Re: general c++ question

[John W. Eaton]

On 28-Aug-2007, Shai Ayal wrote:

| In a patch I submitted some time ago with the subject "exposing
| graphics object properties" I outline what is the call graph for
| getting properties. I quote from that mail:
| 
| -------
| I attach a patch who's purpose is to expose the properties of the
| graphics objects. The purpose of this patch to allow access to
| properties as in:
| 
| if (gh_manager::get_object (h).isa () == "image")
|   image_properties ip = gh_manager::image_properties_value (h);
| 
| It turned out it involved quite a lot of new functions and
| "declaration acrobatics" where function definitions had to be moved
| because of forward declarations. To illustrates, the above functions
| call will set in motions the following:
| 
| gh_manager::image_properties_value
| gh_manager::do_image_properties_value
| graphics_object:::image_properties_value
| virtual base_graphics_object::image_properties_value
| 
| in all these calls the image_properties class is passed by value. I
| also had to un-nest the properties classes from inside their
| respective object classes in order to allow their forward
| declarations.
| 
| I do not like my patch, I hope it turned out this complicated because
| of some oversight by me or my lack of c++ knowledge. Please comment on
| it.
| 
| ---- end of quote.
| as you can see, graphics object & base_graphics_object also need to be
| aware of the properties in the scheme that I ended up with. So just
| moving gh_manager to the end of the declarations would not do.

How about the following changes?

Here is an example of how the new functions can be used:

  DEFUN (doit, args, , "")
  {
    octave_value retval;

    if (args.length () == 1)
      {
        graphics_handle h = octave_NaN;

        double val = args(0).double_value ();

        if (! error_state)
          {
            h = gh_manager::lookup (val);

            if (! xisnan (h))
              {
                graphics_object obj = gh_manager::get_object (h);

                if (obj.isa ("line"))
                  {
                    line::line_properties& lp
                      = dynamic_cast<line::line_properties&> 
(obj.get_properties ());
                    retval = lp.get_xdata ();
                    Matrix m (1, 5);
                    m(0) = 0;
                    m(1) = 1;
                    m(2) = 2;
                    m(3) = 3;
                    m(4) = 4;
                    lp.set_xdata (m);
                    m(0) = 0;
                    m(1) = 1;
                    m(2) = 0.2;
                    m(3) = 0.8;
                    m(4) = 0.4;
                    lp.set_ydata (m);

                    feval ("__request_drawnow__");
                  }
                else
                  error ("doit: looking for line");
              }
            else
              error ("doit: invalid graphics object (= %g)", val);
          }
        else
          error ("doit: invalid graphics object");
      }
    else
      print_usage ();

    return retval;
  }

Using this function, try something like

  h = line ();
  doit (h);

It will return the original xdata property from the handle and also
modify the xdata and ydata properties for the object.  Instead of
using the graphics_object "isa" method, we could use run-time type
identification, but I don't think that detail matters much.

jwe


2007-08-28  John W. Eaton  <address@hidden>

        * graphics.h (OCTAVE_GRAPHICS_PROPERTY_INTERNAL): Also define
        set_X functions for properties.
        (base_properties): Move class definition before definition of
        base_graphics_object class.  Provide forward declaration of
        base_graphics_object prior to definition of base_properties.
        (base_graphics_object::get_properties): New virtual function.
        (graphics_object::get_properties, root_figure::get_properties,
        figure::get_properties, axes::get_properties,
        line::get_properties, text::get_properties, image::get_properties,
        patch::get_properties, surface::get_properties): New functions.
        (root_figure::properties, figure::properties, axes::properties,
        line::properties, text::properties, image::properties,
        patch::properties, surface::properties): Data member now private.


Index: src/graphics.h
===================================================================
RCS file: /cvs/octave/src/graphics.h,v
retrieving revision 1.11
diff -u -u -r1.11 graphics.h
--- src/graphics.h      27 Aug 2007 19:50:23 -0000      1.11
+++ src/graphics.h      28 Aug 2007 21:20:07 -0000
@@ -40,8 +40,11 @@
 #include "ov.h"
 
 #define OCTAVE_GRAPHICS_PROPERTY_INTERNAL(TAG, TYPE, NAME) \
-  private: TAG TYPE NAME; \
-  public: const TYPE& get_ ## NAME () const { return NAME; } \
+  private: \
+    TAG TYPE NAME; \
+  public: \
+    const TYPE& get_ ## NAME () const { return NAME; } \
+    void set_ ## NAME (const TYPE& val) { NAME = val; mark_modified (); } \
   private:
 
 #define OCTAVE_GRAPHICS_PROPERTY(TYPE, NAME) \
@@ -421,6 +424,57 @@
 
 // ---------------------------------------------------------------------
 
+class base_graphics_object;
+
+class base_properties
+{
+public:
+  base_properties (const std::string& t = "unknown",
+                  const graphics_handle& mh = octave_NaN,
+                  const graphics_handle& p = octave_NaN)
+    : type (t), __modified__ (true), __myhandle__ (mh), parent (p),
+      children () { }
+
+  virtual ~base_properties (void) { }
+
+  virtual std::string graphics_object_name (void) const { return "unknonwn"; }
+
+  void mark_modified (void);
+
+  void override_defaults (base_graphics_object& obj);
+
+  // Look through DEFAULTS for properties with given CLASS_NAME, and
+  // apply them to the current object with set (virtual method).
+
+  void set_from_list (base_graphics_object& obj, property_list& defaults);
+
+  virtual void set (const property_name&, const octave_value&) { }
+
+  graphics_handle get_parent (void) const { return parent; }
+
+  void remove_child (const graphics_handle& h);
+
+  void adopt (const graphics_handle& h)
+  {
+    octave_idx_type n = children.numel ();
+    children.resize (1, n+1);
+    children(n) = h;
+  }
+
+  void set_parent (const octave_value& val);
+
+  void reparent (const graphics_handle& new_parent) { parent = new_parent; }
+
+  virtual void delete_children (void);
+
+protected:
+  std::string type;
+  bool __modified__;
+  graphics_handle __myhandle__;
+  graphics_handle parent;
+  Matrix children;
+};
+
 class base_graphics_object
 {
 public:
@@ -511,6 +565,13 @@
     error ("base_graphics_object::default: invalid graphics object");
   }
 
