glCanvas and PseudoDC

petrasovaa · July 16, 2011, 12:35pm

Hi,

is it possible to draw with PseudoDC on glCanvas? I tried it and I get
only black screen,
but maybe I'm missing something.

Thanks

Anna

Chris_Barker1 · July 17, 2011, 10:20pm

no -- glCAnvas provided a canvas you can draw to with OpenGL calls -- it's completely independent of DCs.

-Chris

···

On 7/16/2011 5:35 AM, annakrat wrote:

is it possible to draw with PseudoDC on glCanvas? I tried it and I get
only black screen,
but maybe I'm missing something.

--
Christopher Barker, Ph.D.
Oceanographer

Emergency Response Division
NOAA/NOS/OR&R (206) 526-6959 voice
7600 Sand Point Way NE (206) 526-6329 fax
Seattle, WA 98115 (206) 526-6317 main reception

Chris.Barker@noaa.gov

petrasovaa · July 18, 2011, 7:16am

> is it possible to draw with PseudoDC on glCanvas? I tried it and I get
> only black screen,
> but maybe I'm missing something.

no -- glCAnvas provided a canvas you can draw to with OpenGL calls --
it's completely independent of DCs.

I know it's independent, I just need to draw an overlay image on the
glCanvas via PseudoDC.
I tried drawing with PaintDC and it works but PseudoDC doesn't work
for me. I tried PseudoDC
using the demo for glcanvas and when I call DrawToDC(dc) method, it
worked only for dc = wx.PaintDC
and not for wx.BufferedPaintDC (and it flickerd a lot). Unfortunately
this doesn't work in my program.

I add the modified code of OnPaint method from the demo

def OnPaint(self, event):
        dc = wx.PaintDC(self)
## dc = wx.BufferedPaintDC(self, self._buffer)
        # use PrepareDC to set position correctly
        self.PrepareDC(dc)

dc.SetBackground(wx.TRANSPARENT_BRUSH)
dc.Clear()

self.SetCurrent()

        if not self.init:
            self.InitGL()
            self.init = True
        self.pdc.DrawToDC(dc)
        self.OnDraw()

When I use the similar code in my program, nothing is drawn. If I call
DrawToDC
after calling SwapBuffers (in OnDraw) I can see only black screen.

Thanks for any suggestion

Anna

···

On Jul 18, 12:20 am, Chris Barker <Chris.Bar...@noaa.gov> wrote:

On 7/16/2011 5:35 AM, annakrat wrote:

-Chris

--
Christopher Barker, Ph.D.
Oceanographer

Emergency Response Division
NOAA/NOS/OR&R (206) 526-6959 voice
7600 Sand Point Way NE (206) 526-6329 fax
Seattle, WA 98115 (206) 526-6317 main reception

Chris.Bar...@noaa.gov

Robin · July 18, 2011, 5:27pm

You can try using PseudoDC to draw onto a wx.MemoryDC/bitmap, and then use OpenGL's methods to overlay that bitmap image on the canvas.

···

On 7/18/11 12:16 AM, annakrat wrote:

On Jul 18, 12:20 am, Chris Barker<Chris.Bar...@noaa.gov> wrote:

On 7/16/2011 5:35 AM, annakrat wrote:

is it possible to draw with PseudoDC on glCanvas? I tried it and I get
only black screen,
but maybe I'm missing something.

no -- glCAnvas provided a canvas you can draw to with OpenGL calls --
it's completely independent of DCs.

I know it's independent, I just need to draw an overlay image on the
glCanvas via PseudoDC.
I tried drawing with PaintDC and it works but PseudoDC doesn't work
for me. I tried PseudoDC
using the demo for glcanvas and when I call DrawToDC(dc) method, it
worked only for dc = wx.PaintDC
and not for wx.BufferedPaintDC (and it flickerd a lot). Unfortunately
this doesn't work in my program.

--
Robin Dunn
Software Craftsman

petrasovaa · July 27, 2011, 7:03pm

I finally managed to use PseudoDC to draw an overlay on glCanvas and
it seems to work fine.
B

···

On 18 čnc, 19:27, Robin Dunn <ro...@alldunn.com> wrote:

On 7/18/11 12:16 AM, annakrat wrote:

> On Jul 18, 12:20 am, Chris Barker<Chris.Bar...@noaa.gov> wrote:
>> On 7/16/2011 5:35 AM, annakrat wrote:

>>> is it possible to draw with PseudoDC on glCanvas? I tried it and I get
>>> only black screen,
>>> but maybe I'm missing something.

