[Feat] (ShaderTranspiler, DirectGLES): emulate noperspective on GLES devices lacking GL_NV_shader_noperspective_interpolation - EmulateNoPerspectivePass pre-multiplies each NoPerspective output by gl_Position.w in the vertex stage and recovers each input via gl_FragCoord.w in the fragment stage (exact screen-linear L = P(a*w)*gl_FragCoord.w, handling whole-variable and component/access-chain reads, scalar and vector varyings), forces highp on emulated varyings, and strips what it cannot emulate; replaces the smooth-strip fallback so no NV extension is ever required. Restricts the vertex pre-multiply to the entry function so a non-inlined helper cannot double-scale

MobileGL/MG_Util/ShaderTranspiler/SpirvPasses/EmulateNoPerspectivePass.h

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+// MobileGL - MobileGL/MG_Util/ShaderTranspiler/SpirvPasses/EmulateNoPerspectivePass.h
+// Copyright (c) 2025-2026 MobileGL-Dev
+// Licensed under the GNU Lesser General Public License v3.0:
+//   https://www.gnu.org/licenses/gpl-3.0.txt
+//   https://www.gnu.org/licenses/lgpl-3.0.txt
+// SPDX-License-Identifier: LGPL-3.0-only
+// End of Source File Header
+
+#pragma once
+#include "source/opt/pass.h"
+#include "spirv-tools/optimizer.hpp"
+
+#include <Includes.h>
+
+namespace MobileGL {
+    namespace MG_Util {
+        namespace ShaderTranspiler {
+            // Emulates 'noperspective' (screen-linear) interpolation on GLES devices that lack
+            // GL_NV_shader_noperspective_interpolation, so no NV extension is required. The hardware
+            // interpolates perspective-correct; screen-linear L(a) is recovered from the identity
+            //     L(a) = P(a * w) * gl_FragCoord.w
+            // where P is perspective-correct interpolation and w is the vertex clip-space w. So each
+            // NoPerspective-decorated output is pre-multiplied by gl_Position.w in the vertex stage
+            // and each NoPerspective-decorated input is multiplied by gl_FragCoord.w in the fragment
+            // stage; the decoration is then removed so the varying transports smooth. This is exact
+            // (modulo float precision - the emulated varyings want highp).
+            //
+            // Scope: plain interface variables of float or floatN type. Anything it cannot emulate
+            // (interface-block members, matrices, or a stage lacking the needed builtin) has its
+            // NoPerspective decoration stripped instead, degrading to smooth - the same result the
+            // extension-less fallback produced before, and never invalid SPIR-V. DirectGLES only.
+            class EmulateNoPerspectivePass : public spvtools::opt::Pass {
+            public:
+                const char* name() const override { return "emulate-noperspective"; }
+                Status Process() override;
+
+                static spvtools::Optimizer::PassToken CreateEmulateNoPerspectivePass();
+            };
+        } // namespace ShaderTranspiler
+    } // namespace MG_Util
+} // namespace MobileGL