feat(inserts): copy and paste chains between tracks (phase 92)

docs/CREATIVE_WORKFLOWS.md

@@ -17,3 +17,12 @@ Select a slot, then **Rack actions → Duplicate effect**. The copy appears dire
 after it, retaining controls, automation, wet amount and bypass. It is an
 independent instance with fresh processing history. Eight-slot capacity and
 plugin preparation errors preserve the old chain; Undo removes the copy.
+
+## Copy a chain between tracks
+
+**Rack actions → Copy chain** stores an independent metadata snapshot. Select
+another track and use **Paste chain (replace)** to replace its complete chain,
+including output gain. Copying neither loads modules nor changes undo history;
+pasting prepares the candidate and is undoable. The clipboard is internal to
+this session and clears on successful New/Open. Preparation errors keep both
+the destination and clipboard intact.

docs/ROADMAP.md

@@ -2088,12 +2088,12 @@ Implemented: bounded C99 metadata duplication and Rack actions/Duplicate effect
 Copy and paste independent chain metadata between tracks, with explicit replacement, undo and document-lifecycle cleanup. Clipboard operations must not load modules.
 
 ### Tasks and acceptance criteria
-- [ ] Implement the workflow with bounded validation, safe preparation and documented limits.
+- [x] Implement the workflow with bounded validation, safe preparation and documented limits.
-- [ ] Pass meaningful core and/or GUI checks, including error and undo behavior.
+- [x] Pass meaningful core and/or GUI checks, including error and undo behavior.
-- [ ] Document results and commit this phase separately.
+- [x] Document results and commit this phase separately.
 
 ### Implementation status
-Planned.
+Implemented: session-local independent chain copy/paste with explicit destination replacement, output-gain preservation and prepared undoable adoption. Paste readiness is visible in the menu and successful New/Open clears the clipboard. Focused GUI tests passed for independence, cross-track paste, undo, failed preparation and lifecycle cleanup.
 
 ---
 

src/gui/main_window.cpp

@@ -1405,6 +1405,7 @@ xtc_result MainWindow::install_project(xtc_project *candidate, bool reset_histor
     if (reset_history) {
         history_.swap(new_history);
         for(auto &snapshot:mix_snapshots_)snapshot.reset();
+        if(track_inserts_)track_inserts_->clear_session();
     }
     graph_widget_->reset_layout();
     graph_widget_->set_graph(xtc_project_graph(candidate));

