FLUID: Refactors MergeBack

* moved functionality into its own files
* refactored all methods to be less than a page
* documented all calls
* tested all situations I could think of

fluid/CMakeLists.txt

@@ -38,6 +38,7 @@ set (CPPFILES
   file.cxx
   fluid_filename.cxx
   function_panel.cxx
+  mergeback.cxx
   pixmaps.cxx
   shell_command.cxx
   sourceview_panel.cxx
@@ -71,6 +72,7 @@ set (HEADERFILES
   factory.h
   file.h
   function_panel.h
+  mergeback.h
   print_panel.h
   pixmaps.h
   shell_command.h

fluid/Fl_Function_Type.cxx

@@ -24,6 +24,7 @@
 #include "code.h"
 #include "function_panel.h"
 #include "comments.h"
+#include "mergeback.h"
 
 #include <FL/fl_string_functions.h>
 #include <FL/Fl_File_Chooser.H>
@@ -353,6 +354,7 @@ static bool fd_isspace(int c) {
   return (c>0 && c<128 && isspace(c));
 }
 
+// code duplication: see int is_id(char c) in code.cxx
 static bool fd_iskeyword(int c) {
   return (c>0 && c<128 && (isalnum(c) || c=='_'));
 }

fluid/Fl_Menu_Type.cxx

@@ -29,6 +29,7 @@
 #include "code.h"
 #include "Fluid_Image.h"
 #include "custom_widgets.h"
+#include "mergeback.h"
 
 #include <FL/Fl.H>
 #include <FL/fl_message.H>

fluid/Fl_Widget_Type.cxx

@@ -27,6 +27,7 @@
 #include "alignment_panel.h"
 #include "widget_panel.h"
 #include "undo.h"
+#include "mergeback.h"
 
 #include <FL/Fl.H>
 #include <FL/Fl_Group.H>
@@ -2631,7 +2632,7 @@ void live_mode_cb(Fl_Button*o,void *) {
 }
 
 // update the panel according to current widget set:
-static void load_panel() {
+void load_panel() {
   if (!the_panel) return;
 
   // find all the Fl_Widget subclasses currently selected:

fluid/Makefile

@@ -39,6 +39,7 @@ CPPFILES = \
 	fluid.cxx \
 	fluid_filename.cxx \
 	function_panel.cxx \
+	mergeback.cxx \
 	pixmaps.cxx \
 	shell_command.cxx \
 	sourceview_panel.cxx \

fluid/code.h

@@ -31,31 +31,32 @@ struct Fd_Pointer_Tree;
 int is_id(char c);
 int write_strings(const Fl_String &filename);
 
-const int FD_TAG_GENERIC = 0;
-const int FD_TAG_CODE = 1;
-const int FD_TAG_MENU_CALLBACK = 2;
-const int FD_TAG_WIDGET_CALLBACK = 3;
-const int FD_TAG_LAST = 3;
-
-const int FD_MERGEBACK_CHECK = 0;
-const int FD_MERGEBACK_INTERACTIVE = 1;
-const int FD_MERGEBACK_GO = 2;
-const int FD_MERGEBACK_GO_SAFE = 3;
-
 class Fd_Code_Writer
 {
 protected:
+  /// file pointer for the C++ code file
   FILE *code_file;
+  /// file pointer for the C++ header file
   FILE *header_file;
+
+  /// tree of unique but human-readable identifiers
   Fd_Identifier_Tree* id_root;
+  /// searchable text tree for text that is only written once to the header file
   Fd_Text_Tree *text_in_header;
+  /// searchable text tree for text that is only written once to the code file
   Fd_Text_Tree *text_in_code;
+  /// searchable tree for pointers that are only written once to the code file
   Fd_Pointer_Tree *ptr_in_code;
 
