Slider Scale Graphics

[DaveyBoy]

I recently needed some slider scale graphics so I thought I'd have a go at drawing my own with Ruby.

There are probably better ways of doing this but it works ok for me.

here is the result:

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def init
   @background_brush = Brush.new Color.new 45   
end

def slider_scale(x,y,w,h)
   d_fine = 0.75 # distance between lines
   d_coarse = d_fine * 5 # coarse line every n
   track_brush = Brush.new Color.new 0
   line_brush = Brush.new Color.new 180
   xs =[x,x - 0.125,x - 0.25]
   ys = [y,y + 0.125,y + 0.25]
   ws = [0.125,0.375,0.625]
   hs = [h,h - 0.25,h - 0.5]
   cols = [track_brush] * 3
   a = (y + 0.5..y + h - 0.25).step(d_fine).to_a[1...-1]
   b = (y + 0.5..y + h - 0.25).step(d_coarse).to_a
   
   lxsf = [x - (w * 0.375)] * a.size
   lysf = a
   lwsf = [w * 0.375 - 0.75] * a.size
   lhsf = [0.125] * a.size
   lcolsf = [line_brush] * a.size
   
   rxsf = [x + 0.875] * a.size
   rysf = a
   rwsf = [w * 0.375 - 0.875] * a.size
   rhsf = [0.125] * a.size
   rcolsf = [line_brush] * a.size
   
   lxsc = [x - (w * 0.5)] * b.size
   lysc = b
   lwsc = [w * 0.5 - 0.75] * b.size
   lhsc = [0.125] * b.size
   lcolsc = [line_brush] * b.size
   
   rxsc = [x + 0.875] * b.size
   rysc = b
   rwsc = [w * 0.5 - 0.875] * b.size
   rhsc = [0.125] * b.size
   rcolsc = [line_brush] * b.size
   
   d = lxsf + xs + rxsf + lxsc + rxsc
   e = lysf + ys + rysf + lysc + rysc
   f = lwsf + ws + rwsf + lwsc + rwsc
   g = lhsf + hs + rhsf + lhsc + rhsc
   h = lcolsf + cols + rcolsf + lcolsc + rcolsc      
   h.zip(d,e,f,g)
end

def draw v
   v.setSmoothingMode 0
   v.drawRectangle @background_brush, [0,0,v.width,v.height]
   
   slider_scale(8,5,4.25,28).each do|e|
      v.drawRectangle e.first,e.last(4)
   end
   
   slider_scale(20,5,5.125,35).each do|e|
      v.drawRectangle e.first,e.last(4)
   end   
   
   slider_scale(32,5,8.375,43).each do|e|
      v.drawRectangle e.first,e.last(4)
   end   
end

Slider Scale Demo.fsm

(3.4 KiB) Downloaded 1243 times

Hope it's as useful to others as it is to me

[tulamide]

Well done!
I know how cumbersome the pixel-based relative drawing math in Flowstone's gridsquare units can be. It wasn't an easy task and you made good use of Ruby for it. It may be possible to make it easier to read or maintain the code, in terms of speed it is totally fine though. (Personal opinion)

[Spogg]

Wow!

Very impressive and thanks for sharing. In my toolbox now!

[trogluddite]

Very smart looking, and I like the code too!

What I particularly like is that, rather than making your "slider_scale" method just a "drawing routine", you return an object (the Array). When the size and position don't change, you could potentially just make the Array once, store it, and avoid calculating the same maths for every single redraw (something which the user guide examples do far too often IMHO).

There's only one small improvement I can see, though it's not very obvious, as it means making the Arrays even more deeply nested...

At the moment, the loop bodies are extracting four elements from a five element array, and then re-packaging them into a four element array - so, for every iteration, a temporary 4-element Array has to be created and have its content copied into it. If you double up on the "zip" method, you can make these sub-arrays a permanent part of the data structure...

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rectangles = d.zip(e, f, g)
h.zip(rectangles)


The deeper nesting looks a bit gnarly on the face of it, but it means that the loops can be simplified to...

