Added scroll bounds

Resolves #9
Resolves #6
Resolves #3

data/core/view.lua

@@ -45,13 +45,13 @@ end
 
 
 function View:get_scrollable_size()
-  return 0
+  return math.huge
 end
 
 
 function View:get_scrollbar_rect()
   local sz = self:get_scrollable_size()
-  if sz <= self.size.y then
+  if sz <= self.size.y or sz == math.huge then
     return 0, 0, 0, 0
   end
   local h = math.max(20, self.size.y * self.size.y / sz)
@@ -117,7 +117,14 @@ function View:get_content_offset()
 end
 
 
+function View:clamp_scroll_position()
+  local max = self:get_scrollable_size() - self.size.y
+  self.scroll.to.y = common.clamp(self.scroll.to.y, 0, max)
+end
+
+
 function View:update()
+  self:clamp_scroll_position()
   self:move_towards(self.scroll, "x", self.scroll.to.x, 0.3)
   self:move_towards(self.scroll, "y", self.scroll.to.y, 0.3)
 end