feat: shape MIDI phrase dynamics with bounded velocity scaling

docs/MODERN_EDITING.md

@@ -35,3 +35,7 @@ Edit/MIDI tools/Note gate scales lengths from 1 to 400 percent, rounded to at le
 ## Phase 54
 
 Edit/MIDI tools/Correct to scale takes a root (0=C through 11=B) and chromatic, major or natural minor. Each pitch moves to the nearest permitted MIDI note; ties choose the lower pitch. Timing, channel and velocity remain unchanged. Corrections can produce unison notes; notes are not merged. This changes MIDI notes, not audio pitch or a live scale filter.
+
+## Phase 55
+
+Edit/MIDI tools/Shape velocities scales from 0 to 400 percent, rounds, then applies an offset from -127 to 127. Results clamp to 1..127, keeping every note audible rather than introducing velocity-zero note-offs. Use 0 percent with a positive offset for a fixed velocity. No randomization is applied.

docs/ROADMAP.md

@@ -1438,12 +1438,12 @@ Implemented: root-aware nearest-pitch correction to chromatic, major or natural
 Apply bounded velocity scaling and offsets to selected MIDI clips, with explicit clipping to valid MIDI velocities.
 
 ### Tasks and acceptance criteria
-- [ ] Provide the control/model behavior and accessible GUI commands.
+- [x] Provide the control/model behavior and accessible GUI commands.
-- [ ] Validate bounds and failure rollback; preserve existing project compatibility and callback safety.
+- [x] Validate bounds and failure rollback; preserve existing project compatibility and callback safety.
-- [ ] Test the new workflow and document scope and limitations.
+- [x] Test the new workflow and document scope and limitations.
 
 ### Implementation status
-Planned.
+Implemented: rounded velocity percentage and offset transforms with explicit 1..127 saturation. Core scale/offset/extreme/invalid-input and GUI velocity-refresh tests pass; timing, IDs, pitch and channel remain unchanged.
 
 ---
 

include/xtc/xtc_editing.h

@@ -22,11 +22,13 @@ xtc_result xtc_project_transform_clips(xtc_project *project,const uint64_t *ids,
  * a grid; strength 0..100 blends toward the nearest swung point (ties later).
  * Swing durations stay fixed. LEGATO ends at the next strictly later onset in
  * the same clip/channel (chords stay together), or source end for the last onset. Out-of-source results reject the complete operation. */
-typedef enum { XTC_MIDI_TRANSFORM_SWING, XTC_MIDI_TRANSFORM_GATE, XTC_MIDI_TRANSFORM_LEGATO, XTC_MIDI_TRANSFORM_SCALE } xtc_midi_transform_type;
+typedef enum { XTC_MIDI_TRANSFORM_SWING, XTC_MIDI_TRANSFORM_GATE, XTC_MIDI_TRANSFORM_LEGATO, XTC_MIDI_TRANSFORM_SCALE, XTC_MIDI_TRANSFORM_VELOCITY } xtc_midi_transform_type;
 typedef struct {
     xtc_midi_transform_type type;
     uint64_t grid;
     unsigned int swing,strength;
+    unsigned int velocity_percent; /* VELOCITY: 0..400, rounded scaling then offset, clamp to 1..127. */
+    int velocity_offset; /* -127..127 */
     unsigned int root,scale; /* SCALE: root 0..11 (C..B), scale 0 chromatic, 1 major, 2 natural minor; nearest ties lower. */
     unsigned int gate_percent; /* GATE: 1..400, rounded length, minimum 1 tick. */
 } xtc_midi_transform;

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/Shape velocities...",0,[](Fl_Widget *,void *c){static_cast<SequencerWidget *>(c)->velocity_dialog();},sequencer_);
     menu->add("Edit/MIDI tools/Correct to scale...",0,[](Fl_Widget *,void *c){static_cast<SequencerWidget *>(c)->scale_dialog();},sequencer_);
     menu->add("Edit/MIDI tools/Note gate...",0,[](Fl_Widget *,void *c){static_cast<SequencerWidget *>(c)->gate_dialog();},sequencer_);
     menu->add("Edit/MIDI tools/Legato",0,[](Fl_Widget *,void *c){xtc_midi_transform edit{};edit.type=XTC_MIDI_TRANSFORM_LEGATO;static_cast<SequencerWidget *>(c)->transform_midi(edit);},sequencer_);

src/gui/sequencer_widget.cpp

@@ -562,6 +562,13 @@ xtc_result SequencerWidget::transform_midi(const xtc_midi_transform &edit)
     if(r==XTC_OK)r=xtc_project_transform_midi(project_,ids.data(),ids.size(),&edit);
     changed(r);return r;
 }
+void SequencerWidget::velocity_dialog()
+{
+    const char *input=fl_input("Velocity percentage (0..400), then offset (-127..127)","100 0");if(!input)return;
+    unsigned int percent=0;int offset=0;char extra;std::istringstream values(input);
+    if(!(values>>percent>>offset) || (values>>extra) || percent>400 || offset < -127 || offset>127){fl_alert("Enter a valid percentage and velocity offset.");return;}
+    xtc_midi_transform edit{};edit.type=XTC_MIDI_TRANSFORM_VELOCITY;edit.velocity_percent=percent;edit.velocity_offset=offset;transform_midi(edit);
+}
 void SequencerWidget::scale_dialog()
 {
     const char *input=fl_input("Root (0=C..11=B), scale (0=chromatic, 1=major, 2=natural minor)","0 1");if(!input)return;

