Support for text rendering

[adam-urbanczyk]

This will resolve #48

[codecov]

Codecov Report

Merging #106 into master will increase coverage by 0.04%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #106      +/-   ##
==========================================
+ Coverage   94.21%   94.26%   +0.04%     
==========================================
  Files          19       19              
  Lines        3889     3922      +33     
==========================================
+ Hits         3664     3697      +33     
  Misses        225      225

Impacted Files	Coverage Δ
cadquery/cq.py	93.22% <100%> (+0.14%)	⬆️
cadquery/occ_impl/shapes.py	86.61% <100%> (+0.19%)	⬆️
tests/TestCadQuery.py	98.75% <100%> (+0.01%)	⬆️

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[adam-urbanczyk]

@jmwright @dcowden I think it is ready to be merged. Please take a look at the API:

import cadquery as cq
result = cq.Workplane("XY" ).box(4, 4, 0.5).edges("|Z").fillet(0.125).faces('>Z')\
   .workplane().text('CQ 2.0',0.5,-.05,cut=True,font='Consolas')

[dcowden]

@adam-urbanczyk you are on FIRE! Its great to see this actually happen.

I love the API as you have it, and id recommend merging this.

However, i have some insight to share for future work. TL;DR, you might consider implementing the output on a per-character basis, even though as the API is now, you do not have to. More about that:...

It just so happens that i developed a text plugin for onshape. As a part of that, i learned a lot about what users want from a CAD text package.

There's a list of features that are necessary to be 'perfect' at least based on the user base I was working with:

• bold/italic
• flip/mirror text top/bottom and left/right
• automatically fit the text to a base curve. this coudl be a straight line, but is commonly a curve. This becomes tricker than it sounds, because you need to compute the width of the font, and adjust the height to fit. This can be hard because most fonts dont make it easy to do that.
• justify the text relative to the top, bottom, or middle of the guide curve
• kerning. This was a big deal. Kerning is the ability to slightly change the spacing between each letter, to account for the weirdness of the fonts, combined with following a guide curve
• apply on curved surfaces. This gets complex because you need to offset the base surface, and then use that offset to limit to the tops of each letter. Its also necessary to extrude each letter via a separate surface normal, if the surface is curved.

I mention all this because when faced with all of those requirements, even though the user simply types in the text they want, I actually generated the output one character at a time,because you have to when you consider the above requirements.

You can see some examples here: http://store.parametricparts.com/store/p10/CURVED-TEXT-2.0.html

have a look specifically at the input dialog, which shows all the options I ended up with.

[adam-urbanczyk]

@dcowden cool plugin! On OCC level it is possible to render on per-character basis. I'll leave the features you mentioned for another PR though. I think implementing everything would take quite some effort.

[adam-urbanczyk]

Alright, thanks for all your feedback. Merging.