feat: quantize MIDI clips with deterministic swing and strength

docs/MODERN_EDITING.md

@@ -23,3 +23,7 @@ Edit/Repeat selected phrase asks for 1..1024 additional copies. The bounding spa
 ## Phase 51
 
 Edit/Align clip starts to cursor places every selected start at the cursor. Slip sources earlier/later changes source offsets by the snap step while retaining timeline positions and durations. Trimming must leave source material available; an invalid slip rejects the whole selection. No time stretching or destructive media edits are performed.
+
+## Phase 52
+
+Select MIDI clips and use Edit/MIDI tools/Swing quantize. Grid is in source ticks; swing delays alternate subdivisions by 0..half a grid step, while strength blends the old start toward the nearest swung point. Durations stay fixed. All source notes are affected, including notes outside visible trims. Mixed audio/MIDI selections and notes that would exceed source bounds reject the entire edit. This is destructive note editing with undo, not a live groove engine.

docs/ROADMAP.md

@@ -1393,12 +1393,12 @@ Implemented: selection-wide start alignment and source slip commands reuse atomi
 Apply bounded swing and quantize strength to source note starts with deterministic rounding and source-bound checks.
 
 ### Tasks and acceptance criteria
-- [ ] Provide the control/model behavior and accessible GUI commands.
-- [ ] Validate bounds and failure rollback; preserve existing project compatibility and callback safety.
-- [ ] Test the new workflow and document scope and limitations.
+- [x] Provide the control/model behavior and accessible GUI commands.
+- [x] Validate bounds and failure rollback; preserve existing project compatibility and callback safety.
+- [x] Test the new workflow and document scope and limitations.
 
 ### Implementation status
-Planned.
+Implemented: deterministic nearest swung-grid quantization with 0..100 strength and source-range rollback through a C99 API and MIDI tools dialog. Core timing, strength and late-note rollback tests plus focused GUI/piano refresh tests pass.
 
 ---
 

include/xtc/xtc_editing.h

@@ -15,6 +15,19 @@ extern "C" {
 typedef enum { XTC_CLIPS_MOVE, XTC_CLIPS_DUPLICATE, XTC_CLIPS_DELETE, XTC_CLIPS_ALIGN, XTC_CLIPS_SLIP } xtc_clip_operation;
 xtc_result xtc_project_transform_clips(xtc_project *project,const uint64_t *ids,size_t count,
                                       xtc_clip_operation operation,int64_t amount,uint64_t *out_ids);
+/* MIDI transforms affect ALL source notes in selected MIDI clips, including
+ * notes hidden by trims. Mixed audio/MIDI selections reject; IDs and unaffected
+ * fields persist. No matching notes returns NOT_FOUND. Edits are atomic.
+ * Swing: grid 1..3840, swing 0..100 delays alternate grid points by up to half
+ * a grid; strength 0..100 blends toward the nearest swung point (ties later).
+ * Durations stay fixed. Out-of-source results reject the complete operation. */
+typedef enum { XTC_MIDI_TRANSFORM_SWING } xtc_midi_transform_type;
+typedef struct {
+    xtc_midi_transform_type type;
+    uint64_t grid;
+    unsigned int swing,strength;
+} xtc_midi_transform;
+xtc_result xtc_project_transform_midi(xtc_project *project,const uint64_t *ids,size_t count,const xtc_midi_transform *edit);
 /* Repeat the bounding phrase span, including gaps, 1..1024 additional copies.
  * Originals remain selected by the caller; all copies publish together. */
 xtc_result xtc_project_repeat_clips(xtc_project *project,const uint64_t *ids,size_t count,unsigned int copies);

src/gui/main_window.cpp

@@ -322,6 +322,7 @@ MainWindow::MainWindow(bool prompt_unsaved,const char *configuration)
     Fl_Group::current(parent);
     menu->add("Edit/Nudge selection left",0,[](Fl_Widget *,void *c){static_cast<SequencerWidget *>(c)->nudge_selection(-1);},sequencer_);
     menu->add("Edit/Nudge selection right",0,[](Fl_Widget *,void *c){static_cast<SequencerWidget *>(c)->nudge_selection(1);},sequencer_);
+    menu->add("Edit/MIDI tools/Swing quantize...",0,[](Fl_Widget *,void *c){static_cast<SequencerWidget *>(c)->swing_dialog();},sequencer_);
     menu->add("Edit/Align clip starts to cursor",0,[](Fl_Widget *,void *c){auto *s=static_cast<SequencerWidget *>(c);s->transform_selection(XTC_CLIPS_ALIGN,static_cast<int64_t>(s->position()));},sequencer_);
     menu->add("Edit/Slip sources earlier",0,[](Fl_Widget *,void *c){auto *s=static_cast<SequencerWidget *>(c);s->transform_selection(XTC_CLIPS_SLIP,-static_cast<int64_t>(s->grid()));},sequencer_);
     menu->add("Edit/Slip sources later",0,[](Fl_Widget *,void *c){auto *s=static_cast<SequencerWidget *>(c);s->transform_selection(XTC_CLIPS_SLIP,static_cast<int64_t>(s->grid()));},sequencer_);

