lib/gamebox/core/viewport.rb in gamebox-0.4.1 vs lib/gamebox/core/viewport.rb in gamebox-0.5.0

@@ -8,10 +8,11 @@
   
   attr_accessor :x_offset, :y_offset, :follow_target, :width,
     :height, :x_offset_range, :y_offset_range, :boundary, :rotation
 
   attr_reader :speed
+  alias :follow_target? :follow_target
 
   def debug
     "xoff:#{@x_offset} yoff:#{@y_offset}"
   end
 
@@ -57,68 +58,33 @@
     return @y_offset if layer == 1
     @y_offset / layer
   end
 
   def update(time)
-    scrolled = false
-    if @follow_target
-      x = @follow_target.x
-      y = @follow_target.y
-      if @x_offset_range
-        x = @x_offset_range.min if @x_offset_range.min > x 
-        x = @x_offset_range.max if @x_offset_range.max < x 
-      end
-      if @y_offset_range
-        y = @y_offset_range.min if @y_offset_range.min > y 
-        y = @y_offset_range.max if @y_offset_range.max < y 
-      end
-      x_diff = @width/2 + @follow_offset_x - x - @x_offset
-      if x_diff.abs > @buffer_x
-        # move screen 
-        if x_diff > 0
-          @x_offset += (x_diff - @buffer_x) * @speed
-        else
-          @x_offset += (x_diff + @buffer_x) * @speed
-        end
-
-        scrolled = true
-      end
-
-      y_diff = @height/2 + @follow_offset_y - y - @y_offset
-      if y_diff.abs > @buffer_y
-        # move screen
-        if y_diff > 0
-          @y_offset += (y_diff - @buffer_y) * @speed
-        else
-          @y_offset += (y_diff + @buffer_y) * @speed
-        end
-        scrolled = true
-      end
-
-      # constrain_x_offset
-      if @boundary
-        if @x_offset > 0 - @boundary[0] # Left-wall bump
-          @x_offset = @boundary[0]
-        elsif @x_offset < @width - @boundary[2] # right-wall bump
-          @x_offset = @width - @boundary[2]
-        end
-      end
-
-      # constrain_y_offset
-      if @boundary
-        if @y_offset > 0 - @boundary[1]
-          @y_offset = @boundary[1]
-        elsif @y_offset < @height - @boundary[3]
-          @y_offset = @height - @boundary[3]
-        end
-      end
-
+    if follow_target?
+      scrolled = move_towards_target
+      clamp_to_boundary
       fire :scrolled if scrolled
     end
   end
 
+  # Viewport will stay centered on the targets x,y
+  #
+  # args hash:
+  # :x_offset - keep the viewport centered on x + x_offset
+  # :y_offset - keep the viewport centered on y + y_offset
+  # :x_chain_length - allow this much x slack when following
+  # :y_chain_length - allow this much y slack when following
+  def stay_centered_on(target, args={})
+    offset_x = args[:x_offset] || 0
+    offset_y = args[:y_offset] || 0
+    x_chain_length = args[:x_chain_length] || 0
+    y_chain_length = args[:y_chain_length] || 0
+    follow target, [-offset_x, -offset_y], [x_chain_length, y_chain_length]
+  end
 
+  # deprecated; use #stay_centered_on
   def follow(target, off=[0,0], buff=[0,0])
     @follow_target = target
     @follow_offset_x = off[0]
     @follow_offset_y = off[1]
     @buffer_x = buff[0]
@@ -131,9 +97,67 @@
   end
 
   def bounds
     left = -@x_offset
     top = -@y_offset
-    Rect.new left, top, left + @width, top + @height
+    # Rect.new left, top, left + @width, top + @height
+    Rect.new left, top, @width, @height
+  end
+
+  private
+  def move_towards_target
+    scrolled = false
+
+    x = @follow_target.x
+    y = @follow_target.y
+
+    if @x_offset_range
+      x = @x_offset_range.min if @x_offset_range.min > x 
+      x = @x_offset_range.max if @x_offset_range.max < x 
+    end
+    if @y_offset_range
+      y = @y_offset_range.min if @y_offset_range.min > y 
+      y = @y_offset_range.max if @y_offset_range.max < y 
+    end
+    x_diff = @width/2 + @follow_offset_x - x - @x_offset
+    if x_diff.abs > @buffer_x
+      # move screen 
+      if x_diff > 0
+        @x_offset += (x_diff - @buffer_x) * @speed
+      else
+        @x_offset += (x_diff + @buffer_x) * @speed
+      end
+
+      scrolled = true
+    end
+
+    y_diff = @height/2 + @follow_offset_y - y - @y_offset
+    if y_diff.abs > @buffer_y
+      # move screen
+      if y_diff > 0
+        @y_offset += (y_diff - @buffer_y) * @speed
+      else
+        @y_offset += (y_diff + @buffer_y) * @speed
+      end
+      scrolled = true
+    end
+
+    scrolled
+  end
+
+  def clamp_to_boundary
+    if @boundary
+      if @x_offset > 0 - @boundary[0] # Left-wall bump
+        @x_offset = @boundary[0]
+      elsif @x_offset < @width - @boundary[2] # right-wall bump
+        @x_offset = @width - @boundary[2]
+      end
+
+      if @y_offset > 0 - @boundary[1]
+        @y_offset = @boundary[1]
+      elsif @y_offset < @height - @boundary[3]
+        @y_offset = @height - @boundary[3]
+      end
+    end
   end
 
 end