[Feat] (ShaderTranspiler, DirectGLES): support noperspective conformantly instead of stripping it - let the qualifier reach glslang as the core SPIR-V NoPerspective decoration (native on DirectVulkan; SPIRV-Cross emits ESSL noperspective + GL_NV_shader_noperspective_interpolation on DirectGLES), and for GLES devices lacking that extension add StripNoPerspectivePass to drop the decoration and fall back to smooth; the old naked substring erase discarded the interpolation shader packs need and mangled identifiers containing the word

MobileGL/MG_Util/ShaderTranspiler/ShaderCompiler.cpp

@@ -20,6 +20,7 @@
 #include "SpirvPasses/LowerDrawParametersPass.h"
 #include "SpirvPasses/RebaseInstanceIndexPass.h"
 #include "SpirvPasses/StripUboMemberRelaxedPrecisionPass.h"
+#include "SpirvPasses/StripNoPerspectivePass.h"
 #include "spirv-tools/libspirv.h"
 #include "spirv-tools/optimizer.hpp"
 
@@ -334,6 +335,18 @@ namespace MobileGL {
                 return optimizer.Run(inputBinary.data(), inputBinary.size(), &outputBinary, options);
             }
 
+            bool ShaderCompiler::StripNoPerspectiveForEssl(const Vector<Uint32>& inputBinary,
+                                                           Vector<uint32_t>& outputBinary) {
+                using namespace spvtools;
+                OptimizerOptions options;
+                options.set_run_validator(false);
+
+                Optimizer optimizer(SPV_ENV_VULKAN_1_1);
+                optimizer.RegisterPass(StripNoPerspectivePass::CreateStripNoPerspectivePass());
+
+                return optimizer.Run(inputBinary.data(), inputBinary.size(), &outputBinary, options);
+            }
+
             bool ShaderCompiler::RebaseInstanceIndexForVulkan(const Vector<Uint32>& inputBinary,
                                                               Vector<uint32_t>& outputBinary) {
                 using namespace spvtools;

MobileGL/MG_Util/ShaderTranspiler/ShaderCompiler.h

@@ -33,6 +33,11 @@ namespace MobileGL {
                 // Only for the DirectGLES transpile path.
                 static bool StripUboMemberRelaxedPrecisionForEssl(const Vector<Uint32>& inputBinary,
                                                                   Vector<uint32_t>& outputBinary);
+                // Removes NoPerspective decorations so SPIRV-Cross emits plain (smooth) ESSL varyings.
+                // DirectGLES fallback only, for devices lacking GL_NV_shader_noperspective_interpolation
+                // (SPIRV-Cross would otherwise require that extension and the driver would reject it).
+                static bool StripNoPerspectiveForEssl(const Vector<Uint32>& inputBinary,
+                                                      Vector<uint32_t>& outputBinary);
                 // Rebases loads of the InstanceIndex builtin to (InstanceIndex - BaseInstance) so
                 // shaders see GL's zero-based gl_InstanceID. Vertex shaders only; DirectVulkan
                 // backend only (glslang's relaxed mode aliases gl_InstanceID to gl_InstanceIndex,

MobileGL/MG_Util/ShaderTranspiler/ShaderSourceProcessor.cpp

@@ -1251,15 +1251,13 @@ namespace MobileGL {
 
                 NormalizeLineDirectives(source);
 
-                // remove "noperspective"
-                const char* str_np = "noperspective";
-                const SizeT len_np = strlen(str_np);
-                SizeT noperspectivePos = source.find(str_np);
-                while (noperspectivePos != String::npos) {
-                    // + length of "\n"
-                    source = source.replace(noperspectivePos, len_np, "");
-                    noperspectivePos = source.find(str_np);
-                }
+                // noperspective is intentionally NOT touched here. It is core in desktop GLSL (1.30+)
+                // and maps to the core SPIR-V NoPerspective decoration, which DirectVulkan renders
+                // natively and SPIRV-Cross turns into ESSL `noperspective` + the
+                // GL_NV_shader_noperspective_interpolation extension. The old naked substring erase
+                // both discarded that interpolation (shader packs need it) and corrupted any
+                // identifier that merely contained the word. The GLES fallback for devices without
+                // the extension lives in the backend, where device capabilities are known.
 
