[Newbies] Morph Drop Shadows
benschroeder at acm.org
Mon May 21 16:09:21 UTC 2007
On May 20, 2007, at 3:01 PM, David H. Shanabrook wrote:
> I am experimenting with geometry tutors, such as pentominos. when
> trying to fit shapes precisely together the shadow is very
> disturbing, it is hard to know what is the shadow and what is the
> shape, especially for kids.
When I want to remove the drag-shadow from Morphs, I often use
something like the following methods (implemented on my Morph subclass):
aCanvas isShadowDrawing ifTrue: [^ self].
super fullDrawOn: aCanvas.
#fullDrawOn: is sent to a Morph to ask it to draw itself, its border,
and its submorphs. The Hand uses it to draw a shadow copy of the
Morph. This method says, if that's what's going on, don't draw
anything (therefore preventing any shadow from being shown).
This message is also sent during shadow drawing. It seems to be
necessary to prevent shadows from being drawn, but I'm afraid I have
forgotten why! and I'm not sure I have a chance to track it down
right now. (I almost held off from posting this because of that, but
I thought it would be better to offer the advice and leave an
exercise for the reader. :)
Note that the shadow does serve at least one important purpose. In
the default mouse handling, clicking on a Morph picks it up, and one
must click the mouse again to drop the Morph. It can be confusing to
have a Morph "stuck" to the hand without any visual indication.
I often make a simple mouse override to fix this too, if I am not
doing any more specialized mouse handling on my own. Here is what I do:
This tells Morphic that a particular Morph wants to receive mouse
selectors: #( #click: #doubleClick: #doubleClickTimeout: #startDrag:)
This message is sent on mouse down. The method here tells the Hand to
parse upcoming mouse events, and decide whether a click, double
click, or drag might be happening. The threshold of "0" says to
interpret any mouse movement at all as a drag. (There is a simpler
variant of #waitForClicksOrDrag... that defaults that to 10, which I
find to be too unresponsive.)
evt hand grabMorph: self.
This is called when the Hand detects a drag, after the "wait" message
from above. The method just tells the hand to pick up this Morph.
Of course I'm sure there must be some flag that does the same
thing! ;) If I am writing a system with many Morphs like this, I of
course put all of this code in a superclass to avoid clutter.
Hope this helps,
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