sort of lua for camera logic

camera-logic.lua

-- Code written by Qais Patankar
-- Placed under the public domain, feel free to use this in your project
--
-- Code is also not real Lua code, it's pseudocode-ish, for easy public consumption.
-- 
-- This zooms out the camera if players are far apart.
-- All comments were written at time of Gist creation (2017-11-11).

local zoomAccuracy = 0.05
local maxZoom = 0.25
local minZoom = zoomAccuracy + 0.1

-- determine if the player is "offscreen" but keep a small
-- buffer (a safezone) so that players don't appear to be
-- onscreen if they are right next to the edge of the screen.
--
function player:IsInSafeZone(self, zoom)
  -- STUB: this code in this function was not written by me
  --       so I have not shared it. general idea shared below

  -- return true if the player is onscreen
  -- return false if the player is offscreen
  --
  -- you can return false if the player is almost offscreen
end


function onUpdate(dt)
  local rightmostPlayer, leftmostPlayer
  -- rightmostPlayer: player on one end of the screen
  -- leftmostPlayer: player on the opposite end of the screen
  -- so these are the "edge-most" players
  
  for player in players do
    if not player.dead then
      if not leftmostPlayer then
        -- Set the initial players if the player variables above have not be seen set
        -- (we only need to check if one was not set, because if then the other will not have been set either)
        leftmostPlayer = player
        rightmostPlayer = player
      else
        -- "current player" = context in loop

        -- finds leftmostPlayer (or top-most)
        if player.x < leftmostPlayer.x or (player.x == leftmostPlayer.x and player.y < leftmostPlayer.y) then
          leftmostPlayer = player;
        end
        
        -- finds rightmostPlayer (or bottom-most)
        if player.x > rightmostPlayer or (rightmostPlayer.x == player.x and player.y > rightmostPlayer.y) then
          rightmostPlayer = player;
        end
      end
    end
  end

  -- (at this point we have the edge-most players)
  -- lets follow the rightmost player
  camera:follow(rightmostPlayer)

  local zoom = camera:getZoom(); -- get the target zoom (see line 51)

  if leftmostPlayer:IsInSafeZone(zoom) then
    -- The player is inside the safezone, there is the possibility of zooming in.
    while ( leftmostPlayer:IsInSafeZone(zoom + zoomAccuracy) ) and (zoom < maxZoom) do
      zoom = zoom + zoomAccuracy
    end
  else
    -- Not inside the safezone, so zoom out until inside.
    while ( not leftmostPlayer:IsInSafeZone(zoom) ) and (zoom > minZoom) do
      zoom = zoom - zoomAccuracy
    end
  end

  -- This progressively zooms the camera to the target zoom, rather than snapping
  -- 
  camera:setZoom(zoom - (camera:getZoom() - zoom) * dt * 2)
end