Restore behavioral render preset override coverage

tools/d4r_nvngx_shim.cpp

@@ -74,6 +74,7 @@
 #include <vector>
 #include "d4r_event_wait.h"
 #include "d4r_frame_completion.h"
+#include "d4r_render_presets.h"
 #include "d4r_win32_wait.h"
 #include "d4r_vkd3d_interop.h"
 #include "../engine/game.h"
@@ -7109,18 +7110,18 @@ static NgxResult create_feature(unsigned int featureId, void* parameters, NgxHan
     unsigned int presets[6];
     for (int index = 0; index < 6; ++index)
         presets[index] = get_uint_or(parameters, presetNames[index], 0);
-    const std::string forced = env_string(rayReconstruction ? "D4R_RR_PRESET" : "D4R_DLSS_PRESET");
-    if (!forced.empty())
+    const std::string forced = env_string(d4r_render_preset_variable(rayReconstruction));
+    const auto presetOverride = d4r_parse_render_preset_override(forced.c_str());
+    if (presetOverride.enabled)
     {
-        const unsigned int value = static_cast<unsigned int>(strtoul(forced.c_str(), nullptr, 0));
+        const unsigned int value = presetOverride.value;
         const char* model = value == 5 ? "E" : value == 11 ? "K" : value == 12 ? "L" : value == 13 ? "M" : "custom";
         logf("DLSS model override: D4R_DLSS_PRESET=%s (model %s) overrides game/OptiScaler presets "
              "[DLAA=%u Quality=%u Balanced=%u Performance=%u UltraPerformance=%u UltraQuality=%u]; "
              "using preset=%u for all quality modes",
              forced.c_str(), model, presets[0], presets[1], presets[2], presets[3], presets[4], presets[5], value);
-        for (unsigned int& preset : presets)
-            preset = value;
     }
+    presetOverride.apply(presets);
     feature->preset = presets[1];
     // Direct output needs the native output kernel of the preset in use (verified: K = 11 through
     // hiluma_engine_output, M = 13 through rrlite_downsample_kernel, its last kernel). Only a forced

tools/d4r_render_presets.h

@@ -0,0 +1,32 @@
+#pragma once
+
+#include <cstdlib>
+
+// Platform-specific environment reads stay in the caller. SR and RR deliberately
+// use separate settings, even when both are configured for the same feature call.
+inline constexpr const char* d4r_render_preset_variable(bool rayReconstruction)
+{
+    return rayReconstruction ? "D4R_RR_PRESET" : "D4R_DLSS_PRESET";
+}
+
+// An absent/empty override leaves every game-selected quality preset unchanged.
+// An explicit zero is an override too: it requests NGX's default preset.
+struct D4rRenderPresetOverride
+{
+    bool enabled;
+    unsigned int value;
+
+    void apply(unsigned int (&presets)[6]) const
+    {
+        if (enabled)
+            for (unsigned int& preset : presets)
+                preset = value;
+    }
+};
+
+inline D4rRenderPresetOverride d4r_parse_render_preset_override(const char* overrideValue)
+{
+    if (overrideValue == nullptr || *overrideValue == '\0')
+        return {false, 0};
+    return {true, static_cast<unsigned int>(std::strtoul(overrideValue, nullptr, 0))};
+}