Graphics Contexts and DCs explanations?

Chris Mellon arkanes at gmail.com
Tue Aug 19 20:27:14 CEST 2008


On Tue, Aug 19, 2008 at 1:16 PM, RgeeK <Ross at no.thanks.spammers> wrote:
> Experimenting with graphics in an app: it's AUI based with a few panes, one
> of which has a panel containing a few sizers holding UI elements. One sizer
> contains a panel that needs some basic line-drawing graphics in it.
>
> I use the wxPython demo app heavily to figure this stuff out, and my
> experiments seem to work, but I'm flying blind somewhat.
>
> Can someone englighten me about the wx.GraphicsContext versus wx.PaintDC
>  (BTW what does PaintDC stand for? Drawing Context perhaps?)
>
> The scrolledWindow and GraphicsContext examples are helpful, but it appears
> I can draw a rectangles, lines and text in either just a straight wxPaintDC,
> or can do:
>
> dc = wx.PaintDC(self)
> gc = wx.GraphicsContext.Create(dc)
>
> ...and do the same drawing with gc.DrawText etc...
>
> Can someone clarify the differences or added value of the gc over the dc,
> and is using the dc alone a valid approach?  Where will it end up biting me
> - I don't mean which body part :)  Perhaps I should say in which situation
> will it bite...
>

This is probably better suited to the wxPython ML instead of c.l.p,
because it's so specific.

In short: wxDC (and friends) are traditional raster based drawing
contexts. wxGraphicsContext is a vector/path based API. If you're
doing drawing that's suited for a vector format (like line drawing
probably is), using wxGraphicsContext will give you better image
quality as well as the general vector features like free scaling,
rotation, transforms, etc,



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