[Gdiplus 11/15] Implement GdipCreateRegionRect
adam at tpetaccia.com
Wed Jul 9 09:56:48 CDT 2008
I was just about to reply to your first mail when I found this pop up.
To quote MSDN:
"The Region class describes an area of the display surface. The area can
be any shape. In other words, the boundary of the area can be a
combination of curved and straight lines. Regions can also be created
from the interiors of rectangles, paths, or a combination of these.
Regions are used in clipping and hit-testing operations."
Because the area can be any shape, including curved lines, I chose
GpPath as the base object. I imagined the data you're talking about
stored in an array of regionOperation structs, or something of the like
- so we still have the ability to do non-rectangular hit-testing and can
now getRegionData. I'll write some more tests to confirm/deny this
On Wed, 2008-07-09 at 15:41 +0100, Huw Davies wrote:
> On Wed, Jul 09, 2008 at 11:58:23AM +0100, Huw Davies wrote:
> > This doesn't look right. See the GdipGetRegionData tests (and extend
> > them to add paths), these are supposed to help understanding how
> > regions are stored. It looks to me that a region is stored as a
> > sequence of rects and paths that are combined with various CombineMode
> > ops.
> Hi Adam,
> In fact you want to store the region elements as a binary tree,
> something like this:
> typedef enum element_type
> rect_element = 0x10000000,
> } element_type_t;
> typedef struct region_element
> DWORD type_or_op; /* One of the CombineModes or element_type_t */
> GpRectF rect;
> GpPath *path;
> struct region_element *first;
> struct region_element *second;
> } operands;
> } elem_data;
> } region_element_t;
I had something in mind that resembled this, but without a union. That's
a better idea.
> struct GpRegion
> region_element_t root;
> A region element is either a rect, path or a combining op (in which
> case it has two children, 'first' and 'second'). The data returned by
> GdipGetRegionData is then basically what happens if you walk the tree,
> favouring the 'first' node at every branch.
I had an idea of something like that.
> Does that make sense?
All of it.
I didn't mean to imply that I ignored the region.c header, but I didn't
use any of its information for the bounds tests yet, so I didn't add
them to the struct (and I've learned to add things as needed).
Thanks for the additional help.
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