1. Win32Lib getPixel problem revised
I posted a query about getPixel() in Win32Lib recently. But when I tried
the test here at work I couldn't replicate the problem. Now I have.
The problem is this. I have two bitmaps. They overlay one another. I
click on the top, visible, one with the mouse. I can then read the value
of the top bitmap, which picked up the mouse events, fine. But using the
same coordinates for the other bitmap I get -1 returned.
I attach a sample program which shows the problem - left clicks use
getPixel on one bitmap, right clicks on the other.
So ...... now, does anyone have the answer to this? What have I
missed? Why are you saying "What a dork!"?
---------------------------------------------------------------
include Win32Lib.ew
without warning
with trace
constant Test = createEx( Window, "Left-Click samples 'Page' and
right-click samples 'Copy' - see program details", 0, Center, Center,
756, 526, 0, 0 )
constant Page = createEx( Bitmap, "", Test, 0, 0, 750, 500, 0, 0 )
constant Copy = createEx( Bitmap, "", Test, 0, 0, 750, 500, 0, 0 )
integer Status Status = 0
integer Request Request = 0
object res
sequence Drawing Drawing = {}
sequence Start, Stop
-- Two "identical" bitmaps set to either Red or Green
-- Page will have its mouse events monitored, Copy won't
setPenColor(Copy, Red)
drawRectangle(Copy, w32True, 0,0,750,500)
setPenColor(Page, Green)
drawRectangle(Page, w32True, 0,0,750,500)
-- Collect mouse events on 'Page' only (topmost control)
procedure Page_onMouse (integer self, integer event, sequence params)
sequence pos
event = params[1] -- Replace this with
the mouse event
pos = getPointerRelPos(Page) -- Get coordinate on
'Page' - same on 'Copy'
if event = RightDown then
event = getPixel(Copy, pos[1], pos[2]) -- Sample bitmap NOT
clicked on
elsif event = LeftDown then
event = getPixel(Page, pos[1], pos[2]) -- Sample bitmap
clicked on
else
return -- Any other event
end if
res = message_box("getPixel returned "&sprint(event), "getPixel()",
MB_ICONEXCLAMATION)
end procedure
setHandler( Page, w32HMouse, routine_id("Page_onMouse"))
WinMain( Test,Normal )
---------------------------------------------------------------
2. Re: Win32Lib getPixel problem revised
Andy Drummond wrote:
>
> I posted a query about getPixel() in Win32Lib recently. But when I tried
> the test here at work I couldn't replicate the problem. Now I have.
>
> The problem is this. I have two bitmaps. They overlay one another. I
> click on the top, visible, one with the mouse. I can then read the value
> of the top bitmap, which picked up the mouse events, fine. But using the
> same coordinates for the other bitmap I get -1 returned.
<snipped sample>
Hi Andy,
From what I can see by your example, I think your issue is that you are
confusing a Bitmap control and a Pixmap control. A Bitmap control is a static
control. With a Bitmap control, you stick a bitmap image into it, maybe handle a
click event, and that's about it. Windows will handle redrawing the bitmap in
the control when it's needed. It doesn't appear to me that you can even draw on
a Bitmap control like your example attempts. I believe the reason you are
getting the -1 for 'Page' is because you declared 'Copy' after, and covering,
'Page' and, therefore, it's not accessible. You cannot get a pixel from
something that can't get focus.
However, a pixmap sits in memory so you don't have to worry about that issue.
With a Pixmap, you basically have a bitmap in memory that you can draw to and
blit to your window. I think you can stick a pixmap into a bitmap control but I
usually just copyBlt the Pixmap to the window on repaint.
If you can give me some more details about what you are trying to do, I can
provide a better explanation with a demo but I really can't tell you how you
should proceed based on your example.
-- Brian
3. Re: Win32Lib getPixel problem revised
> However, a pixmap sits in memory so you don't have to worry about that is=
sue. With a Pixmap, you basically have a bitmap in memory that you can dra=
w to and blit to your window. I think you can stick a pixmap into a bitmap=
control but I usually just copyBlt the Pixmap to the window on repaint.
Pixmaps can also parent other controls, like a Window.
4. Re: Win32Lib getPixel problem revised
Greg Haberek wrote:
>
> > However, a pixmap sits in memory so you don't have to worry about that is=
> sue. With a Pixmap, you basically have a bitmap in memory that you can dra=
> w to and blit to your window. I think you can stick a pixmap into a bitmap=
> control but I usually just copyBlt the Pixmap to the window on repaint.
>
> Pixmaps can also parent other controls, like a Window.
>
Really? That's an interesting fact that I wasn't aware of. Do you have a
program that demonstrates this or can you provide a demo? I've never thought of
a reason to do this so I'm looking for a good "what for?".
The only thing that comes to mind is Judith's IDE... which I'm starting to look
at again.
Thanks,
-- Brian
