In addition to the resources you see inside LiveCode itself, there is a tremendous amount of information and a number of tutorials on the RunRev website. A good starting point would be http://lessons.runrev.com/.

This screenshot shows the windows and palettes that we're going to use for now as well as the document window, which is a simple calculator that we will build soon:

In addition to the document window itself, these are the main windows that we need to be familiar with for now:

The upper area of the Tools Palette shows all the interface controls that you need to create an interactive application. Below these are a set of tools to edit vector graphics and a set of tools to edit bitmap graphics.

The Inspector Palette shows all the options for the control that you currently have selected. In the preceding screenshot, nothing is selected in the calculator app, so the Inspector Palette shows information about the stack itself.

Message Box is a window that lets you try out either single or multiple lines of code. You are able to invoke functions in your stacks too, making it a very handy way to test individual functions while you are tracking down issues. We'll use the Message Box in later chapters.

As suggested, read the User Guide to get a deeper understanding of these windows, but let's try putting together something simple for now to get you more familiar with how to use the Tool palette.

In LiveCode, you can drag controls from the Tools palette to the card window without selecting the Edit tool. However, you are not able to select the control to adjust its position or size, and so, in the following instructions, we are intentionally selecting the Edit tool before adding controls to the card window:

Hopefully, you will have made a random bunch of interface controls, perhaps some that are nicely lined up too! Now, select the Close and Remove From Memory option from the File menu and create a new Main Stack to make the Simple Calculator interface.

First though, we should go over some of the structure and hierarchy of a LiveCode stack and create some basic navigation.

Everything goes somewhere, but having things in the wrong place can lead to problems. We should learn more about the structure of a LiveCode stack to avoid this.

As described in the Background history and metaphors section, LiveCode uses a stack of cards metaphor. When you make a new stack, you in effect have a single stack of cards. However, even the simplest application is likely to have more than one card. For example, there could be a splash screen, title card, cards for the actual task at hand, and a credits page. In the calculator stack, we will use two cards. The Tools menu includes an option to view the structure of the stack by showing Project Browser or Application Browser. The Project Browser was introduced in the version 6.0 of LiveCode with additional capabilities

The Project Browser panel is a powerful tool that lets you see all the stacks, cards, and controls that are open at the moment, in one window. In addition to getting an overview of everything, you can use it as a remote control to jump between all the parts of your stack and to select and modify buttons, fields, and so on.

Taking the calculator stack that we are about to make as an example, in the following screenshot, we see a side-by-side view of the stack window and the Project Browser panel, where in the Project Browser panel, we have selected one of the buttons in the stack:

The upper area of Project Browser includes a field where you can type and search text to reduce the list of items in the browser to match the ones you have typed. In the upper-left part of the panel, is a gear icon that is used to take you to the preferences of the browser:

Most of the rest of the browser window lets you expand stacks and cards, and choose individual controls on those cards. Clicking on a control in Project Browser highlights it in the stack window and vice versa. Controls can also be reordered to change layers by dragging them up and down. Controls can also be hidden or locked by clicking on the eye and lock icons. The lower area buttons let you do various alignments of the selected controls to add or duplicate the selected control. Hovering over a button shows a popup of what it does.

A longer overview of how Project Browser works is available at:

http://www.runrev.com/newsletter/april/issue151/newsletter4.php.

In programming languages, such as the one in LiveCode, code is referred to as scripts and methods or functions are known as handlers (though in LiveCode, a handler that returns a value is also called a function). Projects made with hard-to-use programming tools often comprise dozens of external text files, one for each model, view, or controller. In LiveCode, this is simpler, as the scripts are attached to the object that needs that code.

To deal with user interaction in other tools, you will have to write code that receives the event (perhaps just a mouse click on a button) to perform the relevant action. In LiveCode, there is a message path that takes care of these events, and passes the event up the hierarchy. If you click on a LiveCode interface control that doesn't have a mouse event handler, the click goes up the hierarchy to the card level. If the card doesn't have a handler for that event, it continues up to the stack level.

You can have additional levels of hierarchy by putting other stacks in use, but for our purpose, we just need these three: the button, card, and stack.

This message hierarchy allows us to place the code needed via several interface controls at a higher level available to all of these controls. One case with the calculator number buttons is that each one needs to do exactly the same thing, and by putting that code in the card level, all of them can make use of that one handler.

