, the tip of which is named mouse focus. The focus designates the object on which the mouse actions described below will operate.There are three
mouse actions of importance: clicking, dragging and interclicking.
Clicking: pressing a key and releasing it, whithout moving the mouse.
Exercise this: only a tiny portion of the tutorial is visible right now. To continue reading what follows, move the mouse focus into the scroll bar (at the left) at the height of this line and click the left mouse key. If you have a Macintosh single button mouse, click that button. The text will scroll forward, but you will learn more about scrolling very soon.
Dragging: pressing a key and holding it down while moving the mouse.
Interclicking: simply pressing a key or dragging on a key, and pressing one of the other two keys, until finally all keys are released (in any order). The first key pressed determines the action, and the second key pressed modifies it.
The scroll bar features a
position mark 
which is adjusted at each scroll operation.
The relative position of this mark in the scroll bar is the same as the relative position of the first visible line in the entire text.
To exercise scrolling, position the cursor in the scroll bar and verify by yourself that (watch the position mark adjusting itself):
Select each of the following letters or calendar object in succession: A B 
C.
A larger piece of text is selected by first moving the mouse cursor to the start of the desired selection and then dragging on the right mouse key. On the display, the selected area is shown in reverse video and adjusted continuously as the mouse is moved. This adjustment is termed tracking the selection. The selection process is completed when the mouse key is released. Notice that carriage return characters contained in a selection are revealed by the reverse video.
Select the following text from here ->Selected text stretch which goes on and on and on and on and on and on<- to here.
Now learn to improve the selection process: select several lines of text by first moving the mouse vertically and then horizontally left or right as need be. Clear the selection.
Selecting a line: The text stretch from the mouse cursor to the left edge of the viewer is selected if the right mouse key is clicked two times without moving the mouse. It is not necessary for the two clicks to be in quick succession.
Select this line entirely including the full stop.
Note: Double clicking or clicking a key twice in rapid succession as is known from other systems is not used in Oberon.
. The tip at the top is the
caret focus which determines the insertion point: when a character is typed on the keyboard, it is inserted at the right of the caret, and the caret moves one place to the right. The character at the left of the caret is removed by hitting the Backspace key (<-). The caret then moves one place to the left. Also a copied text selection (you will soon learn how this is done) appears to the right of the caret.
Move the mouse cursor inside the viewer below and set the caret in place by clicking the left mouse key. Moving the mouse focus and clicking the left key again moves the caret to a new point.
While dragging on the left key, the caret is tracked, that means it jumps from character to character or from object to object, trying to follow the cursor. This adjustment is termed tracking the caret. Try even to drag the cursor below and around the viewer. You clearly see that the focus viewer does not change.
The focus viewer will only change after you click the left mouse key outside of that small viewer. Interestingly enough, if you click here in this viewer, the caret's shape changes.
In desktops and panels the insertion point of a gadget is made visible by another
caret symbol 
. Place an insertion point of that shape approximately here -> <-. You will have noticed that the caret focus at the center of the cross can be adjusted pixel-wise.
A third
caret symbol 
is used in text fields like this one 
. Set the caret with a left mouse key click. This sets the focus point inside the text field. Text may be inserted and edited according to the rules described in Editing with the mouse, though it is limited to a single line (ending with a carrier return). Have you noticed that the focus viewer is unique?
In Oberon a text is taken literally: a sequence of characters. If this sequence is to be interpreted as a command, it is not necessary for the characters to be in a special place, that is in a command line. In a text viewer like this one, a command and its parameters may appear anywhere and may be executed by pointing at the command name with the mouse cursor and clicking the middle mouse key. While the middle mouse remains pressed, the word pointed at with the mouse cursor is underlined. On release of the key, Oberon tries to execute the command. Try it with this example, and watch the additional line appearing in the Oberon.Log: System.Time
The last line in the log now displays: System.Time dd.mm.yy hh:mm:ss
You will like to use a simple and lean expression such as 'click on ....' (a command or a word) instead of this emphatic but equivalent 'when the mouse focus is positioned on this command, click the middle mouse key and the command will be executed'.
When dragging on the middle key, words are tracked; that is, each new word pointed at is underlined. This adjustment is termed tracking words. The same holds true when graphical objects flow within the text stream.
Try it with this color picker 
which will enlarge and shrink again.
The following standard actions are provided:
While tracking the selection (dragging on the right key):
You should observe the caret's movement (one place to the right) for each character typed on the keyboard and more important still, after having copied a text portion to the caret. Chaining further text portions intermixed with keyboard input is made easy. Likewise the caret is ideally positioned after you have deleted a text portion.
Editing, i.e. inserting, deleting or copying text at the caret, has a side-effect: the selection is removed.
When typing text, the text scrolls up to show what is being typed. If the end of a text is visible and text is inserted at the end, the text scrolls to show the new end of the text.
Now copy (or type) a few words in the next two tiny text viewers and observe the following:
Thus remember this: to copy the same text stretch at different places in a viewer, place the text to copy in a separate viewer, select it and insert it repeatedly at the caret with a left + middle interclick.
Note: The two variants of the "copy selection" correspond to the well-known copy-and-paste used in other text editors. Oberon does not have a cut-and-paste operation.
Once the caret is set, the four arrow keys (left, right, up, down) are used to move the caret to the previous or to the next character or line. The Page Up and Page Down keys are used to scroll one page up or down respectively. By default, pressing the ENTER key does auto-indentation. Pressing ENTER, starts a new paragraph. The same number TAB or space characters found at the beginning of the previous paragraph is inserted at the beginning of the new paragraph.
(Warning: this marker is a fake, it belongs to this text).
The viewer containing the marker focus (the center of the pattern) in its frame boundary is said to be marked.
The marker is unique: if it is set, an attempt to place another one will erase the old one.
To convince yourself try this: set the caret in a free area of a desktop (that is how the work surface on your display is called in Oberon) with a left mouse key click, mark this viewer (F1) and click on this command -> Icons.InsertIcon *
An icon captioned "Mouse.html" appears at the insertion point. You should by now know how to delete the icon: set the mouse focus on the icon and interclick right + left mouse keys.
Note that hitting the Esc key makes the marker invisible only: the viewer, which displayed the marker just before, remains the marked viewer. To verify this assertion, set the caret in a free area of the desktop as you did earlier, and click on -> Icons.InsertIcon * . Delete the icon which just appeared.
Caution: The marker is fixed to the screen, not to the viewer. Therefore, it is good practice to set the marker explicitely if it has a significance in a subsequent action.
Some combinations of keyboard input can be used to create the accented characters: press and release the accent key first, then press the appropriate letter. Accent keys, which also are known as nonescaping keys or dead keys, are intended to be used only in conjunction with other keys. To create the accent character by itself, press the accent key, then the Spacebar.
You can always use this ASCII character table to insert accented characters and any other represented character into a document directly without the help of the keyboard. Refer to ASCIITab.
Additionally to character keys there is a small number of command keys, as follows:
