Instant speed changes

Avoid waiting for next game hour to adjust to speed changes.

Resume previous speed on load if game was saved with Speed Up key pressed.

Fixes CorsixTH#2758

CorsixTH/Lua/world.lua

@@ -732,8 +732,8 @@ end
 
 --! Return true if the given speed the same as the current speed.
 function World:isCurrentSpeed(speed)
-  local numerator, denominator = unpack(tick_rates[speed])
-  return self.hours_per_tick == numerator and self.tick_rate == denominator
+  local hoursPerTick, tickRate = unpack(tick_rates[speed])
+  return self.hours_per_tick == hoursPerTick and self.tick_rate == tickRate
 end
 
 --! Return the name of the current speed, relating to a key in tick_rates.
@@ -760,20 +760,25 @@ function World:setSpeed(speed)
     self.user_actions_allowed = true
   end
 
-  local currentSpeed = self:getCurrentSpeed()
-  if currentSpeed ~= "Pause" and currentSpeed ~= "Speed Up" then
-    self.prev_speed = self:getCurrentSpeed()
+  local oldSpeed = self:getCurrentSpeed()
+  if oldSpeed ~= "Pause" and oldSpeed ~= "Speed Up" then
+    self.prev_speed = oldSpeed
   end
 
-  local was_paused = currentSpeed == "Pause"
-  local numerator, denominator = unpack(tick_rates[speed])
-  self.hours_per_tick = numerator
-  self.tick_rate = denominator
+  local was_paused = oldSpeed == "Pause"
+  local oldTickRate = self.tick_rate or 1
+  local newHoursPerTick, newTickRate = unpack(tick_rates[speed])
 
   if was_paused then
     TheApp.audio:onEndPause()
+    self.tick_timer = newTickRate
+  else
+    self.tick_timer = math.ceil((self.tick_timer or 0) / oldTickRate * newTickRate)
   end
 
+  self.hours_per_tick = newHoursPerTick
+  self.tick_rate = newTickRate
+
   -- Set the blue filter according to whether the user can build or not.
   TheApp.video:setBlueFilterActive(not self.user_actions_allowed and not self.ui:checkForMustPauseWindows())
   return false
@@ -1250,9 +1255,7 @@ function World:winGame(player_no)
       end
     end
     self.hospitals[player_no].game_won = true
-    if self:isCurrentSpeed("Speed Up") then
-      self:previousSpeed()
-    end
+    self:previousSpeed()
     self.ui.bottom_panel:queueMessage("information", message, nil, 0, 2, callback)
     self.ui.bottom_panel:openLastMessage()
   end
@@ -2526,6 +2529,9 @@ function World:afterLoad(old, new)
     self:localiseInitial(staff.profile)
   end
 
+  -- Fix if game was saved with Speed Up
+  self:previousSpeed()
+
   self.earthquake:afterLoad(old, new)
   self.savegame_version = new
   self.release_version = TheApp:getVersion(new)