Centering text in morphic

How can I center text in morphic? I have a RectangleMorph subclass
representing a "tile." I'd like to display a centered string label
within the morph.

My current approach is to just override #drawOn: with:

    TileMorph>>drawOn: aCanvas
        super drawOn: aCanvas.
        aCanvas drawString: 'hi' on: self innerBounds

However, that just always puts the text in the upper-left corner.
(Code is from memory, so I may have got something wrong.)

By "center", I want the baseline-to-max-ascent for the font to be
centered vertically (not the actual height of whatever characters I
have), while the actual width is centered vertically.

Would it be better to use a StringMorph for placing text like this?
I'm afraid I don't yet understand what layout options I'd need to use
to make it work.

Thanks,
- Johann
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Hi Johann, just after you left IRC, I figured out an easy (though
perhaps not the best) way to do what you want:

a := SimpleButtonMorph new openInWorld.
a actWhen: #buttonDown.   "turns off visible button behavior"
a label: 'new label'.              "lets you change the label to a
different string of text"
a clipSubmorphs: true.        "true means that your text doesn't extend
beyond the border of the button"


Hope this helps.

Lawson (saijanai_ on irc)

On 2/8/12 6:51 AM, Johann Hibschman wrote:
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On Wed, Feb 8, 2012 at 12:44 PM, Lawson English <[hidden email]> wrote:
> Hi Johann, just after you left IRC, I figured out an easy (though perhaps
> not the best) way to do what you want:
>
> a := SimpleButtonMorph new openInWorld.
> a actWhen: #buttonDown.   "turns off visible button behavior"
> a label: 'new label'.              "lets you change the label to a different
> string of text"
> a clipSubmorphs: true.        "true means that your text doesn't extend
> beyond the border of the button"

Thanks, that's helpful. I don't think I'm going to use
SimpleButtonMorph, since it builds in a fixed margin, but reading its
implementation was useful. It makes a StringMorph and uses its #extent
to do the centering, and I can just do the same thing. (And I can just
look at StringMorph's #extent if I need to.)

If SimpleButtonMorph works by embedding a StringMorph, I think that's
a sign that I should do that rather than override #drawOn.

Johann
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Sure. My first pass at writing code using Morphic is to see if an
existing class does what I want and then deciding if it is worth the
time to "roll my own" using whatever insight I got from seeing how the
existing code works.

#drawOn should only be used if you need to do things which don't use
exisint morphs and/or need a great deal of speed. The built-in
composition capabilities of Morphic are usually powerful enough to
accomplish any kind of  behavior using compositions of simpler morphs.
Obviously, you don't create high-level paint programs using morphs as
the pixels, but anything higher level than that is probably a good
candidate for composition.

OTOH, if I was to write an educational program showing how line-drawing
algorithms work, I probably WOULD use morphs as pixels. YMMV.

L

On 2/9/12 6:40 AM, Johann Hibschman wrote:
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