Aufgabe 4: Kontextwechsel

Constructor of a text window.

Creates a virtual, rectangular text window on the screen. The coordinates to construct the window are absolute positions in the TextMode screen.

Note

Overlapping windows are neither supported nor prevented – better just try to avoid construction windows with overlapping coordinates!

Warning

Don't use the hardware cursor in more than one window!

Parameters

from_col	Text Window starts in column from_col, the first (leftmost) possible column is 0
to_col	Text Window extends to the right to column to_col (exclusive). This column has to be strictly greater than from_col, the maximum allowed value is TextMode::COLUMNS (rightmost)
from_row	Text Window starts in row from_row, the first possible (uppermost) row is 0
to_row	Text Window extends down to row to_row (exclusive). This row has to be strictly greater than from_row, the maximum allowed value is TextMode::ROWS (bottom-most)
use_cursor	Specifies whether the hardware cursor (true) or a software cursor/variable (false) should be used to store the current position

Default constructor.

Since each core in MPStuBS has its own debug window, but the number of available cores might be different on each system, the arrangement can be done automatically.

However, there is one problem: The number of CPUs is only known after evaluating the ACPI MADT table (which is done in APIC::init(), called during kernel_init()), but global constructors like ‘kout’ are executed earlier.

Therefore this constructor assigns each window 2 separate lines for the output, the actual window split is later done by calling TextStream::arrange() in main().

Automatic arrangement of the output windows (depending on the cores)

After the system information has been read out, the number of available cores can be queried with Core::count(). This information helps to automatically arrange the windows without wasting screen area by pre-saving it for non-existent cores.

Parameters

kout	Pointer to the object for the main output window
dout	Pointer to an array with with debug windows for each core

Output the buffer contents of the base class Stringbuffer.

The method is automatically called when the buffer is full, but can also be called explicitly to force output of the current buffer.

Implements OutputStream.