src/gui/track_inserts.hpp

@@ -26,6 +26,8 @@ class TrackInsertsPanel : public Fl_Group {
     xtc_graph *model_=nullptr;
     uint64_t track_=UINT64_MAX;
     xtc_track_chain cached_{};
+    xtc_track_chain clipboard_{};
+    bool clipboard_ready_=false;
     std::vector<uint64_t> ids_;
     std::vector<std::string> names_;
     void result(xtc_result r) { if(r!=XTC_OK)owner_->report_error("Track inserts",r);refresh(true); }
@@ -51,6 +53,8 @@ class TrackInsertsPanel : public Fl_Group {
         gain_=new Fl_Value_Input(x+360,y+52,100,26,"Chain gain");gain_->bounds(0,4);gain_->step(.01);gain_->when(FL_WHEN_RELEASE);
         for(auto *input:{wet_,gain_})input->callback([](Fl_Widget *,void *c){auto *p=static_cast<TrackInsertsPanel *>(c);p->result(p->set_mix(p->wet_->value(),p->gain_->value()));},this);
         actions_=new Fl_Menu_Button(x+486,y+52,150,26,"Rack actions");
+        actions_->add("Copy chain",0,[](Fl_Widget *,void *c){auto *p=static_cast<TrackInsertsPanel *>(c);p->result(p->copy_chain());},this);
+        actions_->add("Paste chain (replace)",0,[](Fl_Widget *,void *c){auto *p=static_cast<TrackInsertsPanel *>(c);p->result(p->paste_chain());},this,FL_MENU_INACTIVE);
         actions_->add("Duplicate effect",0,[](Fl_Widget *,void *c){auto *p=static_cast<TrackInsertsPanel *>(c);p->result(p->duplicate_slot());},this);
         message_=new Fl_Box(x+16,y+84,w-32,30,"Track input > inserts > output gain > track fader > bus/master");message_->align(FL_ALIGN_LEFT|FL_ALIGN_INSIDE);
         slots_=new Fl_Hold_Browser(x+16,y+126,230,h-142);slots_->format_char(0);slots_->callback([](Fl_Widget *,void *c){static_cast<TrackInsertsPanel *>(c)->update_mix();},this);
@@ -64,6 +68,20 @@ class TrackInsertsPanel : public Fl_Group {
     void select_track(uint64_t id) {track_=id;refresh(true);}
     const xtc_graph *graph() const {return model_;}
     void add(const char *file,unsigned int index) { result(owner_->add_track_effect(track_,file,index)); }
+    void clear_session() {clipboard_={};clipboard_ready_=false;update_actions();}
+    bool clipboard_ready() const {return clipboard_ready_;}
+    void update_actions() {
+        int index=actions_->find_index("Paste chain (replace)");
+        if(index>=0)actions_->mode(index,clipboard_ready_ ? 0 : FL_MENU_INACTIVE);
+    }
+    xtc_result copy_chain() {
+        xtc_track_chain chain{};auto r=xtc_project_get_chain(owner_->project_.get(),track_,&chain);
+        if(r==XTC_OK){clipboard_=chain;clipboard_ready_=true;update_actions();}return r;
+    }
+    xtc_result paste_chain() {
+        if(!clipboard_ready_)return XTC_ERR_NOT_FOUND;
+        return owner_->set_track_chain(track_,clipboard_);
+    }
     xtc_result duplicate_slot() {
         xtc_track_chain chain{};auto r=xtc_project_get_chain(owner_->project_.get(),track_,&chain);size_t index=selected_slot();
         if(r==XTC_OK)r=xtc_track_chain_duplicate(&chain,index,&chain);

tests/integration/test_gui.cpp

@@ -232,6 +232,14 @@ int creative_workflow_tests()
     CHECK(panel->duplicate_slot()==XTC_OK && panel->selected_slot()==1);
     xtc_track_chain chain{};CHECK(xtc_project_get_chain(s->project(),first_track,&chain)==XTC_OK && chain.count==2);
     CHECK(window.undo()==XTC_OK);panel->refresh(true);CHECK(xtc_project_get_chain(s->project(),first_track,&chain)==XTC_OK && chain.count==1);
+    CHECK(!panel->clipboard_ready() && panel->paste_chain()==XTC_ERR_NOT_FOUND);
+    CHECK(panel->copy_chain()==XTC_OK && panel->clipboard_ready());
+    CHECK(panel->set_mix(.2,.6)==XTC_OK);
+    panel->select_track(second_track);CHECK(panel->paste_chain()==XTC_OK);
+    CHECK(xtc_project_get_chain(s->project(),second_track,&chain)==XTC_OK && chain.count==1 && chain.output_gain==1 && chain.slots[0].wet==1);
+    CHECK(window.undo()==XTC_OK);panel->refresh(true);CHECK(xtc_project_get_chain(s->project(),second_track,&chain)==XTC_OK && chain.count==0);
+    submit_result=XTC_ERR_INVALID_STATE;auto *unchanged=s->project();CHECK(panel->paste_chain()==XTC_ERR_INVALID_STATE && s->project()==unchanged);submit_result=XTC_OK;
+    CHECK(window.new_project()==XTC_OK && !panel->clipboard_ready() && panel->paste_chain()==XTC_ERR_NOT_FOUND);
     window.do_callback();puts("Creative workflow GUI checks passed.");return failures ? 1 : 0;
 }
 int track_insert_tests()