Show mouse hover on HotkeyLabels

Labels show the hover colour when on_click is set, HotkeyLabels should
also do the same when they are clickable.

library/lua/gui/widgets.lua

@@ -1274,9 +1274,15 @@ function Label:getTextWidth()
     return self.text_width
 end
 
+-- Overridden by subclasses that also want to add new mouse handlers, see
+-- HotkeyLabel.
+function Label:shouldHover()
+    return self.on_click or self.on_rclick
+end
+
 function Label:onRenderBody(dc)
     local text_pen = self.text_pen
-    if self:getMousePos() and (self.on_click or self.on_rclick) then
+    if self:getMousePos() and self:shouldHover() then
         text_pen = self.text_hpen
     end
     render_text(self,dc,0,0,text_pen,self.text_dpen,is_disabled(self))
@@ -1432,6 +1438,11 @@ function HotkeyLabel:setLabel(label)
     self:initializeLabel()
 end
 
+function HotkeyLabel:shouldHover()
+    -- When on_activate is set, text should also hover on mouseover
+    return HotkeyLabel.super.shouldHover(self) or self.on_activate
+end
+
 function HotkeyLabel:initializeLabel()
     self:setText{{key=self.key, key_sep=self.key_sep, text=self.label,
                   on_activate=self.on_activate}}
@@ -1475,6 +1486,12 @@ function CycleHotkeyLabel:init()
     }
 end
 
+-- CycleHotkeyLabels are always clickable and therefore should always change
+-- color when hovered.
+function CycleHotkeyLabel:shouldHover()
+    return true
+end
+
 function CycleHotkeyLabel:cycle(backwards)
     local old_option_idx = self.option_idx
     if self.option_idx == #self.options and not backwards then