Aseprite fast palette switch

function switch_to_palette(fname)
    if fname == "" then return end

    local newPalette = Palette{ fromFile=fname }
    if not newPalette then
        print("Could not load palette")
        return
    end
    oldPalette = app.activeSprite.palettes[1]
    if #newPalette < #oldPalette then  -- Never move to a smaller palette, to be safe
        newPalette:resize(#oldPalette)
    end
    app.activeSprite:setPalette(newPalette)
end

local dlg = Dialog("Fast Palette Swap")
dlg
  :button{text="1",onclick=function() switch_to_palette(dlg.data.pal1) end}
  :button{text="2",onclick=function() switch_to_palette(dlg.data.pal2) end}
  :button{text="3",onclick=function() switch_to_palette(dlg.data.pal3) end}
  :button{text="4",onclick=function() switch_to_palette(dlg.data.pal4) end}
  :newrow()
  :file{ id="pal1", title="Select a file for palette 1", open=true}
  :file{ id="pal2", title="Select a file for palette 2", open=true}
  :file{ id="pal3", title="Select a file for palette 3", open=true}
  :file{ id="pal4", title="Select a file for palette 4", open=true}
  :show{wait=false}