working on todo.md features

src/layout_store.hpp

@@ -65,6 +65,20 @@ struct LayoutState {
 
   /// The measurements pane, by signal *name* and with the type and options a row was built with.
   std::vector<Measure> measures;
+
+  /// Free text the user attached to this configuration: what it is for, what to look at first.
+  /// A configuration is a *named* session, and the name alone rarely says what makes it different
+  /// from its neighbour.
+  std::string comment;
+
+  /// The startup settings the configuration carries, applied when the chooser opens it -- which is
+  /// why they live here and not only on the command line: two sources on one machine want different
+  /// buffers and different clocks, and retyping the flags to look at the second one is how a
+  /// setting gets forgotten. A zero `buffer_mb` and an empty `capture_packets` mean "not stored":
+  /// the command line's value stands, so an old file cannot silently shrink a buffer.
+  double buffer_mb = 0.0;
+  bool relative_time = false;
+  std::uint32_t capture_packets = 0;
 };
 
 /// A data source udpscope has a stored session for: one row of the startup chooser.
@@ -76,13 +90,23 @@ struct KnownSource {
   int rows = 0;                ///< plots the session had
   int signals = 0;             ///< named slots across those plots
   std::int64_t mtime = 0;      ///< orders the list; never shown
+  /// Which *configuration* of that source this row is. A source may have several, each a named
+  /// session of its own, so the pair (host, port, config) is what identifies a row.
+  std::string config;
+  std::string comment;         ///< the configuration's note, shown beside its name
+  /// The startup settings this configuration carries, so the chooser can apply them.
+  double buffer_mb = 0.0;
+  bool relative_time = false;
+  std::uint32_t capture_packets = 0;
 };
 
-/// Every session file that names at least one signal, newest first.
+/// Every configuration that names at least one signal *or* carries a setting, newest first.
 ///
 /// The filter is what makes the list usable: a development machine accumulates one session file
 /// per probe run on a throwaway port -- 140 of them when this was written -- and every one holds
-/// `signals = ["", "", "", ""]`. A listed source is one somebody actually configured.
+/// `signals = ["", "", "", ""]`. A listed source is one somebody actually configured — and a
+/// buffer size, a note or a clock counts as configuring it, because that is how the chooser's form
+/// sets a host up before it has ever streamed.
 std::vector<KnownSource> known_sources();
 
 /// Deletes one source's session file; the chooser's `x`. False means the file was already gone or
@@ -98,11 +122,39 @@ bool math_node_from_text(const std::string& text, MathNode& out);
 /// The directory session files live in: $XDG_CONFIG_HOME/udpscope, else
 /// ~/.config/udpscope, else /tmp/udpscope-config. Not created by this call.
 std::string config_dir();
+/// `$XDG_CACHE_HOME/udpscope`, or `~/.cache/udpscope`: where bulky, disposable state
+/// lives (the packet captures; item 9's event cache). Created on demand by callers.
+std::string cache_dir();
 
-/// `~/.config/udpscope/<host>_<port>.toml`, with the directory created.
-/// Characters unsafe in a filename are replaced in the host part.
+/// The *legacy* single-file path, `~/.config/udpscope/<host>_<port>.toml`, with the directory
+/// created. Still the import source for a file written before configurations existed; nothing
+/// writes here any more.
 std::string layout_path(const std::string& host, std::uint16_t port);
 
+/// The per-source directory a source's configurations live in:
+/// `~/.config/udpscope/<host>_<port>/`. Not created by this call.
+std::string config_dir_for(const std::string& host, std::uint16_t port);
+
+/// One configuration's file, `<config_dir_for(host, port)>/<name>.toml`, with the directory
+/// created. The name is sanitized the way the host is, so a name the user typed with a slash in it
+/// cannot escape the directory.
+std::string configuration_path(const std::string& host, std::uint16_t port,
+                               const std::string& name);
+
+/// The source's configurations, newest first. A legacy single-file session appears here as the
+/// configuration named `default`, and importing it is the first thing this does.
+std::vector<std::string> configuration_names(const std::string& host, std::uint16_t port);
+
+/// The configuration the source was last left in: `<dir>/active`, or the newest that exists when
+/// nothing wrote one. Never empty for a source that has any configuration at all.
+std::string active_configuration(const std::string& host, std::uint16_t port);
+
+/// Remembers which configuration this source is on. Called by every save.
+bool set_active_configuration(const std::string& host, std::uint16_t port, const std::string& name);
+
+/// Deletes one configuration's file, and `active` if it named it.
+bool forget_configuration(const std::string& host, std::uint16_t port, const std::string& name);
+
 /// Parses the file's TOML subset. Returns false when the file is missing or
 /// malformed; `out` is left usable either way (a malformed file loads as much as
 /// parsed, which beats refusing a hand-edited file over one stray character).