feat: map DisplayGfx internal fields and expose DisplayBase dimensions

Map ~30 named fields across the 0x24E28-byte DisplayGfx struct, replacing
the single opaque blob. Key regions: camera offset, display dimensions,
clip rect, HWND, 3 layer object pointers, palette entries (256x4),
sprite table (1024 entries), two 64KB color mixing LUTs (additive and
gamma-corrected blend), and blend mode flag.

Also expose display_width/height and clip rect fields in DisplayBase
(previously hidden in _pad_3540).

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

crates/openwa-core/src/display/base.rs

@@ -52,8 +52,22 @@ pub struct DisplayBase {
     pub _field_352c: u32,
     // +0x3530..0x3540: indices 0xD4C..0xD4F (4 entries), zeroed by ctor
     pub _fields_3530: [u32; 4],
-    // +0x3540..0x3560: remaining padding to fill 0x3560 total
-    pub _pad_3540: [u8; 0x3560 - 0x3540],
+    // +0x3540: display initialized flag (set to 1 by DDDisplay__Init)
+    pub display_initialized: u32,
+    // +0x3544: unknown
+    pub _unknown_3544: u32,
+    // +0x3548: display width in pixels (set by DDDisplay__Init)
+    pub display_width: u32,
+    // +0x354C: display height in pixels
+    pub display_height: u32,
+    // +0x3550: clip rect x1 (left, init 0)
+    pub clip_x1: i32,
+    // +0x3554: clip rect y1 (top, init 0)
+    pub clip_y1: i32,
+    // +0x3558: clip rect x2 (right, init = width)
+    pub clip_x2: i32,
+    // +0x355C: clip rect y2 (bottom, init = height)
+    pub clip_y2: i32,
 }
 
 const _: () = assert!(core::mem::size_of::<DisplayBase>() == 0x3560);