+  /// crc32 for blocks of text written to the code file
   unsigned long block_crc_;
-  char *block_buffer_;
+  /// if set, we are at the start of a line and can ignore leading spaces in crc
-  int block_buffer_size_;
   bool block_line_start_;
+  /// expanding buffer for vsnprintf
+  char *block_buffer_;
+  /// size of expanding buffer for vsnprintf
+  int block_buffer_size_;
+
   void crc_add(const void *data, int n=-1);
   int crc_printf(const char *format, ...);
   int crc_vprintf(const char *format, va_list args);
@@ -63,19 +64,25 @@ protected:
   int crc_putc(int c);
 
 public:
+  /// current level of source code indentation
   int indentation;
+  /// set if we write abbreviated file for the source code previewer
+  /// (disables binary data blocks, for example)
   bool write_sourceview;
-  // silly thing to prevent declaring unused variables:
+  /// silly thing to prevent declaring unused variables:
-  // When this symbol is on, all attempts to write code don't write
+  /// When this symbol is on, all attempts to write code don't write
-  // anything, but set a variable if it looks like the variable "o" is used:
+  /// anything, but set a variable if it looks like the variable "o" is used:
   int varused_test;
+  /// set to 1 if varused_test found that a variable is actually used
   int varused;
 
 public:
   Fd_Code_Writer();
   ~Fd_Code_Writer();
   const char* unique_id(void* o, const char*, const char*, const char*);
+  /// Increment source code indentation level.
   void indent_more() { indentation++; }
+  /// Decrement source code indentation level.
   void indent_less() { indentation--; }
   const char *indent();
   const char *indent(int set);
@@ -97,7 +104,6 @@ public:
   void write_public(int state); // writes pubic:/private: as needed
   
   void tag(int type, unsigned short uid);
-  int merge_back(const char *s, int task);
 
   static unsigned long block_crc(const void *data, int n=-1, unsigned long in_crc=0, bool *inout_line_start=NULL);
 };

fluid/fluid.cxx

@@ -27,6 +27,7 @@
 #include "undo.h"
 #include "file.h"
 #include "code.h"
+#include "mergeback.h"
 
 #include "alignment_panel.h"
 #include "function_panel.h"
@@ -1284,13 +1285,9 @@ int mergeback_code_files()
     return 0;
   }
 
-  // -- generate the file names with absolute paths
-  Fd_Code_Writer f;
   Fl_String code_filename = g_project.codefile_path() + g_project.codefile_name();
-
-  // -- write the code and header files
   if (!batch_mode) enter_project_dir();
-  int c = f.merge_back(code_filename.c_str(), FD_MERGEBACK_INTERACTIVE);
+  int c = merge_back(code_filename, FD_MERGEBACK_INTERACTIVE);
   if (!batch_mode) leave_project_dir();
   if (c==0) fl_message("MergeBack found no external modifications\n"
                        "in the source code.");

