Code Snippets

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Get screen dimensions 

my_screen_width=Fl:w()
my_screen_height=Fl:h()
print("your screen: "..my_screen_width.."x"..my_screen_height)


Change the default box type 

Fl:set_boxtype(fltk.FL_UP_BOX,fltk.FL_THIN_UP_BOX)
Fl:set_boxtype(fltk.FL_DOWN_BOX,fltk.FL_THIN_DOWN_BOX)


Print the class name (Fl_*) of a given widget 

print(my_widget.bind_lua_typeinfo.name)


perform tasks depending on whether or not X is running (Linux and OSX) 

if os.getenv("DISPLAY") then
  graphical commands
else   
  console commands
end


Grab command output 

my_cmd=io.popen("my_command") -- runs command
my_result=my_cmd:read("*a") -- read output of command to a variable
print(my_result)
my_cmd:close()


Display command output in Fl_Browser() 

for my_line in io.popen("my_command"):lines() do my_browser:add(my_line) end

or... 

my_cmd=io.popen("my_command")
for my_line in my_cmd:lines() do my_browser:add(my_line) end
my_cmd:close()


Write to a file 

my_filename=io.open("my_file.txt","w")
if my_filename then -- always check for write permission
  my_filename:write("some text")
  my_filename:close()
end


Perform an action on an arbitrary series of objects Similar to "for i in one two three; do echo $i; done" in bash. 

for i,v in ipairs({"string", os, os.time}) do print(type(v)) end


Set up an exit confirmation Assumes the main window (named "my_window" here) does not have another function 

function my_exit()
  my_confirm=fltk.fl_choice("sure you want to quit?","no","yes",NULL)
  if my_confirm == 1 then os.exit(0) end
end
my_window:callback(my_exit)

Go through a directory and it's subdirectories (like in a recursive manner) and spit out a table of files (with files in a subdirectory in a subtable) and a list of directories. 

function recurse(dir,maxdepth,depth) -- {{{
    -- Function recurses through a dir, just to maxdepth
    -- depth should only be used for recursing.
    -- it returns the found files as a table, with a table for each subdir.
    local attr = lfs.attributes
    local output = {}
    local outputdirs = {}
    local cd = lfs.chdir
    if depth == nil then depth = 0 end
    
    -- TODO foolproofing
    cd(dir)
    depth = depth+1
    for entry in lfs.dir('./') do
        if not( entry == "." or entry == "..") then
            local attri=attr(entry)
            if attri == nil then
                print ('Skipping file '..pwd()..entry..', not a normal file')
            elseif attri["mode"]=="file" then
                print("Added file "..pwd()..entry)
                table.insert(output,pwd()..entry)
            elseif attri["mode"]=="directory" then
                if not (depth > maxdepth) then
                    print("Added and gone into "..pwd()..entry)
                    table.insert(outputdirs,pwd()..entry)
                    table.insert(output,recurse(entry,maxdepth,depth+1))
                end
            end
        end
    end
    cd('..')
    return output,outputdirs
end --}}}

Mapping function: applies a function to each element in the table, does not work (yet) recursive tables (tables that contain themselves). The support for having the function mapped to tables is experimental ;). 

function map(func,tab,work_on_tab) --{{{
    -- takes a function , a table and the boolean work_on_tab as input.
    -- executes func on each element, recursing into nested tables 
    -- and returns the output in the same structure as the input data.
    -- FIXME stackoverflows when executed on recursive tables (like after table.insert(tab,tab))
    local output = {}
    for k,v in pairs(tab) do
        if (type(v) == 'table' and not (work_on_tab)) then
            output[k] = map(func,v)
        else
            output[k] = func(v)
        end
    end
    return output
end --}}}

Using Ncurses in Linux with alien. 

c,i,v,p,s=alien.load("/usr/lib/libncurses.so"),"int","void","pointer","string"
--variables
TRUE = 1
FALSE = 0
ERR = -1
COLOR_BLACK=0
COLOR_RED=1
COLOR_GREEN=2
COLOR_YELLOW=3
COLOR_BLUE=4
COLOR_MAGENTA=5
COLOR_CYAN=6
COLOR_WHITE=7
NCURSES_ATTR_SHIFT=8
function NCURSES_BITS(mask,shift) return bit.lshift(mask,(shift + NCURSES_ATTR_SHIFT)) end


c.initscr:types(i);     -- initialize the curses library
--c.keypad:types(i,p,b);  -- enable keyboard mapping
--c.nonl:types(i);        -- tell curses not to do NL->CR/NL on output
--c.cbreak:types(i);        -- take input chars one at a time, no wait for \n
--c.echo:types(i);      -- echo input - in color
c.start_color:types(i);
c.has_colors:types(i);
c.init_pair:types(i,i,i,i)  -- number, color1 , color2 --> zoek kleuren op!o
c.endwin:types(i)
c.getch:types(i)
c.attrset:types(i,i)
--c.COLOR_PAIRS:types(i,i)

c.initscr()
--c.keypad("stdscr",1)
--c.nonl()
--c.cbreak()
--c.echo()
    c.start_color()
    c.init_pair(1, COLOR_RED,     COLOR_BLACK);
    c.init_pair(2, COLOR_GREEN,   COLOR_BLACK);
    c.init_pair(3, COLOR_YELLOW,  COLOR_BLACK);
    c.init_pair(4, COLOR_BLUE,    COLOR_BLACK);
    c.init_pair(5, COLOR_CYAN,    COLOR_BLACK);
    c.init_pair(6, COLOR_MAGENTA, COLOR_BLACK);
    c.init_pair(7, COLOR_WHITE,   COLOR_BLACK);

    num = 0
    while char ~= string.byte("q") do
        char = c.getch()
        -- #define
        -- #define COLOR_PAIR(n)   NCURSES_BITS(n, 0)
        c.attrset(NCURSES_BITS(num % 8,0))
        num = num+1
    end
c.endwin()
os.exit()
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