crates/openwa-core/src/display/gfx.rs

@@ -1,20 +1,161 @@
+use super::base::DisplayBase;
+use core::ffi::c_void;
+
 /// DisplayGfx — full display/graphics subsystem (derived from DisplayBase).
 ///
 /// Constructor: DisplayGfx__Constructor (0x569C10), stdcall(this) → DisplayGfx*.
+/// Initializer: DDDisplay__Init (0x569D00), usercall.
 /// Size: 0x24E28 bytes.
 ///
 /// Inheritance: DisplayBase (0x3560) → DisplayGfx (0x24E28).
 /// The constructor calls DisplayBase__Constructor first, then sets the
-/// DisplayGfx vtable (0x66A218) and initializes display-specific fields.
+/// DDDisplay vtable (0x66A218) and initializes display-specific fields.
 ///
 /// Created by GameEngine__InitHardware in normal (non-headless) mode.
 /// Stored in the session's `display` field (shared with DisplayBase in headless).
 ///
-/// OPAQUE: Internal layout not yet mapped.
+/// ## Memory layout overview
+///
+/// ```text
+/// 0x0000 - 0x355F : DisplayBase (sprite cache, slot table, etc.)
+/// 0x3540          : display_initialized flag
+/// 0x3548 - 0x355F : display dimensions and clip rect
+/// 0x3560 - 0x3577 : camera offset, rendering state
+/// 0x3578          : HWND
+/// 0x3580 - 0x358B : bitmap vector
+/// 0x358C - 0x398C : palette entry table (256 × 4 bytes)
+/// 0x3D90 - 0x3D97 : palette metadata
+/// 0x3D98          : render lock flag
+/// 0x3D9C - 0x3DA7 : three layer object pointers (DisplayGfx vtable 0x664144)
+/// 0x3DA8 - 0x3DD3 : DisplayGfx vtable ptr, layer config
+/// 0x3DD4 - 0x4DD3 : sprite/bitmap table (1024 entries)
+/// 0x4DD4 - 0x4DF3 : sprite table metadata
+/// 0x4DF4 - 0x14DF3: color_add_table (256 × 256 additive mixing LUT)
+/// 0x14DF4- 0x24DF3: color_blend_table (256 × 256 gamma-corrected blend LUT)
+/// 0x24DF4- 0x24E27: tail fields (blend mode flag, object vector)
+/// ```
 #[repr(C)]
 pub struct DisplayGfx {
-    pub vtable: *mut u8,
-    pub _unknown_004: [u8; 0x24E28 - 4],
+    // =========================================================================
+    // DisplayBase (0x0000 - 0x355F)
+    // =========================================================================
+    /// 0x0000: DisplayBase fields (vtable, sprite cache, slot table, etc.)
+    pub base: DisplayBase,
+
+    // =========================================================================
+    // Display dimensions and clip rect (0x3560 - 0x357F)
+    // =========================================================================
+    /// 0x3560: Camera X offset (pixels). DDDisplay methods add this to coordinates.
+    pub camera_x: i32,
+    /// 0x3564: Camera Y offset (pixels).
+    pub camera_y: i32,
+    /// 0x3568: Unknown (set to 0 in InitDisplayFinal)
+    pub _unknown_3568: u32,
+    /// 0x356C: Unknown (set from FUN_00541340 result in InitDisplayFinal)
+    pub _unknown_356c: u32,
+    /// 0x3570: Unknown (set to 0 in InitDisplayFinal)
+    pub _unknown_3570: u32,
+    /// 0x3574: Unknown (set to 0 in DDDisplay__Init)
+    pub _unknown_3574: u32,
+    /// 0x3578: Window handle (HWND), used for MoveWindow in DDDisplay__Init
+    pub hwnd: u32,
+    /// 0x357C: Unknown
+    pub _unknown_357c: u32,
+
+    // =========================================================================
+    // Bitmap/sprite storage (0x3580 - 0x358B)
+    // =========================================================================
+    /// 0x3580: Bitmap vector pointer (init 0)
+    pub bitmap_ptr: u32,
+    /// 0x3584: Bitmap vector end (init 0)
+    pub bitmap_end: u32,
+    /// 0x3588: Bitmap vector capacity (init 0)
+    pub bitmap_capacity: u32,
+
+    // =========================================================================
+    // Palette entry table (0x358C - 0x3D8F)
+    // =========================================================================
+    /// 0x358C: Palette entry count or lead byte
+    pub _unknown_358c: u8,
+    /// 0x358D - 0x398C: Palette entries (256 × 4 bytes = 0x400 bytes).
+    /// Each entry is 4 bytes (R, G, B, flags?). Entry 255 (0x3989) = white.
+    pub palette_entries: [u8; 0x400],
+    /// 0x398D - 0x3D8F: Unknown region between palette entries and palette metadata
+    pub _unknown_398d: [u8; 0x3D90 - 0x398D],
+
+    // =========================================================================
+    // Palette metadata and render state (0x3D90 - 0x3D97)
+    // =========================================================================
+    /// 0x3D90: Palette entry count (init 0x100 = 256)
+    pub palette_count: u32,
+    /// 0x3D94: Unknown (init 0xFFFFFFFF)
+    pub _unknown_3d94: u32,
+
+    // =========================================================================
+    // Render state and layer pointers (0x3D98 - 0x3DD3)
+    // =========================================================================
+    /// 0x3D98: Render lock flag. Set during rendering, cleared by FlushRender.
+    pub render_lock: u32,
+    /// 0x3D9C: Layer 0 pointer — 0x4C-byte object with DisplayGfx vtable (0x664144).
+    /// Allocated and initialized in DDDisplay__Init.
+    pub layer_0: *mut c_void,
+    /// 0x3DA0: Layer 1 pointer (same type as layer_0)
+    pub layer_1: *mut c_void,
+    /// 0x3DA4: Layer 2 pointer (same type, uses BitGrid__Init)
+    pub layer_2: *mut c_void,
+    /// 0x3DA8: DisplayGfx vtable pointer (0x664144). Set in constructor.
+    pub displaygfx_vtable: *const c_void,
+    /// 0x3DAC: Layer active flag (init 1)
+    pub layer_active: u32,
+    /// 0x3DB0: Unknown (init 0)
+    pub _unknown_3db0: u32,
+    /// 0x3DB4: Bit depth (init 8 in constructor — 8bpp paletted mode)
+    pub bit_depth: u32,
+    /// 0x3DB8 - 0x3DD3: Unknown fields (all init 0 in constructor)
+    pub _unknown_3db8: [u8; 0x3DD4 - 0x3DB8],
+
+    // =========================================================================
+    // Sprite/bitmap table (0x3DD4 - 0x4DD7)
+    // =========================================================================
+    /// 0x3DD4: Sprite table — 1024 DWORD entries, zeroed in DDDisplay__Init.
+    /// Used for tracking loaded sprites/bitmaps by ID.
+    pub sprite_table: [u32; 0x400],
+    /// 0x4DD4: Sprite table metadata field 1 (init 0)
+    pub sprite_meta_0: u32,
+    /// 0x4DD8: Sprite table metadata field 2 (init 0)
+    pub sprite_meta_1: u32,
+    /// 0x4DDC - 0x4DF3: Unknown gap
+    pub _unknown_4ddc: [u8; 0x4DF4 - 0x4DDC],
+
+    // =========================================================================
+    // Color mixing lookup tables (0x4DF4 - 0x24DF3)
+    // =========================================================================
+    /// 0x4DF4: Additive color mixing LUT (256 × 256 = 0x10000 bytes).
+    /// Maps (color_a, color_b) → blended palette index using additive saturation.
+    /// Built by DDGame__InitDisplayFinal (0x56A830).
+    pub color_add_table: [u8; 0x10000],
+    /// 0x14DF4: Gamma-corrected blend LUT (256 × 256 = 0x10000 bytes).
+    /// Uses gamma-space blending via sqrt approximation.
+    /// Built by DDGame__InitDisplayFinal (0x56A830).
+    pub color_blend_table: [u8; 0x10000],
+
+    // =========================================================================
+    // Tail fields (0x24DF4 - 0x24E27)
+    // =========================================================================
+    /// 0x24DF4: Blend mode flag. Controls color distance weighting in
+    /// InitDisplayFinal (1 = reduced red weight, else normal).
+    pub blend_mode_flag: u32,
+    /// 0x24DF8 - 0x24E07: Object vector (std::vector-like).
+    /// Holds palette/display objects pushed during DDDisplay__Init.
+    pub object_vector_start: u32,
+    /// 0x24DFC: Vector data pointer
+    pub object_vector_ptr: u32,
+    /// 0x24E00: Vector end pointer
+    pub object_vector_end: u32,
+    /// 0x24E04: Vector capacity pointer
+    pub object_vector_cap: u32,
+    /// 0x24E08 - 0x24E27: Remaining tail (0x20 bytes)
+    pub _tail: [u8; 0x24E28 - 0x24E08],
 }
 
 const _: () = assert!(core::mem::size_of::<DisplayGfx>() == 0x24E28);