3 files changed, 53 insertions, 24 deletions

diff --git a/Applications/Piano/RollWidget.cpp b/Applications/Piano/RollWidget.cpp
index d8d0aa670e..9d99f1b67c 100644
--- a/Applications/Piano/RollWidget.cpp
+++ b/Applications/Piano/RollWidget.cpp
@@ -159,29 +159,58 @@ void RollWidget::mousedown_event(GUI::MouseEvent& event)
     if (!widget_inner_rect().contains(event.x(), event.y()))
         return;
 
-    int y = (event.y() + vertical_scrollbar().value()) - frame_thickness();
+    m_note_drag_start = event.position();
+
+    int y = (m_note_drag_start.value().y() + vertical_scrollbar().value()) - frame_thickness();
     y /= note_height;
+    m_drag_note = (note_count - 1) - y;
+
+    mousemove_event(event);
+}
 
-    // There's a case where we can't just use x / m_note_width. For example, if
-    // your m_note_width is 3.1 you will have a rect starting at 3. When that
-    // leftmost pixel of the rect is clicked you will do 3 / 3.1 which is 0
-    // and not 1. We can avoid that case by shifting x by 1 if m_note_width is
-    // fractional, being careful not to shift out of bounds.
-    int x = (event.x() + horizontal_scrollbar().value()) - frame_thickness();
-    bool note_width_is_fractional = m_note_width - static_cast<int>(m_note_width) != 0;
-    bool x_is_not_last = x != widget_inner_rect().width() - 1;
-    if (note_width_is_fractional && x_is_not_last)
-        ++x;
-    x /= m_note_width;
-
-    int note = (note_count - 1) - y;
-    u32 on_sample = roll_length * (static_cast<double>(x) / m_num_notes);
-    u32 off_sample = (roll_length * (static_cast<double>(x + 1) / m_num_notes)) - 1;
-    m_track_manager.current_track().set_roll_note(note, on_sample, off_sample);
+void RollWidget::mousemove_event(GUI::MouseEvent& event)
+{
+    if (!m_note_drag_start.has_value())
+        return;
+
+    if (m_note_drag_location.has_value()) {
+        // Clear previous note
+        m_track_manager.current_track().set_roll_note(m_drag_note, m_note_drag_location.value().on_sample, m_note_drag_location.value().off_sample);
+    }
+
+    auto get_note_x = [&](int x0) {
+        // There's a case where we can't just use x / m_note_width. For example, if
+        // your m_note_width is 3.1 you will have a rect starting at 3. When that
+        // leftmost pixel of the rect is clicked you will do 3 / 3.1 which is 0
+        // and not 1. We can avoid that case by shifting x by 1 if m_note_width is
+        // fractional, being careful not to shift out of bounds.
+        int x = (x0 + horizontal_scrollbar().value()) - frame_thickness();
+        bool note_width_is_fractional = m_note_width - static_cast<int>(m_note_width) != 0;
+        bool x_is_not_last = x != widget_inner_rect().width() - 1;
+        if (note_width_is_fractional && x_is_not_last)
+            ++x;
+        x /= m_note_width;
+        return x;
+    };
+
+    int x0 = get_note_x(m_note_drag_start.value().x());
+    int x1 = get_note_x(event.x());
+
+    u32 on_sample = roll_length * (static_cast<double>(min(x0, x1)) / m_num_notes);
+    u32 off_sample = (roll_length * (static_cast<double>(max(x0, x1) + 1) / m_num_notes)) - 1;
+    m_track_manager.current_track().set_roll_note(m_drag_note, on_sample, off_sample);
+    m_note_drag_location = RollNote({ on_sample, off_sample });
 
     update();
 }
 
+void RollWidget::mouseup_event(GUI::MouseEvent& event)
+{
+    (void)event;
+    m_note_drag_start = {};
+    m_note_drag_location = {};
+}
+
 // FIXME: Implement zoom and horizontal scroll events in LibGUI, not here.
 void RollWidget::mousewheel_event(GUI::MouseEvent& event)
 {
diff --git a/Applications/Piano/RollWidget.h b/Applications/Piano/RollWidget.h
index 28910156cc..bbfcc8bb62 100644
--- a/Applications/Piano/RollWidget.h
+++ b/Applications/Piano/RollWidget.h
@@ -46,6 +46,8 @@ private:
 
     virtual void paint_event(GUI::PaintEvent&) override;
     virtual void mousedown_event(GUI::MouseEvent& event) override;
+    virtual void mousemove_event(GUI::MouseEvent& event) override;
+    virtual void mouseup_event(GUI::MouseEvent& event) override;
     virtual void mousewheel_event(GUI::MouseEvent&) override;
 
     TrackManager& m_track_manager;
@@ -55,4 +57,8 @@ private:
     int m_num_notes { 0 };
     double m_note_width { 0.0 };
     int m_zoom_level { 1 };
+
+    Optional<Gfx::IntPoint> m_note_drag_start;
+    Optional<RollNote> m_note_drag_location;
+    int m_drag_note;
 };
diff --git a/Applications/Piano/Track.cpp b/Applications/Piano/Track.cpp
index 22cbbe03f8..754a43407a 100644
--- a/Applications/Piano/Track.cpp
+++ b/Applications/Piano/Track.cpp
@@ -287,7 +287,7 @@ void Track::set_roll_note(int note, u32 on_sample, u32 off_sample)
             sync_roll(note);
             return;
         }
-        if (it->on_sample == new_roll_note.on_sample && it->off_sample == new_roll_note.off_sample) {
+        if (it->on_sample <= new_roll_note.on_sample && it->off_sample >= new_roll_note.on_sample) {
             if (m_time >= it->on_sample && m_time <= it->off_sample)
                 set_note(note, Off);
             m_roll_notes[note].remove(it);
@@ -301,12 +301,6 @@ void Track::set_roll_note(int note, u32 on_sample, u32 off_sample)
             it = m_roll_notes[note].begin();
             continue;
         }
-        if (it->on_sample < new_roll_note.on_sample && it->off_sample >= new_roll_note.on_sample) {
-            if (m_time >= new_roll_note.off_sample && m_time <= it->off_sample)
-                set_note(note, Off);
-            it->off_sample = new_roll_note.on_sample - 1;
-            ASSERT(it->length() >= 2);
-        }
         ++it;
     }