[Dynapi-Dev] My options on ScrollBar Light

[Raymond I. <xw...@ya...>]

Hi Everyone,

(The views expressed below are my own and are not
intented to hurt anyone. I'm just expressing things as
I see them in my option)


1) First off - In keeping with naming conventions I
would add the prefix btn before buttons (e.g btnUp,
btnDown,etc). This is something that I've learned will
coding in vb. The truth is this is of little value but
it's just my option.

2) The this.KnobListener should not be created inside
the constructor. This IMO is a performance hit as the
javascript engine will have to create an object and a
function for each scrollbar. IMO it should be placed
on the prototype of the scrollbar:

function scrollbar_light(){
   // code here...
   this.knob.addEventListener(this.KnobListener);
};
scrollbar_light.prototype.KnobListener={
  // events here
};

The same should go for the other events. In this
approach the functions and objects are created only
once.

3) Instead of reseting the sizes of the buttons by
calling setSize inside the allignObjects() functions I
would recommend that the setAnchor() function be used.
You just set it and forget it:

// inside constructor
if (this.orientation) { //vertical
   var al={left:0,right:0};
   this.upBTN.setAnchor(al);
   this.downBTN.setAnchor(al);
   this.knob.setAnchor(al);
}else { //horizontal
   var al = {top:0,bottom:0};
   this.upBTN.setAnchor(al);
   this.downBTN.setAnchor(al);
   this.knob.setAnchor(al);
}

For a very good example of anchoring/strecthing see
dynapi.api.dynlayer-anchor-stretching.html and
dynapi.api.dynlayer-anchor.html

The same can be down for the knob by using the
stretchV and stretchH attributes. for example:
stretchV:'40%' can be used to stretch the knob '40%'
of it's parent width or stretchV:90 will set the
knob's height to 90 pixels

3) I've found the scrollbar from dynapi 2.x days to be
very difficult to use. I never liked the setRatio()
and getRatio() functions. I think the the simplicity
of the Visual Basic scrollbar is much prefered than
setRatio(). 

I think the scrollbar should have a setRange(min,man)
function that allows me to set a range of values to
scroll. I can then use getValue() and setValue()
functions to set or get the value of the scrollbar.
When I call setValue(v) it will force the scrollbar
knob to move to the section where the value can be
found.

example:

hscBar.setRange(0,1000);
hscBar.setValue(120); // simulates a user scroll
// ^ set knob to value 120 within the range 0-1000
// some code here.....
var v = hscBar.getValue();

That's it!

Well in summary I think the scrollbar looks good, but
I'd like it better if it had arrows :).
Since this is the light version I would suggest that
you use ←, →, ↑, ↓ or + - to
indicate up/down or left/right.

Keep up the good work.

Best regards.

--
Raymond Irving



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