Tips and Tricks¶
Making a hard-copy of painted graphics¶
The primary use for the Wt painting API is to paint on a WPaintedWidget. Internally, this uses either a VML, SVG or HTML 5 canvas painting device to deliver the painting to the browser.
It is also possible to paint directly to an SVG image, which is a standardized generic vector graphics format, and increasingly supported by various tools.
You could use the SVG image as a starting point for exporting the painted graphics to raster format. Using the imagemagick or graphicsmagick libraries, you can convert from SVG to other formats using the library API or using the command line 'convert' tool. Using inkscape, a sophisticated SVG editor, you may get high quality SVG rendering (with, compared to imagemagick, much better font support) from the command-line (see the manpage). Another option may be librsvg.
The WSvgImage class allows you to easily create an SVG image, and save it to a (file) stream, using the following template:
WSvgImage image(400, 300); WPainter painter(&image); // paint things on the painter, like you normally do in WPaintedWidget::paintEvent(). // // e.g. you could do WCartesianChart *c = ... // c->paint(painter); painter.end(); std::ofstream f("image.svg"); image.write(f); f.close();
Creating .CUR files¶
Creating .CUR files which are valid in Firefox and Chrome can be quite a pickle, especially if you want to specify a custom hotspot.
This program allows you to create such .CUR files:
Under some environments, when linking to the Wt library, 'assert' is removed from the code. This page shows a custom assert to be used with Wt: http://richelbilderbeek.nl/CppWtAssert.htm