Use before_switch and after_switch events for buffers and views.

Moved C code for saving/restoring state when switching buffers to Lua. Also
added saving of folding state.

7 files changed, 57 insertions, 16 deletions

diff --git a/core/.textadept.lua b/core/.textadept.lua
index cd0a4553..0f2b02d9 100644
--- a/core/.textadept.lua
+++ b/core/.textadept.lua
@@ -46,7 +46,7 @@ function new_buffer() end
 
 ---
 -- Goes to the specified view.
--- Activates the 'view_switch' signal.
+-- Activates the 'view_*_switch' signal.
 -- @param n A relative or absolute view index.
 -- @param absolute Flag indicating if n is an absolute index or not.
 function goto_view(n, absolute) end
diff --git a/core/.view.lua b/core/.view.lua
index 2214463f..6cdb4336 100644
--- a/core/.view.lua
+++ b/core/.view.lua
@@ -32,7 +32,7 @@ function view:unsplit() end
 
 ---
 -- Goes to the specified buffer in the indexed view.
--- Activates the 'buffer_switch' signal.
+-- Activates the 'buffer_*_switch' signals.
 -- @param n A relative or absolute buffer index.
 -- @param absolute Flag indicating if n is an absolute index or not.
 function view:goto_buffer(n, absolute) end
diff --git a/core/events.lua b/core/events.lua
index ab664f87..a6060ab9 100644
--- a/core/events.lua
+++ b/core/events.lua
@@ -50,9 +50,11 @@ module('textadept.events', package.seeall)
 -- Textadept events:
 --   buffer_new()
 --   buffer_deleted()
---   buffer_switch()
+--   buffer_before_switch()
+--   buffer_after_switch()
 --   view_new()
---   view_switch()
+--   view_before_switch()
+--   view_after_switch()
 --   quit()
 --     Note: when adding a quit handler, it must be inserted at index 1 because
 --     the default quit handler returns true, which ignores all subsequent
@@ -163,14 +165,20 @@ end
 function buffer_deleted()
   return handle('buffer_deleted')
 end
-function buffer_switch()
-  return handle('buffer_switch')
+function buffer_before_switch()
+  return handle('buffer_before_switch')
+end
+function buffer_after_switch()
+  return handle('buffer_after_switch')
 end
 function view_new()
   return handle('view_new')
 end
-function view_switch()
-  return handle('view_switch')
+function view_before_switch()
+  return handle('view_before_switch')
+end
+function view_after_switch()
+  return handle('view_after_switch')
 end
 function quit()
   return handle('quit')
@@ -398,13 +406,46 @@ add_handler('buffer_new',
     set_title(buffer)
   end)
 
-add_handler('buffer_switch',
+add_handler('buffer_before_switch',
+  function() -- save buffer properties
+    local buffer = buffer
+    -- Save view state.
+    buffer._anchor = buffer.anchor
+    buffer._current_pos = buffer.current_pos
+    buffer._first_visible_line = buffer.first_visible_line
+    -- Save fold state.
+    buffer._folds = {}
+    local folds = buffer._folds
+    local level, expanded = buffer.fold_level, buffer.fold_expanded
+    local header_flag = textadept.constants.SC_FOLDLEVELHEADERFLAG
+    local test = 2 * header_flag
+    for i = 0, buffer.line_count do
+      if level[i] % test >= header_flag and not expanded[i] then
+        folds[#folds + 1] = i
+      end
+    end
+  end)
+
+add_handler('buffer_after_switch',
+  function() -- restore buffer properties
+    local buffer = buffer
+    if not buffer._folds then return end
+    -- Restore fold state.
+    for _, i in ipairs(buffer._folds) do buffer:toggle_fold(i) end
+    -- Restore view state.
+    buffer:set_sel(buffer._anchor, buffer._current_pos)
+    buffer:line_scroll(0,
+      buffer:visible_from_doc_line(buffer._first_visible_line) -
+        buffer.first_visible_line)
+  end)
+
+add_handler('buffer_after_switch',
   function() -- updates titlebar and statusbar
     set_title(buffer)
     update_ui()
   end)
 
-add_handler('view_switch',
+add_handler('view_after_switch',
   function() -- updates titlebar and statusbar
     set_title(buffer)
     update_ui()
diff --git a/core/ext/mime_types.lua b/core/ext/mime_types.lua
index cb9012eb..43ee2f9d 100644
--- a/core/ext/mime_types.lua
+++ b/core/ext/mime_types.lua
@@ -93,5 +93,5 @@ end
 
 textadept.events.add_handler('file_opened', handle_new)
 textadept.events.add_handler('file_saved_as', handle_new)
-textadept.events.add_handler('buffer_switch', set_lexer)
+textadept.events.add_handler('buffer_after_switch', set_lexer)
 textadept.events.add_handler('view_new', set_lexer)
diff --git a/core/ext/pm/buffer_browser.lua b/core/ext/pm/buffer_browser.lua
index d1fa4295..4f2390d3 100644
--- a/core/ext/pm/buffer_browser.lua
+++ b/core/ext/pm/buffer_browser.lua
@@ -75,8 +75,8 @@ textadept.events.add_handler('buffer_new', update_view)
 textadept.events.add_handler('buffer_deleted', update_view)
 textadept.events.add_handler('save_point_reached', update_view)
 textadept.events.add_handler('save_point_left', update_view)
-textadept.events.add_handler('buffer_switch', update_view)
-textadept.events.add_handler('view_switch', update_view)
+textadept.events.add_handler('buffer_after_switch', update_view)
+textadept.events.add_handler('view_after_switch', update_view)
 
 local function set_cursor()
   if matches(textadept.pm.entry_text) then
diff --git a/core/ext/pm/ctags_browser.lua b/core/ext/pm/ctags_browser.lua
index 23556f68..b7c3e76e 100644
--- a/core/ext/pm/ctags_browser.lua
+++ b/core/ext/pm/ctags_browser.lua
@@ -249,5 +249,5 @@ local function update_view()
 end
 textadept.events.add_handler('file_opened', update_view)
 textadept.events.add_handler('buffer_deleted', update_view)
-textadept.events.add_handler('buffer_switch', update_view)
+textadept.events.add_handler('buffer_after_switch', update_view)
 textadept.events.add_handler('save_point_reached', update_view)
diff --git a/core/file_io.lua b/core/file_io.lua
index fec1cc5e..11436cbb 100644
--- a/core/file_io.lua
+++ b/core/file_io.lua
@@ -476,5 +476,5 @@ local function update_modified_file()
     end
   end
 end
-textadept.events.add_handler('buffer_switch', update_modified_file)
-textadept.events.add_handler('view_switch', update_modified_file)
+textadept.events.add_handler('buffer_after_switch', update_modified_file)
+textadept.events.add_handler('view_after_switch', update_modified_file)