#if !defined(__COMPACT__)\r
# if !defined(__LARGE__)\r
# if !defined(__HUGE__)\r
-# error Large data model required! Try compiling with 'bcc -ml lib.c'.\r
+# error Large data model required! Try compiling with 'wcc -0 -ml lib.c'.\r
# endif\r
# endif\r
#endif\r
\r
/* By default we want screen refreshing and drawing operations\r
to be based at offset 0 in the video segment. */\r
- actStart = visStart = 0;\r
+ actStart = visStart = 0;
+
+ /*
+--------------------
+HORIZONTAL SCROLLING
+--------------------
+Horizontal scrolling is essentially the same as vertical scrolling, all
+you do is increment or decrement the VGA offset register by 1 instead of
+80 as with vertical scrolling.
+
+However, horizontal scrolling is complicated by two things
+
+ 1. Incrementing the offset register by one actually scrolls by FOUR
+ pixels (and there are FOUR planes on the VGA, what a coincidence)
+
+ 2. You can't draw the image off the screen and then scroll it on
+ because of the way the VGA wraps to the next row every 80 bytes
+ (80 bytes * 4 planes = 320 pixels), if you tried it, you would
+ actually be drawing to the other side of the screen (which is
+ entirely visible)
+
+I'll solve these problems one at a time.
+
+Firstly, to get the VGA to scroll by only one pixel you use the horizontal
+pixel panning (HPP) register. This register resides at
+
+ PORT: 3C0H
+ INDEX: 13h
+
+and in real life, you use it like this
+
+----------------- Pixel Panning ---------------
+IN PORT 3DAH (this clears an internal
+ flip-flop of the VGA)
+OUT 13H TO PORT 3C0H
+OUT value TO PORT 3C0H (where "value" is the
+ number of pixels to offset)
+-----------------------------------------------
+*/
+ inp(0x3DA)
+ outpw(0x3C0, 0x13);
+ outpw(0x3C0, 0x58);
+\r
}\r
\r
/*\r
outpw(0x3D4, 0xAC11); /* vertical retrace end AND wr.prot */\r
outpw(0x3D4, 0xDF12); /* vertical display enable end */\r
outpw(0x3D4, 0xE715); /* start vertical blanking */\r
- outpw(0x3D4, 0x0616); /* end vertical blanking */\r
-\r
+ outpw(0x3D4, 0x0616); /* end vertical blanking */
+
/* Update mode info, so future operations are aware of the\r
resolution */\r
height = 240;\r
// Scrolling = current start + (rows * bytes in a row)\r
setVisibleStart(visStart + (rows * width));\r
}\r
+
+void scrolly(int bong)\r
+{
+ int boing=0;\r
+ if(bong<0)
+ boing=-1;
+ else if(bong>0)
+ boing=1;
+ else break;
+\r
+ for(int i=0;i<TILEWH;i++)
+ vScroll(boing)
+}
+\r
+/*
+\r
+
+To implement smooth horizontal scrolling, you would do the following:
+
+-------------- Horizontal Scrolling ------------
+FOR X = 0 TO 319 DO
+ SET HPP TO ( X MOD 4 )
+ SET VGA OFFSET TO ( X/4 )
+END FOR
+------------------------------------------------
+
+Okay, no problem at all (although I think you might have to fiddle
+around with the HPP a bit to get it right...try different values and
+see what works :).
+
+So, the next problem is with drawing the images off the screen where
+they aren't visible and then scrolling them on!!! As it turns out,
+there's yet ANOTHER register to accomplish this. This one's called the
+offset register (no, not the one I was talking about before, that one
+was actually the "start address" register) and it's at
+
+ PORT: 3D4H/3D5H
+ OFFSET: 13H
+
+and here's how to use it
+
+-------------- Offset Register ---------------
+OUT 13H TO PORT 3D4H
+OUT value TO PORT 3D5H
+----------------------------------------------
+
+Now, what my VGA reference says is that this register holds the number
+of bytes (not pixels) difference between the start address of each row.
