refactor: rename GameStats → DDDisplayBase, display_gfx → display

GameStats is actually the base class of the display hierarchy —
DisplayGfx__Constructor calls it as its base ctor. Rename to
DDDisplayBase to reflect the inheritance relationship.

Rename GameSession.display_gfx → display since it holds a polymorphic
base class pointer (DisplayGfx in normal, DDDisplayBase in headless).

Update Ghidra: DDDisplayBase__Constructor, DDDisplayBase__Destructor,
DDDisplayBase__Vtable (0x6645F8), DDDisplayBase__HeadlessVtable (0x66A0F8).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/openwa-core/src/address.rs

@@ -45,8 +45,9 @@ pub mod va {
     pub const DDKEYBOARD_VTABLE: u32 = 0x0066_AEC8;
     /// Palette vtable (0x28-byte palette object)
     pub const PALETTE_VTABLE_MAYBE: u32 = 0x0066_A2E4;
-    /// GameStats vtable — overlaid after GameStats__Constructor in headless mode
-    pub const GAMESTATS_VTABLE: u32 = 0x0066_A0F8;
+    /// DDDisplayBase headless vtable — overlaid after DDDisplayBase__Constructor
+    /// in headless mode, filling in stub slots for headless operation.
+    pub const DD_DISPLAY_BASE_HEADLESS_VTABLE: u32 = 0x0066_A0F8;
     /// Input controller vtable (0x1800-byte object, set inline before FUN_0058C0D0)
     pub const INPUT_CTRL_VTABLE: u32 = 0x0066_B3FC;
     /// TaskStateMachine vtable
@@ -276,9 +277,9 @@ pub mod va {
     pub const DDISPLAY_INIT: u32 = 0x0056_9D00;
     /// Alias kept for callers that use the old name.
     pub const CONSTRUCT_DD_DISPLAY: u32 = DDISPLAY_INIT;
-    /// GameStats__Constructor_Maybe — stdcall(this) → GameStats*.
-    /// Constructs the 0x3560-byte GameStats stub used in headless mode.
-    pub const GAMESTATS_CTOR: u32 = 0x0052_2DB0;
+    /// DDDisplayBase__Constructor — stdcall(this) → DDDisplayBase*.
+    /// Constructs the 0x3560-byte base display object (used standalone in headless mode).
+    pub const DD_DISPLAY_BASE_CTOR: u32 = 0x0052_2DB0;
     /// Streaming audio constructor — stdcall(IDirectSound*, path_config_ptr) → *mut u8.
     /// Constructs 0x354-byte streaming audio object (only if GameInfo+0xDAA4 != 0).
     pub const STREAMING_AUDIO_CTOR: u32 = 0x0058_BC10;

crates/openwa-core/src/dd_display_base.rs

@@ -0,0 +1,44 @@
+/// DDDisplayBase — base class of the display subsystem hierarchy.
+///
+/// Constructor: DDDisplayBase__Constructor (0x522DB0), stdcall(this) → DDDisplayBase*.
+/// Vtable (primary): 0x6645F8 (set by constructor).
+/// Vtable (headless overlay): 0x66A0F8 (fills in stub slots for headless mode).
+/// Size: 0x3560 bytes.
+///
+/// Inheritance:
+/// ```text
+/// DDDisplayBase (this)       ← vtable 0x6645F8 / 0x66A0F8
+///   └─ DisplayGfx (derived)  ← vtable 0x66A218
+/// ```
+///
+/// In headless mode (`GameInfo.headless_mode != 0`), only the base is constructed
+/// with the headless vtable overlay. In normal mode, `DisplayGfx` (derived) is
+/// constructed instead. The session's `display` field holds a polymorphic pointer
+/// to whichever variant.
+#[repr(C)]
+pub struct DDDisplayBase {
+    pub vtable: *mut u8,
+    pub _unknown_004: [u8; 0x3560 - 4],
+}
+
+const _: () = assert!(core::mem::size_of::<DDDisplayBase>() == 0x3560);
+
+impl DDDisplayBase {
+    /// Allocate and construct a DDDisplayBase for headless mode.
+    ///
+    /// Calls WA's native constructor, then overlays the headless vtable.
+    ///
+    /// # Safety
+    /// Must be called from within the WA.exe process.
+    pub unsafe fn construct() -> *mut Self {
+        use crate::address::va;
+        use crate::rebase::rb;
+        use crate::wa_alloc::WABox;
+        let this = WABox::<Self>::alloc(0x3560, 0x3560).leak();
+        let ctor: unsafe extern "stdcall" fn(*mut Self) -> *mut Self =
+            core::mem::transmute(rb(va::DD_DISPLAY_BASE_CTOR) as usize);
+        ctor(this);
+        (*this).vtable = rb(va::DD_DISPLAY_BASE_HEADLESS_VTABLE) as *mut u8;
+        this
+    }
+}

crates/openwa-core/src/display_gfx.rs

@@ -1,10 +1,14 @@
-/// DisplayGfx — main display/graphics subsystem container.
+/// DisplayGfx — full display/graphics subsystem (derived from DDDisplayBase).
 ///
 /// Constructor: DisplayGfx__Constructor (0x569C10), stdcall(this) → DisplayGfx*.
 /// Size: 0x24E28 bytes.
 ///
+/// Inheritance: DDDisplayBase (0x3560) → DisplayGfx (0x24E28).
+/// The constructor calls DDDisplayBase__Constructor first, then sets the
+/// DisplayGfx vtable (0x66A218) and initializes display-specific fields.
+///
 /// Created by GameEngine__InitHardware in normal (non-headless) mode.
-/// Stored at GameSession+0xAC.
+/// Stored in the session's `display` field (shared with DDDisplayBase in headless).
 ///
 /// OPAQUE: Internal layout not yet mapped.
 #[repr(C)]

