draw_bg.lua

--[[
Background by londonali1010 (2009)
This script draws a background to the Conky window. It covers the whole of the Conky window, but you can specify rounded corners, if you wish.
To call this script in Conky, use (assuming you have saved this script to ~/scripts/):
    lua_load ~/scripts/draw_bg.lua
    lua_draw_hook_pre draw_bg
Changelog:
+ v1.0 -- Original release (07.10.2009)
]]
-- Change these settings to affect your background.
-- "corner_r" is the radius, in pixels, of the rounded corners. If you don't want rounded corners, use 0.
corner_r=35
-- Set the colour and transparency (alpha) of your background.
bg_colour=0x000000
bg_alpha=0.3
require 'cairo'
function rgb_to_r_g_b(colour,alpha)
    return ((colour / 0x10000) % 0x100) / 255., ((colour / 0x100) % 0x100) / 255., (colour % 0x100) / 255., alpha
end
function conky_draw_bg()
    if conky_window==nil then return end
    local w=conky_window.width
    local h=conky_window.height
    local cs=cairo_xlib_surface_create(conky_window.display, conky_window.drawable, conky_window.visual, w, h)
    cr=cairo_create(cs)

    cairo_move_to(cr,corner_r,0)
    cairo_line_to(cr,w-corner_r,0)
    cairo_curve_to(cr,w,0,w,0,w,corner_r)
    cairo_line_to(cr,w,h-corner_r)
    cairo_curve_to(cr,w,h,w,h,w-corner_r,h)
    cairo_line_to(cr,corner_r,h)
    cairo_curve_to(cr,0,h,0,h,0,h-corner_r)
    cairo_line_to(cr,0,corner_r)
    cairo_curve_to(cr,0,0,0,0,corner_r,0)
    cairo_close_path(cr)

    cairo_set_source_rgba(cr,rgb_to_r_g_b(bg_colour,bg_alpha))
    cairo_fill(cr)
end