Drawing a rubberband on a panel without redrawing everthing

[steve]

Hi,

 

I use a wx.PaintDC() to draw shapes on a panel. After drawing the shapes, when I left click and drag mouse, a rubberband (transparent rectangle) is drawn over shapes. While dragging the mouse, for each motion of mouse, an EVT_PAINT is sent and everything (all shapes and rectangle) is redrawn.

 

How do I just draw the rubberband over the existing shapes (I don't want to redraw the shapes), I mean, it would be nice if I can save the existing shapes on some DC object and just draw the rubberband on it. So that the application will draw it faster.

 

Thanks

Best regards

[Chris Barker]

On Thu, Sep 22, 2016 at 5:45 AM, steve <osloc...@gmail.com> wrote:

I use a wx.PaintDC() to draw shapes on a panel. After drawing the shapes, when I left click and drag mouse, a rubberband (transparent rectangle) is drawn over shapes. While dragging the mouse, for each motion of mouse, an EVT_PAINT is sent and everything (all shapes and rectangle) is redrawn.

 

How do I just draw the rubberband over the existing shapes (I don't want to redraw the shapes), I mean, it would be nice if I can save the existing shapes on some DC object and just draw the rubberband on it. So that the application will draw it faster.

look into:

wx.lib.floatcanvas

   https://wiki.wxpython.org/FloatCanvas

(this may do everything for you already :-) )

Double Buffering:

  https://wiki.wxpython.org/DoubleBufferedDrawing

I have  bunch of demos of various stuff here:

https://github.com/PythonCHB/wxPythonDemos

I haven't tested most of them in years, but there's good stuff in there -- and PRs accepted if you find and fix issues!

Drawing with a "XOR" twice:

  https://github.com/PythonCHB/wxPythonDemos/blob/master/XOR_test.py

wxOverlay:

  I've got 4(!) examples of Overlay here:

https://github.com/PythonCHB/wxPythonDemos

not sure why -- it's been a while!

This demo:

   https://github.com/PythonCHB/wxPythonDemos/blob/master/DrawingWhileMouseMoves.py

may be helpful.

-CHB

 

 

Thanks

Best regards

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[steve]

Sir,

 

Thank you for the info.

 

I'd like to use wx.Overlay() but it doesn't work when Double Buffering is turned on. Thus, I turn it off right before drawing the rubberband, and then turn it on again. Rubberband can be drawn using this workaround. But when I right click on the window to show a pop-up menu and then left click somewhere on the window to remove it, the screen flashes (although I had turned double buffering on). I don't understand. Do you have any ideas why it happens?

 

Best regards

 

Thanks

Best regards

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[Chris Barker]

Sorry,

I found wxOverlay to be a bit tricky -- no idea about the flashing :-(

-CHB

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