More Scrolling Function in Flash 5 - Page 7

These actions are extensively commented in the source file. Since Flash 5 ActionScript is an object-oriented language using dot syntax, it is written differently than Flash 4 code. For example the second line of code is telling the MC instance logic, which lives inside of the scroll_shape MC instance, that it will contain a variable called target. Keep in mind that target is NOT a MC instance, it is a variable. That variable is equated to var_mc, which is another variable that was set in line 1 of the code. Line one sets var_mc equal to "_root.button_list," which is the absolute target path of the MC we want to scroll. Whenever the logic MC loop sees the variable target, it equates that variable with var_mc. Then, since "var_mc" was defined as button_list, target will be equated with the button_list MC when the logic loop is triggered. This way, if we wanted to change the MC that gets scrolled, all we need to do is place an instance of it on the stage (underneath the mask of course), give it a unique name, remove button_list, and change just one line of code so that:

var_mc = _root.unique_instance_name;

This takes away the painful task of having to rewrite all of your code every time you want to scroll a different MC. If the content to the right of the "=" sign in the rest of the code looks confusing, think of it as a simpler Flash 5 way of using the "getProperty" action. For example "var_mc._y" (line 6 of the code) is like as saying "getProperty(var_mc, _y)." Note the last line of code in particular, which establishes the value for the variable clip_height: By subtracting bar_length (see line 3 of the code) from var_mc._height, we are fooling Flash into thinking var_mc._Height is less than it actually is. This gets rid of the dead space below the target MC that would be displayed because of the window mask's dimensions. Here the mask's dimensions are a little bigger than scroll_bar's dimensions, and the extra 10 was subtracted as a tweaking measure because of this difference. Go ahead and change line 7 to the following, if you'd like to see what I'm talking about:

scroll_shape.logic.clip_height = var_mc._Height - 0

Now let's take a look at the drag actions attached to the invisibut instance on the button layer of scroll_shape(_obj), so we can begin to see how these variables will be accessed when the logic loop is triggered into action.