On 22-Nov-03, Mike Loolard wrote:
> I hope you guys don't mind me asking some other questions I have
> come up with meanwhile.
Hi Mike,
A few answers here, if not for all your questions...
> 1) If I have an object - how do I create an array of objects with it
> ? for example
> chicken: make object! [
> tasty: "wings"
> ]
> now I would want to have an array of objects of that type.
> I tried it like that:
> chickenfarm: make chicken [] array 10
> It doesn't seem to work that way, though ? I've read all stuff
> available about objects and array on the REBOL pages, but either I'm
> blind or there isn't anything about creating an array of objects ?
chickenfarm: array/initial 10 chicken
> 2) How do you create custom types ?
> I am talking of a way to emulate the typedef behavour in C ?
> How would you go to create an "enum" type in REBOL ?
Pass...
> 3) Back on objects:
> objects seem to be pretty neat in REBOL - but I didn't find anything
> about implementing
> and using constructor/destructors ?
> I know I could manually add a function that serves as constructor
> each time I create an object, but is that the way REBOL requires it
> ?
Pass...
> 4) In the same context:
> how do I actually 'free' memory/variables ?
Memory's managed automatically with REBOL, so unless you're having
trouble with it, don't worry about it. For instance, if you have
this...
file: read %very-big-file
...
file: none
the memory used by very-big-file will be automatically reclaimed -
unless you've referenced it by another word. That said, you can force
a freeing up of memory with RECYCLE if needs be.
> 5) On the webpage about objects one passage mentioned that
> "sub-objects" don't get cloned-
> what does that mean ? Reading that I would expect that all objects
> within an object aren't
> available when I create an object on the basis of that object. But I
> seem to be able to use it anyway. Maybe I am getting something wrong
> here ?
It means that sub-objects are the same object. ie...
>> obj: make object! [sub-object: make object! [test: "text"]]
>> obj2: make obj []
>> same? obj obj2
== false
>> same? obj/sub-object obj2/sub-object
== true
So, if you alter sub-object in obj2 there, sub-object in obj will also
be altered...
>> probe obj/sub-object/test
"text"
== "text"
>> obj2/sub-object/test: 10
== 10
>> probe obj/sub-object/test
10
== 10
> 6) in VIEW/VID: How do you open/create several windows
> simultaneously ? I am also talking of being able to refresh each
> window.
Here's one way...
win1: layout [f1: field "1" 100]
win2: layout [f2: field "2" 100]
win3: layout [f3: field "3" 100]
view layout [
button "Open Windows" [
view/new/offset win1 180x40
view/new/offset win2 330x40
view/new/offset win3 480x40
]
button "Update Windows" [
append f1/text first f1/text
append f2/text first f2/text
append f3/text first f3/text
show [win1 win2 win3]
]
]
> 7) Trying to find a solution to the problem above I looked around
> the REBOL webpages
> and searched for a possibility to create threads - there doesn't
> seem to be anything
> like that - how is "parallel processing" achieved in REBOL ? How
> would you update a dialog but also keep a timer running as well as
> rotating an image ?
Each face in a layout can have its own event processing using FEEL.
Here's a window with the time being ubdated every second and a box
rotating four times a second...
pic: to-image layout [backdrop black box blue "A Box"]
view layout [
text to-string now/time 100 rate 1 feel [
engage: func [face action event][
if action = 'time [
face/text: to-string now/time
show face
]
]
]
image pic effect [rotate 90] rate 4 feel [
engage: func [face action event][
if action = 'time [
face/effect/2: face/effect/2 + 90 // 360
show face
]
]
]
]
There's a HowTo section on RT's site about FEEL...
http://www.rebol.com/how-to/feel.html
> 8) On image rotation: is there any simple way to overcome the 90°
> restriction -
> I am not tallking of bitshifting manually ;-)
I think you need to be. ;)
> What's the reason for this restriction ?
RT hasn't implimented it yet.
> 9) Image creation/processing
> I read it would be possible to create images on the fly and work
> with these then -
> is it possible to store an entire (view) layout within such an image
> ?
Yes -
to-image layout [whatever]
like I've done above.
> Could you for example draw a line on a "virtual" view and save this
> then to an image file ?
Yes, and to disk if you want...
save/png %test.png to-image layout [
box effect [draw[line 0x0 199x199]]
]
and to view it...
view layout [image load %test.png]
> Or would you rather simply take the coordinates of the line and
> create the image with that data ?
You can do that to...
start: 0x0
view layout [
b: box effect [draw[line start 199x199]]
button "+" [start/x: start/x + 10 show b]
button "-" [start/x: start/x - 10 show b]
]
> 10) Image processing
> Is it possible to create new images (in memory) by adding other
> images to the original image at certain coordinates ?
Doing it in a layout and then using TO-IMAGE is the simpliest, though
you can work directly on the image datatype...
>> pic: make image! 2x2
== make image! [2x2 #{000000000000000000000000}]
>> pic/1: 255.255.255.255
== make image! [2x2 #{FFFFFF000000000000000000}]
>> pic/3: 18.18.18.18
== make image! [2x2 #{FFFFFF000000121212000000}]
Gets a lot trickier to put images into images of course, but is
possible.
> Having tried to overlay transparent GIFs in a VIEW layout, I noticed
> the transparency attribute doesn't seem to be preserved ? At least
> transparent areas of my GIF didn't show the image below that one,
> but rather a WHITE area. IF transparent GIFs are supported: what do
> you need to do to really display them properly ?
Pass...
> 11) VID controls
> If I need certain additional features for a basic control - like a
> progress bar or slider,
> how do I add these ? Do I need to edit the dialect ? For example, I
> want a progress bar with tic-marks as well as a non-continous
> filling of the bar.
> So, is there any way to "sub-class" controls easily to enhace their
> functionality/appearance without having to re-write everything from
> scratch?
Pass...
> 12) Is there any really thorough information available on ACTIONS
> and EVENTS with REBOL/VIEW ?
> They documentation on the REBOL pages seems a bit 'poor' on that
> matter. I don't know yet, how these things are really done behind
> the scenes.
Have you seen the HowTo on FEEL? (Link above.)
> 13) I didn't see any designated function to set pixels at certain
> coordinates in a layout-
> my workaround was using the line word - with 1 width/height.
> How is this really done ?
That's one way, the other being to work directly on an image in a
layout. ie...
pic: make image! 100x100
view layout [
image pic rate 10 feel [
engage: func [face action event][
if action = 'time [
poke face/image random (length? face/image) / 4
random 255.255.255
show face
]
]
]
]
> 14) How do I catch mouse events - such as a mouseover event ? I read
> about 'over' - it seems to do exactly what I need - I want to
> display controls in a certain area only when the mouse cursor is in
> that said area. Also, that functionality could be used to add
> tooltip-like behaviour to buttons
> and menus.
Once again, see the HowTo on FEEL mentioned above.
> Again: thanks for your help and patience folks - it's really
> appreciated !!
Hope that helps!
Hmm - the rugby's started... ;)
--
Carl Read
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