[Fix] (Program): count the tessellation control stage as a transform-feedback capture stage

MobileGL/MG_State/GLState/Core.cpp

@@ -710,8 +710,15 @@ namespace MobileGL::MG_State {
             //     must not, or failing the link and killing every draw. A capture stage with an
             //     empty list is not a reason to look further down: it is the answer, and
             //     glBeginTransformFeedback's INVALID_OPERATION is the correct consequence.
+            //
+            // The order is the pipeline read backwards and includes the tessellation CONTROL
+            // stage, which is a vertex-processing stage too (GL 4.6 core 11): it can only be
+            // the last one in a pipeline that has a TCS but no evaluation or geometry stage,
+            // which is why it sits after TessEval. Same four stages, same order, as
+            // ProgramLinkTask::ResolveTransformFeedbackVaryings - see rule (2).
             for (const ShaderStage captureStage:
-                 {ShaderStage::Geometry, ShaderStage::TessEval, ShaderStage::Vertex}) {
+                 {ShaderStage::Geometry, ShaderStage::TessEval, ShaderStage::TessControl,
+                  ShaderStage::Vertex}) {
                 if (!compositeHasStage[static_cast<SizeT>(captureStage)]) continue;
                 const auto& captureProgram = pipeline->GetStageProgram(captureStage);
                 if (!captureProgram) continue;

MobileGL/MG_State/GLState/ProgramState/ProgramLinkTask.cpp

@@ -1910,10 +1910,18 @@ namespace MobileGL::MG_State::GLState {
             return true;
         }
 
-        // Capture happens at the last vertex-processing stage (geometry, then
-        // tessellation evaluation, then vertex).
+        // Capture happens at the last vertex-processing stage (geometry, then tessellation
+        // evaluation, then tessellation CONTROL, then vertex). All four are vertex-processing
+        // stages in GL 4.6 core 11 - the control shader included - and in a separable program
+        // whose only stage is a TCS it is the last one that exists, so it is the capture stage
+        // and such a program MUST link (GL 4.6 core 7.3/11.1.2.1; the conformance suite spells
+        // the API split out at esextcTessellationShaderXFB.cpp:390-416, where a non-ES context
+        // takes should_succeed=true). TessControl sits AFTER TessEvaluation so a complete
+        // pipeline still captures at the evaluation stage and only a TCS-only program falls
+        // through to it. If MobileGL ever serves an ES context this arm has to be gated on the
+        // advertised API: ES requires the very same link to FAIL.
         const glslang::TIntermediate* captureIntermediate = nullptr;
-        for (EShLanguage stage : {EShLangGeometry, EShLangTessEvaluation, EShLangVertex}) {
+        for (EShLanguage stage : {EShLangGeometry, EShLangTessEvaluation, EShLangTessControl, EShLangVertex}) {
             captureIntermediate = artifacts.program->getIntermediate(stage);
             if (captureIntermediate != nullptr) {
                 break;

MobileGL/MG_State/GLState/ProgramState/ProgramObject.cpp

@@ -554,7 +554,8 @@ namespace MobileGL::MG_State::GLState {
         // asked for is the safer of the two readings.
         if (task->in.requestedXfbVaryings.empty()) {
             for (const ShaderStage captureStage:
-                 {ShaderStage::Geometry, ShaderStage::TessEval, ShaderStage::Vertex}) {
+                 {ShaderStage::Geometry, ShaderStage::TessEval, ShaderStage::TessControl,
+                  ShaderStage::Vertex}) {
                 Bool stagePresent = false;
                 for (const auto& shader : m_shaders) {
                     if (!shader || shader->GetShaderStage() != captureStage) continue;