[Fix, Test] (MG_State, MG_Impl): a reserved program-pipeline name takes state from UseProgramStages and its siblings instead of rejecting them

MobileGL/MG_Impl/GLImpl/Program/GL_ProgramPipeline.cpp

@@ -19,16 +19,26 @@ namespace MobileGL::MG_Impl::GLImpl {
                 code, MakeUnique<GenericErrorInfo>("MG_Impl/GLImpl", function, Move(message)));
         }
 
-        // A pipeline name only names an object once it has been bound or created; querying a
-        // reserved-but-unmaterialised name is INVALID_OPERATION (GL 4.6 core 7.4).
+        // GL 4.6 core 7.4 asks only that the name came from GenProgramPipelines and has not been
+        // deleted - so a name that was reserved and never bound is legal here, and the command
+        // MATERIALIZES it rather than rejecting it.
+        //
+        // Requiring a bound object instead is what broke every separable-program conformance case
+        // across three families: the CTS reserves a name, calls glUseProgramStages three times and
+        // only then binds, which is the order the spec's own example uses. Each of those calls
+        // failed with INVALID_OPERATION, so the stage programs were never recorded - the pipeline
+        // stayed empty, GetProgramForDraw flattened nothing and the draw painted nothing, and the
+        // rejected calls' error was left in the queue for the harness to find. One cause, both
+        // symptoms.
         const SharedPtr<MG_State::GLState::ProgramPipelineObject>* TryGetPipeline(GLuint pipeline,
                                                                                  const char* function) {
-            if (!MG_State::pGLContext->IsProgramPipelineObject(pipeline)) {
+            const auto& object = MG_State::pGLContext->MaterializeProgramPipelineObject(pipeline);
+            if (!object) {
                 RecordPipelineError(ErrorCode::InvalidOperation, function,
                                     std::format("Program pipeline {} does not exist.", pipeline));
                 return nullptr;
             }
-            return &MG_State::pGLContext->GetProgramPipelineObject(pipeline);
+            return &object;
         }
 
         Bool ValidatePipelineCount(GLsizei n, const char* function) {

MobileGL/MG_State/GLState/Core.cpp

@@ -937,13 +937,26 @@ namespace MobileGL::MG_State {
         }
 
         void GLContext::BindProgramPipelineObject(Uint index) {
-            if (index != 0 && m_programPipelines.find(index) == m_programPipelines.end()) {
-                // First bind is what turns a reserved name into an object.
-                m_programPipelines[index] = MakeShared<ProgramPipelineObject>(index);
+            if (index != 0) {
+                MaterializeProgramPipelineObject(index);
             }
             m_boundProgramPipeline = index;
         }
 
+        // Binding is not the only thing that turns a reserved name into an object. GL 4.6 core
+        // 7.4 asks of UseProgramStages, ActiveShaderProgram and ValidateProgramPipeline only that
+        // the name came from GenProgramPipelines and has not been deleted - so a name that was
+        // reserved and never bound must take state from them, not be rejected. glIsProgramPipeline
+        // is the one place the distinction survives (it answers FALSE until the name is used),
+        // which is why IsProgramPipelineObject stays as it is.
+        const SharedPtr<ProgramPipelineObject>& GLContext::MaterializeProgramPipelineObject(Uint index) {
+            static const SharedPtr<ProgramPipelineObject> kNone;
+            if (index == 0 || !m_programPipelineNames.IsValid(index)) return kNone;
+            const auto it = m_programPipelines.find(index);
+            if (it != m_programPipelines.end()) return it->second;
+            return m_programPipelines[index] = MakeShared<ProgramPipelineObject>(index);
+        }
+
         void GLContext::MarkProgramPipelineForDeletion(Uint index) {
             if (index == 0 || !m_programPipelineNames.IsValid(index)) return;
             if (index == m_boundProgramPipeline) {

MobileGL/MG_State/GLState/Core.h

@@ -172,12 +172,16 @@ namespace MobileGL {
 
                 // Program pipeline (GL_ARB_separate_shader_objects, GL 4.6 core 7.4). Like queries
                 // and transform feedbacks, glGenProgramPipelines only RESERVES a name - the object
-                // appears on first bind - while glCreateProgramPipelines makes it immediately.
+                // appears on first USE (any of bind, UseProgramStages, ActiveShaderProgram,
+                // ValidateProgramPipeline) - while glCreateProgramPipelines makes it immediately.
                 void GenProgramPipelineNames(Uint number, Vector<Uint>& pipelines);
                 void CreateProgramPipelineObject(Uint index);
                 Bool ValidateProgramPipelineName(Uint index) const;
                 Bool IsProgramPipelineObject(Uint index) const;
                 void BindProgramPipelineObject(Uint index);
+                // Materializes a reserved name; returns null for 0 or a name that is not a live
+                // GenProgramPipelines name.
+                const SharedPtr<ProgramPipelineObject>& MaterializeProgramPipelineObject(Uint index);
                 void MarkProgramPipelineForDeletion(Uint index);
                 const SharedPtr<ProgramPipelineObject>& GetProgramPipelineObject(Uint index) const;
                 Uint GetBoundProgramPipelineName() const { return m_boundProgramPipeline; }