[etoys-dev] graphing and watching enhancements

Scott Wallace scott.wallace at squeakland.org
Fri Mar 9 06:01:32 EST 2012

On Mar 5, 2012, at 1:56 PM, Steve Thomas wrote:

> Some issues with latest build:

Steve, thank you very much for your comments and recommendations.  Sorry for the delay in responding.

> 	• Take x-y plane from Object Catalog, Open Viewer for "vertical number line", change number lines <min val> to -10, then increase by 1 to -9.  (number line shifts left).

A little round-off error showing through here, I think.  Making the line appear not to "move" as various parameters are changed can involve quite a bit of calculation, and occasionally round-off errors can conspire to bring about effects like this.

> 	• If Number Lines <min val> is greater than zero, its not really a "show negative arrow head" tile. Not sure of good name.

I am also not fond of this nomenclature.  However, the arrowhead in question *does* point in the "negative" direction…  Anyone have a better suggestion?

> 	• If I set <VerticalNumberLine's>:<yOnGraph> to 0, it changes to 8 and moves down. This behavior repeats. It seems to be 8 when min value <=-10 and 4 when >-10.

> 	• Perhaps related to the above items: I would expect the <xOnGraph> and <yOnGraph> to be 0, but they are not.  Perhaps because of how you adjust for the labels and the max # of digits in the label. Perhaps have the "0" point on the number line be 0 at 0 onGraph. 

I've split off my reply for these two items into a separate memo, since this is a weird edge-case that seems to require so much verbiage in explanation that it would swamp the rest of this email, and people would stop reading right here...

>  I was also struck that the playfield does not use origin at center, but there is much I do not understand.

When using the number-lines as axes, the "origin" would be where the two orthogonal number lines intersect, ideally at their zero points.  This situation doesn't leave much room for a playfield's originAtCenter setting to play any role.

> 	• When I turn "use gridding" from the playfield options, I need to reset the the "grid spacing" to match that set via the GraphPaperPanel.

Right, these are independent.  And advisedly so, I think -- I think that people will reasonably want the long-standing "use gridding" feature to grid to something finer than the graph paper grid.

> 	• Should we have Etoys tiles for the grid size, coarse grid boolean and course grid value?  I know I can get them by opening the viewer for the sliders and firing the EtoysUpdatingThreePhaseButton, but most folks won't figure that out.

Some appearance parameters that can be set in property sheets, such as the "origin" and "direction" of a gradient fill, have been considered of too-narrow applicability to earn real-estate space in the viewer.  For now, the graph-paper parameters, which seem marginally less important than the gradient fill parameters, arguably fall into that category.   I think the real need here is to have a more facile UI for setting and *seeing* the values of these parameters within the graph-paper control panel, which is basically Steve's final item below.

> 	• When I delete the x-y plane with the GraphPaperPanel open the panel does not disappear.

Indeed this has always been true of all the various control panels, and is a bug that dates back many years.  But I see that Karl has published a generic fix :)

> 	• Balloon help for Vertical number <show negative arrow head< line states: "Whether to show an arrow-head at the extreme left edge of the axis".  Perhaps "lower end" instead.

Karl has also already fixed that :) 

> 	• It would be nice to have tiles for the offset and the numbers visible, without having to hover.

The same could be claimed, with even greater vigor, for the point-valued parameters that govern the "origin" and "direction" of a gradient fill, in the Object Properties panel.  It's that exact same not-so-satisfactory UI (with a momentary readout in a yellow box telling you the current value as you move the cursor with the button down) that is being re-used at present for specifying the "offset" of graph paper.  Would indeed be nice to improve that -- it's a dubious UI that has been used in our properties panels for a dozen years :)


  -- Scott

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