src/gui/sequencer_widget.cpp

@@ -1,3 +1,4 @@
+#include <sstream>
 #include "sequencer_widget.hpp"
 #include "theme.hpp"
 #include "snap.hpp"
@@ -555,6 +556,20 @@ xtc_result SequencerWidget::transform_selection(xtc_clip_operation op,int64_t am
     }
     changed(r);return r;
 }
+xtc_result SequencerWidget::transform_midi(const xtc_midi_transform &edit)
+{
+    auto ids=selected_clips();xtc_result r=before_edit ? before_edit(context_) : XTC_OK;
+    if(r==XTC_OK)r=xtc_project_transform_midi(project_,ids.data(),ids.size(),&edit);
+    changed(r);return r;
+}
+void SequencerWidget::swing_dialog()
+{
+    const char *input=fl_input("Grid ticks (1..3840), swing (0..100), strength (0..100)","240 50 100");if(!input)return;
+    int grid=0,swing=-1,strength=-1;char extra;
+    std::istringstream values(input);
+    if(!(values>>grid>>swing>>strength) || (values>>extra) || grid<1 || grid>3840 || swing<0 || swing>100 || strength<0 || strength>100){fl_alert("Enter a valid grid, swing and strength.");return;}
+    xtc_midi_transform edit{};edit.type=XTC_MIDI_TRANSFORM_SWING;edit.grid=static_cast<uint64_t>(grid);edit.swing=static_cast<unsigned int>(swing);edit.strength=static_cast<unsigned int>(strength);transform_midi(edit);
+}
 xtc_result SequencerWidget::repeat_selection(unsigned int copies)
 {
     auto ids=selected_clips();xtc_result r=before_edit ? before_edit(context_) : XTC_OK;

src/gui/sequencer_widget.hpp

@@ -38,6 +38,8 @@ class SequencerWidget : public Fl_Group {
     bool clip_selected(uint64_t clip) const;
     std::vector<uint64_t> selected_clips() const;
     xtc_result transform_selection(xtc_clip_operation operation,int64_t amount);
+    xtc_result transform_midi(const xtc_midi_transform &edit);
+    void swing_dialog();
     xtc_result repeat_selection(unsigned int copies);
     void repeat_dialog();
     xtc_result copy_selection();

src/project/editing.c

@@ -115,3 +115,36 @@ xtc_result xtc_project_repeat_clips(xtc_project *p,const uint64_t *ids,size_t co
     if(r==XTC_OK)publish(p,copy);
     xtc_project_destroy(copy);return r;
 }
+
+static uint64_t swung_start(uint64_t start,const xtc_midi_transform *edit)
+{
+    uint64_t base=start/edit->grid,best=0,distance=UINT64_MAX;int offset;
+    for(offset=-2;offset<=2;++offset) {
+        int64_t index=(int64_t)base+offset;uint64_t candidate,d;
+        if(index<0)continue;
+        candidate=(uint64_t)index*edit->grid;
+        if(index%2)candidate+=edit->grid*edit->swing/200;
+        d=start>candidate ? start-candidate : candidate-start;
+        if(d<distance || (d==distance && candidate>best)){distance=d;best=candidate;}
+    }
+    return (start*(100-edit->strength)+best*edit->strength+50)/100;
+}
+xtc_result xtc_project_transform_midi(xtc_project *p,const uint64_t *ids,size_t count,const xtc_midi_transform *edit)
+{
+    xtc_project *copy=NULL;size_t i,j,matched=0;xtc_result r=selection_valid(p,ids,count);
+    if(r!=XTC_OK)return r;
+    if(!edit || edit->type!=XTC_MIDI_TRANSFORM_SWING || !edit->grid || edit->grid>3840 || edit->swing>100 || edit->strength>100)return XTC_ERR_INVALID_ARGUMENT;
+    for(i=0;i<count;++i){xtc_clip_info c;xtc_project_find_clip(p,ids[i],&c);if(!c.midi)return XTC_ERR_INVALID_STATE;}
+    r=xtc_project_clone(p,&copy);if(r!=XTC_OK)return r;
+    for(i=0;r==XTC_OK && i<copy->note_count;++i) {
+        xtc_note_info *n=copy->notes+i;xtc_clip_info c;
+        for(j=0;j<count;++j)if(n->clip_id==ids[j])break;
+        if(j==count)continue;
+        ++matched;xtc_project_find_clip(copy,n->clip_id,&c);
+        n->start_tick=swung_start(n->start_tick,edit);
+        if(n->start_tick>=c.source_length_tick || n->length_tick>c.source_length_tick-n->start_tick)r=XTC_ERR_INVALID_ARGUMENT;
+    }
+    if(r==XTC_OK && !matched)r=XTC_ERR_NOT_FOUND;
+    if(r==XTC_OK)publish(p,copy);
+    xtc_project_destroy(copy);return r;
+}

