awesome/lib/wibox/layout/flex.lua

---------------------------------------------------------------------------
-- @author Uli Schlachter
-- @copyright 2010 Uli Schlachter
-- @release @AWESOME_VERSION@
-- @classmod wibox.layout.flex
---------------------------------------------------------------------------

local base = require("wibox.widget.base")
local table = table
local pairs = pairs
local floor = math.floor
local round = require("awful.util").round

local flex = {}

local function round(x)
    return floor(x + 0.5)
end

--- Layout a flex layout. Each widget gets an equal share of the available space.
-- @param context The context in which we are drawn.
-- @param width The available width.
-- @param height The available height.
function flex:layout(context, width, height)
    local result = {}
    local pos,spacing = 0, self._spacing
    local num = #self.widgets
    local total_spacing = (spacing*(num-1))

    local space_per_item
    if self.dir == "y" then
        space_per_item = height / num - total_spacing/num
    else
        space_per_item = width / num - total_spacing/num
    end

    if self._max_widget_size then
        space_per_item = math.min(space_per_item, self._max_widget_size)
    end

    for k, v in pairs(self.widgets) do
        local x, y, w, h
        if self.dir == "y" then
            x, y = 0, round(pos)
            w, h = width, floor(space_per_item)
        else
            x, y = round(pos), 0
            w, h = floor(space_per_item), height
        end
        table.insert(result, base.place_widget_at(v, x, y, w, h))

        pos = pos + space_per_item + spacing

        if (self.dir == "y" and pos-spacing >= height) or
            (self.dir ~= "y" and pos-spacing >= width) then
            break
        end
    end

    return result
end

--- Fit the flex layout into the given space.
-- @param context The context in which we are fit.
-- @param orig_width The available width.
-- @param orig_height The available height.
function flex:fit(context, orig_width, orig_height)
    local used_in_dir = 0
    local used_in_other = 0

    -- Figure out the maximum size we can give out to sub-widgets
    local sub_height = self.dir == "x" and orig_height or orig_height / #self.widgets
    local sub_width  = self.dir == "y" and orig_width  or orig_width / #self.widgets

    for k, v in pairs(self.widgets) do
        local w, h = base.fit_widget(self, context, v, sub_width, sub_height)

        local max = self.dir == "y" and w or h
        if max > used_in_other then
            used_in_other = max
        end

        used_in_dir = used_in_dir + (self.dir == "y" and h or w)
    end

    if self._max_widget_size then
        used_in_dir = math.min(used_in_dir,
            #self.widgets * self._max_widget_size)
    end

    local spacing = self._spacing * (#self.widgets-1)

    if self.dir == "y" then
        return used_in_other, used_in_dir + spacing
    end
    return used_in_dir + spacing, used_in_other
end

function flex:add(widget)
    base.check_widget(widget)
    table.insert(self.widgets, widget)
    self:emit_signal("widget::layout_changed")
end

--- Set the maximum size the widgets in this layout will take (that is,
-- maximum width for horizontal and maximum height for vertical).
-- @param val The maximum size of the widget.
function flex:set_max_widget_size(val)
    if self._max_widget_size ~= val then
        self._max_widget_size = val
        self:emit_signal("widget::layout_changed")
    end
end

--- Add spacing between each layout widgets
-- @param spacing Spacing between widgets.
function flex:set_spacing(spacing)
    if self._spacing ~= spacing then
        self._spacing = spacing
        self:emit_signal("widget::layout_changed")
    end
end

function flex:reset()
    self.widgets = {}
    self._max_widget_size = nil
    self:emit_signal("widget::layout_changed")
end

local function get_layout(dir)
    local ret = base.make_widget()

    for k, v in pairs(flex) do
        if type(v) == "function" then
            ret[k] = v
        end
    end

    ret.dir = dir
    ret.widgets = {}
    ret:set_spacing(0)

    return ret
end

--- Returns a new horizontal flex layout. A flex layout shares the available space
-- equally among all widgets. Widgets can be added via :add(widget).
function flex.horizontal()
    return get_layout("x")
end

--- Returns a new vertical flex layout. A flex layout shares the available space
-- equally among all widgets. Widgets can be added via :add(widget).
function flex.vertical()
    return get_layout("y")
end

return flex

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