|why is HBRUSH in brackets? |
That is the C-style notation for a cast
(HBRUSH)(COLOR_WINDOW + 1)
Casts can also be written using function style
HBRUSH(COLOR_WINDOW + 1)
and using the more modern (and preferred) C++ casts: static_cast<>, reinterpret_cast<>, etc.
See this part of the tutorial for more info:
|I would like to know what the next line of code does...|
The code is casting a integer identifier (for a color) to an HBRUSH (the handle to a GDI brush).
These days you should only ever come across this when registering a window class; you set the hbrBackground member of the WNDCLASSEX struct (e.g. wcex)
wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
The +1 must be used; it shifts the values by 1 so RegisterClassEx() can tell the difference between CTLCOLOR_MSGBOX (which has value 0) and NULL (which is also 0.)
RegisterClassEx() can tell the difference between a color ID (with a value of 0, 1, 2, ... up to 30 at the moment) and a brush handle (which you get when you create a brush using CreateSolidBrush(), etc) as actual handle values are much bigger, e.g. 0x72102280 (2299531404 as an unsigned int, or -1995435892 as a signed one.)