163 lines
6.1 KiB
Plaintext
163 lines
6.1 KiB
Plaintext
# Editing text
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Collapse OS has 2 levels of text editing capabilities: command-
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based editing and visual editing.
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The command-based editor is a "traditional" Forth text editor as
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described in Starting Forth by Leo Brodie. We call this editor
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the "Block editor" and it is located at B100.
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The visual editor is a full-blown application that takes over
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the interpreter loop with its own key interpreter and takes over
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the whole screen using AT-XY. We call this editor the "Visual
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Editor" and is located at B120.
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When available, the Visual editor is almost always preferable to
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the Block editor. It's much more usable. We have the Block edi-
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tor around because not all machines can implement AT-XY. For ex-
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ample, a machine with only a serial console can't.
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# Block editor
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The Block editor augments the built-in word LIST with words to
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modify the block currently being loaded. Block saving happens
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automatically: Whenever you load a new block, the old block, if
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changed, is saved to disk first. You can force that with FLUSH.
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Editing works around 3 core concepts: cursor, insert buffer
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(IBUF), find buffer (FBUF).
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The cursor is simply the character index in the 64x16 grid. The
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word T allows you to select a line. For example, "3 T" selects
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the 3rd line. It then prints the selected line with a "^" char-
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acter to show your position on it. After a T, that "^" will
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always be at the beginning of the line.
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You can insert text at the current position with "i". For exam-
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ple, "i foo" inserts "foo" at cursor. Text to the right of it
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is shifted right. Any content above 64 chars is lost.
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Why "i" and not "I"? Because "I" is already used and we don't
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want to overshadow it.
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You can "put" a new line with "P". "P foo" will insert a new
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line under the cursor and place "foo" on it. The last line of
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the block is lost. "U" does the same thing, but on the line
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above the cursor.
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Inserting anything also copies the inserted content into IBUF.
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Whenever an inserting command is used with no content (you still
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have to type the whitespace after the word though), what is in-
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serted is the content of IBUF.
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This is all well and good, but a bit more granularity would be
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nice, right? What if you want to insert at a specific position
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in the line? Enter FBUF.
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"F foo" finds the next occurrence of "foo" in the block and
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places the cursor in front of it. It then spits the current line
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in the same way "T" does.
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It's with this command that you achieve granularity. This allows
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you to insert at arbitrary places in the block. You can also
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delete contents with this, using "E". "E" deletes the last found
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contents. So, after you've done "F foo" and found "foo", running
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"E" will delete "foo", shifting the rest of the line left.
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List of commands:
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T ( n -- ): select line n for editing.
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P xxx: put typed IBUF on selected line.
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U xxx: insert typed IBUF on selected line.
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F xxx: find typed FBUF in block, starting from current
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position+1. If not found, don't move.
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i xxx: insert typed IBUF at cursor.
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Y: Copy n characters after cursor into IBUF, n being length of
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FBUF.
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X ( n -- ): Delete X chars after cursor and place in IBUF.
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E: Run X with n = length of FBUF.
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# Visual editor
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This editor, unlike the Block Editor, is grid-based instead of
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being command-based. It requires the Grid subsystem (B401).
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It is loaded with "125 LOAD" and invoked with "VE". Note that
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this also fully loads the Block Editor.
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This editor uses 19 lines. The top line is the status line and
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it's followed by 2 lines showing the contents of IBUF and
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FBUF. There are then 16 contents lines. The contents shown is
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that of the currently selected block.
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The status line displays the active block number, then the
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"modifier" and then the cursor position. When the block is dir-
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ty, an "*" is displayed next. At the right corner, a mode letter
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can appear. 'R' for replace, 'I' for insert, 'F' for find.
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All keystrokes are directly interpreted by VE and have the
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effect described below.
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Pressing a 0-9 digit accumulates that digit into what is named
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the "modifier". That modifier affects the behavior of many
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keystrokes described below. The modifier starts at zero, but
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most commands interpret a zero as a 1 so that they can have an
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effect.
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'G' selects the block specified by the modifier as the current
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block. Any change made to the previously selected block is
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saved beforehand.
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'[' and ']' advances the selected block by "modifier". 't' opens
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the previously opened block.
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'h' and 'l' move the cursor by "modifier" characters. 'j' and
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'k', by lines. 'g' moves to "modifier" line.
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'H' goes to the beginning of the line, 'L' to the end.
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'w' moves forward by "modifier" words. 'b' moves backward.
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'W' moves to end-of-word. 'B', backwards.
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'I', 'F', 'Y', 'X' and 'E' invoke the corresponding command from
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command-based editor.
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'o' inserts a blank line after the cursor. 'O', before.
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'D' deletes "modifier" lines at the cursor. The first of those
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lines is copied to IBUF.
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'f' puts the contents of your previous cursor movement into
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FBUF. If that movement was a forward movement, it brings the
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cursor back where it was. This allows for an efficient combi-
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nation of movements and 'E'. For example, if you want to delete
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the next word, you type 'w', then 'f', then check your FBUF to
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be sure, then press 'E'.
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'R' goes into replace mode at current cursor position.
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Following keystrokes replace current character and advance
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cursor. Press return to return to normal mode.
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'@' re-reads current block even if it's dirty, thus undoing
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recent changes.
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# Tight screens
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Blocks being 64 characters wide, using the Visual editor on a
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screen that is not 64 characters wide is a bit less convenient,
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but very possible.
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When VE is in a "tight screen" situation, it behaves different-
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ly: no gutter, no line number. It displays as much of the "left"
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part of the block as it can, but truncate every line.
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The right part is still accessible, however. If the cursor moves
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to a part of the block that is invisible, VE will "slide" right
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so that the cursor is shown. It will indicate it "slid" mode by
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adding a ">" next to the cursor address in the status bar.
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To slide back left, simply move the cursor to the invisible part
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of the left half of the block.
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Other than that, VE works the same.
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