add splitter widget

* add horizontal/vertical cursor
* possibildiade to resize game map with the new splitter widget
* fix reload warnings in textmessage

modules/core_lib/widgets/uisplitter.lua

@@ -0,0 +1,70 @@
+UISplitter = extends(UIWidget)
+
+function UISplitter.create()
+  local splitter = UISplitter.internalCreate()
+  splitter:setFocusable(false)
+  splitter.canGrow = true
+  splitter.canShrink = true
+  return splitter
+end
+
+function UISplitter:onHoverChange(hovered)
+  if hovered then
+    if self:getWidth() > self:getHeight() then
+      Mouse.setVerticalCursor()
+      self.vertical = true
+    else
+      Mouse.setHorizontalCursor()
+      self.vertical = false
+    end
+  elseif not self:isPressed() then
+    Mouse.restoreCursor()
+  end
+end
+
+function UISplitter:getAttachedTo()
+  local parent = self:getParent()
+  if parent and self.attachedTo then
+    return parent:getChildById(self.attachedTo)
+  end
+end
+
+function UISplitter:onMouseMove(mousePos, mouseMoved)
+  if self:isPressed() then
+    local deltay = mousePos.y - (self:getPosition().y + self:getHeight()/2)
+    local deltax = mousePos.x - (self:getPosition().x + self:getWidth()/2)
+    local attachedToWidget = self:getAttachedTo()
+    if not attachedToWidget then return end
+    if self.vertical then
+      if deltay == 0 then return end
+      if not self.canGrow and deltay > 0 then return end
+      if not self.canShrink and deltay < 0 then return end
+      attachedToWidget:setHeight(attachedToWidget:getHeight() - deltay)
+    else
+      if deltax == 0 then return end
+      attachedToWidget:setWidth(attachedToWidget:getWidth() - deltax)
+    end
+    return true
+  end
+end
+
+function UISplitter:onMouseRelease(mousePos, mouseButton)
+  if not self:isHovered() then
+    Mouse.restoreCursor()
+  end
+  self:ungrabMouse()
+end
+
+function UISplitter:onStyleApply(styleName, styleNode)
+  if styleNode['attached-to'] then
+    self.attachedTo = styleNode['attached-to']
+  end
+end
+
+function UISplitter:setGrow(enabled)
+  self.canGrow = enabled
+end
+
+function UISplitter:setShrink(enabled)
+  self.canShrink = enabled
+end