commit 8978bd1a842124e7c151c3fcdffec5bce103f808
Author:     Matthias Melcher <github@matthiasm.com>
AuthorDate: Thu Nov 24 12:35:20 2022 +0100
Commit:     Matthias Melcher <github@matthiasm.com>
CommitDate: Thu Nov 24 12:35:32 2022 +0100

    FLUID: Fix update of formula input widgets

 fluid/Fl_Widget_Type.cxx  | 37 +++++++++++++++++++++++++++++--------
 fluid/Shortcut_Button.cxx | 17 ++++++++++++-----
 2 files changed, 41 insertions(+), 13 deletions(-)

diff --git fluid/Fl_Widget_Type.cxx fluid/Fl_Widget_Type.cxx
index 12772ea..e933ad6 100644
--- fluid/Fl_Widget_Type.cxx
+++ fluid/Fl_Widget_Type.cxx
@@ -670,17 +670,23 @@ void x_cb(Fluid_Coord_Input *i, void *v) {
     undo_checkpoint();
     widget_i = 0;
     int mod = 0;
+    int v = 0;
     for (Fl_Type *o = Fl_Type::first; o; o = o->next) {
       if (o->selected && o->is_widget()) {
         Fl_Widget *w = ((Fl_Widget_Type *)o)->o;
         i->variables(widget_vars, o);
-        w->resize((int)i->value(), w->y(), w->w(), w->h());
+        v = i->value();
+        w->resize(v, w->y(), w->w(), w->h());
         if (w->window()) w->window()->redraw();
         widget_i++;
         mod = 1;
       }
     }
-    if (mod) set_modflag(1);
+    if (mod) {
+      set_modflag(1);
+      i->value(v);    // change the displayed value to the result of the last
+                      // calculation. Keep the formula if it was not used.
+    }
   }
 }
 
@@ -695,17 +701,22 @@ void y_cb(Fluid_Coord_Input *i, void *v) {
     undo_checkpoint();
     widget_i = 0;
     int mod = 0;
+    int v = 0;
     for (Fl_Type *o = Fl_Type::first; o; o = o->next) {
       if (o->selected && o->is_widget()) {
         Fl_Widget *w = ((Fl_Widget_Type *)o)->o;
         i->variables(widget_vars, o);
-        w->resize(w->x(), (int)i->value(), w->w(), w->h());
+        v = i->value();
+        w->resize(w->x(), v, w->w(), w->h());
         if (w->window()) w->window()->redraw();
         widget_i++;
         mod = 1;
       }
     }
-    if (mod) set_modflag(1);
+    if (mod) {
+      set_modflag(1);
+      i->value(v);
+    }
   }
 }
 
@@ -720,17 +731,22 @@ void w_cb(Fluid_Coord_Input *i, void *v) {
     undo_checkpoint();
     widget_i = 0;
     int mod = 0;
+    int v = 0;
     for (Fl_Type *o = Fl_Type::first; o; o = o->next) {
       if (o->selected && o->is_widget()) {
         Fl_Widget *w = ((Fl_Widget_Type *)o)->o;
         i->variables(widget_vars, o);
-        w->resize(w->x(), w->y(), (int)i->value(), w->h());
+        v = i->value();
+        w->resize(w->x(), w->y(), v, w->h());
         if (w->window()) w->window()->redraw();
         widget_i++;
         mod = 1;
       }
     }
-    if (mod) set_modflag(1);
+    if (mod) {
+      set_modflag(1);
+      i->value(v);
+    }
   }
 }
 
@@ -745,17 +761,22 @@ void h_cb(Fluid_Coord_Input *i, void *v) {
     undo_checkpoint();
     widget_i = 0;
     int mod = 0;
+    int v = 0;
     for (Fl_Type *o = Fl_Type::first; o; o = o->next) {
       if (o->selected && o->is_widget()) {
         Fl_Widget *w = ((Fl_Widget_Type *)o)->o;
         i->variables(widget_vars, o);
-        w->resize(w->x(), w->y(), w->w(), (int)i->value());
+        v = i->value();
+        w->resize(w->x(), w->y(), w->w(), v);
         if (w->window()) w->window()->redraw();
         widget_i++;
         mod = 1;
       }
     }
-    if (mod) set_modflag(1);
+    if (mod) {
+      set_modflag(1);
+      i->value(v);
+    }
   }
 }
 
diff --git fluid/Shortcut_Button.cxx fluid/Shortcut_Button.cxx
index 9c64b76..97fa7f2 100644
--- fluid/Shortcut_Button.cxx
+++ fluid/Shortcut_Button.cxx
@@ -203,7 +203,8 @@ void Fluid_Coord_Input::callback_handler_cb(Fluid_Coord_Input *This, void *v) {
 void Fluid_Coord_Input::callback_handler(void *v) {
   if (user_callback_)
     (*user_callback_)(this, v);
-  value( value() );
+  // do *not* update the value to show the evaluated fomule here, because the
+  // values of the variables have already updated after the user callback.
 }
 
 /**
@@ -238,14 +239,20 @@ int Fluid_Coord_Input::eval_var(uchar *&s) const {
  \return the value so far
  */
 int Fluid_Coord_Input::eval(uchar *&s, int prio) const {
-  int v =0, sgn = 1;
+  int v = 0, sgn = 1;
   uchar c = *s++;
 
+  // check for end of text
+  if (c==0) { s--; return sgn*v; }
+
   // check for unary operator
   if (c=='-') { sgn = -1; c = *s++; }
   else if (c=='+') { sgn = 1; c = *s++; }
 
-  if (c>='0' && c<='9') {
+  // read value, variable, or bracketed term
+  if (c==0) {
+    s--; return sgn*v;
+  } else if (c>='0' && c<='9') {
     // numeric value
     while (c>='0' && c<='9') {
       v = v*10 + (c-'0');
@@ -265,6 +272,7 @@ int Fluid_Coord_Input::eval(uchar *&s, int prio) const {
   // Now evaluate all following binary operators
   for (;;) {
     if (c==0) {
+      s--;
       return v;
     } else if (c=='+' || c=='-') {
       if (prio<=4) { s--; return v; }
@@ -283,8 +291,7 @@ int Fluid_Coord_Input::eval(uchar *&s, int prio) const {
     } else {
       return v; // syntax error
     }
-    c = *s;
-    if (c) s++;
+    c = *s++;
   }
   return v;
 }