amiga-agnus-copperbars/intro.c

/**
 * Intro copperbars demo
 * Copyright 2023 John Bintz
 * Licensed under the MIT License
 * https://theindustriousrabbit.com
 */
#include <clib/exec_protos.h>
#include <clib/dos_protos.h>
#include <clib/alib_protos.h>
#include <clib/intuition_protos.h>
#include <clib/graphics_protos.h>
#include <clib/timer_protos.h>

#include <exec/memory.h>
#include <exec/io.h>

#include <devices/timer.h>

#include <graphics/GfxBase.h>

#include <hardware/cia.h>
#include <hardware/dmabits.h>

#include <stdio.h>

extern struct GfxBase *GfxBase;
extern struct Custom far custom;
extern struct CIA far ciaa, ciab;

// this is faster than
// custom.vhposr + (custom.vposr << 16)
static volatile ULONG *custom_vposr = (volatile ULONG *)0xdff004;

struct Library *TimerBase;
struct MsgPort *TimerMP;
struct timerequest *TimerIO;

#define offsetof(s, m) &((struct s *)0)->m
#define BITPLANE_SIZE (320/8)*256
#define BAR_HEIGHT (50)

#define BPLCON0_COLOR (0x200)
#define BPLCON0_BPU_1 (0x1000)

int main(void) {
  struct View *OldView = ((struct GfxBase *)GfxBase)->ActiView;
  ULONG OldCopper = (ULONG)((struct GfxBase *)GfxBase)->copinit;
  ULONG OldDMACON, OldINTENA, OldINTREQ, OldADKCON;

  unsigned short redY = 0, greenY = 10, blueY = 20;
  unsigned short redSpeed = 1, greenSpeed = 2, blueSpeed = 3;
  unsigned short currentY = 0, currentColor, newColor;
  long randomSeed = 0;

  struct timeval currentSystemTime;

  void *copperlist;
  UWORD *copperlist_ptr;
  APTR *bitplane;

  // how much can we avoid hard coding into our code?
  UWORD custom_bplpt = (UWORD)offsetof(Custom, bplpt);
  UWORD custom_color = (UWORD)offsetof(Custom, color);

  // get a random seed by using the amount of microseconds the machine's
  // been on, modulo 1000000.
  //
  // if for some weird reaon timer.device is not available,
  // we can continue.
  if (TimerMP = CreatePort(NULL, NULL)) {
    if (TimerIO = (struct timerequest *)CreateExtIO(TimerMP, sizeof(struct timerequest))) {
       if (!(OpenDevice(TIMERNAME, UNIT_MICROHZ, (struct IORequest *)TimerIO, 0))) {
         TimerBase = (struct Library *)TimerIO->tr_node.io_Device;

         GetSysTime(&currentSystemTime);

         randomSeed = currentSystemTime.tv_micro;

         CloseDevice((struct IORequest *)TimerIO);
       }

       DeleteExtIO((struct IORequest *)TimerIO);
    }

    DeletePort(TimerMP);
  }

  LoadView(NULL);
  WaitTOF();
  WaitTOF();
  OwnBlitter();
  WaitBlit();
  Forbid();

  OldDMACON = custom.dmaconr | 0x8000;
  OldINTENA = custom.intenar | 0x8000;
  OldINTREQ = custom.intreqr | 0x8000;
  OldADKCON = custom.adkconr | 0x8000;

  // disable interrupts
  custom.intena = 0xc000;
  custom.intena = 0x3fff;

  // set up dma
  // weirdly i need DMAF_AUDIO enabled in order for FastRand() to work...
  custom.dmacon = DMAF_SETCLR | DMAF_COPPER | DMAF_RASTER | DMAF_AUDIO;
  custom.dmacon = DMAF_DISK | DMAF_SPRITE | DMAF_BLITTER;

  copperlist = AllocMem(100, MEMF_CHIP | MEMF_CLEAR);
  bitplane   = (APTR *)AllocMem(BITPLANE_SIZE, MEMF_PUBLIC|MEMF_CHIP|MEMF_CLEAR);

