Solved

How FrameRgn works

Posted on 2001-07-22
9
809 Views
Last Modified: 2012-06-21
var
   Rects  :array of TRect;
   Points :array of TPoint;

Rects is an array of rectangles that is filled indirectly by GetRegionData (and stored in the same order as they were found in the RGNDATA structure).

Points is an ordered array of points I will use to draw an outline of the region.  (This array will be identical to the array of points you would pass into CreatePolyPolygonRgn, if you were to create the region that way)

I can't use FrameRgn for two reasons:

1.  FrameRgn really isn't very powerful.  I want to draw marching ants and FrameRgn apparently only draws solid lines.
2.  I am not using the region for the purposes of directly drawing to a device context.

I would like to know the algorithm FrameRgn uses to draw the outline of a region, so I can convert Rects to Points.
0
Comment
Question by:scrapdog
  • 5
  • 2
  • 2
9 Comments
 
LVL 17

Expert Comment

by:inthe
ID: 6306313
hi scrapdog,
dunno about FrameRgn but i have an example of marching ants if its any help (it doesnt use FrameRgn etc).
0
 
LVL 5

Author Comment

by:scrapdog
ID: 6306396
No thanks, got that one figured out. =)
0
 
LVL 5

Author Comment

by:scrapdog
ID: 6306397
But if your marching ants code takes it's input from a Windows region, that would be very helpful...
0
Courses: Start Training Online With Pros, Today

Brush up on the basics or master the advanced techniques required to earn essential industry certifications, with Courses. Enroll in a course and start learning today. Training topics range from Android App Dev to the Xen Virtualization Platform.

 
LVL 17

Expert Comment

by:inthe
ID: 6306541
nope ,just passes x,y of mouse to lineDDA()
all other examples i have are from tomes which dont look like they help here.

so just listening..
0
 
LVL 5

Accepted Solution

by:
FengYuan earned 275 total points
ID: 6311038
Simple algorithm:

1) Suppose you use (x1,y1,x2,y2) to represent a line to draw.
2) Create a set or sequence of lines.
3) For each rectangle in the region, adding its four edges to the line set using 4).
4) When adding each line to the set, search for lines in the set which intersects with the line to be added.
5) If no intersection is found, append the line.
6) If intersection is found, remove the matched line, add the disjoint portion of the two lines if any.

7) Draw what's left in the line set.

www.fengyuan.com
0
 
LVL 5

Author Comment

by:scrapdog
ID: 6311056
In #6, intersecting two lines will create four line segments...how do I know which line segments to discard (i.e., which of these segments are inside the region)?
0
 
LVL 5

Expert Comment

by:FengYuan
ID: 6311061
I think you should only consider tw vertical lines or two horizontal lines intersect with each other.

In these cases, at most two new lines can be generated.
0
 
LVL 5

Author Comment

by:scrapdog
ID: 6311066
OK, thanks for the info.  I'll try it out.
0
 
LVL 5

Author Comment

by:scrapdog
ID: 6313693
Excellent.  It worked.  I thought everyone was stumped on this one.
0

Featured Post

Announcing the Most Valuable Experts of 2016

MVEs are more concerned with the satisfaction of those they help than with the considerable points they can earn. They are the types of people you feel privileged to call colleagues. Join us in honoring this amazing group of Experts.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Introduction The parallel port is a very commonly known port, it was widely used to connect a printer to the PC, if you look at the back of your computer, for those who don't have newer computers, there will be a port with 25 pins and a small print…
In my programming career I have only very rarely run into situations where operator overloading would be of any use in my work.  Normally those situations involved math with either overly large numbers (hundreds of thousands of digits or accuracy re…
Sending a Secure fax is easy with eFax Corporate (http://www.enterprise.efax.com). First, just open a new email message. In the To field, type your recipient's fax number @efaxsend.com. You can even send a secure international fax — just include t…
This video shows how to quickly and easily add an email signature for all users on Exchange 2016. The resulting signature is applied on a server level by Exchange Online. The email signature template has been downloaded from: www.mail-signatures…

813 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

10 Experts available now in Live!

Get 1:1 Help Now