track: store height in "units" rather than pixels

Fixes DPI scalability issue if a project ever moved from a display with
one DPI to another.

app/widget/timelinewidget/timelinewidget.cpp

@@ -573,7 +573,7 @@ void TimelineWidget::IncreaseTrackHeight()
 
   // Increase the height of each track by one "unit"
   foreach (TrackOutput* t, all_tracks) {
-    t->SetTrackHeight(t->GetTrackHeight() + t->GetTrackHeightIncrement());
+    t->SetTrackHeight(t->GetTrackHeight() + TrackOutput::kTrackHeightInterval);
   }
 }
 
@@ -587,7 +587,7 @@ void TimelineWidget::DecreaseTrackHeight()
 
   // Decrease the height of each track by one "unit"
   foreach (TrackOutput* t, all_tracks) {
-    t->SetTrackHeight(qMax(t->GetTrackHeight() - t->GetTrackHeightIncrement(), t->GetTrackHeightMinimum()));
+    t->SetTrackHeight(qMax(t->GetTrackHeight() - TrackOutput::kTrackHeightInterval, TrackOutput::kTrackHeightMinimum));
   }
 }
 

app/widget/timelinewidget/trackview/trackview.cpp

@@ -84,7 +84,9 @@ void TrackView::ConnectTrackList(TrackList *list)
     foreach (TrackOutput* track, list_->GetTracks()) {
       TrackViewItem* item = new TrackViewItem(track);
       items_.append(item);
-      splitter_->Insert(track->Index(), track->GetTrackHeight(), item);
+      splitter_->Insert(track->Index(),
+                        track->GetTrackHeightInPixels(),
+                        item);
     }
 
     connect(list_, &TrackList::TrackHeightChanged, splitter_, &TrackViewSplitter::SetTrackHeight);
@@ -120,12 +122,14 @@ void TrackView::ScrollbarRangeChanged(int, int max)
 
 void TrackView::TrackHeightChanged(int index, int height)
 {
-  list_->GetTrackAt(index)->SetTrackHeight(height);
+  list_->GetTrackAt(index)->SetTrackHeightInPixels(height);
 }
 
 void TrackView::InsertTrack(TrackOutput *track)
 {
-  splitter_->Insert(track->Index(), track->GetTrackHeight(), new TrackViewItem(track));
+  splitter_->Insert(track->Index(),
+                    track->GetTrackHeightInPixels(),
+                    new TrackViewItem(track));
 }
 
 void TrackView::RemoveTrack(TrackOutput *track)

app/widget/timelinewidget/trackview/trackviewsplitter.cpp

@@ -69,7 +69,7 @@ void TrackViewSplitter::HandleReceiver(TrackViewSplitterHandle *h, int diff)
   int new_ele_sz = old_ele_sz + diff;
 
   // Limit by track minimum height
-  new_ele_sz = qMax(new_ele_sz, TrackOutput::GetTrackHeightMinimum());
+  new_ele_sz = qMax(new_ele_sz, TrackOutput::GetMinimumTrackHeightInPixels());
 
   if (alignment_ == Qt::AlignBottom) {
     ele_id = count() - ele_id - 1;

app/widget/timelinewidget/view/timelineview.cpp

@@ -207,7 +207,7 @@ void TimelineView::drawBackground(QPainter *painter, const QRectF &rect)
   int line_y = 0;
 
   foreach (TrackOutput* track, connected_track_list_->GetTracks()) {
-    line_y += track->GetTrackHeight();
+    line_y += track->GetTrackHeightInPixels();
 
     // One px gap between tracks
     line_y++;
@@ -375,10 +375,10 @@ int TimelineView::GetTrackY(int track_index) const
 int TimelineView::GetTrackHeight(int track_index) const
 {
   if (!connected_track_list_ || track_index >= connected_track_list_->GetTrackCount()) {
-    return TrackOutput::GetDefaultTrackHeight();
+    return TrackOutput::GetDefaultTrackHeightInPixels();
   }
 
-  return connected_track_list_->GetTrackAt(track_index)->GetTrackHeight();
+  return connected_track_list_->GetTrackAt(track_index)->GetTrackHeightInPixels();
 }
 
 QPoint TimelineView::GetScrollCoordinates() const

app/widget/timelinewidget/view/timelineviewblockitem.cpp

@@ -119,7 +119,7 @@ void TimelineViewBlockItem::paint(QPainter *painter, const QStyleOptionGraphicsI
       painter->setPen(Qt::lightGray);
     }
 
-    int text_top = TrackOutput::GetTrackHeightMinimum() / 2 - painter->fontMetrics().height() / 2;
+    int text_top = TrackOutput::GetMinimumTrackHeightInPixels() / 2 - painter->fontMetrics().height() / 2;
     QRectF text_rect = rect();
     text_rect.adjust(0, text_top, 0, 0);
     painter->drawText(text_rect, Qt::AlignLeft | Qt::AlignTop, block_->GetLabel());