Fix resize behavior of treeview and toolbar

Now toolbarview always compute up-to-date sizes and spacing to adapt to
changes in icon big font.

For treeview and toolbarview revert the goto_size approach to use the
original approach of rxi/lite. In order to make it work when user resizes
dragging the divider we use the view optional method set_target_size().
This latter changes the view's target size instead of changing its size
right away. The size is only changed by the lite's layout and animation
system.

Remove the config.treeview_size variable that was no longer working because
plugins are loaded before the user's config.

data/plugins/toolbarview.lua

@@ -4,10 +4,6 @@ local command = require "core.command"
 local style = require "core.style"
 local View = require "core.view"
 
-local icon_h, icon_w = style.icon_big_font:get_height(), style.icon_big_font:get_width("D")
-local toolbar_spacing = icon_w / 2
-local toolbar_height = icon_h + style.padding.y * 2
-
 local ToolbarView = View:extend()
 
 local toolbar_commands = {
@@ -20,36 +16,39 @@ local toolbar_commands = {
 }
 
 
+local function toolbar_height()
+  return style.icon_big_font:get_height() + style.padding.y * 2
+end
+
+
 function ToolbarView:new()
   ToolbarView.super.new(self)
   self.visible = true
-  self.init_size = toolbar_height
+  self.init_size = true
   self.tooltip = false
 end
 
 
 function ToolbarView:update()
+  local dest_size = self.visible and toolbar_height() or 0
   if self.init_size then
-    self.size.y = self.init_size
+    self.size.y = dest_size
     self.init_size = nil
-  elseif self.goto_size then
-    if self.goto_size ~= self.size.y then
-      self:move_towards(self.size, "y", self.goto_size)
-    else
-      self.goto_size = nil
-    end
+  else
+    self:move_towards(self.size, "y", dest_size)
   end
   ToolbarView.super.update(self)
 end
 
 
 function ToolbarView:toggle_visible()
-  self.goto_size = self.visible and 0 or toolbar_height
   self.visible = not self.visible
 end
 
 
 function ToolbarView:each_item()
+  local icon_h, icon_w = style.icon_big_font:get_height(), style.icon_big_font:get_width("D")
+  local toolbar_spacing = icon_w / 2
   local ox, oy = self:get_content_offset()
   local index = 0
   local iter = function()
@@ -68,9 +67,9 @@ end
 function ToolbarView:draw()
   self:draw_background(style.background2)
 
-  for item, x, y in self:each_item() do
+  for item, x, y, w, h in self:each_item() do
     local color = item == self.hovered_item and style.text or style.dim
-    common.draw_text(style.icon_big_font, color, item.symbol, nil, x, y, 0, icon_h)
+    common.draw_text(style.icon_big_font, color, item.symbol, nil, x, y, 0, h)
   end
 end