a bit lost

Hiya
I have tried another tutorial but lost. I have done exactly but I'll
explain after the code. Its a bit long so here goes.

I create a subclass of ShellView. That works fine. This is where it
goes
I have to creat a method called onPaintRequired for the subclass
Greeting.

onPaintRequired: aPaintEvent
       "A portion of the receiver window has been exposed and needs
repainting. The supplied aPaintEvent holds details about the exposed
area. Within #onPaintRequired: you MUST ask for a canvas from
aPaintEvent (not the receiver window) to paint the contents on"

       | canvas |
       canvas := aPaintEvent canvas.
       canvas
              pen: Pen red;
              brush: Brush gray;
              ellipse: (Rectangle origin: 0@0 extent: 250@150);
              text: 'Hello from Dolphin' at: 50@50

This accepts the code.

then we have to create a onPostionChanged method. Is this created in
the subclass Greeting? What I mean is when you Accept the code do you
just go to Method New and type away (next bit coming)?

onPositionChanged: aPositionEvent
          "The receiver has been positioned or resized. Force a repaint
of the entire client area. We need to do this in cases where changing
the extent of a View alters the way in which it is painted (rather than
just the area that is repainted)"

          self invalidate
          ^super onPositionChanged: aPositionEvent

We then modify the #onPaintRequired..(does # mean method)?

same thing in "'s then

           | canvas box textbox |
           box := self clientRectangle.
           canvas := aPaintEvent canvas
           canvas
                   pen: Pen red;
                   brush: Brush gray;
                   ellipse: box;
                   font: (Font name: 'Arial' pointSize: 24);
                   setTextAlign: TA_CENTER | TA_BASELINE;
                   setBkMode:TRANSPARENT;
                   setTextColor: Color red;
                   text: 'Hello from Dolphin' at: box center.

Thia Accepts.

Now, as I say, is the onPositionChanged method supposed to be put in
the Subclass Greeting from the class ShellView directly after I type in
the first method (onPaintRequired)? I just finished the first one, went
to Accept then went to Method - New and entered the second method.

Anyway, I finished all this and it accepted. Then I try and evaluate

w := Greeting new show

and it comes up with the debugger and quite a lot of the pop ups are to
do with pointSize. closed as many as possible but then it freezes.

Any ideas? I have just started so a very newbie but would be grateful
for any replies. Sorry for the long post.

Thank you in advance

Eddie





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Eddie,

[..]
> then we have to create a onPostionChanged method. Is this created in
> the subclass Greeting? What I mean is when you Accept the code do you
> just go to Method New and type away (next bit coming)?

Yes and Yes. After accepting you can omit the Method/New bit and just
overwrite any text in the edit field. As long as you put a new selector
(method name) at the start of the text the compiler will know what you want
to do when you accept the next lot of text.

>           self invalidate
>           ^super onPositionChanged: aPositionEvent

Full stop missing after the 'invalidate'.

> We then modify the #onPaintRequired..(does # mean method)?

In Dolphin (the language) it indicates a Symbol but in the context of an
article like this it does usually indicate a method selector (the method's
name). The >> notation is also used, in documentation or text, to also
indicate the class where the method is defined so
Greeting>>onPositionChanged: is the full description of the above method.

>            | canvas box textbox |
>            box := self clientRectangle.
>            canvas := aPaintEvent canvas
>            canvas
>                    pen: Pen red;
[..]

Full stop needed after canvas in "canvas := aPaintEvent canvas"

> Now, as I say, is the onPositionChanged method supposed to be put in
> the Subclass Greeting from the class ShellView directly after I type in
> the first method (onPaintRequired)? I just finished the first one, went
> to Accept then went to Method - New and entered the second method.

If you are going to immediately overwrite the first #onPaintRequired: then
there is no need to enter it before entering the second #onPaintRequired:. I
imagine the idea of the tutorial was to enter the first #onPaintRequired and
#onPositionChanged:, try it out by "Greeting new show" and then edit
#onPaintRequired to see how it affects the output.  Adding a new method
with the same name as an existing one completely overwrites the current one,
as if it never existed.

> Anyway, I finished all this and it accepted. Then I try and evaluate
>
> w := Greeting new show
>
> and it comes up with the debugger and quite a lot of the pop ups are to
> do with pointSize. closed as many as possible but then it freezes.