+  virtual base_properties& get_properties (void)
+  {
+    static base_properties properties;
+    error ("base_graphics_object::get_properties: invalid graphics object");
+    return properties;
+  }
+
   virtual bool valid_object (void) const { return false; }
 
   virtual std::string type (void) const { return "unknown"; }
@@ -625,6 +686,8 @@
 
   bool isa (const std::string& go_name) const { return rep->isa (go_name); }
 
+  base_properties& get_properties (void) { return rep->get_properties (); }
+
   bool valid_object (void) const { return rep->valid_object (); }
 
   operator bool (void) const { return rep->valid_object (); }
@@ -633,55 +696,6 @@
   base_graphics_object *rep;
 };
 
-class base_properties
-{
-public:
-  base_properties (const std::string& t = "unknown",
-                  const graphics_handle& mh = octave_NaN,
-                  const graphics_handle& p = octave_NaN)
-    : type (t), __modified__ (true), __myhandle__ (mh), parent (p),
-      children () { }
-
-  virtual ~base_properties (void) { }
-
-  virtual std::string graphics_object_name (void) const = 0;
-
-  void mark_modified (void);
-
-  void override_defaults (base_graphics_object& obj);
-
-  // Look through DEFAULTS for properties with given CLASS_NAME, and
-  // apply them to the current object with set (virtual method).
-
-  void set_from_list (base_graphics_object& obj, property_list& defaults);
-
-  virtual void set (const property_name& name, const octave_value& val) = 0;
-
-  graphics_handle get_parent (void) const { return parent; }
-
-  void remove_child (const graphics_handle& h);
-
-  void adopt (const graphics_handle& h)
-  {
-    octave_idx_type n = children.numel ();
-    children.resize (1, n+1);
-    children(n) = h;
-  }
-
-  void set_parent (const octave_value& val);
-
-  void reparent (const graphics_handle& new_parent) { parent = new_parent; }
-
-  virtual void delete_children (void);
-
-protected:
-  std::string type;
-  bool __modified__;
-  graphics_handle __myhandle__;
-  graphics_handle parent;
-  Matrix children;
-};
-
 // ---------------------------------------------------------------------
 
 class root_figure : public base_graphics_object
@@ -713,6 +727,7 @@
     static std::string go_name;
   };
 
+private:
   root_figure_properties properties;
 
 public:
@@ -808,6 +823,8 @@
 
   void reparent (const graphics_handle& np) { properties.reparent (np); }
 
+  base_properties& get_properties (void) { return properties; }
+
   bool valid_object (void) const { return true; }
 
 private:
@@ -854,6 +871,7 @@
     static std::string go_name;
   };
 
+private:
   figure_properties properties;
 
 public:
@@ -935,6 +953,8 @@
 
   void reparent (const graphics_handle& np) { properties.reparent (np); }
 
+  base_properties& get_properties (void) { return properties; }
+
   bool valid_object (void) const { return true; }
 
 private:
@@ -1023,6 +1043,7 @@
     static std::string go_name;
   };
 
+private:
   axes_properties properties;
 
 public:
@@ -1106,6 +1127,8 @@
 
   void reparent (const graphics_handle& np) { properties.reparent (np); }
 
+  base_properties& get_properties (void) { return properties; }
+
   bool valid_object (void) const { return true; }
 
 private:
@@ -1154,6 +1177,7 @@
     static std::string go_name;
   };
 
+private:
   line_properties properties;
 
 public:
@@ -1204,6 +1228,8 @@
 
   void reparent (const graphics_handle& h) { properties.reparent (h); }
 
+  base_properties& get_properties (void) { return properties; }
+
   bool valid_object (void) const { return true; }
 };
 
@@ -1240,6 +1266,7 @@
     static std::string go_name;
   };
 
+private:
   text_properties properties;
 
 public:
@@ -1290,6 +1317,8 @@
 
   void reparent (const graphics_handle& h) { properties.reparent (h); }
 
+  base_properties& get_properties (void) { return properties; }
+
   bool valid_object (void) const { return true; }
 };
 
@@ -1323,6 +1352,7 @@
     static std::string go_name;
   };
 
+private:
   image_properties properties;
 
 public:
@@ -1373,6 +1403,8 @@
 
   void reparent (const graphics_handle& h) { properties.reparent (h); }
 
+  base_properties& get_properties (void) { return properties; }
+
   bool valid_object (void) const { return true; }
 };
 
@@ -1416,6 +1448,7 @@
     static std::string go_name;
   };
 
+private:
   patch_properties properties;
 
 public:
@@ -1466,6 +1499,8 @@
 
   void reparent (const graphics_handle& h) { properties.reparent (h); }
 
+  base_properties& get_properties (void) { return properties; }
+
   bool valid_object (void) const { return true; }
 };
 
@@ -1500,6 +1535,7 @@
     static std::string go_name;
   };
 
+private:
   surface_properties properties;
 
 public:
@@ -1550,6 +1586,8 @@
 
   void reparent (const graphics_handle& h) { properties.reparent (h); }
 
+  base_properties& get_properties (void) { return properties; }
+
   bool valid_object (void) const { return true; }
 };