fluid/mergeback.cxx

@@ -0,0 +1,476 @@
+//
+// Code output routines for the Fast Light Tool Kit (FLTK).
+//
+// Copyright 1998-2023 by Bill Spitzak and others.
+//
+// This library is free software. Distribution and use rights are outlined in
+// the file "COPYING" which should have been included with this file.  If this
+// file is missing or damaged, see the license at:
+//
+//     https://www.fltk.org/COPYING.php
+//
+// Please see the following page on how to report bugs and issues:
+//
+//     https://www.fltk.org/bugs.php
+//
+
+#include "mergeback.h"
+
+#include "fluid.h"
+#include "code.h"
+#include "undo.h"
+#include "Fl_Function_Type.h"
+#include "Fl_Widget_Type.h"
+
+#include <FL/Fl_Window.H>
+#include <FL/fl_ask.H>
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <ctype.h>
+#include <zlib.h>
+
+extern void propagate_load(Fl_Group*, void*);
+extern void load_panel();
+extern void redraw_browser();
+
+// TODO: add application user setting to control mergeback
+//        [] new projects default to mergeback
+//        [] check mergeback when loading project
+//        [] check mergeback when app gets focus
+//          [] always apply if safe
+// TODO: command line option for mergeback
+//        -mb or --merge-back
+//        -mbs or --merge-back-if-safe
+// NOTE: automatic mergeback on timer when file changes if app focus doesn't work
+// NOTE: allow the user to edit comment blocks
+
+/**
+ Merge external changes in a source code file back into the current project.
+
+ This experimental function reads a source code file line by line. When it
+ encounters a special tag in a line, the crc32 stored in the tag is compared
+ to the crc32 that was calculated from the code lines since the previous tag.
+
+ If the crc's differ, the user has modified the source file externally, and the
+ given block differs from the block as it was generated by FLUID. Depending on
+ the block type, the user has modified the widget code (FD_TAG_GENERIC), which
+ can not be transferred back into the project.
+
+ Modifications to code blocks and callbacks (CODE, CALLBACK) can be merged back
+ into the project. Their corresponding Fl_Type is found using the unique
+ node id that is part of the tag. The block is only merged back if the crc's
+ from the project and from the edited block differ.
+
+ The caller must make sure that this code file was generated by the currently
+ loaded project.
+
+ The user is informed in detailed dialogs what the function discovered and
+ offered to merge or cancel if appropriate. Just in case this function is
+ destructive, "undo" restores the state before a MergeBack.
+
+ Callers can set different task. FD_MERGEBACK_ANALYSE checks if there are any
+ modifications in the code file and returns -1 if there was an error, or a
+ bit field where bit 0 is set if internal structures were modified, bit 1 if
+ code was changed, and bit 2 if modified blocks were found, but no Type node.
+ Bit 3 is set, if code was changed in the code file *and* the project.
+
+ FD_MERGEBACK_INTERACTIVE checks for changes and presents a status dialog box
+ to the user if there were conflicting changes or if a mergeback is possible,
+ presenting the user the option to merge or cancel. Returns 0 if the project
+ remains unchanged, and 1 if the user merged changes back. -1 is returned if an
+ invalid tag was found.
+
+ FD_MERGEBACK_APPLY merges all changes back into the project without any
+ interaction. Returns 0 if nothing changed, and 1 if it merged any changes back.
+
+ FD_MERGEBACK_APPLY_IF_SAFE merges changes back only if there are no conflicts.
+ Returns 0 if nothing changed, and 1 if it merged any changes back, and -1 if
+ there were conflicts.
+
+ \note this function is currently part of Fd_Code_Writer to get easy access
+ to our crc32 code that also wrote the code file originally.
+
+ \param[in] s path and filename of the source code file
+ \param[in] task see above
+ \return see above
+ */
+int merge_back(const Fl_String &s, int task) {
+  if (g_project.write_mergeback_data) {
+    Fd_Mergeback mergeback;
+    return mergeback.merge_back(s, task);
+  } else {
+    // nothing to be done if the mergeback option is disabled in the project
+    return 0;
+  }
+}
+
+/** Allocate and initialize MergeBack class. */
