HOOK_MOVECOST (#496)

SFALL_COMPATIBILITY.md

@@ -106,8 +106,8 @@ See [`https://sfall-team.github.io/sfall/`](https://sfall-team.github.io/sfall/)
 | UseObj | `HOOK_USEOBJ` | ✅ | CE notes an sfall-matching inconsistency around return code `2` behavior between interface contexts. |
 | RemoveInvenObj | `HOOK_REMOVEINVENOBJ` | 🚫 | - |
 | BarterPrice | `HOOK_BARTERPRICE` | ✅ | - |
-| MoveCost | `HOOK_MOVECOST` | 🚫 | - |
 | ItemDamage | `HOOK_ITEMDAMAGE` | ✅ | - |
+| MoveCost | `HOOK_MOVECOST` | ✅ | - |
 | AmmoCost | `HOOK_AMMOCOST` | ✅ | Requires `check_weapon_ammo_cost=1` if you want pre-attack ammo validation to respect per-shot/per-round overrides. |
 | KeyPress | `HOOK_KEYPRESS` | ✅ | Third hook arg is currently `0`; CE doesn't use VK codes. |
 | MouseClick | `HOOK_MOUSECLICK` | ✅ | - |

sfall_testing/hooks/gl_movecost.ssl

@@ -0,0 +1,70 @@
+#include "sfall.h"
+#include "dik.h"
+
+variable movecost_mode := 0;
+
+procedure movecost_mode_name(variable mode) begin
+    variable name := "unknown";
+
+    if (mode == 0) then name := "engine";
+    else if (mode == 1) then name := "plus_per_hex";
+    else if (mode == 2) then name := "double";
+
+    return name;
+end
+
+procedure cycle_movecost_mode begin
+    if (movecost_mode == 0) then movecost_mode := 1;
+    else if (movecost_mode == 1) then movecost_mode := 2;
+    else movecost_mode := 0;
+
+    display_msg(string_format1("movecost mode=%s", movecost_mode_name(movecost_mode)));
+end
+
+procedure movecost_handler begin
+    variable
+        args := get_sfall_args,
+        critter := args[0],
+        distance := args[1],
+        defaultCost := args[2],
+        modeName := movecost_mode_name(movecost_mode),
+        newCost := defaultCost;
+
+    if (critter != dude_obj) then return;
+
+    display_msg(string_format3("movecost dist=%d default=%d mode=%s",
+        distance,
+        defaultCost,
+        modeName));
+
+    if (movecost_mode == 1) then begin
+        newCost := defaultCost + distance;
+    end else if (movecost_mode == 2) then begin
+        newCost := defaultCost * 2;
+    end else begin
+        return;
+    end
+
+    set_sfall_return(newCost);
+end
+
+procedure keypress_handler begin
+    variable
+        pressed := get_sfall_arg_at(0),
+        key := get_sfall_arg_at(1);
+
+    if (not pressed) then return;
+    if (key != DIK_M) then return;
+
+    call cycle_movecost_mode;
+end
+
+procedure start begin
+    if (not game_loaded) then return;
+
+    display_msg("movecost manual test ready: enter combat, hover a tile, then move");
+    display_msg("press M to cycle hook override: engine -> plus_per_hex -> double");
+
+    register_hook_proc(HOOK_KEYPRESS, keypress_handler);
+    register_hook_proc(HOOK_MOVECOST, movecost_handler);
+end

src/critter.cc

@@ -1359,13 +1359,16 @@ int critterGetMovementPointCostAdjustedForCrippledLegs(Object* critter, int dist
     }
 
     int flags = critter->data.critter.combat.results;
+    int actionPoints = 0;
     if ((flags & DAM_CRIP_LEG_LEFT) != 0 && (flags & DAM_CRIP_LEG_RIGHT) != 0) {
-        return 8 * distance;
+        actionPoints = 8 * distance;
     } else if ((flags & DAM_CRIP_LEG_ANY) != 0) {
-        return 4 * distance;
+        actionPoints = 4 * distance;
     } else {
-        return distance;
+        actionPoints = distance;
     }
+
+    return scriptHooks_MoveCost(critter, distance, actionPoints);
 }
 
 // 0x42E66C critterIsOverloaded

src/sfall_script_hooks.cc

@@ -570,6 +570,35 @@ int scriptHooks_CalcApCost(Object* critter, int hitMode, bool aiming, int action
     return hook.getReturnValueAt(0).asInt();
 }
 
+/*
+Runs when calculating the AP cost of movement.
+
+The engine calls this both for full-path AP previews and for per-hex AP
+deduction during movement animation. In practice, arg1 may therefore be the
+full path length or 1, depending on the caller. Non-linear overrides can make
+the UI preview diverge from the AP actually spent.
+
+Critter arg0 - The critter doing the moving
+int     arg1 - The number of hexes being moved
+int     arg2 - The original AP cost
+
+int     ret0 - The new AP cost
+*/
+int scriptHooks_MoveCost(Object* critter, int distance, int actionPoints)
+{
+    if (scriptHooks[HOOK_MOVECOST].empty()) {
+        return actionPoints;
+    }
+
+    ScriptHookCall hook(HOOK_MOVECOST, 1, { critter, distance, actionPoints });
+    hook.call();
+
+    if (hook.numReturnValues() <= 0) {
+        return actionPoints;
+    }
+    return hook.getReturnValueAt(0).asInt();
+}
+
 /*
 Runs before moving items between inventory slots in dude interface. You can override the action.
 

src/sfall_script_hooks.h

@@ -302,6 +302,7 @@ bool scriptHooks_CombatTurnEnd(Object* critter, int turnResult, bool reloadedDur
 void scriptHooks_CombatTurnCombatEnd(Object* critter);
 PerceptionResult scriptHooks_WithinPerception(Object* watcher, Object* target, PerceptionType type, PerceptionResult result);
 int scriptHooks_CalcApCost(Object* critter, int hitMode, bool aiming, int actionPoints, Object* weapon);
+int scriptHooks_MoveCost(Object* critter, int distance, int actionPoints);
 int scriptHooks_ToHit(Object* attacker, Object* defender, int tile, int hitMode, int hitLocation, int hitChance, int hitChanceUncapped, bool useDistance);
 int scriptHooks_AfterHitRoll(Object* attacker, Object** defenderPtr, int* hitLocationPtr, int hitChance, int roll);
 void scriptHooks_DeathAnim(Object* attacker, Object* defender, Object* weapon, int damage, int* anim);