/**************************************************************************** * * Hello VBE! * * Copyright (C) 1994 SciTech Software * All rights reserved. * * Language: ANSI C * Environment: IBM PC (MSDOS) 16 bit Real Mode * Author: Kendall Bennett, SciTech Software * * Description: Simple 'Hello World' program to initialise a user * specified 256 color graphics mode, and display a simple * moire pattern. Tested with VBE 1.2 and above. * * This code does not have any hard-coded VBE mode numbers, * but will use the VBE 2.0 aware method of searching for * available video modes, so will work with any new extended * video modes defined by a particular OEM VBE 2.0 version. * * For brevity we dont check for failure conditions returned * by the VBE (but we shouldn't get any). * * $Id: hellovbe.c 1.1 1994/08/22 12:27:00 kjb release $ * ****************************************************************************/ #include #include #include #include /* Uncomment the following to enable direct bank switching, rather than * using the Int 10h software interrupt (requires Borland C++ inline * assembler). */ /* #define DIRECT_BANKING */ /*---------------------- Macro and type definitions -----------------------*/ /* SuperVGA information block */ typedef struct { char VESASignature[4]; /* 'VESA' 4 byte signature */ short VESAVersion; /* VBE version number */ char _far *OEMStringPtr; /* Pointer to OEM string */ long Capabilities; /* Capabilities of video card */ short _far *VideoModePtr; /* Pointer to supported modes */ short TotalMemory; /* Number of 64kb memory blocks */ char reserved[236]; /* Pad to 256 byte block size */ } VgaInfoBlock; /* SuperVGA mode information block */ typedef struct { short ModeAttributes; /* Mode attributes */ char WinAAttributes; /* Window A attributes */ char WinBAttributes; /* Window B attributes */ short WinGranularity; /* Window granularity in k */ short WinSize; /* Window size in k */ short WinASegment; /* Window A segment */ short WinBSegment; /* Window B segment */ void _far *WinFuncPtr; /* Pointer to window function */ short BytesPerScanLine; /* Bytes per scanline */ short XResolution; /* Horizontal resolution */ short YResolution; /* Vertical resolution */ char XCharSize; /* Character cell width */ char YCharSize; /* Character cell height */ char NumberOfPlanes; /* Number of memory planes */ char BitsPerPixel; /* Bits per pixel */ char NumberOfBanks; /* Number of CGA style banks */ char MemoryModel; /* Memory model type */ char BankSize; /* Size of CGA style banks */ char NumberOfImagePages; /* Number of images pages */ char res1; /* Reserved */ char RedMaskSize; /* Size of direct color red mask */ char RedFieldPosition; /* Bit posn of lsb of red mask */ char GreenMaskSize; /* Size of direct color green mask */ char GreenFieldPosition; /* Bit posn of lsb of green mask */ char BlueMaskSize; /* Size of direct color blue mask */ char BlueFieldPosition; /* Bit posn of lsb of blue mask */ char RsvdMaskSize; /* Size of direct color res mask */ char RsvdFieldPosition; /* Bit posn of lsb of res mask */ char DirectColorModeInfo; /* Direct color mode attributes */ char res2[216]; /* Pad to 256 byte block size */ } ModeInfoBlock; typedef enum { memPL = 3, /* Planar memory model */ memPK = 4, /* Packed pixel memory model */ memRGB = 6, /* Direct color RGB memory model */ memYUV = 7, /* Direct color YUV memory model */ } memModels; /*--------------------------- Global Variables ----------------------------*/ int xres,yres; /* Resolution of video mode used */ int bytesperline; /* Logical CRT scanline length */ int curBank; /* Current read/write bank */ int bankShift; /* Bank granularity adjust factor */ int oldMode; /* Old video mode number */ void _far (*bankSwitch)(void); /* Direct bank switching function */ char _far *screenPtr; /* Pointer to start of video memory */ /*------------------------ VBE Interface Functions ------------------------*/ /* Get SuperVGA information, returning true if VBE found */ int getVgaInfo(VgaInfoBlock *vgaInfo) { union REGS regs; struct SREGS sregs; regs.x.ax = 0x4F00; regs.x.di = FP_OFF(vgaInfo); sregs.es = FP_SEG(vgaInfo); int86x(0x10, ®s, ®s, &sregs); return (regs.x.ax == 0x4F); } /* Get video mode information given a VBE mode number. We return 0 if * if the mode is not available, or if it is not a 256 color packed * pixel mode. */ int getModeInfo(int mode, ModeInfoBlock *modeInfo) { union REGS regs; struct SREGS sregs; if (mode < 0x100) return 0; /* Ignore non-VBE modes */ regs.x.ax = 0x4F01; regs.x.cx = mode; regs.x.di = FP_OFF(modeInfo); sregs.es = FP_SEG(modeInfo); int86x(0x10, ®s, ®s, &sregs); if (regs.x.ax != 0x4F) return 0; if ((modeInfo->ModeAttributes & 0x1) && modeInfo->MemoryModel == memPK && modeInfo->BitsPerPixel == 8 && modeInfo->NumberOfPlanes == 1) return 1; return 0; } /* Set a VBE video mode */ void setVBEMode(int mode) { union REGS regs; regs.x.ax = 0x4F02; regs.x.bx = mode; int86(0x10,®s,®s); } /* Return the current VBE video mode */ int getVBEMode(void) { union REGS regs; regs.x.ax = 0x4F03; int86(0x10,®s,®s); return regs.x.bx; } /* Set new read/write bank. We must set both Window A and Window B, as * many VBE's have these set as separately available read and write * windows. We also use a simple (but very effective) optimisation of * checking if the requested bank is currently active. */ void setBank(int bank) { union REGS regs; if (bank == curBank) return; /* Bank is already active */ curBank = bank; /* Save current bank number */ bank <<= bankShift; /* Adjust to window granularity */ #ifdef DIRECT_BANKING asm { mov bx,0; mov dx,bank; } bankSwitch(); asm { mov bx,1; mov dx,bank; } bankSwitch(); #else regs.x.ax = 0x4F05; regs.x.bx = 0; regs.x.dx = bank; int86(0x10, ®s, ®s); regs.x.ax = 0x4F05; regs.x.bx = 1; regs.x.dx = bank; int86(0x10, ®s, ®s); #endif } /*-------------------------- Application Functions ------------------------*/ /* Plot a pixel at location (x,y) in specified color (8 bit modes only) */ void putPixel(int x,int y,int color) { long addr = (long)y * bytesperline + x; setBank(addr >> 16); *(screenPtr + (addr & 0xFFFF)) = color; } /* Draw a line from (x1,y1) to (x2,y2) in specified color */ void line(int x1,int y1,int x2,int y2,int color) { int d; /* Decision variable */ int dx,dy; /* Dx and Dy values for the line */ int Eincr,NEincr; /* Decision variable increments */ int yincr; /* Increment for y values */ int t; /* Counters etc. */ #define ABS(a) ((a) >= 0 ? (a) : -(a)) dx = ABS(x2 - x1); dy = ABS(y2 - y1); if (dy <= dx) { /* We have a line with a slope between -1 and 1 * * Ensure that we are always scan converting the line from left to * right to ensure that we produce the same line from P1 to P0 as the * line from P0 to P1. */ if (x2 < x1) { t = x2; x2 = x1; x1 = t; /* Swap X coordinates */ t = y2; y2 = y1; y1 = t; /* Swap Y coordinates */ } if (y2 > y1) yincr = 1; else yincr = -1; d = 2*dy - dx; /* Initial decision variable value */ Eincr = 2*dy; /* Increment to move to E pixel */ NEincr = 2*(dy - dx); /* Increment to move to NE pixel */ putPixel(x1,y1,color); /* Draw the first point at (x1,y1) */ /* Incrementally determine the positions of the remaining pixels */ for (x1++; x1 <= x2; x1++) { if (d < 0) d += Eincr; /* Choose the Eastern Pixel */ else { d += NEincr; /* Choose the North Eastern Pixel */ y1 += yincr; /* (or SE pixel for dx/dy < 0!) */ } putPixel(x1,y1,color); /* Draw the point */ } } else { /* We have a line with a