tests/integration/test_gui.cpp

@@ -1331,6 +1331,11 @@ int main(int argc, char **argv)
         s->select_all_clips();CHECK(s->transform_selection(XTC_CLIPS_ALIGN,3840)==XTC_OK);
         CHECK(xtc_project_find_clip(s->project(),first,&moved)==XTC_OK && moved.start_tick==3840);
         CHECK(s->transform_selection(XTC_CLIPS_SLIP,0)==XTC_OK);
+        CHECK(s->select(s->selected_track(),first));CHECK(window.open_piano_roll()==XTC_OK);
+        CHECK(window.piano_roll()->add_note(230,120,61)==XTC_OK);
+        xtc_midi_transform edit{};edit.grid=240;edit.swing=50;edit.strength=100;
+        CHECK(s->transform_midi(edit)==XTC_OK);xtc_note_info quantized{};
+        CHECK(xtc_project_get_note(s->project(),0,&quantized)==XTC_OK && quantized.start_tick==300);
         window.do_callback();
     }
     if (failures != 0) return 1;

tests/unit/test_modern_editing.c

@@ -2,6 +2,25 @@
 #include <assert.h>
 #include <stdio.h>
 
+static void test_swing(void)
+{
+    xtc_project *p=NULL;uint64_t t,c,n;xtc_note_info note;xtc_midi_transform edit={0};
+    assert(xtc_project_create(&p)==XTC_OK && xtc_project_add_track(p,"Track",&t)==XTC_OK);
+    assert(xtc_project_add_midi_clip(p,t,0,1920,&c)==XTC_OK);
+    assert(xtc_project_add_note(p,c,230,120,60,100,0,&n)==XTC_OK);
+    edit.grid=240;edit.swing=50;edit.strength=100;
+    assert(xtc_project_transform_midi(p,&c,1,&edit)==XTC_OK);
+    assert(xtc_project_get_note(p,0,&note)==XTC_OK && note.start_tick==300 && note.id==n && note.length_tick==120);
+    edit.strength=50;edit.swing=0;
+    assert(xtc_project_transform_midi(p,&c,1,&edit)==XTC_OK);
+    assert(xtc_project_get_note(p,0,&note)==XTC_OK && note.start_tick==270);
+    assert(xtc_project_add_note(p,c,1850,70,64,100,0,&n)==XTC_OK);
+    edit.strength=100;
+    assert(xtc_project_transform_midi(p,&c,1,&edit)==XTC_ERR_INVALID_ARGUMENT);
+    assert(xtc_project_get_note(p,0,&note)==XTC_OK && note.start_tick==270);
+    edit.grid=0;assert(xtc_project_transform_midi(p,&c,1,&edit)==XTC_ERR_INVALID_ARGUMENT);
+    xtc_project_destroy(p);
+}
 static void test_align_slip(void)
 {
     xtc_project *p=NULL;uint64_t t,ids[2];xtc_clip_info c;
@@ -35,7 +54,7 @@ static void test_repeat(void)
 }
 int main(void)
 {
-    test_repeat();test_align_slip();
+    test_repeat();test_align_slip();test_swing();
     xtc_project *p=NULL;uint64_t track,a,b,n,ids[2],out[2]={999,999};xtc_clip_info c;
     size_t tracks,clips,notes;
     assert(xtc_project_create(&p)==XTC_OK);