Overview of the API

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Note: Neither the io nor os libraries are present for the TI-Nspire, which seems to be running a light version of Lua 5.1.4.

Standard Library

( This has been taken from a WoWWiki page - See the full, official documentation here )

  • G - Global Variable - A global variable (not a function) that holds the global environment (that is, _G._G = _G). Lua itself does not use this variable; changing its value does not affect any environment, nor vice-versa. (Use setfenv to change environments.) - taken from Lua docs
  • assert(value[, errormsg]) - asserts a value evaluates to true. If it is, returns value, otherwise causes a Lua error to be thrown.
  • getfenv(function or integer) - Returns the table representing the stack frame of the given function or stack level.
  • getmetatable(obj, mtable) - Returns the metatable of the given table or userdata object.
  • next(table, index) - Returns the next key, value pair of the table, allowing you to walk over the table.
  • newproxy(boolean or proxy) - Creates a userdata with a sharable metatable.
  • print - print (···) - Receives any number of arguments, and prints their values to stdout, using the tostring function to convert them to strings. print is not intended for formatted output, but only as a quick way to show a value, typically for debugging. For formatted output, use string.format. - taken from Lua Docs
  • select(index, list) - Returns the number of items in list or the value of the item in list at index.
  • setfenv(function or integer, table) - Sets the table representing the stack frame of the given function or stack level.
  • setmetatable(obj, mtable) - Sets the metatable of the given table or userdata object.
  • tostring - tostring (e) - Receives an argument of any type and converts it to a string in a reasonable format. For complete control of how numbers are converted, use string.format. If the metatable of e has a "__tostring" field, then tostring calls the corresponding value with e as argument, and uses the result of the call as its result. - taken from Lua Docs.
  • type(var) - Returns the type of variable as a string, "number", "string", "table", "function" or "userdata".
  • unpack(table[, start][, end]) - Returns the contents of its argument as separate values.
  • xpcall(func, err) - Returns a boolean indicating successful execution of func and calls err on failure, additionally returning func's or err's results.

Concepts and Basics

This part will explain you how the Lua actually works inside the OS and help you to figure out what you're doing when you write a script for the TI-Nspire. Before reading this, you have to know all about the Lua basics.

The Lua is an interpreted script language which means that it isn't as fast as ASM/C programs, but is still better than the TI-BASIC. One good thing is that this language is in a complete harmony with the OS with basic events and a powerfull graphic context. First, we have to understand how this works. Basicly the script is launched before the executive engine. This means that we can neither evaluate expressions nor use some of the standard API (like platform, var) until the engine is launched. Here is a call summary :

  • Launch string library
  • Launch math library
  • ...
  • Open and launch User's Lua script
  • ...
  • Launch var API (store, recall, ...)
  • Launch platform API (window, gc, ...)
  • ...
  • Link events (pseudo code)
while(Exit)
 	------- Some OS routines here
 
  	---- Begin of Event link
 	buffer:captureDataFromKeyPad() 	 	 	--  (N) some underground routines to catch events
 	if buffer.charInput ~= "" then 	 	 	--  (N)
 		on.charIn(buffer.charInput)
 		buffer.charInput= "" 	 	 	--  (N)
 	end
 	if buffer.arrowKey ~= "" then 	 	 	--  (N)
 		on.arrowKey(buffer.arrowKey)
 		buffer.arrowKey = "" 	 	 	--  (N)
 	end
 	----- etc ... 	
 	if platform.window.isInvalidate then 
 	 	platform.gc():purge()	 	 	--  (N) Empty buffer before starting to draw
 		on.paint(platform.gc()) 	  	-- save all the things we have to draw
 	 	platform:paint() 	 	  	--  (N) draw all those things
 		platform.window.isInvalidate = false 	-- say that the window has been drawn
 	end
 	----- End of Event link
end''
Note : the (N) commented line only indicates the meaning of the routine. Those functions don't really exist.

Now we can understand how everything is linked, just by a main loop. This helps you to understand that you don't have to code a loop yourself, because the screen wouldn't be refreshed. This also helps to see when the screen gets refreshed. In other words, we cannot use niether gc nor platform.gc() (which are the same) in order to draw somthing on the screen if we are outside of on.paint() (except if your outside function is called within on.paint() ). This also means that we don't need to pass gc as parameter, because we can rather use platform.gc() for any functions called within on.paint(). This is exactly what the BetterLuaAPI library for Nspire does.

