Revision a044f8c1a6c049da9f398bfb9a063fcd5bc09512 authored by brianharvey on 11 August 2008, 21:48:58 UTC, committed by brianharvey on 11 August 2008, 21:48:58 UTC
git-svn-id: https://svn.code.sf.net/p/ucblogo/code@144 fc4ef4ee-df3e-0410-84de-fb01f5d6c4f7
1 parent 165c13f
newtermnotes
How the GUI communicates with Logo in wxWidgets:
Everything is done with a single thread. We have overriden the
main event loop from wxWidgets (via LogoApplication::OnRun()),
and events are handled periodically through calls to
check_wx_stop(), which calls LogoEventManager::ProcessEvents().
To prevent yielding too much time for event checking, we have a
"fudge factor" that delays how often we yield to the wxWidgets
GUI event checking code, and a parameter that let's us force
yielding if we are say polling for user input. All events (key
press events, window resize, etc) are handled during the yield.
There is a trade-off between responsiveness in the UI (how fast
the GUI recognizes that a key has been pressed) and overall speed
of the program (when crunching numbers or painting) when adjusting
the fudge factor.
Character buffers
in wxTerminal:
char input_buffer[MAXINBUFF]; //stores typed input (before send to logo)
in wxMain:
char output_buffer[MAXOUTBUFF]; //stores output to send to terminal (from logo)
char buff[BUFF_LEN]; //stores input to send to logo (from input_buffer)
When polling for input, any typed characters are stored in input_buffer, which
keeps track of total characters and where the cursor position is (because you can
use the left and right arrow keys to go back).
When the enter key is pressed, one line is put into the logo buffer (buff) and
will be read from logo.
Whenever logo needs to print characters to screen, the characters are put in
output_buffer and will be displayed by the GUI.
Terminal Display Character Storage
The contents of the terminal are stored in a linked list of character arrays.
There are two structures, one that stores the actual characters and mode flags
(bold, standout mode, etc), and one that stores line information (where each
line starts). Both are linked lists of blocks.
struct wxterm_char_buffer {
unsigned char cbuf[WXTERM_CB_SIZE]; //characters
unsigned char mbuf[WXTERM_CB_SIZE]; //mode flags
wxterm_char_buffer *next; //next part of buffer
} ;
struct wxterm_charpos {
wxterm_char_buffer *buf; //which char buffer
int offset; //offset into buffer
int line_length; //length of line
} ;
A charpos points to some character in the character buffer. There are macros
to help navigate. (line_length may or may not be used, depending on the situation).
char_of(charpos) retrieves the character referenced by charpos
mode_of(charpos) retrieves the mode of the character referenced by charpos
inc_charpos(charpos) puts charpos to next character
(goes to next block if necessary)
adjust_charpos(charpos) if offset too large, adjusts charpos so that it points to
the right block (commonly used to jump many characters
forward)
struct wxterm_line_buffer {
wxterm_charpos lbuf[WXTERM_LB_SIZE]; //lines
wxterm_line_buffer *next; //next part of buffer
};
struct wxterm_linepos {
wxterm_line_buffer *buf; //which line buffer
int offset; //offset into line buffer
};
A linepos references a particular line. A line is just a charpos, keeping track of
where the start of the line is, and how long the line is. There are macros to help
navigate this structure as well:
line_of(linepos) gets line referenced by linepos.
inc_linepos(linepos) puts linepos to next line
adjust_linepos(linepos) if offset is too large, adjusts linepos so it points to the
right block.
So, our terminal references the start of the character buffer / line buffer with
wxterm_char_buffer *term_chars;
wxterm_line_buffer *term_lines;
and references the current position (where the cursor is) with
wxterm_charpos curr_char_pos;
wxterm_linepos curr_line_pos;
With this, it's easy to retrieve a particular line:
wxterm_linepos wxTerminal::GetLinePosition(int y)
{
wxterm_linepos lpos;
lpos.buf = term_lines;
lpos.offset = y;
adjust_linepos(lpos);
return lpos;
}
Set the offset and adjust the position!
DebugOutputBuffer() can be called to print out the contents
and properties of the terminal.
![swh spinner](/static/img/swh-spinner.gif)
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