There isn't a performance advantage if you have the shared handler in the card level or much of a file size improvement, but as you develop the code for the simple calculator example, you can make changes in the single-card script instead of the 11 calculator button scripts.

We will now start building the calculator and add scripts to the 14 buttons, a field, and the card.

These may have seemed like a lot of steps, but we did create the two cards we needed, laid out a nice looking title field, and a begin button with its own script. In reality, these steps take well under two minutes and will be even quicker to carry out as you gain experience in LiveCode.

If you want to make it big in the multimedia authoring tool world, which of these names would be a bad choice?

Answer: 1

In the early days of multimedia, it seemed like everyone had one of just a few popular names. There was Bill Atkinson, who created HyperCard, and Bill Appleton, who created SuperCard. Kevin Calhoun was the lead HyperCard programmer for a while and Kevin Miller is the head of LiveCode. Bob Stein was one of the founders of The Voyager Company and along with Bob Abel who was one of the pioneers in visual effects. Dan was another good choice as there was Dan Winkler, the author of the HyperTalk language, and Danny Goodman, the author of many famous programming books. Henry would be a good name if you wanted to make motorcars or marry lots of queens.

You will find yourself using the Inspector palette a lot; so, take a moment to study how it behaves. When you select an object on the card, you will see that the Inspector palette changes its appearance, sometimes even its height, to show the options for the item you have selected. It is smart enough to notice when you have selected multiple items and shows the align tools.

Sometimes, you will want to keep an Inspector palette set to view the options of a particular object on the card, and not switch so as to show a different object as you make other selections. In the upper-right corner of the Inspector palette is a padlock icon, which will let you lock the Inspector to the current object.

So far, most of the Inspector palette options haven't affected us, but one that is about to be relevant is the fact that you can set a name for an item that is different from its label. You may know from other programming languages, and this does apply to LiveCode too, that some names are less legal than others. Perhaps you can't have spaces in the name or use a colon or backslash. If you name a button with a number, button "1" may not be button 1 and this could lead to confusion.

For the calculator keys, we will set a label to make it look correct and a name that doesn't lead to confusion. Speaking of those calculator keys…

Quite a lot just happened! We have now made all the card level objects and typed in their scripts. Most of the scripts are "calling" up to a card level handler that we will be setting up next. Before doing that, it's worth trying to understand some of the lines we just entered.

The English-like nature of the programming language in LiveCode is amazingly powerful, but rigidly so. In some other tools, you have a choice of whether you want to use verbose English-like syntax, less verbose, or what is called dot syntax. The Lingo language, in Adobe Director, is a good comparison.

Suppose we want to change the text inside a field, that is the first entry of a director movie's cast, we can perform the following verbose syntax:

put "hello world" into the text of member 1

We can perform a slightly less verbose syntax:

the text of member 1 = "hello world"

Or, we can perform a dot-syntax:

member(1).text = "hello world"

In LiveCode, there isn't a choice. What you type has to be in the form of:

put value into container

However, you do have a choice about whether to use a long version of a word, short version, or an abbreviated form. There are also synonyms, which allow you to use a word that makes more sense to you.

Here are the two ways of saying the same thing, with the second variation using an abbreviated form of the keywords:

put character 3 of word 2 of card field "name of field 1" into aVariable
put char 3 of word 2 of fld 1 into aVariable

When you are dealing with the contents of the object that has the script running, you can use the keyword me to save on some typing, and LiveCode will also try to work out what you have in mind, if possible.

Take the lines we have entered as examples:

numberPressed the label of me

Here, numberPressed will propagate up to a card handler that we will add (soon) and the label of me will look at the Label that you have set for the object that the script is inside of:

set the clipboarddata["TEXT"] to me

In this case, me would normally refer to the object (as is the case with the label of me), but because we gave the extra clue of ["TEXT"], LiveCode knows that it's the text contents of the field that have the script and not the field itself. Still, because there is potential for confusion, when reading your own code later, you could add a couple of words to make the meaning more clear:

set the clipboarddata["TEXT"] to the text of me

You might choose to be more verbose than is needed, just for readability reasons, and in these chapters, this is going to be the case. It is easier to tell what is going to happen by using:

put the text of me into textvariable

The following will be less verbose compared to the preceding entry, even though they are equally valid:

put me into textVariable

In either case, as it's a field, LiveCode knows what you meant.

