Re: new frame-parameter "alpha"

[Seiji Zenitani]

Hi,

Thank you for your comments.
I have attached an revised code to this email.

On 2008/03/14, at 14:28, Stefan Monnier wrote:
> > The attached patch adds the window (frame) opacity feature to GNU  
> > Emacs.
> > The user can control the frame opacity via a frame parameter   
> > 'alpha'.
> > If you like the code, I'll start to contact major  contributors.
>
> I do not personally care for transparency, and I'm wondering if  
> it's not
> better handled by the (compositing) window-manager, but if some people
> like this feature, I'm not opposed to it.
I would like to mention that we can potentially use this frame  
parameter on various platforms.  I have another code for emacs 22,  
which works both on X11 and on Mac/Carbon.  As soon as the Mac/Carbon  
port or other mac port comes back in emacs 23, it will be easy to  
port the code to the mac port.  In addition, some people use the  
frame opacity code on the win32 platform.

> A few comments on the code:
>
> > +  (defun set-alpha (alpha &optional frame)
(snip)
> Is this necessary/important?

I have removed it.

> > +#ifdef HAVE_X_WINDOWS
> > +/* Lower limit value of frame transparency.  */
> > +
> > +Lisp_Object Vframe_alpha_lower_limit;
> > +#endif
> > +
> >  #endif
>
> Only use #ifdef conditional compilation if either it's necessary to  
> get
> the code to compile, or for code which is inherently only  
> meaningful for
> a particular configuration.  Since Vframe_alpha_lower_limit makes  
> sense
> with other GUIs than X11, it should not be protected with #ifdef
> HAVE_X_WINDOWS.
>
> > +#ifdef HAVE_X_WINDOWS
> > +Lisp_Object Qalpha;
> > +#endif
>
> Same here and various other places.
I have reduced #ifdef ... #endif.

> > +#ifdef HAVE_X_WINDOWS
> > +void
> > +x_set_alpha (f, arg, oldval)
> > +     struct frame *f;
> > +     Lisp_Object arg, oldval;
> > +{
(snip)
> > +}
> > +#endif
>
> Explain why you do things twice.

This is because two kinds of frame opacity are set: one for an active  
frame (the frontmost frame), the other for inactive frames  
(background frames).

> Also, note the coding conventions we use and try to reproduce them.
> E.g. we place a space before open parentheses but no space after (and
> no space before the close parenthesis either).
I have modified the coding style.

> > +#ifdef HAVE_X_WINDOWS
> > +  /* Opacity of the Frame  */
> > +  double alpha[2];
> > +#endif
>
> The comment should describe what the field holds, so in this case it
> should describe *both* entries of the table.
Done.

> Also in the docstring, don't just use "alpha" but "alpha transparency"
> or something like that, for people who don't know what you mean by  
> "alpha".
>
>         Stefan


At present I call the parameters/variables "alpha" ('alpha, frame- 
alpha-lower-limit, x_set_frame_alpha, etc.) similar to Meadow.  If  
"alpha" is ambiguous, we can rename them to "opacity" etc.

transparency4-x23.patch
Description: Binary data

P.S.
Meadow has four settings for the frame opacity: (1) active frame, (2)  
inactive frames, (3) moving frame, and (4) resizing frame.
e.g. (set-frame-parameter (selected-frame) 'alpha '(<active>  
[<inactive> [<moving> [sizing]]]))


Seiji Zenitani
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