Snippet "snapshots" enable backtracking; /modules/textadept/lsnippets.lua

1 files changed, 18 insertions, 0 deletions

diff --git a/modules/textadept/lsnippets.lua b/modules/textadept/lsnippets.lua
index 0e1ad0a7..7a8a4e13 100644
--- a/modules/textadept/lsnippets.lua
+++ b/modules/textadept/lsnippets.lua
@@ -139,6 +139,7 @@ function insert(s_text)
     -- Initialize the new snippet. If one is running, push it onto the stack.
     if snippet.index then snippet_stack[#snippet_stack + 1] = snippet end
     snippet = {}
+    snippet.snapshots = {}
     snippet.start_pos = start or caret
     snippet.prev_sel_text = buffer:get_sel_text()
     snippet.index, snippet.max_index = 0, 0
@@ -182,6 +183,7 @@ function next()
   if not s_text then cancel_current() return end
 
   local index = snippet.index
+  snippet.snapshots[index] = s_text
   if index > 0 then
     buffer:begin_undo_action()
     local caret = math.max(buffer.anchor, buffer.current_pos)
@@ -240,6 +242,22 @@ function next()
 end
 
 ---
+-- Goes back to the previous placeholder or tab stop, reverting changes made to
+-- subsequent ones.
+function prev()
+  if not snippet.index then return end
+  local buffer = buffer
+  local index = snippet.index
+  if index > 1 then
+    local s_start, s_end = snippet_info()
+    local s_text = snippet.snapshots[index - 2]
+    buffer:set_sel(s_start, s_end) buffer:replace_sel(s_text)
+    snippet.index = index - 2
+    next()
+  end
+end
+
+---
 -- Cancels the active snippet, reverting to the state before its activation,
 -- and restores the previous running snippet (if any).
 function cancel_current()