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The Undiscoverable/Squeak (view source)
Revision as of 18:15, 24 August 2012
, 18:15, 24 August 2012→Creating an Object: Smalltalk
Left-clicking puts a cursor in the text. Try it. Clicking again in the same spot selects the surrounding word, and clicking yet again anywhere in the same word deselects the word and puts the cursor under the mouse. You can click and drag to select any contiguous portion of the text, and you can use keyboard combinations such as shift-cursor or control-cursor, or both: shift-control-cursor to extend or retract the current selection by words or lines, or to move around. Try them. It is not difficult to discover what these combinations do. You might even be familiar with them from text editors or word processors. Shift-clicking also extends the selection. It is much easier to understand how that works by trying it than by reading an explanation, so I won't give one.
Left-clicking puts a cursor in the text. Try it. Clicking again in the same spot selects the surrounding word, and clicking yet again anywhere in the same word deselects the word and puts the cursor under the mouse. You can click and drag to select any contiguous portion of the text, and you can use keyboard combinations such as shift-cursor or control-cursor, or both: shift-control-cursor to extend or retract the current selection by words or lines, or to move around. Try them. It is not difficult to discover what these combinations do. You might even be familiar with them from text editors or word processors. Shift-clicking also extends the selection. It is much easier to understand how that works by trying it than by reading an explanation, so I won't give one.
Right-clicking in a window, indeed on any object, brings up a set of icons in a rectangle, as shown above, with a title at the bottom of the array. This array of icons is known as an object halo, or halo for short. Every graphical object in Squeak or Etoys has one. A single right click in a Workspace window brings up a halo with the title Workspace. A second right click shifts to a smaller halo with the title PluggableText. A third shifts to a larger halo labeled Text, with a different set of icons. We will explore the Halo below.
Right-clicking in a window, indeed on any object, brings up a set of icons in a rectangle, as shown above, with a title at the bottom of the array. This array of icons is known as an [[The Undiscoverable/Squeak/Halo|object halo]], or halo for short. Every graphical object in Squeak or Etoys has one. A single right click in a Workspace window brings up a halo with the title Workspace. A second right click shifts to a smaller halo with the title PluggableText. A third shifts to a larger halo labeled Text, with a different set of icons.
Middle-clicking in a Workspace window brings up an untitled editing menu with font commands, cut, copy, and paste, print, and a number of other options.
[[File:SqueakWorkspaceMenu.png|right]]
Middle-clicking in a Workspace window brings up an untitled text menu with editing commands to choose fonts, cut, copy, and paste, print, and so on, plus options for executing code and saving the contents of the window.
==World==
==World==
Left-clicking and middle-clicking bring up two different world menus, both currently full of mysteries for us. A very determined learner can discover what many of the options on these menus do, but most people will prefer to get hints at least, and in some cases real explanations.
Left-clicking and middle-clicking bring up two different world menus, both currently full of mysteries for us. A very determined learner can discover what many of the options on these menus do, but most people will prefer to get hints at least, and in some cases real explanations.
==Windows==
==Windows==
==The World menus==
==The World menus==
[[File:SqueakWorldMenu.png|left]]
[[File:SqueakWorldMenu2.png|right]]
All of Squeak is accessible to the user with a few mouse clicks. The problem is first to determine which mouse clicks, and second to determine what has been made available to you. There is a lot of it.
All of Squeak is accessible to the user with a few mouse clicks. The problem is first to determine which mouse clicks, and second to determine what has been made available to you. There is a lot of it.
==The Object Halo==
==The Object Halo==
The [[The Undiscoverable/Squeak/Halo|Halo]] has its own page, which introduces the set of tools provided by the halo, including [[The Undiscoverable/Squeak/Object Viewer|Object Viewers]].
[[File:SqueakWorkspaceHalo.png]]
==The System Browser==
If you open the Tools tab and drag a System Browser onto the Desktop, you will get a display similar to this. If you select Kernel-Numbers in the leftmost pane, and then Fraction in the next pane over, you should see almost exactly this.
[[File:SqueakSystemBrowserFraction.png]]
The System Browser window has the same top toolbar and outer frame around the other three sides as a Workspace window, but is divided into several panes. The four panes on top allow users to explore the Smalltalk Object hierarchy. The panes are called, from left to right,
* System Category pane
* Class pane
* Class category pane
* Method pane
Next may come an optional Annotation pane, which can be turned on or off in the Preferences, and is omitted here.
Below those are a text pane for various purposes, with a row of buttons at the top These buttons open other windows for various purposes. At the bottom is a comment pane where the programmer can explain the purpose of the Object type being viewed and how it is to be used.
==Smalltalk Language==
Smalltalk is an extremely powerful, expressive, modular language with a number of other virtues. All of a Smalltalk system is written in Smalltalk, including a compiler that turns Smalltalk program text into platform-independent bytecodes. At runtime, a Smalltalk image runs on top of a highly portable Virtual Machine that provides system facilities and the lowest-level object functions, including a bytecode interpreter that runs all of the higher-level code.
The VM also exists inside Smalltalk as a model written in a subset of Smalltalk, allowing Smalltalk to run on a modified VM inside the current Smalltalk in order to debug the new VM. A satisfactory new VM is then translated to a highly portable subet of C, which can be compiled for all supported platforms in short order. The new compiled VMs are then packaged with the new Smalltalk (or Squeak or Etoys) image, including the Smalltalk model of the new VM, for distribution.
Everything in Smalltalk is an object. All Smalltalk programming consists of defining object classes and sending messages to objects, where the messages can refer to other objects. Every object is a member of a class that defines its structure in terms of internal data objects and methods of interpreting messages sent to the object
Open the Tools palette and drag a new Workspace into the world. Type 3+4 in the window, and make sure to leave the cursor on that line. Middle-click and select print it from the menu.
[[File:SqueakWorkspaceMenu.png]]
Smalltalk evaluates the expression and displays the value in the Workspace, thus.
[[File:Squeak3+4PrintIt.png]]
The number 3 is an object, a member of a numeric class of small integers. We send it the message + 4, invoking the method for + on that kind of integer with the argument 4, referring to a different object. We get back the object 7, and the interpreter invokes a method for printing that result in our Workspace.
A brief introduction to the subset of Smalltalk used in these pages is on the [[The Undiscoverable/Smalltalk|Smalltalk]] page. There are several good textbooks on Smalltalk.
==Creating an Object==
The mechanics of object creation using a [[The Undiscoverable/Squeak/System Browser Use|System Browser]] with a bit of Smalltalk programming are on a separate page.
==Tutorials==
At this point, if you have gone through the material above plus the pages linked to, you know enough to follow many of the available introductory [http://wiki.squeak.org/squeak/792/ Squeak tutorials].
For those who wish to dive deeper into Smalltalk, there are a number of free digital books available at [http://stephane.ducasse.free.fr/FreeBooks.html Stef's Free Online Smalltalk Books]
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