Settings changes take effect, and keep this copy respects the plan

Five of the Settings window's controls - the sort order, the three
column toggles and the preview height - were read when it built its new
preferences but never connected to anything, so changing them did
nothing until some other control happened to fire, and then they all
landed at once out of nowhere. Every control is connected now.

The same closure composed a whole Prefs from its own widgets, which
wrote the remembered divider positions back as zeros: dragging the
panes to taste and then ticking any checkbox threw them away. A
settings change is now applied over the preferences as they are, by
model.Prefs.WithDisplay - which is where it can be tested, and is.

"Keep this copy, replace the other" wrote a Displaces straight into the
chain. internal/plan refuses to build two steps that displace one path,
because the second destroys what the first put there; the window went
round that code, so choosing it for two duplicates of one file left
both rows saying "done" with the first file in the Trash. It now
refuses the second, naming the file that has the place.

1 files changed, 38 insertions, 0 deletions

diff --git a/gui/internal/model/prefs.go b/gui/internal/model/prefs.go
index f5ffee5..9ae79a0 100644
--- a/gui/internal/model/prefs.go
+++ b/gui/internal/model/prefs.go
@@ -112,3 +112,41 @@ func (p Prefs) Save() error {
 	}
 	return os.WriteFile(file, append(data, '\n'), 0o644)
 }
+
+// Display is everything the Settings window can change about the window
+// itself. It deliberately leaves out the divider positions: those are set
+// by dragging, and a settings change must not disturb them. Composing a
+// whole Prefs in the Settings window instead is what used to write
+// PreviewWidth, ListWidth and ListHeight back as zeros, so dragging the
+// panes to taste and then ticking any checkbox threw the panes away.
+type Display struct {
+	Sort          string
+	Layout        string
+	ShowSize      bool
+	ShowAge       bool
+	ShowRule      bool
+	Colours       bool
+	Preview       bool
+	SelectAll     bool
+	PreviewHeight int
+}
+
+// DisplayOf is the part of p the Settings window shows.
+func (p Prefs) DisplayOf() Display {
+	return Display{
+		Sort: p.Sort, Layout: p.Layout,
+		ShowSize: p.ShowSize, ShowAge: p.ShowAge, ShowRule: p.ShowRule,
+		Colours: p.Colours, Preview: p.Preview, SelectAll: p.SelectAll,
+		PreviewHeight: p.PreviewHeight,
+	}
+}
+
+// WithDisplay is p with d applied and everything else - where each divider
+// was left - kept as it was.
+func (p Prefs) WithDisplay(d Display) Prefs {
+	p.Sort, p.Layout = d.Sort, d.Layout
+	p.ShowSize, p.ShowAge, p.ShowRule = d.ShowSize, d.ShowAge, d.ShowRule
+	p.Colours, p.Preview, p.SelectAll = d.Colours, d.Preview, d.SelectAll
+	p.PreviewHeight = d.PreviewHeight
+	return p
+}