src/ui.cpp

@@ -4013,10 +4013,14 @@ gboolean tick(gpointer user) {
         app->sidebar_syncing = false;
       }
     }
-    // The readouts strip is on screen exactly when the dock is not. Decided here, right after the wish was
-    // re-asserted and *before* the collapsing below (which makes the split view write `show-sidebar`
-    // false itself until the next frame re-asserts it): read after it, the strip would show for one frame
-    // each time the window narrowed.
+    // The readouts strip is on screen when the dock is not beside the plot: `!show-sidebar || collapsed`.
+    // Decided here, right after the wish was re-asserted and *before* the collapsing below (which makes
+    // the split view write `show-sidebar` false itself until the next frame re-asserts it): read after
+    // it, `show-sidebar` would be that transient false. The strip reads `collapsed` too, and here that is
+    // the previous frame's value (`set_collapsed()` follows): on a collapse or a widening the strip
+    // changes one tick after the split view does, but never to a wrong state -- `show-sidebar` is always
+    // the re-asserted wish and `collapsed` a settled value -- so it does not flash. Moving the call after
+    // `set_collapsed()` would bring back the transient `show-sidebar` for nothing.
     sync_readouts_strip(*app);
     const int window_w = gtk_widget_get_width(app->window);
     if (window_w > 0) {

src/ui_app.hpp

@@ -610,8 +610,8 @@ struct App {
   GtkWidget* dock_measures_edit = nullptr;
   /// One value label per measurement, in `measures` order (the dock's copy of `measure_labels`).
   std::vector<GtkWidget*> dock_measure_labels;
-  /// The readouts strip under the plot (`main-window.ui` `readouts_strip`, `src/ui_dock.cpp`): shown only
-  /// while the dock is not. Its value labels mirror the dock's one for one -- `strip_cursor_deltas` the
+  /// The readouts strip under the plot (`main-window.ui` `readouts_strip`, `src/ui_dock.cpp`): shown
+  /// whenever the dock is not beside the plot (`!show-sidebar || collapsed`). Its value labels mirror the dock's one for one -- `strip_cursor_deltas` the
   /// `d` cell of each `dock_cursor_lines` entry, `strip_measure_labels` each of `dock_measure_labels` --
   /// and `strip_cursor_who` the cursor lines' `who` cells, all written from the dock setters' arguments.
   GtkWidget* readouts_strip = nullptr;
@@ -1797,8 +1797,9 @@ void dock_cursor_cell(App& app, std::size_t line, const std::string& a, const st
 void dock_measure_value(App& app, std::size_t i, const std::string& text);
 /// The readouts strip under the plot (`src/ui_dock.cpp`): the third reader of the same strings. It is
 /// filled by the `dock_*` rebuilds and written by the `dock_*` setters above (so nothing here formats),
-/// and shown exactly when the dock is not: `sync_readouts_strip()` is called by the tick after the
-/// show-sidebar reconciliation. `dock_set_cursors_sensitive()` is the one writer of the cursor readouts'
+/// and shown whenever the dock is not beside the plot (`!show-sidebar || collapsed`, a collapsed dock being
+/// an overlay on it): `sync_readouts_strip()` is called by the tick after the show-sidebar reconciliation
+/// and before `set_collapsed()`, so it reads the previous frame's `collapsed`. `dock_set_cursors_sensitive()` is the one writer of the cursor readouts'
 /// sensitivity, for the dock's grid and the strip's chips together.
 void sync_readouts_strip(App& app);
 void dock_set_cursors_sensitive(App& app, bool on);

src/ui_dock.cpp

@@ -11,7 +11,8 @@
 //
 // The same strings are shown a third time in the readouts strip under the plot (`readouts_strip`, one
 // fixed-height line: a "Cursors" button, one chip per cursor line with its delta, a "Measures" button, one
-// chip per measurement with its value), which is on screen exactly when the dock is not. The setters below
+// chip per measurement with its value), which is on screen whenever the dock is not beside the plot (hidden
+// with the Dock button, or the window collapsed and the dock an overlay). The setters below
 // write the strip's labels in the same call as the dock's, from the same argument, so there is still one
 // string and no second formatter.
 //
@@ -345,10 +346,14 @@ void dock_set_cursors_sensitive(App& app, bool on) {
 