  // default copperlist has just STOP
  ((ULONG *)copperlist)[0] = 0xfffffffe;

  // set up 1 bitplane pal display
  custom.bplcon0 = BPLCON0_COLOR | BPLCON0_BPU_1;
  custom.bplcon1 = 0;
  custom.bpl1mod = 0;
  custom.diwstrt = 0x2c21;
  custom.diwstop = 0x2cc1;
  custom.ddfstrt = 0x0038;
  custom.ddfstop = 0x00d0;

  // substitute our minimal copperlist now
  custom.cop1lc = (ULONG)copperlist;

  // neither HID button 0 is down
  while ((ciaa.ciapra >> 6) == 3) {
    // rebuild copperlist
    copperlist_ptr = (UWORD *)copperlist;

    // bpl1pth
    *(copperlist_ptr++) = custom_bplpt;
    *(copperlist_ptr++) = ((ULONG)bitplane >> 16) & 0xffff;
    // bpl1ptl
    *(copperlist_ptr++) = custom_bplpt + 2;
    *(copperlist_ptr++) = (ULONG)bitplane & 0xffff;

    *(copperlist_ptr++) = custom_color;
    *(copperlist_ptr++) = 0x0f00;

    // impossible color
    currentColor = 0xFFFF;

    for (currentY = 0; currentY < 300; currentY++) {
      newColor = 0x000;
      if (currentY >= redY && currentY < (redY + BAR_HEIGHT)) {
        newColor = newColor | 0xf00;
      }

      if (currentY >= greenY && currentY < (greenY + BAR_HEIGHT)) {
        newColor = newColor | 0x0f0;
      }

      if (currentY >= blueY && currentY < (blueY + BAR_HEIGHT)) {
        newColor = newColor | 0x00f;
      }

      if (newColor != currentColor) {
        //printf("Color change at %d: %x to %x\n", currentY, currentColor, newColor);
        *(copperlist_ptr++) = ((currentY & 0xff) << 8) | 0x26 | 0x1;
        *(copperlist_ptr++) = 0xfffe;

        *(copperlist_ptr++) = custom_color;
        *(copperlist_ptr++) = newColor;

        currentColor = newColor;
      }

      // PAL workaround
      if (currentY == 255) {
        *(copperlist_ptr++) = 0xffdf;
        *(copperlist_ptr++) = 0xfffe;
      }
    }

    // end the copperlist
    *(copperlist_ptr++) = 0xffff;
    *(copperlist_ptr++) = 0xfffe;

    // advance the bars and loop them around, changing
    // speed randomly on every loop
    redY += redSpeed;
    if (redY > 300) {
      redSpeed = (FastRand(randomSeed) + 1) % 5;
      randomSeed += redSpeed;
      redY %= 300;
    }
    greenY += greenSpeed;

    if (greenY > 300) {
      greenSpeed = (FastRand(randomSeed) + 1) % 5;
      randomSeed += greenSpeed;
      greenY %= 300;
    }

    blueY += blueSpeed;

    if (blueY > 300) {
      blueSpeed = (FastRand(randomSeed) + 1) % 5;
      randomSeed += blueSpeed;
      blueY %= 300;
    }

    randomSeed %= 0xffffff;

    // vbl wait
    // this will not work on NTSC!
    while ((*custom_vposr & 0x1FF00) != (300 << 8)) {}
  }

  FreeMem(bitplane, BITPLANE_SIZE);
  FreeMem(copperlist, 100);

  custom.dmacon = 0x7FFF;
  custom.dmacon = OldDMACON;
  custom.intena = 0x7FFF;
  custom.intena = OldINTENA;
  custom.intreq = 0x7FFF;
  custom.intreq = OldINTREQ;
  custom.adkcon = 0x7FFF;
  custom.adkcon = OldADKCON;

  custom.cop1lc = OldCopper;
  LoadView(OldView);
  WaitTOF();
  WaitTOF();
  WaitBlit();
  DisownBlitter();
  Permit();
}