world
    icon_size = 64
obj/thing/one
    icon = 'things.dmi'
    icon_state = "one"

obj/thing/two
    icon = 'things.dmi'
    icon_state = "two"

obj/thing/three
    icon = 'things.dmi'
    icon_state = "three"

equipment_grid

    var/list/slots[3][4]

    proc/set_slot(x, y, atom/movable/atom)
        slots[x][y] = atom

    proc/get_slot(x, y)
        return slots[x][y]

    proc/empty()
        for(var/ix = 1 to 3)
            for(var/iy = 1 to 4)
                slots[ix][iy] = null

equipment_grid_client_display
    var/equipment_grid/equipment_grid = new

    var/client/viewer = null

    var/list/screen_references = list()

    var/tmp/state = 0 //1 == shown

    proc/show(screen_x, screen_y)
        if(!viewer) CRASH("You tried to show a display without setting client first!")

        if(state) return
        state = 1

        for(var/ix = 1 to 3)
            for(var/iy = 1 to 4)
                var/atom/movable/a = equipment_grid.get_slot(ix, iy)
                if(!a) continue
                var/atom/movable/display = new
                display.icon = a.icon
                display.icon_state = a.icon_state
                display.maptext = a.maptext
                display.maptext_width = a.maptext_width
                display.maptext_height = a.maptext_height

                display.screen_loc = "[screen_x + (ix * world.icon_size)],[screen_y]" //the problem is this line

                viewer.screen += display
                screen_references += display

    proc/hide()
        if(!state) return
        state = 0

        for(var/o in screen_references)
            viewer.screen -= o
        screen_references.Cut()

mob
    var/equipment_grid_client_display/grid = new
    verb
        test_equipment_grid()

            if(grid.state) grid.hide()
            else

                grid.viewer = src.client

                grid.equipment_grid.set_slot(2, 4, new /obj/thing/one)
                grid.equipment_grid.set_slot(2, 3, new /obj/thing/two)
                grid.equipment_grid.set_slot(1, 3, new /obj/thing/two)
                grid.equipment_grid.set_slot(3, 3, new /obj/thing/two)
                grid.equipment_grid.set_slot(2, 2, new /obj/thing/three)
                grid.equipment_grid.set_slot(2, 1, new /obj/thing/three)

                grid.show(4, 4)