Font Management and GlyphVectors

Fonts and text are always a pain when drawing vector graphics!

After hitting myself over the head over a stupid bug in my zoom tests (like this:)

JButton inButton = new JButton("IN");
inButton.setActionCommand("IN");
JButton outButton = new JButton("OUT");
inButton.setActionCommand("OUT");

I got center scaling implemented in my branch. Which lets me test a different approach to managing fonts. I had tried to be clever and do something like:

GlyphVector glyphs = font.createGlyphVector("N");
ArrayList shapes = new ArrayList();
for (int i = 0; i < glyphs.getNumberOfGlyphs(); i++) {
shapes.add(affineTransform.getTransformedShape(glyphs.get(i)));
}

but letter shapes fill horribly with lots of missing pixels. Anyway, I eventually settled on just storing the Glyphs themselves. Less pure, but it works, and it allows the size of TextSymbols to be computed and used by the class in between drawing.

So, for fonts there had to be a way in my architecture to change the font size when the whole molecule is scaled. The nicer approach is the obvious one - just to transform the Graphics object. However, it turns out there are advantages to the more cumbersome approach. Here's an image:

which shows rings at various sizes, with the numbers at their centers showing the font size at that scale. An important one is the 'size' (9-5) - which is 4, but there is no readable size of font at that size. However, the FontManager class keeps track of how far below (or above) the minimum and maximum font sizes, and then returns to that size at the appropriate point.

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Adamantane, Diamantane, Twistane

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1,2-dichlorocyclopropane and a spiran

As I am reading a book called "Symmetry in Chemistry" (H. H. Jaffé and M. Orchin) I thought I would try out a couple of examples that they use. One is 1,2-dichlorocylopropane : which is, apparently, dissymmetric because it has a symmetry element (a C2 axis) but is optically active. Incidentally, wedges can look horrible in small structures - this is why: The box around the hydrogen is shaded in grey, to show the effect of overlap. A possible fix might be to shorten the wedge, but sadly this would require working out the bounds of the text when calculating the wedge, which has to be done at render time. Oh well. Another interesting example is this 'spiran', which I can't find on ChEBI or ChemSpider: Image again courtesy of JChempaint . I guess the problem marker (the red line) on the N suggests that it is not a real compound? In any case, some simple code to determine potential chiral centres (using signatures) finds 2 in the cyclopropane structure, and 4 in the ...

General Graph Layout : Putting the Parts Together

An essential tool for graph generation is surely the ability to draw graphs. There are, of course, many methods for doing so along with many implementations of them. This post describes one more (or perhaps an existing method - I haven't checked). Firstly, lets divide a graph up into two parts; a) the blocks, also known as ' biconnected components ', and b) trees connecting those blocks. This is illustrated in the following set of examples on 6 vertices: Trees are circled in green, and blocks in red; the vertices in the overlap between two circles are articulation points. Since all trees are planar, a graph need only have planar blocks to be planar overall. The layout then just needs to do a tree layout on the tree bits and some other layout on the embedding of the blocks. One slight wrinkle is shown by the last example in the image above. There are three parts - two blocks and a tree - just like the one to its left, but sharing a single articulation point. I had...

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