Add Dolphin-compatible input expressions and GCPadNew.ini import, DualSense L/R remapping, vibration toggle (#89)

* Add Dolphin-compatible input expressions and GCPadNew.ini import

Rebased onto current main; addresses both CodeRabbit reviews on #89.

- Expression engine matching Dolphin's semantics: doubles rather than
  booleans, 0.5 press threshold, & as min, | as max, and the functions if,
  min, max, clamp, abs, sqrt, pow, sin, cos, tan, deadzone, timer, toggle,
  hold, tap, pulse and smooth. Timing uses a steady clock in seconds, as
  Dolphin does, so a copied expression behaves identically.

- Expressions bind to the GameCube buttons and triggers, combined with the
  existing button mapping rather than replacing it, and are skipped while
  the settings overlay holds input.

- Import reads [GCPadN] from the Dolphin config directory or from
  GCPadNew.ini beside the executable. Stick axes are not expression driven
  and keep their normal mapping.

- Fixes #74: a digital button bound to L or R now reports a fully pulled
  analog trigger, plus a PlayStation preset and a vibration toggle.

Review fixes: config paths round-trip through RuntimeConfigFile::PathToUtf8
and PathFromUtf8 so non-ASCII paths open correctly on Windows, and the
duplicated exists branch is gone; the tap count is clamped before the
unsigned conversion; the expression editor uses resizable storage via
ImGuiInputTextFlags_CallbackResize so a long expression cannot be saved
truncated; clamp bounds are ordered before std::clamp; <cstdlib> is included
for std::strtod; non-finite values are rejected at the evaluator boundary as
well as at the deadzone and timer divisions; and InputBindings::Reload() runs
from InitializeRuntimeSettings rather than the vibration handler.

runtime/tests/test_expr.cpp covers operator precedence, each stateful
function and every case raised in review.

Third review round: smooth() guards NaN as well as infinity so a zero rate
cannot latch a non-finite value in node state; division evaluates both operands
so stateful functions in the left subtree still update when the divisor is zero;
the expression editor clears stale errors when the port changes; and
runtime/tests/test_expr.cpp is registered with CTest as mkw_input_expr_tests,
following the existing test targets.

* Update runtime/src/input_expr.cpp

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

* Update runtime/src/input_expr.cpp

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

* Update runtime/src/input_expr.cpp

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

---------

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

runtime/src/hle/input/pad.cpp

@@ -1,18 +1,75 @@
 #include "hle_stubs.h"
 #include "memory.h"
 #include "hle/controller_status_contract.h"
+#include "input_bindings.h"
 #include "wii_remote_input.h"
 
 #include <algorithm>
+#include <atomic>
 #include <cstdio>
 #include <cstdint>
 #include <cstdlib>
 #include <cstring>
 
+#include <SDL3/SDL_gamepad.h>
 #include <dolphin/pad.h>
 
 namespace {
 
+std::atomic<bool> g_rumbleEnabled{true};
+
+bool NativeButtonHeld(SDL_Gamepad* gamepad, uint32_t nativeButton) {
+    if (gamepad == nullptr || nativeButton == PAD_NATIVE_BUTTON_INVALID ||
+        nativeButton >= SDL_GAMEPAD_BUTTON_COUNT) {
+        return false;
+    }
+    return SDL_GetGamepadButton(gamepad, static_cast<SDL_GamepadButton>(nativeButton));
+}
+
+// A digital button bound to L or R has no analog travel of its own. On real
+// hardware the click only engages at full depression, so report a full pull.
+void FillTriggersHeldByButtons(PADStatus* statuses) {
+    if (InputBindings::InputBlocked()) {
+        return;
+    }
+    for (uint32_t port = 0; port < PAD_CHANMAX; ++port) {
+        if (statuses[port].err != PAD_ERR_NONE) {
+            continue;
+        }
+        const s32 index = PADGetIndexForPort(port);
+        if (index < 0) {
+            continue;
+        }
+        SDL_Gamepad* gamepad = PADGetSDLGamepadForIndex(static_cast<u32>(index));
+        if (gamepad == nullptr) {
+            continue;
+        }
+        const auto scan = [&](PADButtonMapping* mappings, u32 count) {
+            if (mappings == nullptr) {
+                return;
+            }
+            for (u32 i = 0; i < count; ++i) {
+                const PADButtonMapping& mapping = mappings[i];
+                if (mapping.padButton != PAD_TRIGGER_L && mapping.padButton != PAD_TRIGGER_R) {
+                    continue;
+                }
+                if (!NativeButtonHeld(gamepad, mapping.nativeButton)) {
+                    continue;
+                }
+                if (mapping.padButton == PAD_TRIGGER_L) {
+                    statuses[port].triggerLeft = 255;
+                } else {
+                    statuses[port].triggerRight = 255;
+                }
+            }
+        };
+        u32 count = 0;
+        scan(PADGetButtonMappings(port, &count), count);
+        count = 0;
+        scan(PADGetAltButtonMappings(port, &count), count);
+    }
+}
+
 void WritePadStatus(uint32_t base, const PADStatus& status) {
     const auto guestStatus = PadStatusContract::Encode({
         status.button,
@@ -32,6 +89,11 @@ void WritePadStatus(uint32_t base, const PADStatus& status) {
 
 } // namespace
 
+extern "C" void PAD_HLE_SetRumbleEnabled(bool enabled)
+{
+    g_rumbleEnabled.store(enabled, std::memory_order_relaxed);
+}
+
 extern "C" uint32_t PAD__Init_HLE()
 {
     return PADInit() ? 1u : 0u;
@@ -54,6 +116,9 @@ extern "C" uint32_t PAD__Read_HLE(uint32_t statusPtr)
     // between "connected" and "no controller" every time the overlay toggles.
     WiiRemoteInput::HideRemotesFromPad(statuses, PAD_CHANMAX);
 
+    FillTriggersHeldByButtons(statuses);
+    InputBindings::Apply(statuses);
+
     try {
         for (uint32_t i = 0; i < PAD_CHANMAX; ++i) {
             WritePadStatus(statusPtr + static_cast<uint32_t>(i * PadStatusContract::kGuestStatusSize),
@@ -81,6 +146,9 @@ PPC_NATIVE_OVERRIDE(801AF1E4, PAD__Recalibrate_HLE, uint32_t, (uint32_t mask), (
 
 extern "C" void PAD__ControlMotor_HLE(int32_t chan, uint32_t command)
 {
+    if (command == PAD_MOTOR_RUMBLE && !g_rumbleEnabled.load(std::memory_order_relaxed)) {
+        command = PAD_MOTOR_STOP;
+    }
     PADControlMotor(chan, command);
 }
 PPC_NATIVE_OVERRIDE_VOID(801AF908, PAD__ControlMotor_HLE, (int32_t chan, uint32_t command), (chan, command));