• Brad Anderson <brad sankaty.dot.com> May 31 2004
• "Vathix" <vathixSpamFix dprogramming.com> May 31 2004
• Brad Anderson <brad dsource.dot.org> May 31 2004
• Ben Hinkle <bhinkle4 juno.com> Jun 01 2004
• Brad Anderson <brad sankaty.dot.com> Jun 01 2004

Brad Anderson <brad sankaty.dot.com> writes:

I am porting some Java code that used classes as structs (because Java lacks 
structs).

 LOGFONT oldFont;


and later:

 void releaseWidget() {
     oldFont = null;
 }


The compiler (dmd 0.89, WinXP) complains that you cannot implicitly convert 
void* to LOGFONT.

So, what options do I have to set this struct to null or point to nothing?

 oldFont = '\0';  (now it's char to LOGFONT)


Also, how do I do the following?

 if(oldFont == null) return;


I poked around the DM website and the Wiki, and found constructors for structs 
with opCall() but nothing about destructors or setting/comparing structs to
null.

BA

"Vathix" <vathixSpamFix dprogramming.com> writes:

"Brad Anderson" <brad sankaty.dot.com> wrote in message
news:c9eloi$2d83$1 digitaldaemon.com...
 I am porting some Java code that used classes as structs (because Java


 structs).

  > LOGFONT oldFont;

 and later:

  > void releaseWidget() {
  >     oldFont = null;
  > }

 The compiler (dmd 0.89, WinXP) complains that you cannot implicitly


 void* to LOGFONT.

 So, what options do I have to set this struct to null or point to nothing?

  > oldFont = '\0';  (now it's char to LOGFONT)

 Also, how do I do the following?

  > if(oldFont == null) return;

 I poked around the DM website and the Wiki, and found constructors for


 with opCall() but nothing about destructors or setting/comparing structs


 BA


Maybe you should use a pointer and set it to null when you're done with it.
You can't set a struct to null just like you can't set an int to null.
Sometimes you do want to initialize all data to zero, but that's different,
I do this:
   (cast(byte*)(&struct))[0 .. struct.size] = 0;
I admit it's ugly, memset() is actually cleaner. To reinitialize the struct
you could do this:
   struct = struct.init;
But either would be very inefficient to do often and worse to check for
those values (especially for that huge LOGFONT).

Brad Anderson <brad dsource.dot.org> writes:

Vathix,

What about another struct member/property (whatever they're called).

struct LOGFONT {
     ...
     bool isCurrent
}

I could set it to true or false and not bother with re-initializing 
everything.

Any thoughts as to how it would affect any .sizeof calcs in its use? 
I.E. any negative effects because the WinAPI is expecting a certain set 
of data and it would receive extra?

Thanks for the response.

BA

Vathix wrote:
 "Brad Anderson" <brad sankaty.dot.com> wrote in message
 news:c9eloi$2d83$1 digitaldaemon.com...
 
I am porting some Java code that used classes as structs (because Java


 lacks
 
structs).

 LOGFONT oldFont;


and later:

 void releaseWidget() {
     oldFont = null;
 }


The compiler (dmd 0.89, WinXP) complains that you cannot implicitly


 convert
 
void* to LOGFONT.

So, what options do I have to set this struct to null or point to nothing?

 oldFont = '\0';  (now it's char to LOGFONT)


Also, how do I do the following?

 if(oldFont == null) return;


I poked around the DM website and the Wiki, and found constructors for


 structs
 
with opCall() but nothing about destructors or setting/comparing structs


 to null.
 
BA


 
 Maybe you should use a pointer and set it to null when you're done with it.
 You can't set a struct to null just like you can't set an int to null.
 Sometimes you do want to initialize all data to zero, but that's different,
 I do this:
    (cast(byte*)(&struct))[0 .. struct.size] = 0;
 I admit it's ugly, memset() is actually cleaner. To reinitialize the struct
 you could do this:
    struct = struct.init;
 But either would be very inefficient to do often and worse to check for
 those values (especially for that huge LOGFONT).
 
 

Ben Hinkle <bhinkle4 juno.com> writes:

Brad Anderson wrote:

 I am porting some Java code that used classes as structs (because Java
 lacks structs).
 
  > LOGFONT oldFont;
 
 and later:
 
  > void releaseWidget() {
  >     oldFont = null;
  > }
 
 The compiler (dmd 0.89, WinXP) complains that you cannot implicitly
 convert void* to LOGFONT.
 
 So, what options do I have to set this struct to null or point to nothing?
 
  > oldFont = '\0';  (now it's char to LOGFONT)
 
 Also, how do I do the following?
 
  > if(oldFont == null) return;
 
 I poked around the DM website and the Wiki, and found constructors for
 structs with opCall() but nothing about destructors or setting/comparing
 structs to null.
 
 BA


I bet the Java code is explicitly setting oldFont to null to help the GC
collect the LOGFONT as garbage. I would skip the oldFont=null in D.
A related question has to do with how the port passes LOGFONT to functions:
are you passing by value or pointer or inout?

-Ben

Brad Anderson <brad sankaty.dot.com> writes:

Ben Hinkle wrote:
 
 I bet the Java code is explicitly setting oldFont to null to help the GC
 collect the LOGFONT as garbage. I would skip the oldFont=null in D.


And I would too, except that later, there's a test to see if LOGFONT is 
null.

if(LOGFONT == null)

 A related question has to do with how the port passes LOGFONT to functions:
 are you passing by value or pointer or inout?


I believe we are switching to pass them by pointer.  Which is better?

BTW, LOGFONT will have extra properties if version(Unicode) is true. 
The old way in Java is to have a base class and the unicode and 
non-unicode classes inherit from it and add their wchar/char properties.

BA