View: Make signals_changed() more predictable

Newly created trace groups have their traces restacked
immediately to make sure we can rely on the group's v_extents.

We no longer unconditionally add trace groups that could
actually be empty.

The code that adds the new top-level items is more
straightforward now.

diff --git a/pv/view/view.cpp b/pv/view/view.cpp
index 9a46bab8c4c4d41ea9f91e36b05d84c96c05b9c7..8e48ae444582ffd96b9f3d5af407dcd28b3abe17 100644 (file)
--- a/pv/view/view.cpp
+++ b/pv/view/view.cpp
@@ -911,13 +911,11 @@ void View::signals_changed()
 
        vector< shared_ptr<TraceTreeItem> > new_top_level_items;
 
-       const auto device = session_.device();
-       if (!device)
+       if (!session_.device())
                return;
 
-       shared_ptr<sigrok::Device> sr_dev = device->device();
+       shared_ptr<sigrok::Device> sr_dev = session_.device()->device();
        assert(sr_dev);
-
        const vector< shared_ptr<Channel> > channels(
                sr_dev->channels());
 
@@ -992,6 +990,9 @@ void View::signals_changed()
                                offset += extents.second;
                }
 
+               // Assign proper vertical offsets to each channel in the group
+               new_trace_group->restack_items();
+
                // If this is a new group, enqueue it in the new top level
                // items list
                if (!new_traces_in_group.empty() && new_trace_group)
@@ -1003,19 +1004,23 @@ void View::signals_changed()
        copy_if(channels.begin(), channels.end(), back_inserter(logic_channels),
                [](const shared_ptr<Channel>& c) {
                        return c->type() == sigrok::ChannelType::LOGIC; });
+
        const vector< shared_ptr<Trace> > non_grouped_logic_signals =
-               extract_new_traces_for_channels(logic_channels,
-                       signal_map, add_traces);
-       const shared_ptr<TraceGroup> non_grouped_trace_group(
-               make_shared<TraceGroup>());
-       for (shared_ptr<Trace> trace : non_grouped_logic_signals)
-               non_grouped_trace_group->add_child_item(trace);
-       new_top_level_items.push_back(non_grouped_trace_group);
+               extract_new_traces_for_channels(logic_channels, signal_map, add_traces);
+
+       if (non_grouped_logic_signals.size() > 0) {
+               const shared_ptr<TraceGroup> non_grouped_trace_group(
+                       make_shared<TraceGroup>());
+               for (shared_ptr<Trace> trace : non_grouped_logic_signals)
+                       non_grouped_trace_group->add_child_item(trace);
+
+               non_grouped_trace_group->restack_items();
+               new_top_level_items.push_back(non_grouped_trace_group);
+       }
 
        // Enqueue the remaining channels as free ungrouped traces
        const vector< shared_ptr<Trace> > new_top_level_signals =
-               extract_new_traces_for_channels(channels,
-                       signal_map, add_traces);
+               extract_new_traces_for_channels(channels, signal_map, add_traces);
        new_top_level_items.insert(new_top_level_items.end(),
                new_top_level_signals.begin(), new_top_level_signals.end());
 
@@ -1032,16 +1037,15 @@ void View::signals_changed()
 
        // Add and position the pending top levels items
        for (auto item : new_top_level_items) {
+               // Position the item after the last item or at the top if there is none
+               int offset = v_extents().second;
+
                add_child_item(item);
+               item->force_to_v_offset(offset);
 
-               // Position the item after the last present item
-               int offset = v_extents().second;
                const pair<int, int> extents = item->v_extents();
                if (item->enabled())
-                       offset += -extents.first;
-               item->force_to_v_offset(offset);
-               if (item->enabled())
-                       offset += extents.second;
+                       offset += (extents.second - extents.first);
        }
 
        update_layout();