src/gui/sequencer_widget.hpp

@@ -42,6 +42,7 @@ class SequencerWidget : public Fl_Group {
     void swing_dialog();
     void gate_dialog();
     void scale_dialog();
+    void velocity_dialog();
     xtc_result repeat_selection(unsigned int copies);
     void repeat_dialog();
     xtc_result copy_selection();

src/project/editing.c

@@ -133,9 +133,10 @@ xtc_result xtc_project_transform_midi(xtc_project *p,const uint64_t *ids,size_t
 {
     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->type>XTC_MIDI_TRANSFORM_SCALE)return XTC_ERR_INVALID_ARGUMENT;
+    if(!edit || edit->type<XTC_MIDI_TRANSFORM_SWING || edit->type>XTC_MIDI_TRANSFORM_VELOCITY)return XTC_ERR_INVALID_ARGUMENT;
     if(edit->type==XTC_MIDI_TRANSFORM_SWING && (!edit->grid || edit->grid>3840 || edit->swing>100 || edit->strength>100))return XTC_ERR_INVALID_ARGUMENT;
     if(edit->type==XTC_MIDI_TRANSFORM_GATE && (!edit->gate_percent || edit->gate_percent>400))return XTC_ERR_INVALID_ARGUMENT;
+    if(edit->type==XTC_MIDI_TRANSFORM_VELOCITY && (edit->velocity_percent>400 || edit->velocity_offset < -127 || edit->velocity_offset>127))return XTC_ERR_INVALID_ARGUMENT;
     if(edit->type==XTC_MIDI_TRANSFORM_SCALE && (edit->root>11 || edit->scale>2))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;
@@ -163,6 +164,9 @@ xtc_result xtc_project_transform_midi(xtc_project *p,const uint64_t *ids,size_t
                 if(d<distance){distance=d;best=pitch;}
             }
             n->pitch=best;
+        } else if(edit->type==XTC_MIDI_TRANSFORM_VELOCITY) {
+            int velocity=(int)((n->velocity*edit->velocity_percent+50)/100)+edit->velocity_offset;
+            n->velocity=(unsigned int)(velocity<1 ? 1 : velocity>127 ? 127 : velocity);
         }
         if(n->start_tick>=c.source_length_tick || n->length_tick>c.source_length_tick-n->start_tick)r=XTC_ERR_INVALID_ARGUMENT;
     }

tests/integration/test_gui.cpp

@@ -1342,6 +1342,8 @@ int main(int argc, char **argv)
         CHECK(xtc_project_get_note(s->project(),0,&quantized)==XTC_OK && quantized.length_tick==3540);
         edit.type=XTC_MIDI_TRANSFORM_SCALE;edit.root=0;edit.scale=1;CHECK(s->transform_midi(edit)==XTC_OK);
         CHECK(xtc_project_get_note(s->project(),0,&quantized)==XTC_OK && quantized.pitch==60);
+        edit.type=XTC_MIDI_TRANSFORM_VELOCITY;edit.velocity_percent=50;edit.velocity_offset=10;CHECK(s->transform_midi(edit)==XTC_OK);
+        CHECK(xtc_project_get_note(s->project(),0,&quantized)==XTC_OK && quantized.velocity==60);
         window.do_callback();
     }
     if (failures != 0) return 1;

tests/unit/test_modern_editing.c

@@ -2,6 +2,22 @@
 #include <assert.h>
 #include <stdio.h>
 
+static void test_velocity(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,0,960,&c)==XTC_OK);
+    assert(xtc_project_add_note(p,c,0,120,61,100,0,&n)==XTC_OK);
+    edit.type=XTC_MIDI_TRANSFORM_VELOCITY;edit.velocity_percent=50;edit.velocity_offset=10;
+    assert(xtc_project_transform_midi(p,&c,1,&edit)==XTC_OK);
+    assert(xtc_project_get_note(p,0,&note)==XTC_OK && note.velocity==60 && note.pitch==61);
+    edit.velocity_percent=400;assert(xtc_project_transform_midi(p,&c,1,&edit)==XTC_OK);
+    assert(xtc_project_get_note(p,0,&note)==XTC_OK && note.velocity==127);
+    edit.velocity_percent=0;edit.velocity_offset=-127;assert(xtc_project_transform_midi(p,&c,1,&edit)==XTC_OK);
+    assert(xtc_project_get_note(p,0,&note)==XTC_OK && note.velocity==1 && note.id==n);
+    edit.velocity_percent=401;assert(xtc_project_transform_midi(p,&c,1,&edit)==XTC_ERR_INVALID_ARGUMENT);
+    xtc_project_destroy(p);
+}
 static void test_scale(void)
 {
     xtc_project *p=NULL;uint64_t t,c,n;xtc_note_info note;xtc_midi_transform edit={0};
@@ -90,7 +106,7 @@ static void test_repeat(void)
 }
 int main(void)
 {
-    test_repeat();test_align_slip();test_swing();test_gate_legato();test_scale();
+    test_repeat();test_align_slip();test_swing();test_gate_legato();test_scale();test_velocity();
     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);