 void sync_readouts_strip(App& app) {
   if (app.readouts_strip == nullptr || app.side_view == nullptr) return;
-  // The strip is on screen exactly when the dock is not: `show-sidebar` is false when the dock is hidden
-  // with the Dock button, and when the window is collapsed and the dock is not currently overlaid.
-  const bool want =
-      !adw_overlay_split_view_get_show_sidebar(ADW_OVERLAY_SPLIT_VIEW(app.side_view));
+  // The strip is on screen whenever the dock is not *beside* the plot: hidden with the Dock button, or
+  // the window collapsed (compact mode), where the dock overlays the plot -- even while the overlay is
+  // open -- and is not a readout you can keep an eye on while looking at the trace. `collapsed` is the
+  // split view's value from the previous frame (the tick calls this before `set_collapsed()`), so the
+  // strip follows a collapse or a widening one tick late; `show-sidebar` is the wish just re-asserted.
+  AdwOverlaySplitView* split = ADW_OVERLAY_SPLIT_VIEW(app.side_view);
+  const bool want = !adw_overlay_split_view_get_show_sidebar(split) ||
+                    adw_overlay_split_view_get_collapsed(split);
   if ((gtk_widget_get_visible(app.readouts_strip) != FALSE) != want) {
     gtk_widget_set_visible(app.readouts_strip, want);
   }

src/ui_probe.cpp

@@ -4338,8 +4338,10 @@ static int dock_width_fits(App& a, int* dock_w, int* side_w) {
 }
 
 /// The readouts strip against the dock it mirrors: `same_text=1` when every strip label's text equals the
-/// dock's (the cursors' `who` and delta cells, the measurements' values) and the counts agree. `visible` must
-/// be the opposite of `dock_shown` (`show-sidebar`), and `h` the strip's fixed 26 whenever it is visible.
+/// dock's (the cursors' `who` and delta cells, the measurements' values) and the counts agree. The strip is
+/// shown whenever the dock is not beside the plot, so `expected` is `!dock_shown || collapsed` (`dock_shown`
+/// is `show-sidebar`, `collapsed` the split view's, both read in the same frame as `visible`), `visible_ok`
+/// is `visible == expected`, and `h` is the strip's fixed 26 whenever it is visible.
 /// `sens_same` is the strip's cursor chips sharing the dock grid's sensitivity.
 static void strip_report(App& a, const char* tag, const char* what) {
   const auto text = [](GtkWidget* w) { return std::string(gtk_label_get_text(GTK_LABEL(w))); };
@@ -4363,13 +4365,15 @@ static void strip_report(App& a, const char* tag, const char* what) {
   const bool collapsed =
       a.side_view != nullptr &&
       adw_overlay_split_view_get_collapsed(ADW_OVERLAY_SPLIT_VIEW(a.side_view)) != FALSE;
+  const bool expected = !dock_shown || collapsed;
   const bool sens_same =
       a.strip_cursor_box != nullptr && a.dock_cursor_grid != nullptr &&
       gtk_widget_get_sensitive(a.strip_cursor_box) == gtk_widget_get_sensitive(a.dock_cursor_grid);
   std::fprintf(stderr,
-               "[%s-probe] %-14s strip: visible=%d dock_shown=%d cursors=%zu measures=%zu same_text=%d "
-               "h=%d sens_same=%d collapsed=%d window=%d\n",
-               tag, what, visible ? 1 : 0, dock_shown ? 1 : 0, a.strip_cursor_deltas.size(),
+               "[%s-probe] %-14s strip: visible=%d expected=%d visible_ok=%d dock_shown=%d cursors=%zu "
+               "measures=%zu same_text=%d h=%d sens_same=%d collapsed=%d window=%d\n",
+               tag, what, visible ? 1 : 0, expected ? 1 : 0, visible == expected ? 1 : 0,
+               dock_shown ? 1 : 0, a.strip_cursor_deltas.size(),
                a.strip_measure_labels.size(), same, a.readouts_strip != nullptr
                    ? gtk_widget_get_height(a.readouts_strip) : -1,
                sens_same ? 1 : 0, collapsed ? 1 : 0,
@@ -4378,10 +4382,10 @@ static void strip_report(App& a, const char* tag, const char* what) {
 
 /// Puts the dock away through the wish the tick re-asserts and reads the strip with it hidden
 /// (`<tag>-probe ... strip:`: visible must be 1, h 26, same_text 1), then restores the wish and reads it
-/// again (visible must be 0). Under `xvfb-run` the window is 756 px wide, below `kSidebarRoom`, so the split
-/// view is `collapsed` on every line: both legs are the collapsed case (the tick keeps a wished dock
-/// overlaid, a hidden one off), and `collapsed=0` is not reachable from a probe -- a window with no
-/// manager cannot be resized by `gtk_window_set_default_size()`.
+/// again. Under `xvfb-run` the window is 756 px wide, below `kSidebarRoom`, so the split view is `collapsed`
+/// on every line and the strip is visible on every line, the restored one included (the tick keeps a wished
+/// dock overlaid, a hidden one off); the wide case, where the restored dock hides the strip, is not reachable
+/// from a probe -- a window with no manager cannot be resized by `gtk_window_set_default_size()`.
 struct StripDrive {
   App* app;
   const char* tag;