Scratch

This tutorial will give you a basic feel for the MIT squeak editor, and altering Scratch in general. I have tried to include numerous images and such to make it as clear as possible, but feel free to comment with any suggestions.

Let's begin with the blank gray screen of squeak. First left click on that gray, select “open…,” and select “Scratch/Streak”.
This opens a draggable-around Scratch/Streak window.
To resize hold alt and click on the window, and drag the “”pin.
OK, now do the same as above, but this time select “browser” from the “open” list.
This opens the system browser, what most of the programming will go in to:

The little green circle allows you to resize this window. Just hover over the edge to get it. The X quits the window, the “O” minimizes, and the paper opens the window options. You’ll notice the 4 navigation panes above, and the coding pane below. These let you navigate and change the hierarchy of Scratch/Streak. The “instance|?|class”
Is for the 3 main categories. “Class” generally defines that an object exists, whereas instance defines what it does. ? is for comments, which don’t work. Lets get started. Navigate as follows: 1 Scratch-Objects, 2 ScriptableScratchMorph, 3 Class, 4 Scratch, 5 Blockspecs:

See how I highlighted “(‘if %b’ #c #doIfElse)”? This is the basic syntax for defining the existence of a block. There is:
• opening bracket
• single quote
• The text to be displayed on the block, input areæ represented by %letter, such as %n is a numerical inserter, %b is Boolean. Here's the full list:

a:attribute of another sprite, such as X position or size.
b:a boolean inserter
c:a colour picker that shows the menu.
C:a colour picker that doesn't
d: the sprite direction menu/numerical inserter.
D: the menu for midi drums
e: The broadcast message menu
f: math function menu (with sin, abs, etc.)
g: menu for the different graphic effects.
h: numerical sensor board selector menu
H: boolean sensor board selector menu
i: midi instrument menu/numerical inserter
k: menu for the names of the different keys, used in the key sensor blocks.
l: menu with the costume names of the given sprite.
L: list name menu.
m: sprite list
n: numerical inserter
N: note name menu/inserter
s: string inserter
S: sound selector menu
v: variable labels menu
y: menu used to delete either a number of the last value or all of a list.

• Single quote
• “#” sign.
• Letter representing the block type, - being a normal command block, b is Boolean, r a reporter, c is a bar.
• “#” sign.
• Message to be corresponded in the instance side.
• This may be followed by Another one or few stand alone numbers, # followed by a number, or value in single quotes. These define the default value of the inserters.
• Closing bracket.
The message can also define special forms, such as the above’s corresponding function tells how to do the else bar.
What we now want to do is go over to “obsoleteBlockSpecs.”
Highlight each section…

And Copy/Paste into the corresponding section of “blockSpecs”: (See that ‘numbers’ before? All following this will show under numbers.

Now right click “accept”

Et Voila! You’ve resurrected an “obsolete” block!
Repeat this process for the rest. These blocks will work in normal Scratch/Streak, they’ll just be red.
Now that we have the obsoletes’, lets try some other cheats. Go to:
1 Scratch-Objects, 2 ScratchSpriteMorph, 3 Class, 4 Scratch, 5 Blockspecs:

See in the single quotes of both where it’s says 'color'?
Change this to, say saturation:
Which, when accepted, gives this: , Which produces this:

Neat,eh? Try setting it to blur, pointillize, or water as well!
One more thing: go back to 1 Scratch-Objects, 2 ScriptableScratchMorph, 3 Class, 4 Scratch, 5 Blockspecs, and find the equals block: . See the
‘#- #-‘? This means that the two inserters will be blank. If, however, you put a string into them (replacing the dash), then they will be forced to hold it. How scratch does this is to “temporarily” make it a square string inserter. () You could also change the “%n” to a “%s” which is the “code” for a string inserter, but that would render it incompatible with normal Scratch/Streak. Using the above methods you can also make entirely new blocks:
And force stuff into other blocks:


Another thing you can do is:
Drag a block out to the gray, and Alt+click it.

Click the red menu icon, and select change colour…
Edit as you wish… And use in your Scripts!


Certain other blocks can only easily be gotten by going to the version of Scratch/Streak it came from. The 1.2beta comment block is an example:

It’ll show up red in everything after 1.1, gray in 1.2beta. It is obsolete before 1.2.

Hope this helps in your endeavor to utilise the scratch source code!
I will make a more advanced collection of information soon, for those who want to continue.

Last edited by billyedward (2011-04-24 22:56:39)