You see in the script that we typed short name of me, what's that all about? Objects in LiveCode have a lengthy description of where they are located, for example, the buttonname button of the 1234 card ID of the path/to/stack.livecode stack. In the calculator application, we need only the single word that you set as the name of the button. If we asked for name of me, it would still say "the buttonname button". To just grab the name itself, we use short name of me.

There are times when you will want to use the other variations of name, including the long name and the abbreviated name, which you can read about in the LiveCode Dictionary entry for name. In addition to a description of the different ways to use name, there are a number of cautions you need to be aware of.

If you dared to go ahead and tried using the calculator buttons, you will see a lot of script errors. We need to add in the card level handlers to be at the receiving end of the calls that the buttons make. Instead of walking you through, typing a line of code at a time, it probably would be quicker to present the lines in one go and explain what each line does. As a practice run, here are the lines that we have entered so far:

On all the number buttons and the decimal point button, you should have this script:

on mouseup
  numberPressed the label of me
end mouseup

The on mouseUp event is triggered when you press and release the left mouse button while on the numberPressed call. This event will call a card handler named numberPressed, passing with it, the label that you had set for the button that holds this script.

The C (clear) button has this script:

on mouseUp
  clearPressed
end mouseUp

The clearPressed event will call a card script named clearPressed.

The other buttons all work the same way; they call a handler of the name used, which we're about to add to the card script. This is script for the +, -, *, and / buttons, passing to the card level, the name of the button in question:

on mouseUp
  operatorPressed the short name of me
end mouseUp

The following script is for the +- button:

on mouseUp
  toggleSign
end mouseUp

The display field has this script:

on mouseUp
  set the clipboardData["TEXT"] to me
end mouseUp

In the field's case, only one line of code is being executed, so no need to put that up on the card level, unless we had a lot of fields doing the same thing.

So, why don't we add all those card level scripts! We will take them one at a time, with an explanation of how each one works. But first, let's see how LiveCode handles variables.

Generally speaking, variables are memory locations where you store values that you need to access later, but in most programming languages, you can dictate which routines have access to which variables. Less English-like languages may include the terms public, private, and protected. Things are not that different in LiveCode, but words are used that more accurately describe the region that the variable can be used in. If a variable is to be readable everywhere, it would be global. If it's just to be used in the current script, it's local.

LiveCode also has custom property variables, and as an aside, many people would use these for performing the calculator button values instead of relying on the label of the button. Perhaps, we'll use them later!

Now, where was I… oh yes, card level scripts. This is the first line of the card script:

global currentTotal,currentValue,currentCommand,newNumber

As discussed, these are the variables that will allow the many handlers to pass values to each other. In this case, the variables could be local, but often, you may make them global instead, thinking that a case may come up later where you need to get at the variables from outside the script you're in.

It's good to reset things when you start the app and LiveCode has an openCard event that we can pick up on. The following code resets things:

on openCard
  clearPressed
end openCard

on clearPressed
  put true into newNumber
  put 0 into field "display"
  put 0 into currentTotal
  put 0 into currentValue
  put empty into currentCommand
end clearPressed

Having the reset lines in their own clearPressed handler will allow us to call it at other times, not just when the card opens, and we do call it directly when we click on the C clear button. This will zero out the display field, the running total for your calculation and the last number that you entered into the calculator. It also clears the variable that is used to remember which operator button you last pressed, and a Boolean (true or false) variable is used to recognize whether a number button that you press should clear the display or append to the display.

All the numbered buttons and the decimal point button call this handler:

on numberPressed n
  if newnumber is true then
    put n into field "display"
    put false into newnumber
  else
    put n after field "display"
  end if
end numberPressed

The n comment after the handler name, is a parameter variable that stores the content that was sent to the handler. In this case, it's the label of the button that was pressed. All this routine needs to add is a character to the end of the display field, except when you are typing in a new number. That's where the newNumber Boolean variable comes in; if it is set to true, the incoming character replaces all the contents of the display field. If it's false, the character is added to the end of the field.

This is the handler to be used when you press the +, -, *, or /, buttons:

on operatorPressed operator
  if currentCommand is empty then
    put field "display" into currentTotal
    put operator into currentCommand
    put true into newNumber
  else
    put operator into currentCommand
    equalsPressed
  end if
end operatorPressed

When you use a calculator, you type in one number, an operator, and then another number, followed by either another operator or the equals button. Now you press the operator button as there is no way to know what you're doing (since you haven't entered the next number in the calculation yet), so we have to remember the operator when we press the equals button. If the currentCommand variable doesn't already have a value, we store the display field text into a currentTotal variable, store the operator character that you pressed into the currentCommand variable, and make sure that newNumber is set to true. Doing this makes sure that the next number button you press will clear the display field. If currentCommand already has a value, we replace it with the new value and then call the same handler that is used when you press the equals button.

