Initial support for user configurable modeline with the modelinefmt option

modelinefmt is first sent through a command line expander (so %sh{...},
%val{...} et al. are expanded), then through markup expand (so that
{face} are interpreted as well)

src/client.cc

@@ -3,10 +3,12 @@
 #include "face_registry.hh"
 #include "context.hh"
 #include "buffer_manager.hh"
+#include "buffer_utils.hh"
 #include "user_interface.hh"
 #include "file.hh"
 #include "remote.hh"
 #include "client_manager.hh"
+#include "command_manager.hh"
 #include "event_manager.hh"
 #include "window.hh"
 
@@ -97,30 +99,39 @@ void Client::print_status(DisplayLine status_line)
 
 DisplayLine Client::generate_mode_line() const
 {
-    auto pos = context().selections().main().cursor();
-    auto col = context().buffer()[pos.line].char_count_to(pos.column);
+    Face status_face = get_face("StatusLine");
+
+    DisplayLine modeline;
+    try
+    {
+        const String& modelinefmt = context().options()["modelinefmt"].get<String>();
+
+        modeline = parse_display_line(expand(modelinefmt, context()), status_face);
+    }
+    catch (runtime_error& err)
+    {
+        write_to_debug_buffer(format("Error while parsing modelinefmt: {}", err.what()));
+        modeline.push_back({ "modelinefmt error, see *debug* buffer", get_face("Error") });
+    }
 
-    DisplayLine status;
     Face info_face = get_face("Information");
 
-    status.push_back({ context().buffer().display_name() });
-    status.push_back({ format(" {}:{} ", pos.line+1, col+1) });
     if (context().buffer().is_modified())
-        status.push_back({ "[+]", info_face });
+        modeline.push_back({ "[+]", info_face });
     if (m_input_handler.is_recording())
-        status.push_back({ format("[recording ({})]", m_input_handler.recording_reg()), info_face });
+        modeline.push_back({ format("[recording ({})]", m_input_handler.recording_reg()), info_face });
     if (context().buffer().flags() & Buffer::Flags::New)
-        status.push_back({ "[new file]", info_face });
+        modeline.push_back({ "[new file]", info_face });
     if (context().user_hooks_disabled())
-        status.push_back({ "[no-hooks]", info_face });
+        modeline.push_back({ "[no-hooks]", info_face });
     if (context().buffer().flags() & Buffer::Flags::Fifo)
-        status.push_back({ "[fifo]", info_face });
-    status.push_back({ " " });
+        modeline.push_back({ "[fifo]", info_face });
+    modeline.push_back({ " " });
     for (auto& atom : m_input_handler.mode_line())
-        status.push_back(std::move(atom));
-    status.push_back({ format(" - {}@[{}]", context().name(), Server::instance().session()) });
+        modeline.push_back(std::move(atom));
+    modeline.push_back({ format(" - {}@[{}]", context().name(), Server::instance().session()) });
 
-    return status;
+    return modeline;
 }
 
 void Client::change_buffer(Buffer& buffer)

src/command_manager.hh

@@ -104,8 +104,8 @@ private:
 };
 
 String expand(StringView str, const Context& context,
-              ConstArrayView<String> shell_params,
-              const EnvVarMap& env_vars);
+              ConstArrayView<String> shell_params = {},
+              const EnvVarMap& env_vars = EnvVarMap{});
 
 }
 

src/main.cc

@@ -229,6 +229,8 @@ void register_options()
                        "colon separated list of <key>=<value> options that are"
                        "passed to and interpreted by the user interface",
                        UserInterface::Options{});
+    reg.declare_option("modelinefmt", "format string used to generate the modeline",
+                       "%val{bufname} %val{cursor_line}:%val{cursor_char_column} "_str);
 }
 
 std::unique_ptr<UserInterface> create_local_ui(bool dummy_ui)