crates/openwa-core/src/game_session.rs

@@ -74,9 +74,9 @@ pub struct GameSession {
     pub keyboard: *mut DDKeyboard,
     /// 0x0A8: `DSSound*` — 0xBE0 bytes, vtable `DSSound_vtable` (0x66AF20)
     pub sound: *mut DSSound,
-    /// 0x0AC: `DisplayGfx*` — 0x24E28 bytes (normal), or `GameStats*` in headless mode.
-    /// Stays `*mut u8` because it's dual-purpose (DisplayGfx vs GameStats).
-    pub display_gfx: *mut u8,
+    /// 0x0AC: Polymorphic display — `DisplayGfx*` (normal) or `DDDisplayBase*` (headless).
+    /// Stays `*mut u8` because the concrete type depends on mode.
+    pub display: *mut u8,
     /// 0x0B0: `Palette*` — 0x28 bytes, vtable `Palette_vtable_Maybe`
     pub palette: *mut Palette,
     /// 0x0B4: streaming audio object — 0x354 bytes (`FUN_0058bc10`)

crates/openwa-core/src/game_stats.rs

@@ -1,36 +0,0 @@
-/// GameStats — headless mode display stub.
-///
-/// Constructor: GameStats__Constructor (0x522DB0), stdcall(this) → GameStats*.
-/// Vtable overlay: 0x66A0F8 (applied after constructor returns).
-/// Size: 0x3560 bytes.
-///
-/// Created by GameEngine__InitHardware in headless mode (GameInfo+0xF914 != 0)
-/// instead of DisplayGfx. Stored in the same GameSession+0xAC slot.
-///
-/// OPAQUE: Internal layout not yet mapped.
-#[repr(C)]
-pub struct GameStats {
-    pub vtable: *mut u8,
-    pub _unknown_004: [u8; 0x3560 - 4],
-}
-
-const _: () = assert!(core::mem::size_of::<GameStats>() == 0x3560);
-
-impl GameStats {
-    /// Allocate and construct a GameStats via WA's native constructor,
-    /// then overlay the GameStats vtable (used in headless mode).
-    ///
-    /// # Safety
-    /// Must be called from within the WA.exe process.
-    pub unsafe fn construct() -> *mut Self {
-        use crate::address::va;
-        use crate::rebase::rb;
-        use crate::wa_alloc::WABox;
-        let stats = WABox::<Self>::alloc(0x3560, 0x3560).leak();
-        let ctor: unsafe extern "stdcall" fn(*mut Self) -> *mut Self =
-            core::mem::transmute(rb(va::GAMESTATS_CTOR) as usize);
-        ctor(stats);
-        (*stats).vtable = rb(va::GAMESTATS_VTABLE) as *mut u8;
-        stats
-    }
-}

crates/openwa-core/src/lib.rs

@@ -37,4 +37,4 @@ pub mod input_ctrl;
 pub mod game_timer;
 pub mod streaming_audio;
 pub mod ddnetgame_wrapper;
-pub mod game_stats;
+pub mod dd_display_base;

crates/openwa-wormkit/src/replacements/hardware_init.rs

@@ -52,7 +52,7 @@ use openwa_core::dssound::DSSound;
 use openwa_core::palette::Palette;
 use openwa_core::input_ctrl::{InputCtrl, InputCtrlVtable};
 use openwa_core::game_timer::GameTimer;
-use openwa_core::game_stats::GameStats;
+use openwa_core::dd_display_base::DDDisplayBase;
 use openwa_core::display_gfx::DisplayGfx;
 use openwa_core::streaming_audio::StreamingAudio;
 use openwa_core::ddnetgame_wrapper::DDNetGameWrapper;
@@ -335,7 +335,7 @@ unsafe extern "cdecl" fn impl_init_hardware(
     if !headless {
         // ── DisplayGfx ───────────────────────────────────────────────────────
         let display_gfx = DisplayGfx::construct();
-        (*session).display_gfx = display_gfx as *mut u8;
+        (*session).display = display_gfx as *mut u8;
 
         // ── DDDisplay::Init retry loop ────────────────────────────────────────
         let flags = gi.display_flags;
@@ -430,7 +430,7 @@ unsafe extern "cdecl" fn impl_init_hardware(
         }
     } else {
         // ── Headless / stats mode ─────────────────────────────────────────────
-        (*session).display_gfx      = GameStats::construct() as *mut u8;
+        (*session).display      = DDDisplayBase::construct() as *mut u8;
         (*session).keyboard         = core::ptr::null_mut();
         (*session).sound            = core::ptr::null_mut();
         (*session).palette          = core::ptr::null_mut();
@@ -445,7 +445,7 @@ unsafe extern "cdecl" fn impl_init_hardware(
     let wrapper = game_session::construct_ddgame_wrapper(
         game_info,
         WABox::<DDGameWrapper>::alloc(0x6F10, 0x6EF0).leak(),
-        (*session).display_gfx as *mut DDDisplay,
+        (*session).display as *mut DDDisplay,
         (*session).sound,
         (*session).keyboard as *mut u8,
         (*session).palette,