>> no -- glCAnvas provided a canvas you can draw to with OpenGL calls --
>> it's completely independent of DCs.

> I know it's independent, I just need to draw an overlay image on the
> glCanvas via PseudoDC.
> I tried drawing with PaintDC and it works but PseudoDC doesn't work
> for me. I tried PseudoDC
> using the demo for glcanvas and when I call DrawToDC(dc) method, it
> worked only for dc = wx.PaintDC
> and not for wx.BufferedPaintDC (and it flickerd a lot). Unfortunately
> this doesn't work in my program.

You can try using PseudoDC to draw onto a wx.MemoryDC/bitmap, and then
use OpenGL's methods to overlay that bitmap image on the canvas.

--
Robin Dunn
Software Craftsmanhttp://wxPython.org

petrasovaa · July 27, 2011, 7:16pm

Sorry, I wanted to continue but I sent it by mistake.

The problem is that a user with Mac tested it and it didn't work for
him. No overlay is drawn.
I really don't understand where the problem is.

I edited the glcanvas demo:

class MyCanvasBase(glcanvas.GLCanvas):
    def __init__(self, parent):
...
        self.pdc = wx.PseudoDC()
        self.pdc.BeginDrawing()
        pen = wx.GREEN_PEN
        self.pdc.SetPen(pen)
        self.pdc.DrawLine(20,20,200,200)
        self.pdc.EndDrawing()

    def OnPaint(self, event):
        dc = wx.PaintDC(self)
        self.SetCurrent()
        if not self.init:
            self.InitGL()
            self.init = True
        self.OnDraw()
        self.PrepareDC(dc)
        self.pdc.DrawToDC(dc)

I can see both the line and the cube/cone. On Mac only the cone/cube
is visible.

Thanks for any ideas

Anna

···

On 27 čnc, 21:03, annakrat <kratocha...@gmail.com> wrote:

On 18 čnc, 19:27, Robin Dunn <ro...@alldunn.com> wrote:

> On 7/18/11 12:16 AM, annakrat wrote:

> > On Jul 18, 12:20 am, Chris Barker<Chris.Bar...@noaa.gov> wrote:
> >> On 7/16/2011 5:35 AM, annakrat wrote:

> >>> is it possible to draw with PseudoDC on glCanvas? I tried it and I get
> >>> only black screen,
> >>> but maybe I'm missing something.

> >> no -- glCAnvas provided a canvas you can draw to with OpenGL calls --
> >> it's completely independent of DCs.

> > I know it's independent, I just need to draw an overlay image on the
> > glCanvas via PseudoDC.
> > I tried drawing with PaintDC and it works but PseudoDC doesn't work
> > for me. I tried PseudoDC
> > using the demo for glcanvas and when I call DrawToDC(dc) method, it
> > worked only for dc = wx.PaintDC
> > and not for wx.BufferedPaintDC (and it flickerd a lot). Unfortunately
> > this doesn't work in my program.

> You can try using PseudoDC to draw onto a wx.MemoryDC/bitmap, and then
> use OpenGL's methods to overlay that bitmap image on the canvas.

> --
> Robin Dunn
> Software Craftsmanhttp://wxPython.org

I finally managed to use PseudoDC to draw an overlay on glCanvas and
it seems to work fine.
B

Robin · July 27, 2011, 8:51pm

My guess is that since the OSX UI is based on OpenGL that probably there is some additional or out of order buffering, refreshing and/or context swapping that OSX is doing for the GL canvas, and so your DC operations are getting drawn over by GL. You might try using a wx.Overlay, at least on Mac. On the Mac it is a native UI tool that allows you to draw over some other widgets without actually blending the foreground and background drawing. You can think of the overlay as an extra piece of glass laid on top of your window, and any drawing you do on the overlay is kept separate. On MSW and GTK the overlay is just a simple simulation using a wx.ClientDC, so if you current approach works ok on those platforms then you will probably want to avoid it there and just leave them as-is.

Unfortunately the wx.Overlay classes are not documented, but I've attached a sample that I've used in the past for testing overlays that should help you figure it out. The example uses the overlay in some mouse event handlers, so as you can see it doesn't have to be done in the paint event handler. If you're pseudo dc drawing is constant (or mostly) then you can probably do it once and forget about it (until it needs to change) and then just do nothing except the GL stuff in the paint handler.

test_Overlay.py (2.64 KB)

···

On 7/27/11 12:16 PM, annakrat wrote:

I finally managed to use PseudoDC to draw an overlay on glCanvas and
it seems to work fine.
B

Sorry, I wanted to continue but I sent it by mistake.

