[cairo] Transformations usage

[cecashon at aol.com]

Hi Daniele,

Is the map background coming from a file or a pixbuf, or are you drawing the map entirely with Cairo?

Cairo can draw pretty fast so usually you don't have to worry about storing a surface and reusing it in GTK. A good technique though. If you draw a complicated background that doesn't change often, it can speed drawing up. There is a GTK gauge widget that uses some of those ideas.

https://github.com/cecashon/OrderedSetVelociRaptor/tree/master/Misc/AdjustableGauge

For transformations, there is a GTK drawing program that might be helpful.

https://github.com/cecashon/OrderedSetVelociRaptor/blob/master/Misc/cairo_drawings/bezier_points1.c

It will draw polygons and let you drag points around for interactive drawing along with transforms and animation. If you are using Cairo to draw everything with transforms it might give you some ideas.

Eric


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