spk77_Set volume for selected tracks.lua

--[[
   * ReaScript Name: Set volume for selected tracks
   * Lua script for Cockos REAPER
   * Author: spk77
   * Author URI: http://forum.cockos.com/member.php?u=49553
   * Licence: GPL v3
   * Version: 1.0
]]
  
-- Set volume for selected track(s)
-- Lua script by SPK77 27-Sep-2015
-- Version: 0.2015.9.27
--
-- range:
--  min: -inf
--  max: 12

function dialog(title, def_value)
  local ret, retvals = reaper.GetUserInputs(title, 1, "Set volume for selected track(s)", def_value)
  if ret then
    return retvals
  end
  return ret
end


----------
-- Main --
----------

function main()
  local tr_count = reaper.CountSelectedTracks(0)
  if tr_count == 0 then
    return
  end

  local def_value = 0.0

  if tr_count == 1 then
    -- if only one track is selected -> show current pan value in edit box
    def_value = reaper.GetMediaTrackInfo_Value(reaper.GetSelectedTrack(0, 0), "D_VOL")
    def_value = 20*math.log(def_value,10)
    if def_value < -150 then
      def_value = "-inf"
    end
  end
  
  local new_vol = dialog("Set volume for selected track(s)", def_value)
  
  if not new_vol then
    return
  elseif new_vol == "-inf" then
    new_vol = 0.0
  elseif not tonumber(new_vol) then
    return
  else
    new_vol = tonumber(new_vol)
    if new_vol > 12 then 
      new_vol = 12
    end
    new_vol = 10^(new_vol / 20)
  end
  
  for i = 1, tr_count do
    local tr = reaper.GetSelectedTrack(0, i-1)
    if tr ~= nil then
      reaper.SetMediaTrackInfo_Value(tr, "D_VOL", new_vol)
    end
  end
  reaper.Undo_OnStateChangeEx("Set volume for selected track(s)", -1, -1)
end

reaper.defer(main)