Added `move_buffer()` function and made tabs rearrangeable via drag and drop.

6 files changed, 103 insertions, 3 deletions

diff --git a/core/init.lua b/core/init.lua
index 4290c901..56b7519f 100644
--- a/core/init.lua
+++ b/core/init.lua
@@ -134,6 +134,14 @@ local view
 -- The functions below are Lua C functions.
 
 ---
+-- Moves the buffer at index *from* to index *to*, shifting other buffers as necessary.
+-- @param from Index of the buffer to move.
+-- @param to Index to move the buffer to.
+-- @class function
+-- @name move_buffer
+local move_buffer
+
+---
 -- Emits a `QUIT` event, and unless any handler returns `false`, quits Textadept.
 -- @see events.QUIT
 -- @class function
diff --git a/docs/api.md b/docs/api.md
index f2c7239c..2c98084c 100644
--- a/docs/api.md
+++ b/docs/api.md
@@ -98,6 +98,16 @@ The path to the user's *~/.textadept/* directory, where all preferences and user
 
 ### Functions defined by `_G`
 
+<a id="move_buffer"></a>
+#### `move_buffer`(*from, to*)
+
+Moves the buffer at index *from* to index *to*, shifting other buffers as necessary.
+
+Parameters:
+
+* *`from`*: Index of the buffer to move.
+* *`to`*: Index to move the buffer to.
+
 <a id="quit"></a>
 #### `quit`()
 
diff --git a/modules/lua/ta_api b/modules/lua/ta_api
index f3d6de54..000ca551 100644
--- a/modules/lua/ta_api
+++ b/modules/lua/ta_api
@@ -728,6 +728,7 @@ modify buffer.modify (bool, Read-only)\nWhether or not the buffer has unsaved ch
 modify_rule lexer.modify_rule(lexer, id, rule)\nReplaces in lexer *lexer* the existing rule identified by string *id* with pattern *rule*.\n@param lexer The lexer to modify.\n@param id The id associated with this rule.\n@param rule The LPeg pattern of the rule.
 mouse_dwell_time view.mouse_dwell_time (number)\nThe number of milliseconds the mouse must idle before generating a `DWELL_START` event. A\ntime of `view.TIME_FOREVER` will never generate one.
 mouse_selection_rectangular_switch view.mouse_selection_rectangular_switch (bool)\nWhether or not pressing `view.rectangular_selection_modifier` when selecting text\nnormally with the mouse turns on rectangular selection.\nThe default value is `false`.
+move_buffer _G.move_buffer(from, to)\nMoves the buffer at index *from* to index *to*, shifting other buffers as necessary.\n@param from Index of the buffer to move.\n@param to Index to move the buffer to.
 move_caret_inside_view buffer.move_caret_inside_view(buffer)\nMoves the caret into view if it is not already, removing any selections.\n@param buffer A buffer.
 move_extends_selection buffer.move_extends_selection (bool, Read-only)\nWhether or not regular caret movement alters the selected text.\n`buffer.selection_mode` dictates this property.
 move_selected_lines_down buffer.move_selected_lines_down(buffer)\nShifts the selected lines down one line.\n@param buffer A buffer.
diff --git a/modules/lua/ta_tags b/modules/lua/ta_tags
index 7443c621..6a448c2e 100644
--- a/modules/lua/ta_tags
+++ b/modules/lua/ta_tags
@@ -730,6 +730,7 @@ modify	_HOME/core/.buffer.luadoc	/^module('buffer')$/;"	F	class:buffer
 modify_rule	_HOME/lexers/lexer.lua	/^function M.modify_rule(lexer, id, rule)$/;"	f	class:lexer
 mouse_dwell_time	_HOME/core/.view.luadoc	/^module('view')$/;"	F	class:view
 mouse_selection_rectangular_switch	_HOME/core/.view.luadoc	/^module('view')$/;"	F	class:view
+move_buffer	_HOME/core/init.lua	/^local move_buffer$/;"	f	
 move_caret_inside_view	_HOME/core/.buffer.luadoc	/^function move_caret_inside_view(buffer) end$/;"	f	class:buffer
 move_extends_selection	_HOME/core/.buffer.luadoc	/^module('buffer')$/;"	F	class:buffer
 move_selected_lines_down	_HOME/core/.buffer.luadoc	/^function move_selected_lines_down(buffer) end$/;"	f	class:buffer
diff --git a/src/textadept.c b/src/textadept.c
index 022f4604..40e6c641 100644
--- a/src/textadept.c
+++ b/src/textadept.c
@@ -1038,7 +1038,7 @@ static void register_command_entry_doc() {
 static void remove_doc(lua_State *L, sptr_t doc) {
   lua_getfield(L, LUA_REGISTRYINDEX, "ta_views");
   for (size_t i = 1; i <= lua_rawlen(L, -1); lua_pop(L, 1), i++) {
-    Scintilla *view = (lua_rawgeti(L, -1, i), lua_toview(L, -1)); // ^popped
+    Scintilla *view = (lua_rawgeti(L, -1, i), lua_toview(L, -1)); // popped on loop
     if (doc == SS(view, SCI_GETDOCPOINTER, 0, 0)) goto_doc(L, view, -1, true);
   }
   lua_pop(L, 1); // views
@@ -1412,6 +1412,7 @@ static void new_buffer(sptr_t doc) {
   tab_sync = true;
   int i = gtk_notebook_append_page(GTK_NOTEBOOK(tabbar), tab, NULL);
   gtk_widget_show(tab), gtk_widget_set_visible(tabbar, show_tabs(i > 0));
+  gtk_notebook_set_tab_reorderable(GTK_NOTEBOOK(tabbar), tab, true);
   gtk_notebook_set_current_page(GTK_NOTEBOOK(tabbar), i);
   tab_sync = false;
   lua_pop(lua, 2); // tab_pointer and buffer
@@ -1423,6 +1424,42 @@ static void new_buffer(sptr_t doc) {
   if (!initing) emit(lua, "buffer_new", -1);
 }
 
