room_layout.cc

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#include "room_layout.h"
 
#include "absl/strings/str_format.h"
#include "rom/snes.h"
#include "util/log.h"
#include "zelda3/dungeon/dungeon_rom_addresses.h"
#include "zelda3/dungeon/object_drawer.h"
 
namespace yaze::zelda3 {
 
namespace {
 
// Returns true if the object ID is a pit or layer mask that should be on BG2.
// These objects create transparency holes in BG1 to show BG2 content through.
// Based on ALTTP object IDs and draw routine analysis.
bool IsPitOrMaskObject(int16_t id) {
  // Pit and layer-2 masks that rely on BG1 transparency to reveal BG2.
  //
  // Source of truth for names: RoomObjectNames in room_object.h.
  // USDASM: These are "layer 2 mask" objects that operate by clearing BG1.
  if (id == 0xA4)
    return true;  // Pit
  if (id >= 0xA5 && id <= 0xAC)
    return true;  // Diagonal layer 2 masks
  if (id == 0xC2 || id == 0xC3)
    return true;  // Layer 2 pit masks (large/medium)
  if (id == 0xC6 || id == 0xD7 || id == 0xD9)
    return true;  // Layer 2 masks (large/medium/swim)
  if (id == 0xFE6)
    return true;  // Type 3 pit
  if (id == 0xFF3)
    return true;  // Type 3 layer 2 mask (full)
 
  return false;
}
 
}  // namespace
 
absl::StatusOr<int> RoomLayout::GetLayoutAddress(int layout_id) const {
  if (!rom_ || !rom_->is_loaded()) {
    return absl::FailedPreconditionError("ROM not loaded");
  }
 
  if (layout_id < 0 ||
      layout_id >= static_cast<int>(kRoomLayoutPointers.size())) {
    return absl::InvalidArgumentError(
        absl::StrFormat("Invalid layout id %d", layout_id));
  }
 
  uint32_t snes_addr = kRoomLayoutPointers[layout_id];
  int pc_addr = SnesToPc(static_cast<int>(snes_addr));
  if (pc_addr < 0 || pc_addr >= static_cast<int>(rom_->size())) {
    return absl::OutOfRangeError(
        absl::StrFormat("Layout pointer %d out of range", layout_id));
  }
  return pc_addr;
}
 
absl::Status RoomLayout::LoadLayout(int layout_id) {
  objects_.clear();
 
  auto addr_result = GetLayoutAddress(layout_id);
  if (!addr_result.ok()) {
    return addr_result.status();
  }
 
  int pos = addr_result.value();
  const auto& rom_data = rom_->data();
  int layer = 0;
 
  LOG_DEBUG("RoomLayout", "Loading layout %d from PC address 0x%05X", layout_id,
            pos);
 
  int obj_index = 0;
  while (pos + 2 < static_cast<int>(rom_->size())) {
    uint8_t b1 = rom_data[pos];
    uint8_t b2 = rom_data[pos + 1];
 
    if (b1 == 0xFF && b2 == 0xFF) {
      // $FF $FF is the END terminator for this layout
      LOG_DEBUG("RoomLayout",
                "Layout %d terminated at pos=0x%05X after %d objects",
                layout_id, pos, obj_index);
      break;
    }
 
    if (pos + 2 >= static_cast<int>(rom_->size())) {
      break;
    }
 
    uint8_t b3 = rom_data[pos + 2];
    pos += 3;
 
    RoomObject obj = RoomObject::DecodeObjectFromBytes(
        b1, b2, b3, static_cast<uint8_t>(layer));
 
    // Pit/mask objects should be on BG2 layer to create transparency holes.
    // This allows them to show through BG1 content (walls, floor).
    if (IsPitOrMaskObject(obj.id_)) {
      obj.layer_ = RoomObject::LayerType::BG2;
      LOG_DEBUG("RoomLayout", "Pit/mask object 0x%03X assigned to BG2 layer",
                obj.id_);
    }
 
    obj.SetRom(rom_);
    obj.EnsureTilesLoaded();
    objects_.push_back(obj);
 
    LOG_DEBUG("RoomLayout",
              "Layout %d obj[%d]: bytes=[%02X,%02X,%02X] -> id=0x%03X x=%d "
              "y=%d size=%d tiles=%zu",
              layout_id, obj_index, b1, b2, b3, obj.id_, obj.x_, obj.y_,
              obj.size_, obj.tiles().size());
    obj_index++;
  }
 
  LOG_DEBUG("RoomLayout", "Layout %d loaded with %zu objects", layout_id,
            objects_.size());
 
  return absl::OkStatus();
}
 
absl::Status RoomLayout::Draw(int room_id, const uint8_t* gfx_data,
                              gfx::BackgroundBuffer& bg1,
                              gfx::BackgroundBuffer& bg2,
                              const gfx::PaletteGroup& palette_group,
                              DungeonState* state) const {
  if (!rom_ || !rom_->is_loaded()) {
    return absl::FailedPreconditionError("ROM not loaded");
  }
 
  if (objects_.empty()) {
    return absl::OkStatus();
  }
 
  ObjectDrawer drawer(rom_, room_id, gfx_data);
  // Pass bg1 as layout_bg1 so BG2 objects (pits/masks) will mark the
  // corresponding area in BG1 as transparent via MarkBG1Transparent().
  // This creates "holes" in BG1 that allow BG2 content to show through.
  return drawer.DrawObjectList(objects_, bg1, bg2, palette_group, state, &bg1);
}
 
}  // namespace yaze::zelda3