[Bug 18145] FillRect: Undocumented feature

http://bugs.winehq.org/show_bug.cgi?id=18145

--- Comment #3 from Marintsev Miron   2009-04-29 05:18:28 ---
(In reply to comment #2)
> Probably what happens is that FillRect() ignores an error of SelectObject()
> when an invalid brush handle is passed. That needs a test case.

#1. FillRect && GetSysColorBrush
FillRect code:
...
if ( hbrush <= (HBRUSH) (COLOR_MAX + 1)) hbrush = GetSysColorBrush(
HandleToULong(hbrush) - 1 );
...

GetSysColorBrush( (unsigned) -1 ) returns NULL under windows, but wine returns
GetStockObject( LTGRAY_BRUSH ).

So it's necessary to add such code to dlls/user32/sysparams.c/GetSysColorBrush:
if( (unsigned int) -1 == index ) return NULL;

MSDN says:

Return Value

The return value identifies a logical brush if the nIndex parameter is
supported by the current platform. Otherwise, it returns NULL.

#2. SelectObject( hdc, 0 )
There is no problem with SelectObject( hdc, 0 ). It returns 0 and do nothing
both under Windows and wine.

#3. FillRect && SelectObject( hdc, 0 )

dlls/user32/uitools.c/FillRect code:

...
if ( !(prevBrush = SelectObject( hdc, hbrush ))) return 0;
PatBlt( hdc, rect->left, rect->top,
              rect->right - rect->left, rect->bottom - rect->top, PATCOPY );
SelectObject( hdc, prevBrush );
...

SelectObject( hdc, 0 ) will return 0, so prevBrush will be 0 and FillRect
returns 0, before drawing using PatBlt. It's improper.

According to item #2 it's safely to use SelectObject( hdc, 0 ) before and after
PatBlt, but lacks performance.

So this is my vision of FillRect reconstruction:
if ( hbrush && !(prevBrush = SelectObject( hdc, hbrush ))) return 0;
PatBlt( hdc, rect->left, rect->top,
              rect->right - rect->left, rect->bottom - rect->top, PATCOPY );
if( hbrush ) SelectObject( hdc, prevBrush );