xC/xF: make it possible to insert newlines directly

That should do for us to stop claiming that the interface needs polish.

README.adoc

@@ -11,9 +11,7 @@ They're all lean on dependencies, and offer a maximally permissive licence.
 xC
 --
 The IRC client, and the core of 'xK'.  Its interface should feel somewhat
-familiar for WeeChat or irssi users.  Currently the terminal interface
-experience deserves some polishing, because we've just got rid of
-Readline/Editline dependencies, which kept breaking in exciting ways.
+familiar for WeeChat or irssi users.
 
 image::xC.webp[align="center"]
 

xC.c

@@ -815,6 +815,23 @@ INPUT_FN (kill_line)
 	return true;
 }
 
+INPUT_FN (transpose_chars)
+	// TODO(p): Better Unicode processing.
+	if (buffer->point < 1 || buffer->len < 2)
+		return false;
+	if (buffer->point == (int) buffer->len)
+		buffer->point--;
+
+	uint32_t cp = buffer->line[buffer->point];
+	int width   = buffer->w[buffer->point];
+	buffer->line[buffer->point] = buffer->line[buffer->point - 1];
+	buffer->w   [buffer->point] = buffer->w   [buffer->point - 1];
+	buffer->line[buffer->point - 1] = cp;
+	buffer->w   [buffer->point - 1] = width;
+	buffer->point++;
+	return true;
+}
+
 INPUT_FN (upcase_word)
 	// TODO(p): Better Unicode processing.
 	int i = buffer->point;
@@ -938,6 +955,9 @@ g_input_actions[] =
 	{ "kill-line", "Delete everything up to EOL",
 		input_kill_line,
 		(const char *[]) { "C-k", NULL } },
+	{ "transpose-chars", "Transpose characters before and at the cursor",
+		input_transpose_chars,
+		(const char *[]) { "C-t", NULL } },
 
 	{ "upcase-word", "Convert word to uppercase",
 		input_upcase_word,
@@ -14422,6 +14442,15 @@ on_insert_attribute (int key, void *user_data)
 	return true;
 }
 
+static bool
+on_insert_newline (int key, void *user_data)
+{
+	(void) key;
+
+	struct app_context *ctx = user_data;
+	return input_insert (ctx->input, "\n");
+}
+
 #define BRACKETED_PASTE_LIMIT 102400    ///< How much text can be pasted
 
 static bool
@@ -14616,6 +14645,7 @@ app_input_init (struct input *self)
 	XX ("edit-input",         "Edit input",        on_edit_input)
 	XX ("redraw-screen",      "Redraw screen",     on_redraw_screen)
 	XX ("insert-attribute",   "IRC formatting",    on_insert_attribute)
+	XX ("insert-newline",     "Insert newline",    on_insert_newline)
 	XX ("start-paste-mode",   "Bracketed paste",   on_start_paste_mode)
 	XX ("accept-line",        "Send line",         on_input_return)
 	XX ("complete",           "Complete word",     on_input_complete)
@@ -14636,6 +14666,7 @@ app_input_init (struct input *self)
 	input_bind (self, "M-a",     "goto-activity");
 	input_bind (self, "M-A",     "goto-backtivity");
 	input_bind (self, "M-m",     "insert-attribute");
+	input_bind (self, "M-Enter", "insert-newline");
 	input_bind (self, "M-h",     "display-full-log");
 	input_bind (self, "M-H",     "toggle-unimportant");
 	input_bind (self, "M-e",     "edit-input");

xF.c

@@ -278,6 +278,7 @@ enum action
 	ACTION_EDIT_INPUT,
 	ACTION_VIEW_TRANSCRIPT,
 	ACTION_OPEN,
+	ACTION_INSERT_NEWLINE,
 	ACTION_FORMAT,
 	ACTION_FORMAT_BOLD,
 	ACTION_FORMAT_ITALIC,
@@ -3980,6 +3981,9 @@ app_process_action (enum action action)
 		return app_launch_transcript_editor ();
 	case ACTION_OPEN:
 		return app_open_last_link ();
+	case ACTION_INSERT_NEWLINE:
+		app_editor_insert ('\n');
+		return true;
 	case ACTION_FORMAT:
 		g.inserting_attribute = true;
 		return true;
@@ -4155,6 +4159,7 @@ g_default_bindings[] =
 	{ "M-e",        ACTION_EDIT_INPUT                },  // xC
 	{ "M-E",        ACTION_VIEW_TRANSCRIPT           },  // xF
 	{ "C-o",        ACTION_OPEN                      },  // xF
+	{ "M-Enter",    ACTION_INSERT_NEWLINE            },
 	{ "M-m",        ACTION_FORMAT                    },  // xC
 	{ "PageUp",     ACTION_SCROLL_UP                 },
 	{ "PageDown",   ACTION_SCROLL_DOWN               },