There are most likely shorter ways to cope with the equals button being pressed, but here, we'll use several if statements and run the appropriate calculation code:

on equalsPressed
  put field "display" into currentValue
  if currentCommand is empty then exit equalsPressed
  if currentCommand is "divide" then put currentTotal / currentValue into field "display"
  if currentCommand is "multiply" then put currentTotal * currentValue into field "display"
  if currentCommand is "minus" then put currentTotal - currentValue into field "display"
  if currentCommand is "plus" then put currentTotal + currentValue into field "display"
  put field "display" into currentTotal
  put true into newNumber
  put empty into currentCommand
end equalsPressed

The contents of the display field are stored in the currentValue variable and the last operator button you pressed (that is stored in currentCommand) is looked at, to see what happens next. If there wasn't a previous operator, as would be the case if you pressed "equals" twice in a row, we'd ignore the button press and exit the routine. For the four operators, we do the appropriate calculation. Afterwards, we store the new running total in the currentTotal variable, make sure that the newNumber Boolean is true (so that the next number button pressed will clear the display field), and we forget the last operator button that was pressed by putting empty in the currentCommand variable.

One thing to note is that LiveCode is smart enough to know that the text string inside the display field is to be treated as a floating-point number.

The togglesign last handler is as follows:

on togglesign
  if character 1 of field "display" is "-" then
    delete character 1 of field "display"
  else
    put "-" before field "display"
  end if
end togglesign

This is a very simple routine that doesn't have to understand that it's floating point numbers are being represented. It simply checks whether the first character is a minus or not and if it is, it deletes the character; if not, it inserts a hyphen that LiveCode will later interpret as a negative value.

As you get to learn a new tool, you can end up taking a lot of time remembering where everything you may need, is located. You know what you want to do, you know how to do it, but you can't remember where that thing is located! For example:

Q1. Where did you go to set the text styling for the calculator's title field?

Answer: 3

Getting to this section involved selecting the Edit tool from the Tools palette, clicking on the title field on card 1, and choosing Text Formatting from the Inspector palette drop-down menu. However, there is indeed a Text menu. Really, that's what we should have used!

It is possible to add more features to the simple calculator. If we consider the functions in the card script and how the buttons are named, we can start to see the processes that are involved in adding a new ability, some of these processes are as follows:

On Windows, you can add a square root symbol with Alt 251 and on Mac, with the shortcut option + v. Unfortunately, LiveCode doesn't like these as button labels! At least on Mac, when you type the character in the Inspector palette, the character immediately vanishes. One workaround would be to use the message box and type this:

set the label of btn "squareroot" to "√"

This should give you the right symbol as the button label.

LiveCode has a square root function; typing this in the Message Box would produce the square root of 10:

put sqrt(10)

Now that you are armed with the given information, try to add a square root feature to the calculator.

LiveCode can play movies using the Player control type. These can be added to the card in several ways and then using a script command:

Having added the player to the card, you can then set the video file to be played by entering the file path or URL of the file under the Basic Settings option of the Inspector palette. You can also set the path to the video with script:

set the filename of player "player name" to "file path or URL"

In much the same way as you just saw for the playing of video, still images can be added to a stack. All of the options shown to add a video player can be done in the same way for images. Here, for example, is the script needed to add the RunRev company logo to the card:

new image "revlogo"
set the filename of image "revlogo" to "http://runrev.com/wp-content/themes/runrev2013/ims/runrev_logo.png"

Images that you import can be used as icons in a button. To set up a button, so that it has a nice idle state image and an associated highlight image, you would have to go through the following steps:

In the following screenshot, we can see two images that have been imported in order to give the Begin button a more iOS-like appearance. The button is selected and the Inspector palette shows the icon selection choices:

When you choose an image for use, the button itself is updated. In this case, the Hilite icon has been set to the darker version of the graphic, but as shown here, the button still needs to be resized.

LiveCode has a lot of different controls. Many are just slight variations, but there are plenty that are quite different from each other. Look at the Object menu and New Control. As you'll see, the list is very long!