+Fd_Mergeback::Fd_Mergeback() :
+  code(NULL),
+  line_no(0),
+  tag_error(0),
+  num_changed_code(0),
+  num_changed_structure(0),
+  num_uid_not_found(0),
+  num_possible_override(0)
+{
+}
+
+/** Release allocated resources. */
+Fd_Mergeback::~Fd_Mergeback()
+{
+  if (code) ::fclose(code);
+}
+
+/** Remove the first two spaces at every line start.
+ \param[inout] s block of C code
+ */
+void Fd_Mergeback::unindent(char *s) {
+  char *d = s;
+  bool line_start = true;
+  while (*s) {
+    if (line_start) {
+      if (*s>0 && isspace(*s)) s++;
+      if (*s>0 && isspace(*s)) s++;
+      line_start = false;
+    }
+    if (*s=='\r') s++;
+    if (*s=='\n') line_start = true;
+    *d++ = *s++;
+  }
+  *d = 0;
+}
+
+/**
+ Read a block of text from the source file and remove the leading two spaces in every line.
+ \param[in] start start of the block within the file
+ \param[in] end end of text within the file
+ \return a string holding the text that was found in the file
+ */
+Fl_String Fd_Mergeback::read_and_unindent_block(long start, long end) {
+  long bsize = end-start;
+  long here = ::ftell(code);
+  ::fseek(code, start, SEEK_SET);
+  char *block = (char*)::malloc(bsize+1);
+  size_t n = ::fread(block, bsize, 1, code);
+  if (n!=1)
+    block[0] = 0; // read error
+  else
+    block[bsize] = 0;
+  unindent(block);
+  Fl_String str = block;
+  ::free(block);
+  ::fseek(code, here, SEEK_SET);
+  return str;
+}
+
+/** Tell user the results of our MergeBack analysis and pop up a dialog to give
+ the user a choice to merge or cancel.
+ \return 1 if the user wants to merge (choice dialog was shown)
+ \return 0 if there is nothing to merge (no dialog was shown)
+ \return -1 if the user wants to cancel or an error occurred or an issue was presented
+        (message or choice dialog was shown)
+ */
+int Fd_Mergeback::ask_user_to_merge() {
+  if (tag_error) {
+    fl_message("MergeBack found an error in line %d while reading tags\n"
+               "from the source code. Merging code back is not possible.", line_no);
+    return -1;
+  }
+  if (!num_changed_code && !num_changed_structure) {
+    return 0;
+  }
+  if (num_changed_structure && !num_changed_code) {
+    fl_message("MergeBack found %d modifications in the project structure\n"
+               "of the source code. These kind of changes can no be\n"
+               "merged back and will be lost when the source code is\n"
+               "generated again from the open project.", num_changed_structure);
+    return -1;
+  }
+  Fl_String msg = "MergeBack found %1$d modifications in the source code.";
+  if (num_possible_override)
+    msg += "\n\nWARNING: %4$d of these modified blocks appear to also have\n"
+    "changed in the project. Merging will override changes in\n"
+    "the project with changes from the source code file.";
+  if (num_uid_not_found)
+    msg += "\n\nWARNING: for %2$d of these modifications no Type node\n"
+    "can be found and these modification can't be merged back.";
+  if (!num_possible_override && !num_uid_not_found)
+    msg += "\nMerging these changes back appears to be safe.";
+
+  if (num_changed_structure)
+    msg += "\n\nWARNING: %3$d modifications were found in the project\n"
+    "structure. These kind of changes can no be merged back\n"
+    "and will be lost when the source code is generated again\n"
+    "from the open project.";
+
+  if (num_changed_code==num_uid_not_found) {
+    fl_message(msg.c_str(),
+               num_changed_code, num_uid_not_found,
+               num_changed_structure, num_possible_override);
+    return -1;
+  } else {
+    msg +=    "\n\nClick Cancel to abort the MergeBack operation.\n"
+    "Click Merge to merge all code changes back into\n"
+    "the open project.";
+    int c = fl_choice(msg.c_str(), "Cancel", "Merge", NULL,
+                      num_changed_code, num_uid_not_found,
+                      num_changed_structure, num_possible_override);
+    if (c==0) return -1;
+    return 1;
+  }
+}
+
+/** Analyse the block and its corresponding widget callback.
+ Return findings in num_changed_code, num_changed_code, and num_uid_not_found.
+ */
+void Fd_Mergeback::analyse_callback(unsigned long code_crc, unsigned long tag_crc, int uid) {
