WIP moving difficulty selection to engine

Signed-off-by: Hans Kokx <hans.d.kokx@gmail.com>

packages/wolf_3d_dart/lib/wolf_3d_menu.dart

@@ -0,0 +1,167 @@
+/// Shared menu helpers for Wolf3D hosts.
+library;
+
+import 'package:wolf_3d_dart/wolf_3d_data_types.dart';
+
+/// Known VGA picture indexes used by the original Wolf3D control-panel menus.
+///
+/// Values below are picture-table indexes (not raw chunk ids).
+/// For example, `C_CONTROLPIC` is chunk 26 in `GFXV_WL6.H`, so its picture
+/// index is `26 - STARTPICS(3) = 23`.
+abstract class WolfMenuPic {
+  static const int hBj = 0; // H_BJPIC
+  static const int hTopWindow = 3; // H_TOPWINDOWPIC
+  static const int cOptions = 7; // C_OPTIONSPIC
+  static const int cCursor1 = 8; // C_CURSOR1PIC
+  static const int cCursor2 = 9; // C_CURSOR2PIC
+  static const int cNotSelected = 10; // C_NOTSELECTEDPIC
+  static const int cSelected = 11; // C_SELECTEDPIC
+  static const int cBabyMode = 16; // C_BABYMODEPIC
+  static const int cEasy = 17; // C_EASYPIC
+  static const int cNormal = 18; // C_NORMALPIC
+  static const int cHard = 19; // C_HARDPIC
+  static const int cControl = 23; // C_CONTROLPIC
+  static const int cEpisode1 = 27; // C_EPISODE1PIC
+  static const int cEpisode2 = 28; // C_EPISODE2PIC
+  static const int cEpisode3 = 29; // C_EPISODE3PIC
+  static const int cEpisode4 = 30; // C_EPISODE4PIC
+  static const int cEpisode5 = 31; // C_EPISODE5PIC
+  static const int cEpisode6 = 32; // C_EPISODE6PIC
+  static const int statusBar = 83; // STATUSBARPIC
+  static const int title = 84; // TITLEPIC
+  static const int pg13 = 85; // PG13PIC
+  static const int credits = 86; // CREDITSPIC
+  static const int highScores = 87; // HIGHSCORESPIC
+
+  static const List<int> episodePics = [
+    cEpisode1,
+    cEpisode2,
+    cEpisode3,
+    cEpisode4,
+    cEpisode5,
+    cEpisode6,
+  ];
+}
+
+/// Structured accessors for classic Wolf3D menu art.
+class WolfClassicMenuArt {
+  final WolfensteinData data;
+
+  WolfClassicMenuArt(this.data);
+
+  int? _resolvedIndexOffset;
+
+  VgaImage? get controlBackground {
+    final preferred = mappedPic(WolfMenuPic.cControl);
+    if (_looksLikeMenuBackdrop(preferred)) {
+      return preferred;
+    }
+
+    // Older data layouts may shift/control-panel art around nearby indices.
+    for (int delta = -4; delta <= 4; delta++) {
+      final candidate = mappedPic(WolfMenuPic.cControl + delta);
+      if (_looksLikeMenuBackdrop(candidate)) {
+        return candidate;
+      }
+    }
+
+    return preferred;
+  }
+
+  VgaImage? get title => mappedPic(WolfMenuPic.title);
+
+  VgaImage? get heading => mappedPic(WolfMenuPic.hTopWindow);
+
+  VgaImage? get selectedMarker => mappedPic(WolfMenuPic.cSelected);
+
+  VgaImage? get unselectedMarker => mappedPic(WolfMenuPic.cNotSelected);
+
+  VgaImage? get optionsLabel => mappedPic(WolfMenuPic.cOptions);
+
+  VgaImage? get credits => mappedPic(WolfMenuPic.credits);
+
+  VgaImage? episodeOption(int episodeIndex) {
+    if (episodeIndex < 0 || episodeIndex >= WolfMenuPic.episodePics.length) {
+      return null;
+    }
+    return mappedPic(WolfMenuPic.episodePics[episodeIndex]);
+  }
+
+  VgaImage? difficultyOption(Difficulty difficulty) {
+    switch (difficulty) {
+      case Difficulty.baby:
+        return mappedPic(WolfMenuPic.cBabyMode);
+      case Difficulty.easy:
+        return mappedPic(WolfMenuPic.cEasy);
+      case Difficulty.medium:
+        return mappedPic(WolfMenuPic.cNormal);
+      case Difficulty.hard:
+        return mappedPic(WolfMenuPic.cHard);
+    }
+  }
+
+  /// Returns [index] after applying a detected version/layout offset.
+  VgaImage? mappedPic(int index) {
+    return pic(index + _indexOffset);
+  }
+
+  int get _indexOffset {
+    if (_resolvedIndexOffset != null) {
+      return _resolvedIndexOffset!;
+    }
+
+    // Retail and shareware generally place STATUSBAR/TITLE/PG13/CREDITS as a
+    // contiguous block. If files are from a different release, infer a shift.
+    for (int i = 0; i < data.vgaImages.length - 3; i++) {
+      final status = data.vgaImages[i];
+      if (!_looksLikeStatusBar(status)) {
+        continue;
+      }
+
+      final title = data.vgaImages[i + 1];
+      final pg13 = data.vgaImages[i + 2];
+      final credits = data.vgaImages[i + 3];
+      if (_looksLikeFullScreen(title) &&
+          _looksLikeFullScreen(pg13) &&
+          _looksLikeFullScreen(credits)) {
+        _resolvedIndexOffset = i - WolfMenuPic.statusBar;
+        return _resolvedIndexOffset!;
+      }
+    }
+
+    _resolvedIndexOffset = 0;
+    return 0;
+  }
+
+  bool _looksLikeStatusBar(VgaImage image) {
+    return image.width >= 280 && image.height >= 24 && image.height <= 64;
+  }
+
+  bool _looksLikeFullScreen(VgaImage image) {
+    return image.width >= 280 && image.height >= 140;
+  }
+
+  bool _looksLikeMenuBackdrop(VgaImage? image) {
+    if (image == null) {
+      return false;
+    }
+    return image.width >= 180 && image.height >= 100;
+  }
+
+  VgaImage? pic(int index) {
+    if (index < 0 || index >= data.vgaImages.length) {
+      return null;
+    }
+    final image = data.vgaImages[index];
+
+    // Ignore known gameplay HUD art in menu composition.
+    if (index == WolfMenuPic.statusBar + _indexOffset) {
+      return null;
+    }
+    if (image.width <= 0 || image.height <= 0) {
+      return null;
+    }
+
+    return image;
+  }
+}