Visual Basic Tutorial - 173 - Paint Part 6 Fixing The Screen Flicker Video Lecture | Mastering Visual Basic - Web Development

hello YouTube sam here from youtube.com
slash on live gamer for the new Boston
and in this tutorial I'm going to
continue working on our paint program
now if you remember from the previous
tutorial or before that the paint
program that we have been using in the
previous tutorials or that we've been
learning how to make is almost directly
from beginning Microsoft Visual Basic
2008 by Theron Willis and Brian Newsome
I've changed maybe a couple little
things in there I'm not very noticeable
well I just want to give them full
credit I'm just teaching you guys the
logic behind this and I'm taking you
step-by-step so you can understand it
better so now that we got that aside if
you remember from the previous tutorial
whenever we started painting the the
whole screen would flash and it would
repaint each time so you can see here
then if I start drawing you've seen that
the whole thing is flashing and it just
looks really bad so there's an easy way
we can fix this so we need to come over
to paint canvas dot V B and you can see
here we have me dot invalidate so what
we can do instead of invalidating the
entire control which will flash it each
time
what we can do is we can invalidate that
one rectangle so under me down validate
we can pass a an argument to it so you
can see we've got invalidate children as
we leave here invalidate rectangle s
system giant rectangle now that's what
we're going to be using so you got RC as
a rectangle so we're only going to be
invalidating an area the size of a
rectangle well how do we know a size of
rectangle we want to use well what we
can do is we can use object graphics
item dot rectangle now rectangle is a
public variable of type rectangle and
that is in object graphics item so we go
to graphics items at VB
rectangle as our rectangle and we made a
new rectangle and just set some sizes
for it just to initialize the rectangle
so come back to pinky and stop VB so
it's gonna invalidate an area this size
of this rectangle right here so we'll go
ahead and run this you see here we've
got paint dot VB go ahead and make this
bigger you can see that if I start
drawing here maybe you'll be able to see
this a little bit you can see that it's
only invalidating the area right where
my mouse is you can see it's kind of
flashing right there I mean there's a
white in front of the dots now we can
draw and the faster you move the more
spread out the dots are going to be but
that doesn't really matter you can just
draw a little bit slower let's go ahead
and close out of this and we'll just
play with some of the options before we
move on to the next tutorials so we can
change the size so all we have to do is
just change one variable here and we'll
change it to large so we've got graphics
sizes dot large you can see that when we
start drawing we draw with large circles
and you can see the invalidation right
here a lot better
it's invalidating an area the size of
the rectangle that we have now it
doesn't look the best but it's better
than the whole screen flashing now we
can even come in to our graphic sizes
and we can set large equal to let's say
50 so this is gonna double the size of
our brush come into paint VB you can see
here that we're drawing with these big
huge circles and once again the
invalidation is even more visible in
this demonstration so go ahead add the
invalidating a small area that we used
here to just instead of flashing the
entire control and repainting it it's
just going to invalidate the area the
size of the wreck
that we have in object graphics item and
once you put that code in I'm even play
around with your program some go ahead
and move on to the next tutorial