Merge pull request #18793 from dmatveev:dm/in_graph_metadata

G-API: Introduce runtime in-graph metadata

* G-API: In-graph metadata -- initial implementation

* G-API: Finish the in-graph metadata implementation for Streaming

* G-API: Fix standalone build & warnings for in-graph metadata

* G-API: In-graph meta -- fixed review comments

* G-API: Fix issues with desync causing failing tests

modules/gapi/src/compiler/gcompiler.cpp

@@ -35,6 +35,7 @@
 #include "executor/gexecutor.hpp"
 #include "executor/gstreamingexecutor.hpp"
 #include "backends/common/gbackend.hpp"
+#include "backends/common/gmetabackend.hpp"
 
 // <FIXME:>
 #if !defined(GAPI_STANDALONE)
@@ -58,7 +59,8 @@ namespace
             for (const auto &b : pkg.backends()) {
                 aux_pkg = combine(aux_pkg, b.priv().auxiliaryKernels());
             }
-            return combine(pkg, aux_pkg);
+            // Always include built-in meta<> implementation
+            return combine(pkg, aux_pkg, cv::gimpl::meta::kernels());
         };
 
         auto has_use_only = cv::gapi::getCompileArg<cv::gapi::use_only>(args);

modules/gapi/src/compiler/gislandmodel.cpp

@@ -357,26 +357,21 @@ void GIslandExecutable::run(GIslandExecutable::IInput &in, GIslandExecutable::IO
     for (auto &&it: ade::util::zip(ade::util::toRange(in_desc),
                                    ade::util::toRange(in_vector)))
     {
-        // FIXME: Not every Island expects a cv::Mat instead of own::Mat on input
-        // This kludge should go as a result of de-ownification
         const cv::GRunArg& in_data_orig = std::get<1>(it);
         cv::GRunArg in_data;
-#if !defined(GAPI_STANDALONE)
         switch (in_data_orig.index())
         {
         case cv::GRunArg::index_of<cv::Mat>():
-            in_data = cv::GRunArg{cv::make_rmat<cv::gimpl::RMatAdapter>(cv::util::get<cv::Mat>(in_data_orig))};
-            break;
-        case cv::GRunArg::index_of<cv::Scalar>():
-            in_data = cv::GRunArg{(cv::util::get<cv::Scalar>(in_data_orig))};
+            // FIXME: This whole construct is ugly, from
+            // its writing to a need in this in general
+            in_data = cv::GRunArg{ cv::make_rmat<cv::gimpl::RMatAdapter>(cv::util::get<cv::Mat>(in_data_orig))
+                                 , in_data_orig.meta
+                                 };
             break;
         default:
             in_data = in_data_orig;
             break;
         }
-#else
-        in_data = in_data_orig;
-#endif // GAPI_STANDALONE
         in_objs.emplace_back(std::get<0>(it), std::move(in_data));
     }
     for (auto &&it: ade::util::indexed(ade::util::toRange(out_desc)))
@@ -385,9 +380,27 @@ void GIslandExecutable::run(GIslandExecutable::IInput &in, GIslandExecutable::IO
                               out.get(ade::util::checked_cast<int>(ade::util::index(it))));
     }
     run(std::move(in_objs), std::move(out_objs));
+
+    // Propagate in-graph meta down to the graph
+    // Note: this is not a complete implementation! Mainly this is a stub
+    // and the proper implementation should come later.
+    //
+    // Propagating the meta information here has its pros and cons.
+    // Pros: it works here uniformly for both regular and streaming cases,
+    //   also for the majority of old-fashioned (synchronous) backends
+    // Cons: backends implementing the asynchronous run(IInput,IOutput)
+    //   won't get it out of the box
+    cv::GRunArg::Meta stub_meta;
+    for (auto &&in_arg : in_vector)
+    {
+        stub_meta.insert(in_arg.meta.begin(), in_arg.meta.end());
+    }
+    // Report output objects as "ready" to the executor, also post
+    // calculated in-graph meta for the objects
     for (auto &&it: out_objs)
     {
-        out.post(std::move(it.second)); // report output objects as "ready" to the executor
+        out.meta(it.second, stub_meta);
+        out.post(std::move(it.second));
     }
 }
 

modules/gapi/src/compiler/gislandmodel.hpp

@@ -172,6 +172,10 @@ struct GIslandExecutable::IOutput: public GIslandExecutable::IODesc {
     virtual GRunArgP get(int idx) = 0;  // Allocate (wrap) a new data object for output idx
     virtual void post(GRunArgP&&) = 0;  // Release the object back to the framework (mark available)
     virtual void post(EndOfStream&&) = 0; // Post end-of-stream marker back to the framework
+
+    // Assign accumulated metadata to the given output object.
+    // This method can only be called after get() and before post().
+    virtual void meta(const GRunArgP&, const GRunArg::Meta &) = 0;
 };
 
 // GIslandEmitter - a backend-specific thing which feeds data into