+/**
+ * Moves the buffer from the given index to another index, shifting other buffers as necessary.
+ * @param from Index of the buffer to move.
+ * @param to Index to move the buffer to.
+ * @reorder_tabs Flag indicating whether or not to reorder tabs in the GUI. This is `false`
+ *   when responding to a GUI reordering event and `true` when calling from Lua.
+ */
+static void move_buffer(int from, int to, bool reorder_tabs) {
+  lua_getglobal(lua, "table"), lua_getfield(lua, -1, "insert"), lua_replace(lua, -2);
+  lua_getfield(lua, LUA_REGISTRYINDEX, "ta_buffers"), lua_pushinteger(lua, to);
+  lua_getglobal(lua, "table"), lua_getfield(lua, -1, "remove"), lua_replace(lua, -2);
+  lua_getfield(lua, LUA_REGISTRYINDEX, "ta_buffers"), lua_pushinteger(lua, from),
+    lua_call(lua, 2, 1); // table.remove(_BUFFERS, from) --> buf
+  lua_call(lua, 3, 0); // table.insert(_BUFFERS, to, buf)
+  lua_getfield(lua, LUA_REGISTRYINDEX, "ta_buffers");
+  for (int i = 1; i <= lua_rawlen(lua, -1); i++)
+    lua_rawgeti(lua, -1, i), lua_pushinteger(lua, i), lua_settable(lua, -3); // t[buffer] = i
+  lua_pop(lua, 1);
+  if (!reorder_tabs) return;
+#if GTK
+  gtk_notebook_reorder_child(
+    GTK_NOTEBOOK(tabbar), gtk_notebook_get_nth_page(GTK_NOTEBOOK(tabbar), from - 1), to - 1);
+//#elif CURSES
+// TODO: tabs
+#endif
+}
+
+/** `_G.move_buffer` Lua function. */
+static int move_buffer_lua(lua_State *L) {
+  lua_getfield(lua, LUA_REGISTRYINDEX, "ta_buffers");
+  int from = luaL_checkinteger(L, 1), to = luaL_checkinteger(L, 2);
+  luaL_argcheck(L, from >= 1 && from <= lua_rawlen(L, -1), 1, "position out of bounds");
+  luaL_argcheck(L, to >= 1 && to <= lua_rawlen(L, -1), 2, "position out of bounds");
+  return (lua_pop(L, 1), move_buffer(luaL_checkinteger(L, 1), luaL_checkinteger(L, 2), true), 0);
+}
+
 /** `_G.quit()` Lua function. */
 static int quit(lua_State *L) {
 #if GTK
@@ -1575,6 +1612,7 @@ static bool init_lua(lua_State *L, int argc, char **argv, bool reinit) {
   set_metatable(L, -1, "ta_ui", ui_index, ui_newindex);
   lua_setglobal(L, "ui");
 