                 FilterUnsupportedGpuShaderInt64(source);
                 CoerceUniformBlockPackingToStd140(source);

MobileGL/MG_Util/ShaderTranspiler/SpirvPasses/StripNoPerspectivePass.cpp

@@ -0,0 +1,72 @@
+// MobileGL - MobileGL/MG_Util/ShaderTranspiler/SpirvPasses/StripNoPerspectivePass.cpp
+// 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
+
+#include "StripNoPerspectivePass.h"
+
+#include "spirv.hpp"
+#include "source/opt/instruction.h"
+#include "source/opt/ir_context.h"
+#include "source/util/make_unique.h"
+
+#include <vector>
+
+namespace MobileGL {
+    namespace MG_Util {
+        namespace ShaderTranspiler {
+            namespace {
+                using spvtools::opt::Instruction;
+                using spvtools::opt::IRContext;
+
+                // OpDecorate       <target-id> <decoration> [literals...]
+                // OpMemberDecorate <struct-id>  <member> <decoration> [literals...]
+                constexpr uint32_t kDecorateDecorationOperand = 1;
+                constexpr uint32_t kMemberDecorateDecorationOperand = 2;
+            } // namespace
+
+            spvtools::opt::Pass::Status StripNoPerspectivePass::Process() {
+                auto* irContext = context();
+
+                // Collect first: KillInst mutates the annotation list being walked.
+                std::vector<Instruction*> toKill;
+                for (Instruction& annotation : irContext->annotations()) {
+                    uint32_t decorationOperand = 0;
+                    if (annotation.opcode() == spv::Op::OpDecorate) {
+                        decorationOperand = kDecorateDecorationOperand;
+                    } else if (annotation.opcode() == spv::Op::OpMemberDecorate) {
+                        decorationOperand = kMemberDecorateDecorationOperand;
+                    } else {
+                        continue;
+                    }
+
+                    if (annotation.NumInOperands() <= decorationOperand) {
+                        continue;
+                    }
+                    if (static_cast<spv::Decoration>(annotation.GetSingleWordInOperand(decorationOperand)) ==
+                        spv::Decoration::NoPerspective) {
+                        toKill.push_back(&annotation);
+                    }
+                }
+
+                if (toKill.empty()) {
+                    return Status::SuccessWithoutChange;
+                }
+
+                for (Instruction* inst : toKill) {
+                    irContext->KillInst(inst);
+                }
+
+                irContext->InvalidateAnalysesExceptFor(IRContext::kAnalysisNone);
+                return Status::SuccessWithChange;
+            }
+
+            spvtools::Optimizer::PassToken StripNoPerspectivePass::CreateStripNoPerspectivePass() {
+                return spvtools::Optimizer::PassToken(MakeUnique<StripNoPerspectivePass>());
+            }
+        } // namespace ShaderTranspiler
+    } // namespace MG_Util
+} // namespace MobileGL

MobileGL/MG_Util/ShaderTranspiler/SpirvPasses/StripNoPerspectivePass.h

@@ -0,0 +1,35 @@
+// MobileGL - MobileGL/MG_Util/ShaderTranspiler/SpirvPasses/StripNoPerspectivePass.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 {
+            // Removes the NoPerspective decoration from every interface variable and block member.
+            // DirectGLES fallback only, for devices that lack GL_NV_shader_noperspective_interpolation:
+            // SPIRV-Cross renders a NoPerspective-decorated varying as ESSL `noperspective` plus
+            // `#extension GL_NV_shader_noperspective_interpolation : require`, which such a driver
+            // rejects. Dropping the decoration falls the varying back to smooth (perspective-correct)
+            // interpolation - the same visible result the old text-level strip produced, but without
+            // corrupting identifiers and without touching DirectVulkan, where NoPerspective is native.
+            // (The exact screen-linear emulation via gl_Position.w / gl_FragCoord.w is a later step.)
+            class StripNoPerspectivePass : public spvtools::opt::Pass {
+            public:
+                const char* name() const override { return "strip-noperspective"; }
+                Status Process() override;
+
+                static spvtools::Optimizer::PassToken CreateStripNoPerspectivePass();
+            };
+        } // namespace ShaderTranspiler
+    } // namespace MG_Util
+} // namespace MobileGL