mirror of
https://github.com/hsoft/collapseos.git
synced 2024-11-01 14:40:56 +11:00
d3049b2404
In VE on the SMS, the first contents line would always be cleared because of NEWLN being called when the FBUF would spit its last char. Inconvenient... I've added a "graphical" mode to the grid subsystem to inhibit this behavior in a graphical situation such as in VE. Also, write a more complete Grid documentation.
41 lines
1.6 KiB
Plaintext
41 lines
1.6 KiB
Plaintext
# The Grid subsystem
|
|
|
|
The grid subsystem at B401 supplies a set of words on top of
|
|
the Grid protocol (see doc/protocol.txt) that facilitates the
|
|
development of programs presenting a complex text interface,
|
|
for example, the Visual Editor.
|
|
|
|
It create the concept of a cursor, always being a some position
|
|
on screen. That position is in the variable XYPOS, which is a
|
|
simple integer following the same "pos" logic as in the Grid
|
|
protocol.
|
|
|
|
It implements (emit), which sets the cell under the cursor to
|
|
the specified character, then moves the cursor right. If the
|
|
cursor is at the last column of the screen, it overflows to the
|
|
next line. If it's on the last line, it overflows to the first
|
|
line.
|
|
|
|
Grid's (emit) handles 0xd by moving the cursor to the next line
|
|
and 0x8 by moving the cursor left.
|
|
|
|
AT-XY ( x y -- ) moves the cursor to the specified position. It
|
|
is equivalent to setting XYPOS directly, but uses separate X
|
|
and y numbers.
|
|
|
|
When the grid's cursor enters a new line, it clears its
|
|
contents through a repeated call to CELL!. That implementation
|
|
is in its world named NEWLN ( ln -- ). This word can be over-
|
|
ridden. If it exists when the grid subsystem is loaded, the ex-
|
|
isting NEWLN will be used.
|
|
|
|
The clearing of the newly entered line is usually only desirable
|
|
when in "shell" mode. In "graphical" mode, we usually don't
|
|
want this to happen. XYMODE is a flag to indicate whether the
|
|
grid system is in "graphical" mode. When its value is nonzero,
|
|
NEWLN is not called when entering a new line.
|
|
|
|
At build time, the Grid subsystem needs 3 bytes of system me-
|
|
mory through the GRID_MEM constant. At run time, GRID$ needs to
|
|
be called to initialize the system.
|