+  Fl_Type *tp = Fl_Type::find_by_uid(uid);
+  if (tp && tp->is_true_widget()) {
+    Fl_String cb = tp->callback(); cb += "\n";
+    unsigned long proj_crc = Fd_Code_Writer::block_crc(cb.c_str());
+    // check if the code and project crc are the same, so this modification was already applied
+    if (proj_crc!=code_crc) {
+      num_changed_code++;
+      // check if the block change on the project side as well, so we may override changes
+      if (proj_crc!=tag_crc) {
+        num_possible_override++;
+      }
+    }
+  } else {
+    num_uid_not_found++;
+    num_changed_code++;
+  }
+}
+
+/** Analyse the block and its corresponding Code Type.
+ Return findings in num_changed_code, num_changed_code, and num_uid_not_found.
+ */
+void Fd_Mergeback::analyse_code(unsigned long code_crc, unsigned long tag_crc, int uid) {
+  Fl_Type *tp = Fl_Type::find_by_uid(uid);
+  if (tp && tp->is_a(ID_Code)) {
+    Fl_String code = tp->name(); code += "\n";
+    unsigned long proj_crc = Fd_Code_Writer::block_crc(code.c_str());
+    // check if the code and project crc are the same, so this modification was already applied
+    if (proj_crc!=code_crc) {
+      num_changed_code++;
+      // check if the block change on the project side as well, so we may override changes
+      if (proj_crc!=tag_crc) {
+        num_possible_override++;
+      }
+    }
+  } else {
+    num_changed_code++;
+    num_uid_not_found++;
+  }
+}
+
+
+/** Analyse the code file and return findings in class member variables.
+
+ The code file must be open for reading already.
+
+ * tag_error is set if a tag was found, but could not be read
+ * line_no returns the line where an error occured
+ * num_changed_code is set to the number of changed code blocks in the file.
+   Code changes can be merged back to the project.
+ * num_changed_structure is set to the number of structural changes.
+   Structural changes outside of code blocks can not be read back.
+ * num_uid_not_found number of blocks that were modified, but the corresponding
+   type or widget can not be found in the project
+ * num_possible_override number of blocks that were changed in the code file,
+   but also were changed in the project.
+ 
+ \return -1 if reading a tag failed, otherwise 0
+ */
+int Fd_Mergeback::analyse() {
+  // initialize local variables
+  unsigned long code_crc = 0;
+  bool line_start = true;
+  char line[1024];
+  // bail if the caller has not opened a file yet
+  if (!code) return 0;
+  // initialize member variables to return our findings
+  line_no = 0;
+  tag_error = 0;
+  num_changed_code = 0;
+  num_changed_structure = 0;
+  num_uid_not_found = 0;
+  num_possible_override = 0;
+  code_crc = 0;
+  // loop through all lines in the code file
+  ::fseek(code, 0, SEEK_SET);
+  for (;;) {
+    // get the next line until end of file
+    if (fgets(line, 1023, code)==0) break;
+    line_no++;
+    const char *tag = strstr(line, "//~fl~");
+    if (!tag) {
+      // if this line has no tag, add the contents to the CRC and continue
+      code_crc = Fd_Code_Writer::block_crc(line, -1, code_crc, &line_start);
+    } else {
+      // if this line has a tag, read all tag data
+      int tag_type = -1, uid = 0;
+      unsigned long tag_crc = 0;
+      int n = sscanf(tag, "//~fl~%d~%04x~%08lx~~", &tag_type, &uid, &tag_crc);
+      if (n!=3 || tag_type<0 || tag_type>FD_TAG_LAST ) { tag_error = 1; return -1; }
+      if (code_crc != tag_crc) {
+        switch (tag_type) {
+          case FD_TAG_GENERIC: 
+            num_changed_structure++;
+            break;
+          case FD_TAG_MENU_CALLBACK:
+          case FD_TAG_WIDGET_CALLBACK:
+            analyse_callback(code_crc, tag_crc, uid);
+            break;
+          case FD_TAG_CODE:
+            analyse_code(code_crc, tag_crc, uid);
+            break;
+        }
+      }
+      // reset everything for the next block
+      code_crc = 0;
+      line_start = true;
+    }
+  }
+  return 0;
+}
+
+/** Apply callback mergebacks from the code file to the project.
+ \return 1 if the project changed
+ */
+int Fd_Mergeback::apply_callback(long block_end, long block_start, unsigned long code_crc, int uid) {
+  Fl_Type *tp = Fl_Type::find_by_uid(uid);
+  if (tp && tp->is_true_widget()) {
+    Fl_String cb = tp->callback(); cb += "\n";