I cut and pasted the above into Dolphin 2.1 (is that what you are using)?
and it works correctly for me (after adding the two missing full stops). Is
the text you posted the actual text copied from the browser.?

> Any ideas? I have just started so a very newbie but would be grateful
> for any replies. Sorry for the long post.

Check through for typos, or copy the text from your post, and try again. If
it still doesn't work then post the text from the walkback window [1] for
the _first_ error that appears.

<insert>Standard 'Smalltalk is hard work at the start but worth it in the
end' speech</insert>

Ian

[1] The easy way. When you get the walkback (the initial grey box that
indicates an error has occurred) point at the error list and right click.
Choose "Select All" then  "Copy" from the context menu and then paste the
clipboard contents back into the reply.

Thanks Ian. I put the full stops in but it still does it. The window
that pops up has the oval and is grey but then the good old walkbak is
there. Here it is as requested.

Font class(Object)>>doesNotUnderstand:
Greeting>>onPaintRequired:
[] in Greeting(View)>>wmPaint:wParam:lParam:
ExceptionHandler(ExceptionHandlerAbstract)>>markAndTry
[] in ExceptionHandler(ExceptionHandlerAbstract)>>try:
BlockClosure>>ensure:
ExceptionHandler(ExceptionHandlerAbstract)>>try:
BlockClosure>>on:do:
Greeting(View)>>wmPaint:wParam:lParam:
Greeting(View)>>dispatchMessage:wParam:lParam:
[] in InputState>>wndProc:message:wParam:lParam:
BlockClosure>>ifCurtailed:
ProcessorScheduler>>callbackEvaluate:
InputState>>wndProc:message:wParam:lParam:
InputState>>pumpMessage:
InputState>>loopWhile:
InputState>>mainLoop
[] in InputState>>forkMain
ExceptionHandler(ExceptionHandlerAbstract)>>markAndTry
[] in ExceptionHandler(ExceptionHandlerAbstract)>>try:
BlockClosure>>ensure:
ExceptionHandler(ExceptionHandlerAbstract)>>try:
BlockClosure>>on:do:
[] in BlockClosure>>newProcess


Regards

Eddie

Yes, I am using 2.1

In article <9492b4$1l3$[hidden email]>,
  "Ian Bartholomew" <[hidden email]> wrote:
> Eddie,
>
> [..]
> > then we have to create a onPostionChanged method. Is this created in
> > the subclass Greeting? What I mean is when you Accept the code do
you
> > just go to Method New and type away (next bit coming)?
>
> Yes and Yes. After accepting you can omit the Method/New bit and just
> overwrite any text in the edit field. As long as you put a new
selector
> (method name) at the start of the text the compiler will know what
you want an
> article like this it does usually indicate a method selector (the
method's
> name). The >> notation is also used, in documentation or text, to also
> indicate the class where the method is defined so
> Greeting>>onPositionChanged: is the full description of the above
method. type in
> > the first method (onPaintRequired)? I just finished the first one,
went
> > to Accept then went to Method - New and entered the second method.
>
> If you are going to immediately overwrite the first #onPaintRequired:
then
> there is no need to enter it before entering the second
#onPaintRequired:. I
> imagine the idea of the tutorial was to enter the first
#onPaintRequired and
> #onPositionChanged:, try it out by "Greeting new show" and then edit
> #onPaintRequired to see how it affects the output.  Adding a new
method
> with the same name as an existing one completely overwrites the
current one,
> as if it never existed.
>
> > Anyway, I finished all this and it accepted. Then I try and evaluate
> >
> > w := Greeting new show
> >
> > and it comes up with the debugger and quite a lot of the pop ups
are to
> > do with pointSize. closed as many as possible but then it freezes.
>
> I cut and pasted the above into Dolphin 2.1 (is that what you are
using)?
> and it works correctly for me (after adding the two missing full
stops). Is
> the text you posted the actual text copied from the browser.?
>
> > Any ideas? I have just started so a very newbie but would be
grateful
> > for any replies. Sorry for the long post.
>
> Check through for typos, or copy the text from your post, and try
again. If
> it still doesn't work then post the text from the walkback window [1]
for
> the _first_ error that appears.
>
> <insert>Standard 'Smalltalk is hard work at the start but worth it in
the
> end' speech</insert>
>
> Ian
>
> [1] The easy way. When you get the walkback (the initial grey box that
> indicates an error has occurred) point at the error list and right
click.
> Choose "Select All" then  "Copy" from the context menu and then paste
the
> clipboard contents back into the reply.
>
>