+So, in X-mode it normally contains the value 80 (as we remember,
+80 bytes * 4 planes = 320 pixels). This register does not affect the
+VISIBLE width of the display, only the difference between addresses on
+each row.
+
+When we scroll horizontally, we need a little bit of extra working space
+so we can draw off the edge of the screen.
+
+Perhaps a little diagram will clarify it. The following picture is of a
+standard X-mode addressing scheme with the OFFSET register set to 80.
+
+ ROW OFFSET
+ 0 0 ========================
+ 1 80 [ ]
+ 2 160 [ ]
+ .. .. [ VISIBLE ]
+ [ SCREEN ]
+ [ ]
+ [ ]
+ .. .. [ ]
+ 199 15920 ========================
+
+and the next diagram is of a modified addressing scheme with the OFFSET
+register set to 82 (to give us 4 extra pixels on each side of the screen)
+
+ROW OFFSET
+0 0 ------========================------
+1 82 | V [ ] V |
+2 164 | I [ ] I |
+.. .. | N S [ VISIBLE ] N S |
+ | O I [ SCREEN ] O I |
+ | T B [ ] T B |
+ | L [ ] L |
+.. .. | E [ ] E |
+199 16318 ------========================------
+
+Beautiful!!!
+
+As with vertical scrolling, however, you still have the problem of when
+you reach the bottom of page 4...and it's fixed in the same manner.
+
+I haven't actually managed to get infinite horizontal scrolling working,
+but the method I have just stated will give you a horizontal scrolling
+range of over 200 screens!!!! So if you need more (which is extremely
+unlikely), figure it out yourself.
+
+
+------------------
+COMBINED SCROLLING
+------------------
+To do both horizontal and vertical scrolling, all you have to do is combine
+the two methods with a few little extras (it's always the way isn't it).
+
+You have to start off with the original screen on the current page and the
+next page as well. When you scroll horizontally, you have to draw the edge
+that's coming in to the screen to BOTH pages (that means you'll be drawing
+the incoming edge twice, once for each page). You do this so that when you
+have scrolled vertically down through a complete page, you can jump back
+to the first page and it will (hopefully) have an identical copy, and you
+can then continue scrolling again.
+
+I'm sorry about this being so confusing but it's a bit difficult to explain.
+
\r
-/*OFFSET = 0\r
-WHILE NOT FINISHED DO\r
- OFFSET = OFFSET + 80\r
- IF OFFSET >= (200 * 80) THEN OFFSET = 0\r
- DRAW TO ROW 200\r
- SET VGA OFFSET = OFFSET\r
- DRAW TO ROW -1 (was row 0 before scroll)\r
-END WHILE*//*\r
-void scrolly(){\r
- int OFFSET = 0\r
- WHILE NOT FINISHED DO\r
- OFFSET = OFFSET + 80\r
- IF OFFSET >= (240 * 80) THEN OFFSET = 0\r
- RAW TO ROW 240\r
- SET VGA OFFSET = OFFSET\r
- DRAW TO ROW -1 (was row 0 before scroll)\r
- }\r
-}\r
*/\r
//---------------------------------------------------\r
//\r
//\r
// You need a font if you are going to draw text.\r
//\r
-\r
+/*\r
int far *\r
getFont()\r
{\r
string++;\r
}\r
}\r
-\r
+*/\r
/////////////////////////////////////////////////////////////////////////////\r
// //\r
// setvideo() - This function Manages the video modes //\r
if(yy<height){\r
setActivePage(0);\r
setVisiblePage(0);\r
- }
+ }\r
if((height)<yy<(height*2)){\r
setActivePage(1);\r
setVisiblePage(1);\r
- }
+ }\r
if((height*2)<yy<(height*3)){\r
setActivePage(2);\r
setVisiblePage(2);\r
projects / 16.git / commitdiff