+    unsigned long project_crc = Fd_Code_Writer::block_crc(cb.c_str());
+    if (project_crc!=code_crc) {
+      tp->callback(read_and_unindent_block(block_start, block_end).c_str());
+      return 1;
+    }
+  }
+  return 0;
+}
+
+/** Apply callback mergebacks from the code file to the project.
+ \return 1 if the project changed
+ */
+int Fd_Mergeback::apply_code(long block_end, long block_start, unsigned long code_crc, int uid) {
+  Fl_Type *tp = Fl_Type::find_by_uid(uid);
+  if (tp && tp->is_a(ID_Code)) {
+    Fl_String cb = tp->name(); cb += "\n";
+    unsigned long project_crc = Fd_Code_Writer::block_crc(cb.c_str());
+    if (project_crc!=code_crc) {
+      tp->name(read_and_unindent_block(block_start, block_end).c_str());
+      return 1;
+    }
+  }
+  return 0;
+}
+
+/** Apply all possible mergebacks from the code file to the project.
+ The code file must be open for reading already.
+ \return -1 if reading a tag failed, 0 if nothing changed, 1 if the project changed
+ */
+int Fd_Mergeback::apply() {
+  // initialize local variables
+  unsigned long code_crc = 0;
+  bool line_start = true;
+  char line[1024];
+  int changed = 0;
+  long block_start = 0;
+  long block_end = 0;
+  // bail if the caller has not opened a file yet
+  if (!code) return 0;
+  // initialize member variables to return our findings
+  line_no = 0;
+  tag_error = 0;
+  code_crc = 0;
+  // loop through all lines in the code file
+  ::fseek(code, 0, SEEK_SET);
+  for (;;) {
+    // get the next line until end of file
+    if (fgets(line, 1023, code)==0) break;
+    line_no++;
+    const char *tag = strstr(line, "//~fl~");
+    if (!tag) {
+      // if this line has no tag, add the contents to the CRC and continue
+      code_crc = Fd_Code_Writer::block_crc(line, -1, code_crc, &line_start);
+      block_end = ::ftell(code);
+    } else {
+      // if this line has a tag, read all tag data
+      int tag_type = -1, uid = 0;
+      unsigned long tag_crc = 0;
+      int n = sscanf(tag, "//~fl~%d~%04x~%08lx~~", &tag_type, &uid, &tag_crc);
+      if (n!=3 || tag_type<0 || tag_type>FD_TAG_LAST ) { tag_error = 1; return -1; }
+      if (code_crc != tag_crc) {
+        if (tag_type==FD_TAG_MENU_CALLBACK || tag_type==FD_TAG_WIDGET_CALLBACK) {
+          changed |= apply_callback(block_end, block_start, code_crc, uid);
+        } else if (tag_type==FD_TAG_CODE) {
+          changed |= apply_code(block_end, block_start, code_crc, uid);
+        }
+      }
+      // reset everything for the next block
+      code_crc = 0;
+      line_start = true;
+      block_start = ::ftell(code);
+    }
+  }
+  return changed;
+}
+
+/** Dispatch the MergeBack into analysis, interactive, or apply directly.
+ \param[in] s source code filename and path
+ \param[in] task one of FD_MERGEBACK_ANALYSE, FD_MERGEBACK_INTERACTIVE,
+            FD_MERGEBACK_APPLY_IF_SAFE, or FD_MERGEBACK_APPLY
+ \return see ::merge_back(const Fl_String &s, int task)
+ */
+int Fd_Mergeback::merge_back(const Fl_String &s, int task) {
+  int ret = 0;
+  code = fl_fopen(s.c_str(), "r");
+  if (!code) return -1;
+  do { // no actual loop, just make sure we close the code file
+    if (task == FD_MERGEBACK_ANALYSE) {
+      analyse();
+      if (tag_error) {ret = -1; break; }
+      if (num_changed_structure) ret |= 1;
+      if (num_changed_code) ret |= 2;
+      if (num_uid_not_found) ret |= 4;
+      if (num_possible_override) ret |= 8;
+      break;
+    }
+    if (task == FD_MERGEBACK_INTERACTIVE) {
+      analyse();
+      ret = ask_user_to_merge();
+      if (ret != 1)
+        return ret;
+      task = FD_MERGEBACK_APPLY; // fall through
+    }
+    if (task == FD_MERGEBACK_APPLY_IF_SAFE) {
+      analyse();
+      if (tag_error || num_changed_structure || num_possible_override) {
+        ret = -1;
+        break;
+      }
+      if (num_changed_code==0) {
+        ret = 0;
+        break;
+      }
+      task = FD_MERGEBACK_APPLY; // fall through
+    }
+    if (task == FD_MERGEBACK_APPLY) {
+      ret = apply();
+      if (ret == 1) {
+        set_modflag(1);
+        redraw_browser();
+        load_panel();
+      }
+      ret = 1; // avoid message box in caller
+    }
+  } while (0);
+  fclose(code);
+  code = NULL;
+  return ret;
+}

