Merge branch 'develop' into 43-infinity-scroll

# Conflicts:
#	druid/base/grid.lua
#	druid/const.lua
#	druid/system/druid_instance.lua

druid/extended/infinity_list.lua

@@ -0,0 +1,117 @@
+--- Manage data for huge dataset in scroll
+--- It requires basic druid scroll and druid grid components
+local const = require("druid.const")
+local component = require("druid.component")
+
+local M = component.create("infinity_list", { const.ON_UPDATE })
+
+
+function M:init(data_list, scroll, grid, create_function)
+    self.view_size = gui.get_size(scroll.view_node)
+    self.prefab_size = grid.node_size
+    self.druid = self:get_druid()
+    self.scroll = scroll
+    self.grid = grid
+
+    self.data = data_list
+    self.top_index = 1
+
+    self.create_function = create_function
+
+    self.nodes = {}
+    self.components = {}
+
+    self.elements_view_count = vmath.vector3(
+        math.min(math.ceil(self.view_size.x / self.prefab_size.x), self.grid.in_row),
+        math.ceil(self.view_size.y / self.prefab_size.y),
+        0)
+
+    self:_refresh()
+    self.scroll.on_scroll:subscribe(function() self._check_elements(self) end)
+end
+
+
+function M:on_remove()
+    -- TODO: make this work
+    -- self.scroll.on_scroll:unsubscribe(self._check_elements)
+end
+
+
+function M:update(dt)
+    if self.scroll.animate then
+        self:_check_elements()
+    end
+end
+
+
+function M:set_data(data_list)
+    self.data = data_list
+    self:_refresh()
+end
+
+
+function M:_add_at(index)
+    if self.nodes[index] then
+        self:_remove_at(index)
+    end
+
+    local node, instance = self.create_function(self.data[index], index)
+    self.grid:add(node, index)
+    self.nodes[index] = node
+    self.components[index] = instance
+end
+
+
+function M:_remove_at(index)
+    self.grid:remove(index)
+
+    local node = self.nodes[index]
+    gui.delete_node(node)
+    self.nodes[index] = nil
+
+    if self.components[index] then
+        self.druid:remove(self.components[index])
+        self.components[index] = nil
+    end
+end
+
+
+function M:_refresh()
+    for index, _ in pairs(self.nodes) do
+        self:_remove_at(index)
+    end
+    self:_check_elements()
+    self:_recalc_scroll_size()
+end
+
+
+function M:_check_elements()
+    local pos = gui.get_position(self.scroll.content_node)
+    pos.y = -pos.y
+
+    local top_index = self.grid:get_index(pos)
+    local last_index = top_index + (self.elements_view_count.x * self.elements_view_count.y) + self.grid.in_row - 1
+
+    -- Clear outside elements
+    for index, _ in pairs(self.nodes) do
+        if index < top_index or index > last_index then
+            self:_remove_at(index)
+        end
+    end
+
+    -- Spawn current elements
+    for index = top_index, last_index do
+        if self.data[index] and not self.nodes[index] then
+            self:_add_at(index)
+        end
+    end
+end
+
+
+function M:_recalc_scroll_size()
+    local element_size = self.grid:get_size_for_elements_count(#self.data)
+    self.scroll:set_size(element_size)
+end
+
+
+return M