some rework in UIWidget input

modules/core_lib/mouse.lua

@@ -17,7 +17,7 @@ function Mouse.restoreCursor()
 end
 
 function Mouse.isPressed()
-  return g_ui.getPressedWidget() == nil
+  return g_ui.getPressedWidget() ~= nil
 end
 
 function Mouse.bindAutoPress(widget, callback)

modules/core_lib/widgets/uiscrollarea.lua

@@ -33,7 +33,9 @@ function UIScrollArea:updateScrollBars()
   if scrollbar then
     if self.inverted then
       scrollbar:setMinimum(-scrollheight)
+      scrollbar:setMaximum(0)
     else
+      scrollbar:setMinimum(0)
       scrollbar:setMaximum(scrollheight)
     end
   end
@@ -50,10 +52,8 @@ end
 
 function UIScrollArea:setVerticalScrollBar(scrollbar)
   self.verticalScrollBar = scrollbar
-  scrollbar:setMaximum(0)
   self.verticalScrollBar.onValueChange = function(scrollbar, value)
     local virtualOffset = self:getVirtualOffset()
-    if self.inverted then value = -value end
     virtualOffset.y = value
     self:setVirtualOffset(virtualOffset)
   end
@@ -72,3 +72,14 @@ end
 function UIScrollArea:onLayoutUpdate()
   self:updateScrollBars()
 end
+
+function UIScrollArea:onMouseWheel(mousePos, mouseWheel)
+  if self.verticalScrollBar then
+    if mouseWheel == MouseWheelUp then
+      self.verticalScrollBar:decrement()
+    else
+      self.verticalScrollBar:increment()
+    end
+  end
+  return true
+end

modules/core_lib/widgets/uiscrollbar.lua

@@ -22,7 +22,7 @@ local function calcValues(self)
   local px = math.max(math.floor(proportion * pxrange), 10)
   local offset = 0
   if range > 1 then
-    offset = (((self.value - self.minimum) / (range - 1)) - 0.5) * (pxrange - px)
+    offset = math.ceil((((self.value - self.minimum) / (range - 1)) - 0.5) * (pxrange - px))
   end
 
   return range, pxrange, px, offset, center
@@ -153,6 +153,15 @@ function UIScrollBar:onGeometryChange()
   updateSlider(self)
 end
 
+function UIScrollBar:onMouseWheel(mousePos, mouseWheel)
+  if mouseWheel == MouseWheelUp then
+    self:decrement()
+  else
+    self:increment()
+  end
+  return true
+end
+
 function UIScrollBar:getMaximum() return self.maximum end
 function UIScrollBar:getMinimum() return self.minimum end
 function UIScrollBar:getValue() return self.value end

modules/core_lib/widgets/uisplitter.lua

@@ -46,7 +46,6 @@ function UISplitter:onMouseRelease(mousePos, mouseButton)
   if not self:isHovered() then
     Mouse.restoreCursor()
   end
-  self:ungrabMouse()
 end
 
 function UISplitter:onStyleApply(styleName, styleNode)