slope between -1 and 1 (ie: includes * vertical lines). We must swap our x and y coordinates for this. * * Ensure that we are always scan converting the line from left to * right to ensure that we produce the same line from P1 to P0 as the * line from P0 to P1. */ if (y2 < y1) { t = x2; x2 = x1; x1 = t; /* Swap X coordinates */ t = y2; y2 = y1; y1 = t; /* Swap Y coordinates */ } if (x2 > x1) yincr = 1; else yincr = -1; d = 2*dx - dy; /* Initial decision variable value */ Eincr = 2*dx; /* Increment to move to E pixel */ NEincr = 2*(dx - dy); /* Increment to move to NE pixel */ putPixel(x1,y1,color); /* Draw the first point at (x1,y1) */ /* Incrementally determine the positions of the remaining pixels */ for (y1++; y1 <= y2; y1++) { if (d < 0) d += Eincr; /* Choose the Eastern Pixel */ else { d += NEincr; /* Choose the North Eastern Pixel */ x1 += yincr; /* (or SE pixel for dx/dy < 0!) */ } putPixel(x1,y1,color); /* Draw the point */ } } } /* Draw a simple moire pattern of lines on the display */ void drawMoire(void) { int i; for (i = 0; i < xres; i += 5) { line(xres/2,yres/2,i,0,i % 0xFF); line(xres/2,yres/2,i,yres,(i+1) % 0xFF); } for (i = 0; i < yres; i += 5) { line(xres/2,yres/2,0,i,(i+2) % 0xFF); line(xres/2,yres/2,xres,i,(i+3) % 0xFF); } line(0,0,xres-1,0,15); line(0,0,0,yres-1,15); line(xres-1,0,xres-1,yres-1,15); line(0,yres-1,xres-1,yres-1,15); } /* Display a list of available resolutions. Be careful with calls to * function 00h to get SuperVGA mode information. Many VBE's build the * list of video modes directly in this information block, so if you * are using a common buffer (which we aren't here, but in protected * mode you will), then you will need to make a local copy of this list * of available modes. */ void availableModes(void) { short *p; VgaInfoBlock vgaInfo; ModeInfoBlock modeInfo; if (!getVgaInfo(&vgaInfo)) { printf("No VESA VBE detected\n"); exit(1); } printf("VESA VBE Version %d.%d detected (%s)\n\n", vgaInfo.VESAVersion >> 8, vgaInfo.VESAVersion & 0xF, vgaInfo.OEMStringPtr); printf("Available 256 color video modes:\n"); for (p = vgaInfo.VideoModePtr; *p != -1; p++) { if (getModeInfo(*p, &modeInfo)) { printf(" %4d x %4d %d bits per pixel\n", modeInfo.XResolution, modeInfo.YResolution, modeInfo.BitsPerPixel); } } printf("\nUsage: hellovbe \n"); exit(1); } /* Initialise the specified video mode. Notice how we determine a shift * factor for adjusting the Window granularity for bank switching. This * is much faster than doing it with a multiply (especially with direct * banking enabled). */ void initGraphics(int x,int y) { short *p; VgaInfoBlock vgaInfo; ModeInfoBlock modeInfo; if (!getVgaInfo(&vgaInfo)) { printf("No VESA VBE detected\n"); exit(1); } for (p = vgaInfo.VideoModePtr; *p != -1; p++) { if (getModeInfo(*p, &modeInfo) && modeInfo.XResolution == x && modeInfo.YResolution == y) { xres = x; yres = y; bytesperline = modeInfo.BytesPerScanLine; bankShift = 0; while ((64 >> bankShift) != modeInfo.WinGranularity) bankShift++; bankSwitch = modeInfo.WinFuncPtr; curBank = -1; screenPtr = MK_FP(0xA000,0); oldMode = getVBEMode(); setVBEMode(*p); return; } } printf("Valid video mode not found\n"); exit(1); } /* Main routine. Expects the x & y resolution of the desired video mode * to be passed on the command line. Will print out a list of available * video modes if no command line is present. */ void main(int argc,char *argv[]) { int x,y; if (argc != 3) availableModes(); /* Display list of available modes */ x = atoi(argv[1]); /* Get requested resolution */ y = atoi(argv[2]); initGraphics(x,y); /* Start requested video mode */ drawMoire(); /* Draw a moire pattern */ getch(); /* Wait for keypress */ setVBEMode(oldMode); /* Restore previous mode */ }