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Eddie,

> Font class(Object)>>doesNotUnderstand:
> Greeting>>onPaintRequired:

I should have asked for the actual contents of the walkback window caption
as well but it looks like the line in #onPaintRequested: that reads

    font: (Font name: 'Arial' pointSize: 24);

is wrong, specifically the "name:" or "pointSize:" bits are spelt
wrong/capitalized incorrectly.  The wording of the walkback caption should
show the error as it will show something different to the expected
#name:pointSize:

One other alternative is that you have accidentally deleted a method from
the Font class.  Using the class browser navigate to the Font class, select
the "class" tab in the central view and look for a method named
#name:pointSize:  If it's missing that will also cause the error. If this is
the case you should start again with a clean image as you don't know what
else has been deleted.

doesNotUnderstand is a very common error and means that the object that is
receiving a selector does not understand what to do with it as there is no
corresponding method defined in it's class or superclass. Usually caused by
spelling mistakes in either the sending or receiving selector or as part of
the development process when testing a partially completed class.

Ian

Ian

 This is a bit of a strange reply as I haven't been home this weekend.
Been at York on a course. Anyway, whilst I was there bored out of my
skull I had a little think. Could this be the answer?

font: (FontName: 'Arial' PointSize: 24);


I thought that as you put ShellView that you might also put FontName.
Later tonight I will try those things that you have written here ( at
work now) and I thought I might look for the FontName and PointSize
under the ShellView class. I assume that they should be there somewhere.

Regards

Eddie
In article <94a5lc$d215s$[hidden email]>,
  "Ian Bartholomew" <[hidden email]> wrote:
> Eddie,
>
> > Font class(Object)>>doesNotUnderstand:
> > Greeting>>onPaintRequired:
>
> I should have asked for the actual contents of the walkback window
caption
> as well but it looks like the line in #onPaintRequested: that reads
>
>     font: (Font name: 'Arial' pointSize: 24);
>
> is wrong, specifically the "name:" or "pointSize:" bits are spelt
> wrong/capitalized incorrectly.  The wording of the walkback caption
should
> show the error as it will show something different to the expected
> #name:pointSize:
>
> One other alternative is that you have accidentally deleted a method
from
> the Font class.  Using the class browser navigate to the Font class,
select
> the "class" tab in the central view and look for a method named
> #name:pointSize:  If it's missing that will also cause the error. If
this is
> the case you should start again with a clean image as you don't know
what
> else has been deleted.
>
> doesNotUnderstand is a very common error and means that the object
that is
> receiving a selector does not understand what to do with it as there
is no
> corresponding method defined in it's class or superclass. Usually
caused by
> spelling mistakes in either the sending or receiving selector or as
part of
> the development process when testing a partially completed class.
>
> Ian
>
>


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Eddie,

>  This is a bit of a strange reply as I haven't been home this weekend.
> Been at York on a course. Anyway, whilst I was there bored out of my
> skull

Heh. I've been on a few courses like that

>  I had a little think. Could this be the answer?
>
> font: (FontName: 'Arial' PointSize: 24);

No. Although the problem is almost certainly spelling/capitalisation that
would definitely be wrong.

The name of the class is Font. This must start with a capital letter or it
wouldn't have got past the compiler when the class was created.

There must be a space after the class name and before the selector of the
message being sent to the Font class.

The selector for the method #name:pointSize:  Methods selectors normally,
although not compulsorily, start with a lowercase letter. Each part of a
multiple keyword selector (pointSize:) will also (usually) start with a
lowercase letter

The complete expression works in two parts

Font name: 'Arial' pointSize: 24

sends the #name:pointSize: message to the Font class with two arguments
('Arial' and 24). The Font class answers a new Font instance.

canvas
.....
    font: (aNewFontInstance)

sends the #font: message to the canvas object (an instance of the Canvas
class in this case) passing the new font that was created above as an
argument.

> I thought that as you put ShellView that you might also put FontName.

ShellView is the name of a class. The capital V is just an aid, splitting
the class name up to make it more readable. You could rename the class to
Shellview without making any difference to the code although you would have
to edit all the references to ShellView to mirror the change.  Font and Name
are two different things, a class name and a selector, and should be
separated.

Ian