container: Add a tile container.

It will be used for the new awful.wallpaper module. The idea is to
first close the gap with `gears.wallpaper` before it gets deprecated.

lib/wibox/container/init.lua

@@ -17,6 +17,7 @@ return setmetatable({
     radialprogressbar = require("wibox.container.radialprogressbar");
     arcchart = require("wibox.container.arcchart");
     place = require("wibox.container.place");
+    tile = require("wibox.container.tile");
 }, {__call = function(_, args) return base.make_widget_declarative(args) end})
 
 -- vim: filetype=lua:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:textwidth=80

lib/wibox/container/tile.lua

@@ -0,0 +1,211 @@
+---------------------------------------------------------------------------
+-- Replicate the content of the widget over and over.
+--
+-- This contained is intended to be used for wallpapers. It currently doesn't
+-- support mouse input in the replicated tiles.
+--
+--@DOC_wibox_container_defaults_tile_EXAMPLE@
+-- @author Emmanuel Lepage-Vallee
+-- @copyright 2021 Emmanuel Lepage-Vallee
+-- @containermod wibox.container.tile
+-- @supermodule wibox.container.place
+local place = require("wibox.container.place")
+local cairo = require("lgi").cairo
+local widget = require("wibox.widget")
+local gtable = require("gears.table")
+
+local module = {mt = {}}
+
+function module:draw(context, cr, width, height)
+    if not self._private.tiled then return end
+    if not self._private.widget then return end
+
+    local x, y, w, h = self:_layout(context, width, height)
+
+    local vspace, hspace = self.vertical_spacing, self.horizontal_spacing
+    local vcrop, hcrop = self.vertical_crop, self.horizontal_crop
+
+    -- In theory we could avoid a few repaints by tracking the child widget
+    -- redraw independently from the container redraw. However it is nearly a
+    -- 1:1 march, so there's little reasons to do it.
+    if not self._private.surface then
+        self._private.surface = cairo.ImageSurface(cairo.Format.ARGB32, w+hspace, h+vspace)
+        self._private.cr = cairo.Context(self._private.surface)
+        self._private.pattern = cairo.Pattern.create_for_surface(self._private.surface)
+        self._private.pattern.extend = cairo.Extend.REPEAT
+        self._private.cr:translate(math.ceil(hspace), math.ceil(vspace))
+    else
+        self._private.cr:set_operator(cairo.Operator.CLEAR)
+        self._private.cr:set_source_rgba(0,0,0,1)
+        self._private.cr:paint()
+        self._private.cr:set_operator(cairo.Operator.SOURCE)
+    end
+
+    widget.draw_to_cairo_context(self._private.widget, self._private.cr, w, h, context)
+
+    cr:save()
+
+    -- We do our own clip.
+    cr:reset_clip()
+
+    local x0, y0 = 0, 0
+
+    -- Avoid painting incomplete tiles
+    if hcrop and x ~= 0 then
+        x0 = x - math.floor(x/(w+hspace))*(w+hspace)
+    end
+
+    if hcrop then
+        width = x + w + hspace + math.floor((width - (x + w + hspace))/(w+hspace))*(w+hspace)
+    end
+
+    if vcrop and y ~= 0 then
+        y0 = y - math.floor(y/(h+vspace))*(h+vspace)
+    end
+
+    if vcrop then
+        height = (y+h+vspace) + math.floor((height - (y+h+vspace))/(h+vspace))*(h+vspace)
+    end
+
+    -- Create a clip around the "real" widget in case there is some transparency.
+    cr:rectangle(x0, y0, width-x0, y-y0)
+    cr:rectangle(x0, y0, x-hspace-x0, height-y0)
+    cr:rectangle(x+hspace+w, y0, width - (x+w+hspace), height-y0)
+    cr:rectangle(x, y+vspace+h, w+hspace, height - (y+h+vspace))
+    cr:clip()
+
+    -- Make sure the tiles are aligned with the child widget.
+    cr:translate(x - hspace, y - vspace)
+
+
+    -- Use OVER rather than SOURCE to preserve the alpha.
+    cr.operator = cairo.Operator.OVER
+    cr.source = self._private.pattern
+    cr:paint()
+
+    cr:restore()
+end
+
+--- The horizontal spacing between the tiled.
+--
+--@DOC_wibox_container_tile_horizontal_spacing_EXAMPLE@
+--
+-- @property horizontal_spacing
+-- @tparam number horizontal_spacing
+-- @propemits true false
+-- @see vertical_spacing
+
+--- The vertical spacing between the tiled.
+--
+--@DOC_wibox_container_tile_vertical_spacing_EXAMPLE@
+--
+-- @property vertical_spacing
+-- @tparam number vertical_spacing
+-- @propemits true false
+-- @see horizontal_spacing
+
+--- Avoid painting incomplete horizontal tiles.
+--
+--@DOC_wibox_container_tile_horizontal_crop_EXAMPLE@
+--
+-- @property horizontal_crop
+-- @tparam[opt=false] boolean tiled
+-- @see vertical_crop
+
+--- Avoid painting incomplete vertical tiles.
+--
+--@DOC_wibox_container_tile_vertical_crop_EXAMPLE@
+--
+-- @property vertical_crop
+-- @tparam[opt=false] boolean tiled
+-- @see horizontal_crop
+
+--- Enable or disable the tiling.
+--
+-- When set to `false`, this container behaves exactly like
+-- `wibox.container.place`.
+--
+--@DOC_wibox_container_tile_tiled_EXAMPLE@
+--
+-- @property tiled
+-- @tparam[opt=true] boolean tiled
+
+local defaults = {
+    horizontal_spacing = 0,
+    vertical_spacing   = 0,
+    tiled              = true,
+    horizontal_crop    = false,
+    vertical_crop      = false,
+}
+
+for prop in pairs(defaults) do
+
+    module["set_"..prop] = function(self, value)
+        self._private[prop] = value
+        self:emit_signal("widget::redraw_needed", value)
+    end
+
+    module["get_"..prop] = function(self)
+        if self._private[prop] == nil then
+            return defaults[prop]
+        end
+
+        return self._private[prop]
+    end
+end
+
+local function new(_, args)
+    args = args or {}
+    local ret = place(args.widget, args.halign, args.valign)
+    gtable.crush(ret, module, true)
+    ret._private.tiled = true
+
+    local function redraw()
+        ret:emit_signal("widget::redraw_needed")
+    end
+
+    -- Resize the pattern as needed.
+    local function reset()
+        if ret._private.surface then
+            ret._private.surface:finish()
+        end
+
+        ret._private.cr = nil
+        ret._private.surface = nil
+        ret._private.pattern = nil
+    end
+
+    local w = nil
+
+    ret:connect_signal("property::widget", function()
+        reset()
+
+        if w then
+            w:disconnect_signal("widget::redraw_needed", redraw)
+            w:disconnect_signal("widget::layout_changed", reset)
+        end
+
+        w = ret._private.widget
+
+        if w then
+            w:connect_signal("widget::redraw_needed", redraw)
+            w:connect_signal("widget::layout_changed", reset)
+        end
+    end)
+
+    return ret
+end
+
+--- Create a new tile container.
+-- @tparam table args
+-- @tparam wibox.widget widget args.widget The widget to tile.
+-- @tparam string args.halign Either `left`, `right` or `center`.
+-- @tparam string args.valign Either `top`, `bottom` or `center`.
+-- @constructorfct wibox.container.tile
+function module.mt:__call(...)
+    return new(...)
+end
+
+return setmetatable(module, module.mt)
+
+-- vim: filetype=lua:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:textwidth=80