The diagrams are made with a JavaFX program I wrote myself. I hope to release it to the general public in the future.
Are the diagrams made manually or generated based on the source code?
You have to decide which types should be part of a diagram. Also some initial layout is required.
The rest is generated from source code. The diagrams then track the source code.
So any changes in the source code will be reflected in the diagrams.
The program is a WYSIWYG editor,
which allows modification of many aspects of the diagram appearance.
Nice tool, does it support other languages?
The basis of the program is a graphical expert system.
The current main driver is the construction of Java diagrams.
There are other modules in work but they are not about programming languages.
Why not use the UML arrow for inheritances and extensions?
Arrows maybe the standard, but they violate important UI principles.
Lines are perceptional weak, you have to trace them to the end to know the direction and if many of them land on the same spot it is
not only visually unappealing but also impossible to distinguish between incoming and outgoing connections.
Therefore arrows don't work well in real world circumstances.
A better way to show inheritance, is the rule that sub types always have to be under or to the right of super types.
Why the dusty background? Why not have a uniform white or other colored background?
Different backgrounds will be used for different versions and libraries.
Older versions will be yellowing, different background patterns will help to distinguish between libraries.