refactor: type CoordEntry fields as Fixed and eliminate pointer arithmetic in level_bounds

Retype CoordEntry fields from raw i32 to named Fixed center_x/y and
center_x_target/y_target. Extend viewport_coords array to 5 entries to
cover the init spill. Retype init_game_state_level_bounds param from
*mut u8 to *mut DDGame, removing all raw pointer arithmetic.

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

crates/openwa-core/src/engine/coord.rs

@@ -2,16 +2,22 @@
 // Coordinate types — DDGame sub-structs for screen and terrain coords
 // ============================================================
 
-/// Coordinate entry used in DDGame screen coordinate tables (stride 0x10).
+/// Coordinate entry used in DDGame viewport/camera tables (stride 0x10).
 ///
-/// InitFields zeroes x and y; at runtime they contain fixed-point screen
-/// coordinates used for camera tracking and rendering regions.
+/// Each entry tracks a camera center position as two pairs of Fixed16.16
+/// coordinates (current and target). InitGameState initializes all four
+/// fields to the level center.
 #[repr(C)]
 #[derive(Clone, Copy)]
 pub struct CoordEntry {
-    pub x: i32,
-    pub y: i32,
-    pub _unknown: [u8; 8],
+    /// +0x00: Camera center X (Fixed16.16).
+    pub center_x: crate::fixed::Fixed,
+    /// +0x04: Camera center Y (Fixed16.16).
+    pub center_y: crate::fixed::Fixed,
+    /// +0x08: Camera center X target (Fixed16.16).
+    pub center_x_target: crate::fixed::Fixed,
+    /// +0x0C: Camera center Y target (Fixed16.16).
+    pub center_y_target: crate::fixed::Fixed,
 }
 
 const _: () = assert!(core::mem::size_of::<CoordEntry>() == 0x10);

crates/openwa-core/src/engine/ddgame.rs

@@ -499,13 +499,13 @@ pub struct DDGame {
     /// - 0x8174: value 0x3FC (1020) at runtime
     pub _unknown_81cc: [u8; 0x8CBC - 0x81CC],
 
-    /// 0x8CBC-0x8CFB: 4 coordinate entries (0x10-byte stride).
-    /// InitFields zeroes x and y of each. At runtime contains fixed-point
-    /// screen coordinates (e.g. 393.0, 532.0, 960.0, 348.0).
-    pub screen_coords: [CoordEntry; 4],
+    /// 0x8CBC-0x8D0B: 5 viewport coordinate entries (0x10-byte stride).
+    /// InitGameState writes camera center to entries 1..5 (indexed from base 0..4).
+    /// Entry 0 is not written by init (used for other purposes).
+    pub viewport_coords: [CoordEntry; 5],
 
-    /// 0x8CFC-0x984F: Unknown
-    pub _unknown_8cfc: [u8; 0x9850 - 0x8CFC],
+    /// 0x8D0C-0x984F: Unknown
+    pub _unknown_8d0c: [u8; 0x9850 - 0x8D0C],
 
     /// 0x9850-0x988F: 4 coordinate entries (0x10-byte stride, zeroed by InitFields).
     pub screen_coords_2: [CoordEntry; 4],
@@ -618,12 +618,15 @@ impl DDGame {
         }
     }
 
-    /// Listener position for 3D audio — stored at DDGame+0x8CEC (screen_coords[3]).
+    /// Listener position for 3D audio — stored at DDGame+0x8CEC (viewport_coords[3]).
     ///
     /// Returns `(x, y)` as raw i32 values (fixed-point 16.16).
     /// Used by ComputeDistanceParams / Distance3D_Attenuation.
     pub fn listener_pos(&self) -> (i32, i32) {
-        (self.screen_coords[3].x, self.screen_coords[3].y)
+        (
+            self.viewport_coords[3].center_x.0,
+            self.viewport_coords[3].center_y.0,
+        )
     }
 }
 

crates/openwa-core/src/engine/ddgame_constructor.rs

@@ -17,6 +17,7 @@ use crate::engine::coord::{CoordList, CoordListEntry};
 use crate::engine::ddgame_wrapper::DDGameWrapper;
 use crate::engine::game_info::GameInfo;
 use crate::engine::net_bridge::NetBridge;
+use crate::fixed::Fixed;
 use crate::input::keyboard::DDKeyboard;
 use crate::rebase::rb;
 use crate::render::display::gfx::DisplayGfx;
@@ -72,13 +73,13 @@ pub unsafe fn ddgame_init_fields(ddgame: *mut DDGame) {
     ddgame_init_render_indices(ddgame);
 
     // Zero x and y of each screen coordinate entry (4 entries each)
-    for entry in &mut (*ddgame).screen_coords {
-        entry.x = 0;
-        entry.y = 0;
+    for entry in &mut (*ddgame).viewport_coords {
+        entry.center_x = Fixed(0);
+        entry.center_y = Fixed(0);
     }
     for entry in &mut (*ddgame).screen_coords_2 {
-        entry.x = 0;
-        entry.y = 0;
+        entry.center_x = Fixed(0);
+        entry.center_y = Fixed(0);
     }
 }
 

crates/openwa-core/src/engine/game_state_init.rs

@@ -938,7 +938,7 @@ pub unsafe fn init_game_state(wrapper: *mut DDGameWrapper) {
     init_landscape_flags(wrapper as *mut u8);
 
     // ===== Level bounds and camera initialization =====
-    init_game_state_level_bounds(ddgame_raw, game_info);
+    init_game_state_level_bounds(ddgame, game_info);
 
     // ===== Display objects for HUD (headful only) =====
     if is_headful {
@@ -1526,9 +1526,7 @@ unsafe fn create_camera_object(
 }
 
 /// Initialize level bounds and camera center positions.
-unsafe fn init_game_state_level_bounds(ddgame_raw: *mut u8, game_info: *const GameInfo) {
-    let ddgame = ddgame_raw as *mut DDGame;
-
+unsafe fn init_game_state_level_bounds(ddgame: *mut DDGame, game_info: *const GameInfo) {
     (*ddgame)._field_7794 = 0;
     (*ddgame)._field_7798 = 0;
 
@@ -1551,15 +1549,17 @@ unsafe fn init_game_state_level_bounds(ddgame_raw: *mut u8, game_info: *const Ga
     }
 
     // Camera center initialization (4 viewports)
-    for viewport_offset in [0x8CBCu32, 0x8CCCu32, 0x8CDCu32, 0x8CECu32] {
-        let level_w = (*ddgame).level_width as i32;
-        let level_h = (*ddgame).level_height as i32;
-        let cx = (level_w << 16) / 2;
-        let cy = (level_h * 0x10000) / 2;
-        *(ddgame_raw.add(viewport_offset as usize + 0x18) as *mut i32) = cx;
-        *(ddgame_raw.add(viewport_offset as usize + 0x10) as *mut i32) = cx;
-        *(ddgame_raw.add(viewport_offset as usize + 0x1C) as *mut i32) = cy;
-        *(ddgame_raw.add(viewport_offset as usize + 0x14) as *mut i32) = cy;
+    // Each iteration writes to viewport_coords[i+1] (entries 1..5).
+    let level_w = (*ddgame).level_width as i32;
+    let level_h = (*ddgame).level_height as i32;
+    let cx = Fixed((level_w << 16) / 2);
+    let cy = Fixed((level_h << 16) / 2);
+    for i in 0..4 {
+        let entry = &mut (*ddgame).viewport_coords[i + 1];
+        entry.center_x = cx;
+        entry.center_y = cy;
+        entry.center_x_target = cx;
+        entry.center_y_target = cy;
     }
 
     // Map dimension fields