Here is an example of a simple Lua program that displays a message only when a key is pressed (and let the screen blank otherwise). 

 function on.paint(gc)
 	if message then
 	 	gc:setFont("sansserif", "r", 10)	-- initialize font drawing
 	 	gc:drawString(message, 0, 0, "top")	-- display the message at (0, 0) coordinates
 	 	message = nil 				-- erase the message
 	 	timer.start(1) 	 	 	-- start a timer to exit on.paint() but keep in mind that we have to redraw the screen
 	end
 end
 
 function on.timer()
 	timer.stop()
 	platform.window:invalidate()
 end
 
 function on.charIn(ch)
 	message = "Hello World !"		-- store a message
 	platform.window:invalidate()		-- force display
 end

When you open the document, the script is read once. It initializes and overwrites all the functions and globals with the ones you defined. Thus, message is nil. Once the on.paint() event is called, message is nil, thus, nothing is done. When you press a key that calls on.charIn() (see below for more information), message is now "Hello World" and we tell the platform that the screen has to be refreshed. Then, on.paint() is called again, message is not nil then we display it, erase message and launch a timer. Why is that ? Because if we call platform.window:invalidate() right there, we won't refresh the screen. Why again ? Just look at the pseudo-code above. We set the window as drawn after each call of on.paint(). Thus a timer is necessary to manually recall on.paint() and exit the on.paint() function to draw the screen. When the timer is ended, on.timer() is called and we refresh the screen. The screen is then redrawn but there is nothing to draw because message is nil. Thus, the graphic context lets the screen blank.

gc (as in Graphics Context)

Note: You need to add “gc:” before each of these commands in order to use them. ex. gc:setAlpha(...). You can also call gc like this : platform.gc():setAlpha(...). Then you can use the gc library in a function where gc is not passed as an argument. but this function *has* to be called within on.paint(gc)

The maximum screen resolution available to Lua programs is 318 by 212 pixels.

  • gc:begin -
  • gc:clipRect -
  • gc:drawArc(x, y, width, height, start angle, finish angle) Note, to draw a circle, use drawArc(x - diameter/2, y - diameter/2, diameter,diameter,0,360) where x and y are the coordinates of the middle.
  • gc:drawImage(image,x,y) First argument in format “TI.Image”, x and y the coords.
  • gc:drawLine(xstart, ystart, xend, yend) Draws a line starting at the point (xstart,ystart) and ending at the point (xend, yend)
  • gc:drawPolyLine(int list1 [,int list2, .., int listN]) Draws a shape from a list contaning successively the x and y coordinates of each point the line have to draw.
  • gc:drawRect(x, y, xwidth, yheight) Draws a rectangle at (x,y) with the “x” side being “xwidth” long and the “y” side being “yheight” long
  • gc:drawString(string, x, y, PositionString) PositionString is the string’s anchor point and can be “bottom”, “middle”, or “top”.
  • gc:fillArc(x, y, width, height, start angle, finish angle) see drawArc
  • gc:fillPolygon(int list1 [,int list2, .., int listN]) see drawPolyLine
  • gc:fillRect(x, y, width, height) see drawRect
  • gc:finish -
  • gc:getStringHeight(string)
  • gc:getStringWidth(string)
  • gc:isColorDisplay Bool (Read-only) Returns 1 if color, 0 if not.
  • gc:setAlpha(int) - where the argument is an int between 0 and 255. Sets the transparency.
  • gc:setColorRGB(red, green, blue) RGB values are integers, from 0 to 255.
  • gc:setFont(font, type, size), with font : {“sansserif”, "serif", ..}, type {“b”, “r”, “i”}, size(int)
  • gc:setPen(size, smooth) size {“thin”, “medium”, "thick"}, smooth {“smooth”, "dotted", "dashed"}

platform

These are mainly read-only. These work by writing "platform." in front of them. Example : "platform.window:invalidate()"

  • platform.isDeviceModeRendering Returns true or false whether the unit is "rendering" or not
  • platform.gc - Other way to call gc. Use it like that : platform.gc():setAlpha(...) for example. This is useful when you're in a function outside on.paint(gc) (but this function has to be called within on.paint(gc).)
  • platform.isColorDisplay Returns true if the unit the code is being run on has a color display (-> Nspire CX), and false otherwise.