fluid/mergeback.h

@@ -0,0 +1,77 @@
+//
+// MergeBack routines for the Fast Light Tool Kit (FLTK).
+//
+// Copyright 2023 by Bill Spitzak and others.
+//
+// This library is free software. Distribution and use rights are outlined in
+// the file "COPYING" which should have been included with this file.  If this
+// file is missing or damaged, see the license at:
+//
+//     https://www.fltk.org/COPYING.php
+//
+// Please see the following page on how to report bugs and issues:
+//
+//     https://www.fltk.org/bugs.php
+//
+
+#ifndef _FLUID_MERGEBACK_H
+#define _FLUID_MERGEBACK_H
+
+#include <FL/fl_attr.h>
+
+#include "../src/Fl_String.H"
+
+#include <stdio.h>
+
+const int FD_TAG_GENERIC = 0;
+const int FD_TAG_CODE = 1;
+const int FD_TAG_MENU_CALLBACK = 2;
+const int FD_TAG_WIDGET_CALLBACK = 3;
+const int FD_TAG_LAST = 3;
+
+const int FD_MERGEBACK_ANALYSE = 0;
+const int FD_MERGEBACK_INTERACTIVE = 1;
+const int FD_MERGEBACK_APPLY = 2;
+const int FD_MERGEBACK_APPLY_IF_SAFE = 3;
+
+/** Class that implements the MergeBack functionality.
+ \see merge_back(const Fl_String &s, int task)
+ */
+class Fd_Mergeback
+{
+protected:
+  /// Pointer to the C++ code file.
+  FILE *code;
+  /// Current line number in the C++ code file.
+  int line_no;
+  /// Set if there was an error reading a tag.
+  int tag_error;
+  /// Number of code blocks that were different than the CRC in their tag.
+  int num_changed_code;
+  /// Number of generic structure blocks that were different than the CRC in their tag.
+  int num_changed_structure;
+  /// Number of code block that were modified, but a type node by that uid was not found.
+  int num_uid_not_found;
+  /// Number of modified code block where the corresponding project block also changed.
+  int num_possible_override;
+
+  void unindent(char *s);
+  Fl_String read_and_unindent_block(long start, long end);
+  void analyse_callback(unsigned long code_crc, unsigned long tag_crc, int uid);
+  void analyse_code(unsigned long code_crc, unsigned long tag_crc, int uid);
+  int apply_callback(long block_end, long block_start, unsigned long code_crc, int uid);
+  int apply_code(long block_end, long block_start, unsigned long code_crc, int uid);
+
+public:
+  Fd_Mergeback();
+  ~Fd_Mergeback();
+  int merge_back(const Fl_String &s, int task);
+  int ask_user_to_merge();
+  int analyse();
+  int apply();
+};
+
+extern int merge_back(const Fl_String &s, int task);
+
+
+#endif // _FLUID_MERGEBACK_H