1 files changed, 139 insertions, 0 deletions
diff --git a/source/blender/editors/interface/interface_undo.c b/source/blender/editors/interface/interface_undo.c
new file mode 100644
index 00000000000..016bc4159db
--- /dev/null
+++ b/source/blender/editors/interface/interface_undo.c
@@ -0,0 +1,139 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * Copyright (C) 2020 Blender Foundation.
+ * All rights reserved.
+ */
+
+/** \file
+ * \ingroup edinterface
+ *
+ * Undo stack to use for UI widgets that manage their own editing state.
+ */
+
+#include <string.h>
+
+#include "BLI_listbase.h"
+
+#include "DNA_listBase.h"
+
+#include "MEM_guardedalloc.h"
+
+#include "interface_intern.h"
+
+/* -------------------------------------------------------------------- */
+/** \name Text Field Undo Stack
+ * \{ */
+
+typedef struct uiUndoStack_Text_State {
+  struct uiUndoStack_Text_State *next, *prev;
+  int cursor_index;
+  char text[0];
+} uiUndoStack_Text_State;
+
+typedef struct uiUndoStack_Text {
+  ListBase states;
+  uiUndoStack_Text_State *current;
+} uiUndoStack_Text;
+
+static const char *ui_textedit_undo_impl(uiUndoStack_Text *stack, int *r_cursor_index)
+{
+  /* Don't undo if no data has been pushed yet. */
+  if (stack->current == NULL) {
+    return NULL;
+  }
+
+  /* Travel backwards in the stack and copy information to the caller. */
+  if (stack->current->prev != NULL) {
+    stack->current = stack->current->prev;
+
+    *r_cursor_index = stack->current->cursor_index;
+    return stack->current->text;
+  }
+  return NULL;
+}
+
+static const char *ui_textedit_redo_impl(uiUndoStack_Text *stack, int *r_cursor_index)
+{
+  /* Don't redo if no data has been pushed yet. */
+  if (stack->current == NULL) {
+    return NULL;
+  }
+
+  /* Only redo if new data has not been entered since the last undo. */
+  if (stack->current->next) {
+    stack->current = stack->current->next;
+
+    *r_cursor_index = stack->current->cursor_index;
+    return stack->current->text;
+  }
+  return NULL;
+}
+
+const char *ui_textedit_undo(uiUndoStack_Text *stack, int direction, int *r_cursor_index)
+{
+  BLI_assert(ELEM(direction, -1, 1));
+  if (direction < 0) {
+    return ui_textedit_undo_impl(stack, r_cursor_index);
+  }
+  else {
+    return ui_textedit_redo_impl(stack, r_cursor_index);
+  }
+}
+
+/**
+ * Push the information in the arguments to a new state in the undo stack.
+ *
+ * \note Currently the total length of the undo stack is not limited.
+ */
+void ui_textedit_undo_push(uiUndoStack_Text *stack, const char *text, int cursor_index)
+{
+  /* Clear all redo actions from the current state. */
+  if (stack->current != NULL) {
+    while (stack->current->next) {
+      uiUndoStack_Text_State *state = stack->current->next;
+      BLI_remlink(&stack->states, state);
+      MEM_freeN(state);
+    }
+  }
+
+  /* Create the new state  */
+  const int text_size = strlen(text) + 1;
+  stack->current = MEM_mallocN(sizeof(uiUndoStack_Text_State) + text_size, __func__);
+  stack->current->cursor_index = cursor_index;
+  memcpy(stack->current->text, text, text_size);
+  BLI_addtail(&stack->states, stack->current);
+}
+/**
+ * Start the undo stack.
+ *
+ * \note The current state should be pushed immediately after calling this.
+ */
+uiUndoStack_Text *ui_textedit_undo_stack_create(void)
+{
+  uiUndoStack_Text *stack = MEM_mallocN(sizeof(uiUndoStack_Text), __func__);
+  stack->current = NULL;
+  BLI_listbase_clear(&stack->states);
+
+  return stack;
+}
+
+void ui_textedit_undo_stack_destroy(uiUndoStack_Text *stack)
+{
+  BLI_freelistN(&stack->states);
+  MEM_freeN(stack);
+}
+
+/** \} */