cursor

  • cursor.hide() - hides the cursor (mouse pointer)
  • cursor.set(string) - string can be one of those : (interrogation, crosshair, text, pointer, link select, diag resize, wait busy, hollow pointer, rotation, pencil, zoom box, arrow, zoom out, dotted arrow, clear, animate, excel plus, mod label, writing, unavailable, resize row, resize column, drag grab, hand open, hand closed, hand pointer, zoom in, dilation, translation).
  • cursor.show() - Shows the cursor on screen

document

clipboard

locale

  • locale.name() - Returns the current language the calculator is set in, formatted as ISO-639 (i.e : "fr", "en", "it" ...).

image

  • image.copy(image, width, height) - returns a new Image which has a new scale. Width is the final width, Heigth, the final height of the image.
  • image.height(image) - returns the height of the image given in parameter
  • image.new(string) - Creates a new image from the string given in parameter (see TI.Image).
  • image.width(image) - returns the width of the image given in parameter

timer

  • timer.getMilliSecCounter() - Returns the amount of milliseconds elapsed since last calculator reboot. (in TI's Computer software, returns an absolute negative time)
  • timer.start(int) - Starts a timer with 1 second.
  • timer.stop() - Stops a timer

toolpalette

var

  • var.list() - returns a list of all the variables in the entire Activity
  • var.monitor() - ?
  • var.recall(string) - returns the variable value which name is given in parameter
  • var.recallstr(string) - returns the variable value converted to string which name is given in parameter
  • var.store(string, value) - store in the variable, which name is given in parameter, the value
  • var.unmonitor() - ?

Events

  • on.paint(gc) is called when the GUI is painted. 'gc' is the Graphics Context (see above)
  • on.resize() is called when the window is rezised
  • on.timer() is called when the timer has been finished. Here an example of using timer to play an animation :
 x = 1
 animating = false
 function on.paint(gc)
 	gc:setFont("sansserif", "r", 10)
 	gc:drawString(tostring(x), 0, 0, "top")
 	if animating then
 		x = x + 1
 		timer.start(0.5)
 	end
 end
 
 function on.charIn(ch)
 	animating = not animating -- switch state
 	platform.window:invalidate() -- recall graph engine
 end
 
 function on.timer()
 	timer.stop()
 	platform.window:invalidate() -- recall graph engine
 end
  • on.arrowKey(key) is called when an arrow key from the clickPad/TouchPad is pressed (right, left, up, down)
  • on.arrowLeft() is called when the left arrow is pressed
  • on.arrowRight() is called when the right arrow is pressed
  • on.arrowUp() is called when the up arrow is pressed
  • on.arrowDown() is called when the down arrow is pressed
  • on.up() -- probably for the touchpad up motion
  • on.down() -- probably for the touchpad down motion
  • on.enterKey() is called when the enter key is pressed.
  • on.escapeKey() is called when the escape key is pressed.
  • on.tabKey() is called when the tab key is pressed.
  • on.deleteKey() is called when the delete key is pressed.
  • on.backspaceKey() is called when the clear key is pressed.
  • on.returnKey() is called when the return key is pressed.
  • on.contextMenu() is called when the combo-key Ctrl Menu is pressed.
  • on.backtabKey() is called when the combo-key Maj Tab is pressed.
  • on.clearKey() is called when the combo-key Ctrl Clear is pressed.
  • on.help() is called when the combo-key Ctrl H is pressed.
  • on.charIn(string) is called when the Nspire detects a non arrow key being pressed. ch is the character it detect. If you want to auto start an event in the file linked to key r(like a reset) put on.charIn(“r”) where you want.
  • on.blink() ? is called when the focus is lost on the page (like launching the document, changing page etc...)
  • on.deactivate() ? is called when the focus is lost on the page (like launching the document, changing page etc...)
  • on.activate() ? is called when the focus is on the page (like launching the document, changing page etc...)

D2Editor

Example of a valid function using the D2Editor 

 function createRichTextBox
 	box = D2Editor.newRichText()
 	box:move(50, 50)
 	box:resize(50, 50)
 	box:setText("Hello World !")
 end

External Links

An interesting page about LUA code optimization, that can be really useful, especially for calculators : Lua Performance

Online Demo

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