rockbox/apps/plugins/helloworld.lua

--[[
             __________               __   ___.
   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
                     \/            \/     \/    \/            \/
 $Id$

 Example Lua script

 Copyright (C) 2009 by Maurus Cuelenaere

 This program is free software; you can redistribute it and/or
 modify it under the terms of the GNU General Public License
 as published by the Free Software Foundation; either version 2
 of the License, or (at your option) any later version.

 This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 KIND, either express or implied.

]]--

dofile("actions.lua") -- Contains rb.actions & rb.contexts

-- Example function which splashes a message for x seconds
function sayhello(seconds)
    message = string.format("Hello world from LUA for %d seconds", seconds)
    rb.splash(seconds * rb.HZ, message)
end

-- Helper function which draws a transparent image at the center of the screen
function draw_image(img)
    local x, y = (rb.LCD_WIDTH - img:width()) / 2, (rb.LCD_HEIGHT - img:height()) / 2
    rb.lcd_bitmap_transparent_part(img, 0, 0, img:width(), x, y, img:width(), img:height())
    rb.lcd_update()
end

-- Helper function that acts like a normal printf() would do
line = 0
function printf(...)
    local msg = string.format(...)
    local res, w, h = rb.font_getstringsize(msg, rb.FONT_UI)

    if(w >= rb.LCD_WIDTH) then
        rb.lcd_puts_scroll(0, line, msg)
    else
        rb.lcd_puts(0, line, msg)
    end
    rb.lcd_update()

    line = line + 1

    if(h * line >= rb.LCD_HEIGHT) then
        line = 0
    end
end

-- Helper function which reads the contents of a file
function file_get_contents(filename)
    if(not rb.file_exists(filename)) then
        return nil
    end

    local fd = rb.open(filename, rb.O_RDONLY)
    if(fd == -1) then
        return nil
    end

    local contents = rb.read(fd, rb.filesize(fd))
    rb.close(fd)

    return contents
end

-- Helper function which saves contents to a file
function file_put_contents(filename, contents)
    local flags = rb.O_WRONLY
    if(rb.file_exists(filename)) then
        flags = bit.bor(flags, rb.O_APPEND) -- binary OR O_APPEND if the file exists
    else
        flags = bit.bor(flags, rb.O_CREAT) -- binary OR O_CREAT if the file doesn't exist
    end

    local fd = rb.open(filename, flags)
    if(fd == -1) then
        return false
    end

    local ret = rb.write(fd, contents) ~= string.len(contents)
    rb.close(fd)
    return ret
end

-- Clear the screen
rb.lcd_clear_display()

-- Draw an X on the screen
rb.lcd_drawline(0, 0, rb.LCD_WIDTH, rb.LCD_HEIGHT)
rb.lcd_drawline(rb.LCD_WIDTH, 0, 0, rb.LCD_HEIGHT)

local rectangle = rb.new_image(10, 15) -- Create a new image with width 10 and height 15
for i=1, 10 do
    for j=1, 15 do
        rectangle:set(i, j, rb.lcd_rgbpack(200, i*20, j*20)) -- Set the pixel at position i, j to the specified color
    end
end

-- rb.lcd_bitmap_part(src, src_x, src_y, stride, x, y, width, height)
rb.lcd_bitmap_part(rectangle, 0, 0, 10, rb.LCD_WIDTH/2-5, rb.LCD_HEIGHT/10-1, 10, 10) -- Draws our rectangle at the top-center of the screen

-- Load a BMP file in the variable backdrop
local backdrop = rb.read_bmp_file("/.rockbox/icons/tango_small_viewers.bmp") -- This image should always be present?
-- Draws the image using our own draw_image() function; see up
draw_image(backdrop)

-- Flush the contents from the framebuffer to the LCD
rb.lcd_update()

-- Sleep for 2 seconds
seconds = 2
rb.sleep(seconds * rb.HZ) -- rb.HZ equals to the amount of ticks that fit in 1 second

-- Call the function sayhello() with arguments seconds
sayhello(seconds)

-- Clear display
rb.lcd_clear_display()

-- Construct a pathname using the current path and a file name
local pathname = rb.current_path() .. "test.txt"

-- Put the string 'Hello from Lua!' in pathname
file_put_contents(pathname, "Hello from Lua!")

-- Splash the contents of pathname
printf(file_get_contents(pathname))

line = line + 1 -- empty line

-- Display some long lines
local tmp = ""
for i=1, 5 do
    printf("This is a %s long line!", tmp)
    tmp = tmp .. " very very very"
    rb.yield()
end

-- Loop until the user exits the program
repeat
    local action = rb.get_action(rb.contexts.CONTEXT_STD, rb.HZ)
until action == rb.actions.ACTION_STD_CANCEL

-- For a reference list of all functions available, see apps/plugins/lua/rocklib.c (and apps/plugin.h)