Fix one compiler warning (STR 3529)

fluid/undo.cxx: fix warning [-Wformat-truncation=]

This fix also removes some static variables and simplifies the
function undo_filename(). It does no longer copy the full filename
string back to a given buffer. Now it returns a pointer to the
internal filename string.

Summary: fix compiler warning, save memory, simplify a function, and
  speed up code by not copying data unnecessarily.

1 files changed, 25 insertions, 21 deletions

diff --git a/fluid/undo.cxx b/fluid/undo.cxx
index fc23e60a1..98dff5ea2 100644
--- a/fluid/undo.cxx
+++ b/fluid/undo.cxx
@@ -54,26 +54,34 @@ int undo_save = -1;			// Last undo level that was saved
 static int undo_paused = 0;		// Undo checkpointing paused?
 
 
-// Return the undo filename
-static char *undo_filename(int level, char *buf, int bufsize) {
-  static char	undo_path[FL_PATH_MAX] = "";	// Undo path
-
-
-  if (!undo_path[0]) fluid_prefs.getUserdataPath(undo_path, sizeof(undo_path));
+// Return the undo filename.
+// The filename is constructed in a static internal buffer and
+// this buffer is overwritten by every call of this function.
+// The return value is a pointer to this internal string.
+static char *undo_filename(int level) {
+  static char undo_path[FL_PATH_MAX] = ""; // Undo path
+  static unsigned int undo_path_len = 0;   // length w/o filename
+
+  if (!undo_path_len) {
+    fluid_prefs.getUserdataPath(undo_path, sizeof(undo_path));
+    undo_path_len = strlen(undo_path);
+  }
 
-  snprintf(buf, bufsize, "%sundo_%d_%d.fl", undo_path, getpid(), level);
-  return buf;
+  // append filename: "undo_PID_LEVEL.fl"
+  snprintf(undo_path + undo_path_len,
+	   sizeof(undo_path) - undo_path_len - 1,
+	   "undo_%d_%d.fl", getpid(), level);
+  return undo_path;
 }
 
 
 // Redo menu callback
 void redo_cb(Fl_Widget *, void *) {
-  char	filename[FL_PATH_MAX];			// Undo checkpoint file
 
   if (undo_current >= undo_last) return;
 
   undo_suspend();
-  if (!read_file(undo_filename(undo_current + 1, filename, sizeof(filename)), 0)) {
+  if (!read_file(undo_filename(undo_current + 1), 0)) {
     // Unable to read checkpoint file, don't redo...
     undo_resume();
     return;
@@ -91,16 +99,15 @@ void redo_cb(Fl_Widget *, void *) {
 
 // Undo menu callback
 void undo_cb(Fl_Widget *, void *) {
-  char	filename[FL_PATH_MAX];			// Undo checkpoint file
 
   if (undo_current <= 0) return;
 
   if (undo_current == undo_last) {
-    write_file(undo_filename(undo_current, filename, sizeof(filename)));
+    write_file(undo_filename(undo_current));
   }
 
   undo_suspend();
-  if (!read_file(undo_filename(undo_current - 1, filename, sizeof(filename)), 0)) {
+  if (!read_file(undo_filename(undo_current - 1), 0)) {
     // Unable to read checkpoint file, don't undo...
     undo_resume();
     return;
@@ -119,16 +126,15 @@ void undo_cb(Fl_Widget *, void *) {
 
 // Save current file to undo buffer
 void undo_checkpoint() {
-  char	filename[FL_PATH_MAX];			// Undo checkpoint filename
-
-//  printf("undo_checkpoint(): undo_current=%d, undo_paused=%d, modflag=%d\n",
-//         undo_current, undo_paused, modflag);
+  //  printf("undo_checkpoint(): undo_current=%d, undo_paused=%d, modflag=%d\n",
+  //         undo_current, undo_paused, modflag);
 
   // Don't checkpoint if undo_suspend() has been called...
   if (undo_paused) return;
 
   // Save the current UI to a checkpoint file...
-  if (!write_file(undo_filename(undo_current, filename, sizeof(filename)))) {
+  const char *filename = undo_filename(undo_current);
+  if (!write_file(filename)) {
     // Don't attempt to do undo stuff if we can't write a checkpoint file...
     perror(filename);
     return;
@@ -150,12 +156,10 @@ void undo_checkpoint() {
 
 // Clear undo buffer
 void undo_clear() {
-  char	filename[FL_PATH_MAX];			// Undo checkpoint filename
-
 
   // Remove old checkpoint files...
   for (int i = 0; i <= undo_max; i ++) {
-    fl_unlink(undo_filename(i, filename, sizeof(filename)));
+    fl_unlink(undo_filename(i));
   }
 
   // Reset current, last, and save indices...