Miles Lee wrote:
> My goal is to draw shapes on the transparent background.
>
> I did the research and found out two ways to get transparent
> background without floatcanvas.
> One way is to use wx.EVT_ERASE_BACKGROUND tricky,
> that is, leave the event handler empty.
> The other way is to take a screenshot to get a background
> image, then draw it on wx.Panel as background.
>
> However, the both do not work with floatcanvas. For the former,
> I tried to bind the wx.EVT_ERASE_BACKGROUND to canvas.window
That's not going to work, as FloatCanvas is fully double buffered, so it
fills the whole window every time.
Also, the code pre-dates any wx support for alpha channels in Bitmaps,
the the buffer is opaque.
> and for the later, I tried to create dc like:
> dc = wx.ClientDC(canvas.window)
> dc.DrawBitmap(background_image, 0, 0, True)
>
> So I tried this,
> canvas = fc.NavCanvas(frame)
> # take a screenshot to get backgound image
> ...
> canvas.create('Bitmap', background_image, pos = ......)
>
> but the background_image is moveable, that is not I want.
right. With this construction, the background image is part of the main
drawing, and it will move when you move around the canvas, as you have seen.
> How can I fix the background image in its position and the shapes drawn
> on it can be moved, rotated and zoomed.
I can't think of a way to do that with the current structure, however:
> import wx.lib.floatcanvas.floatcanvas2 as fc
Ah, so this is FC2 -- same thinks apply, really. Except:
Matt, can the main buffer be a an alpha bitmap, and then you could set
the background color to transparent, and do the wx.EVT_ERASE_BACKGROUND
trick?
-Chris
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