Re: granularity in xml terminals

[Ethan A M. <sf...@us...>]

On Wednesday, April 25, 2012 02:09:19 am pl...@pi... wrote:
> Hi,
> 
> I have not tested this problem on canvas but I'm guessing it would be 
> the same as seen in svg.
> 
> Part of the value of scalable formats is the lack of granularity and the 
> ability to zoom to the desired resolution.
> 
> In testing mouse coords on svg I find there is granularity at the scale 
> of the decimal point character. (or one dot of the colon).

The precision of the coordinates is indeed one decimal place.
Not sure what you mean by "one dot of the colon".
 
> I have configured Firefox to allow very high zoom levels , this is 
> excellent for looking at my data plots and allows seeing this problem 
> clearly.

I cannot speak to exactly what happens when you zoom in Firefox.
Ideally it would employ the precision of the coordinates in the file,
meaning that it would still be accurate to one display pixel when the zoom
factor is 10X.

> The mouse cursor moves smoothly as expected but the coord readout only 
> moves in jumps that are the size of the dot.
> Each jump moves the cursor text by a similar amount and updates to coords.

Quantization of mouse movement is a whole separate issue.
If there is a limitation there, it's at the level of the X input layer
or whatever serves that purpose on your platform. I am told that some newer
platforms treat mouse position as a continuous variable, but to the best of
my knowledge X only provides an integer pixel coordinate, and the minimum
"delta" of mouse motion may be larger than one pixel.

> Is this due to the svg_scale  bug I caught last week?

The internal precision of the plot is set by SVG_SCALE, yes.
You could set it to 100. rather than 10. to get higher precision.
The tradeoff is that printing an additional decimal place in every 
coordinate of every command in the output file will make the file
significantly larger for a typical gnuplot graph.

It is also possible that changing the precision would uncover additional 
bugs, but we could consider that a good thing rather than a bad thing :-)

	Ethan