tl.x = @p3.x if @p3.x < tl.x
+        tl.y = @p3.y if @p3.y < tl.y
+        br.x = @p0.x if @p0.x > br.x
+        br.y = @p0.y if @p0.y > br.y
+
+        extremeties.each do |e|
+          e.try do |e|
+            tl.x = e.x if e.x < tl.x
+            tl.y = e.y if e.y < tl.y
+            br.x = e.x if e.x > br.x
+            br.y = e.y if e.y > br.y
+          end
+        end
+
+        {tl, br}
       end
     end
   end