Re: [perl-win32-gui-hackers] Win32::GUI::Button align problem

[Glenn L. <pe...@ne...>]

On approximately 10/7/2004 3:15 PM, came the following characters from 
the keyboard of Glenn Linderman:

> On approximately 10/7/2004 2:23 PM, came the following characters from 
> the keyboard of Laurent ROCHER:
> 
>> Hi Blair,
>>
>>     Fix and commit on CVS.
>>
>>     Problem come from BS_CENTER style is BS_LEFT | BS_RIGHT so SwitchBit
>> order it's important.
>>
>>     I rewrite like this :
>>
>>     if(strcmp(option, "-align") == 0) {
>>         // BS_CENTER is BS_LEFT | BS_RIGHT
>>         if(strcmp(SvPV_nolen(value), "left") == 0) {
>>             SwitchBit(perlcs->cs.style, BS_RIGHT, 0);
>>             SwitchBit(perlcs->cs.style, BS_LEFT, 1);
>>         } else if(strcmp(SvPV_nolen(value), "center") == 0) {
>>             SwitchBit(perlcs->cs.style, BS_CENTER, 1);
> 
> 
> Shouldn't this be
> 
>               SwitchBit(perlcs->cs.style, BS_CENTER, 3);

No, not this one.  I misread how SwitchBit works.  Sorry for multiple 
postings, but I remembered tha SwitchBit was pretty obscure... but I 
forgot in what way it was obscure.

> or alternately (to expose that BS_CENTER is BS_LEFT | BS_RIGHT)
> 
>               SwitchBit(perlcs->cs.style, BS_RIGHT, 1);
>               SwitchBit(perlcs->cs.style, BS_LEFT, 1);

This is the only one that will work.  SwitchBit is not smart enough to 
deal with multi-bit values.  If the previous value was BS_RIGHT or 
BS_LEFT, SwitchBit is not smart enough to only turn on the other bit. 
Because of its "if(!(mask & bit)) test, which will be false.  Nor is it 
smart enough to turn off both bits with "SwitchBit(perlcs->cs.style, 
BS_CENTER,0);", because it uses "mask ^= bit;" which will turn on the 
other bit.

Really, it would be easier if there were a primitive that dealt with 
setting bitfields of variable width.  Such exist, but not as part of 
Win32::GUI.

#define SetBits(mask, bits)  {mask |= bits;}
#define ResetBits(mask, bits)  {mask &= ~(bits);}
#define SwitchBits(mask, bits, set) \
  {if (set) SetBits(mask,bits) else ResetBits(mask,bits);}

would be more useful, in my opinion.

> 
>>         } else if(strcmp(SvPV_nolen(value), "right") == 0) {
>>             SwitchBit(perlcs->cs.style, BS_LEFT, 0);
>>             SwitchBit(perlcs->cs.style, BS_RIGHT, 1);
>>         } else {
>>             if(PL_dowarn) warn("Win32::GUI: Invalid value for -align!");
>>         }
>>     }
>>
>>     Thank for bug report.
>>
>> Laurent.
>>
>>
>>
>>> I've noticed that the button attribute "align" breaks if you specify
>>> "center", if empty it works (i.e. default).
>>>
>>> <pre>
>>> use Win32::GUI;
>>> my $W = new GUI::Window(-height=>100,-width=>100);
>>> my $B = $W->AddButton(-text=>'Test', -width=>'100', -align=>'center');
>>> $W->Center();
>>> $W->Show();
>>> Win32::GUI::Dialog;
>>> </pre>
>>>
>>> If one replaces "center" with "right" it works as expected. The error is
>>> not apparent in Button.xs and I've happens on XPsp2 and W2Ksp4.
>>>
>>> Blair
>>>
>>
>>
>>
>>
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>>
>>
>>
> 

-- 
Glenn -- http://nevcal.com/
===========================
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