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slider_scale(8,5,4.25,28).each do |e|
    v.drawRectangle e.first, e.last
end

# Or even, courtesy of Ruby's * operator to expand arrays into arguments...
slider_scale(8,5,4.25,28).each do |e|
    v.drawRectangle *e
end


But that's just tinkering around the edges, and would probably only be quicker when the Arrays are being re-used, which you might not always be able to. In any case, it's still a better Ruby drawing example than many of DSPr's stock GUI modules!

[DaveyBoy]

Thanks for the kind words guys.

When I first tried this I was drawing the track and the scale seperately with rectangles and lines respectively. Then I noticed you can draw a rectangle with a height of just 1 pixel and I realized it could all be rolled into one, a bit hacky but it does the job.

I also used a brush rather than a pen because the pen draws 1 pixel longer than it should ( I seem to remember Tulamide mentioning this in another post quite some time ago).

I'll have a play with your suggestions Trog and see if I can whittle the code down a bit.

[tulamide]

I also used a brush rather than a pen because the pen draws 1 pixel longer than it should ( I seem to remember Tulamide mentioning this in another post quite some time ago).

Not quite. It's a bit more complicated. Flowstone's gridsquare units are a relative measure and therefore allow subpixels. When 1 pixel covers 0.125 gu, you can "draw" half a pixel by using 0.0625 gu. It was meant to free you from pixel limitations, but comes at a price.
Since a pixel covers the range of almost 0.125 gu, you have to be specific when using grid units. At exactly 0.125 you already touch the next pixel, so you're actually drawing over 2 pixels, not one. Unfortunately, all methods that return sizes, don't make this distinction. If they report a width of 1.0 gu, they mean 8 pixels. But due to a pixel having a specific width, when drawing 1.0 gu, you actually draw over 9 pixels (1.0 gu is the end of the 8th pixel, which is the start of the 9th, ergo the ninth pixel will be drawn).

This is true for both, pen and brush, and it is up to you, to adjust it. That's why the stock scope always cuts the right and bottom line of a signal. It draws over the width reported, while it should be (width - 0.125) or (height - 0.125). This gets complicated if you also have an offset.

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[0, 0, width, height] ##will draw one more pixel than the actual width and height
[0, 0, width - 0.125, height - 0.125] ##will draw exactly the dimension of width and height
[0.25, 0.25, width - 0.5, height - 0.5] ##will not draw centered as expected, but one pixel off to the right and bottom
[0.25, 0.25, width - 0.625, height - 0.625] ## will draw exactly centered

And that is only true of course, if you didn't change the default zoom value of 8 pixels per gu! If you changed it, you have to adapt it (instead of 1/8, you take 1/x, where x is the number of pixels per gu that you set in the zoom settings).

I'm pretty sure my text was a bit confusing. But if you wait a bit, Trog might give a clearer description. He's much better at formulating.

[trogluddite]

^^ Made perfect sense to me, tulamide - especially with the Ruby examples to show how to make the adjustment in practice.

[DaveyBoy]

Thanks for the detailed explanation there Tulamide. I was aware to make adjustments for width and height though I wasn't aware that adding the offset changed the maths slightly . . . you learn something new everyday as they say!

Please take look at the attached schematic though . . it clearly shows a difference between brush and pen . . . or am I just not getting it?

Brush vs Pen.fsm

(642 Bytes) Downloaded 1237 times

Thanks again

[tulamide]

You spotted something that was new to me! It seems that the rectangle calculations are slightly off. If you replace "drawRectangle" by "drawEllipse", you will see it drawing even more strange, as it leaves a gap to the outer borders on all 4 sides, when drawing with the brush. Also, if you turn on smoothing, both are drawn correctly.

You can get away with it, because smoothing off for clear lines is mostly needed when drawing lines, not rectangles. Nevertheless, it is annoying!

[DaveyBoy]

Yes I've noticed other anomalies with drawing dimensions too . . but they're not major issues, as long as we know about these things we can make adjustments.