cool-bun-demo/screen.c

#include "screen.h"
#include "types.h"

#include <clib/exec_protos.h>
#include <exec/memory.h>

/**
 * Includes double buffer space
 */
#define TOTAL_SCREEN_SETUP_SIZE(s) ((s->width / 8) * s->height * s->bitplanes * 2)

/**
 * Stores internal allocation details in screenSetup.
 * Sets current
 */
void allocateDoubleBufferedScreenMemory(
  struct ScreenDefinition *screenDefinition,
  struct ActiveScreenBufferDetails *activeScreenBufferDetails,
  uint16_t width,
  uint16_t height,
  uint8_t bitplanes
) {
  unsigned char *memory;

  screenDefinition->width = width;
  screenDefinition->height = height;
  screenDefinition->bitplanes = bitplanes;

  memory = (unsigned char *)AllocMem(
    TOTAL_SCREEN_SETUP_SIZE(screenDefinition),
    MEMF_CLEAR | MEMF_CHIP
  );

  screenDefinition->memoryStart = memory;
  screenDefinition->byteWidth = width / 8;

  // memory is not interleaved
  screenDefinition->nextBitplaneAdvance = screenDefinition->byteWidth * height;
  screenDefinition->nextBufferAdvance = screenDefinition->nextBitplaneAdvance * bitplanes;

  setActiveScreenBuffer(screenDefinition, activeScreenBufferDetails, 0);
}

void teardownScreen(
  struct ScreenDefinition *screenDefinition
) {
  FreeMem(
    screenDefinition->memoryStart,
    TOTAL_SCREEN_SETUP_SIZE(screenDefinition)
  );
}

void setActiveScreenBuffer(
  struct ScreenDefinition *screenDefinition,
  struct ActiveScreenBufferDetails *currentScreen,
  short int buffer
) {
  int plane;
  currentScreen->currentBuffer = buffer;

  for (plane = 0; plane < screenDefinition->bitplanes; ++plane) {
    currentScreen->planes[plane] = screenDefinition->memoryStart +
      buffer * screenDefinition->nextBufferAdvance +
      plane * screenDefinition->nextBitplaneAdvance;
  }
}

void swapCurrentScreenBuffer(
  struct ScreenDefinition *screenDefinition,
  struct ActiveScreenBufferDetails *currentScreen
) {
  setActiveScreenBuffer(
    screenDefinition,
    currentScreen,
    1 - currentScreen->currentBuffer
  );
}