+  lua_pushcfunction(L, move_buffer_lua), lua_setglobal(L, "move_buffer");
   lua_pushcfunction(L, quit), lua_setglobal(L, "quit");
   lua_pushcfunction(L, reset), lua_setglobal(L, "reset");
   lua_pushcfunction(L, add_timeout), lua_setglobal(L, "timeout");
@@ -1785,8 +1823,8 @@ static void close_lua(lua_State *L) {
   closing = true;
   while (unsplit_view(focused_view)) {}
   lua_getfield(L, LUA_REGISTRYINDEX, "ta_buffers");
-  for (size_t i = 1; i <= lua_rawlen(L, -1); i++)
-    lua_rawgeti(L, -1, i), delete_buffer(lua_todoc(L, -1)), lua_pop(L, 1);
+  for (size_t i = 1; i <= lua_rawlen(L, -1); lua_pop(L, 1), i++)
+    lua_rawgeti(L, -1, i), delete_buffer(lua_todoc(L, -1)); // popped on loop
   lua_pop(L, 1); // buffers
   scintilla_delete(focused_view), scintilla_delete(dummy_view);
   scintilla_delete(command_entry);
@@ -1844,6 +1882,16 @@ static void terminate(GtkosxApplication *_, void *L) {
 static void tab_changed(GtkNotebook *_, GtkWidget *__, int tab_num, void *L) {
   if (!tab_sync) emit(L, "tab_clicked", LUA_TNUMBER, tab_num + 1, LUA_TNUMBER, 1, -1);
 }
+
+/** Signal for reordering tabs. */
+static void tab_reordered(GtkNotebook *_, GtkWidget *tab, int to, void *L) {
+  lua_getfield(L, LUA_REGISTRYINDEX, "ta_buffers");
+  for (size_t i = 1; i <= lua_rawlen(L, -1); lua_pop(L, 2), i++)
+    if (tab == (lua_rawgeti(L, -1, i), lua_getfield(L, -1, "tab_pointer"), lua_touserdata(L, -1))) {
+      lua_pop(L, 3), move_buffer(i, to + 1, false);
+      break;
+    }
+}
 #endif // if GTK
 
 /**
@@ -2281,6 +2329,7 @@ static void new_window() {
 
   tabbar = gtk_notebook_new();
   g_signal_connect(tabbar, "switch-page", G_CALLBACK(tab_changed), lua);
+  g_signal_connect(tabbar, "page-reordered", G_CALLBACK(tab_reordered), lua);
   gtk_notebook_set_scrollable(GTK_NOTEBOOK(tabbar), true);
   gtk_widget_set_can_focus(tabbar, false);
   gtk_box_pack_start(GTK_BOX(vbox), tabbar, false, false, 0);
diff --git a/test/test.lua b/test/test.lua
index c3c7a695..ed8fd3f5 100644
--- a/test/test.lua
+++ b/test/test.lua
@@ -4021,6 +4021,37 @@ function test_ui_restore_view_state()
   buffer:close()
 end
 
+function test_move_buffer()
+  local buffer1 = buffer.new()
+  buffer1:set_text('1')
+  local buffer2 = buffer.new()
+  buffer2:set_text('2')
+  local buffer3 = buffer.new()
+  buffer3:set_text('3')
+  local buffer4 = buffer.new()
+  buffer4:set_text('4')
+  move_buffer(_BUFFERS[buffer4], _BUFFERS[buffer1])
+  assert(_BUFFERS[buffer4] < _BUFFERS[buffer1], 'buffer4 not before buffer1')
+  assert(_BUFFERS[buffer1] < _BUFFERS[buffer2], 'buffer1 not before buffer2')
+  assert(_BUFFERS[buffer2] < _BUFFERS[buffer3], 'buffer2 not before buffer3')
+  move_buffer(_BUFFERS[buffer2], _BUFFERS[buffer3])
+  assert(_BUFFERS[buffer4] < _BUFFERS[buffer1], 'buffer4 not before buffer1')
+  assert(_BUFFERS[buffer1] < _BUFFERS[buffer3], 'buffer1 not before buffer3')
+  assert(_BUFFERS[buffer3] < _BUFFERS[buffer2], 'buffer3 not before buffer2')
+
+  assert_raises(function() move_buffer('') end, 'number expected')
+  assert_raises(function() move_buffer(1) end, 'number expected')
+  assert_raises(function() move_buffer(1, true) end, 'number expected')
+  assert_raises(function() move_buffer(1, 10) end, 'out of bounds')
+  assert_raises(function() move_buffer(1, -1) end, 'out of bounds')
+  assert_raises(function() move_buffer(10, 1) end, 'out of bounds')
+  assert_raises(function() move_buffer(-1, 1) end, 'out of bounds')
+  buffer1:close(true)
+  buffer2:close(true)
+  buffer3:close(true)
+  buffer4:close(true)
+end
+
 function test_reset()
   local _persist
   _G.foo = 'bar'