The problem is that a user with Mac tested it and it didn't work for
him. No overlay is drawn.
I really don't understand where the problem is.

I edited the glcanvas demo:

class MyCanvasBase(glcanvas.GLCanvas):
     def __init__(self, parent):
...
         self.pdc = wx.PseudoDC()
         self.pdc.BeginDrawing()
         pen = wx.GREEN_PEN
         self.pdc.SetPen(pen)
         self.pdc.DrawLine(20,20,200,200)
         self.pdc.EndDrawing()

     def OnPaint(self, event):
         dc = wx.PaintDC(self)
         self.SetCurrent()
         if not self.init:
             self.InitGL()
             self.init = True
         self.OnDraw()
         self.PrepareDC(dc)
         self.pdc.DrawToDC(dc)

I can see both the line and the cube/cone. On Mac only the cone/cube
is visible.

--
Robin Dunn
Software Craftsman

petrasovaa · July 27, 2011, 8:55pm

Thanks very much, I'll definitely try it.

Anna

···

On Wed, Jul 27, 2011 at 10:51 PM, Robin Dunn <robin@alldunn.com> wrote:

On 7/27/11 12:16 PM, annakrat wrote:
I finally managed to use PseudoDC to draw an overlay on glCanvas and
it seems to work fine.
B

Sorry, I wanted to continue but I sent it by mistake.

The problem is that a user with Mac tested it and it didn't work for
him. No overlay is drawn.
I really don't understand where the problem is.

I edited the glcanvas demo:

class MyCanvasBase(glcanvas.GLCanvas):
def __init__(self, parent):
...
self.pdc = wx.PseudoDC()
self.pdc.BeginDrawing()
pen = wx.GREEN_PEN
self.pdc.SetPen(pen)
self.pdc.DrawLine(20,20,200,200)
self.pdc.EndDrawing()
def OnPaint\(self, event\):
    dc = wx\.PaintDC\(self\)
    self\.SetCurrent\(\)
    if not self\.init:
        self\.InitGL\(\)
        self\.init = True
    self\.OnDraw\(\)
    self\.PrepareDC\(dc\)
    self\.pdc\.DrawToDC\(dc\)
I can see both the line and the cube/cone. On Mac only the cone/cube
is visible.
My guess is that since the OSX UI is based on OpenGL that probably there is
some additional or out of order buffering, refreshing and/or context
swapping that OSX is doing for the GL canvas, and so your DC operations are
getting drawn over by GL. You might try using a wx.Overlay, at least on
Mac. On the Mac it is a native UI tool that allows you to draw over some
other widgets without actually blending the foreground and background
drawing. You can think of the overlay as an extra piece of glass laid on
top of your window, and any drawing you do on the overlay is kept separate.
On MSW and GTK the overlay is just a simple simulation using a wx.ClientDC,
so if you current approach works ok on those platforms then you will
probably want to avoid it there and just leave them as-is.

Unfortunately the wx.Overlay classes are not documented, but I've attached a
sample that I've used in the past for testing overlays that should help you
figure it out. The example uses the overlay in some mouse event handlers,
so as you can see it doesn't have to be done in the paint event handler. If
you're pseudo dc drawing is constant (or mostly) then you can probably do it
once and forget about it (until it needs to change) and then just do nothing
except the GL stuff in the paint handler.

--
Robin Dunn
Software Craftsman
http://wxPython.org

--
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Chris_Barker1 · July 27, 2011, 9:06pm

You also might try using GL more -- draw to a wx.Bitmap, turn that into a texture, and draw the texture with GL.

That way your DC drawing stuff could be anywhere in the draw order, not just on top.

-Chris

···

On 7/27/11 1:51 PM, Robin Dunn wrote:

You might try using a wx.Overlay, at least
on Mac. On the Mac it is a native UI tool that allows you to draw over
some other widgets without actually blending the foreground and
background drawing.

--
Christopher Barker, Ph.D.
Oceanographer

Emergency Response Division
NOAA/NOS/OR&R (206) 526-6959 voice
7600 Sand Point Way NE (206) 526-6329 fax
Seattle, WA 98115 (206) 526-6317 main reception

Chris.Barker@noaa.gov

petrasovaa · July 28, 2011, 6:32am

>> I finally managed to use PseudoDC to draw an overlay on glCanvas and
>> it seems to work fine.
>> B

> Sorry, I wanted to continue but I sent it by mistake.

> The problem is that a user with Mac tested it and it didn't work for
> him. No overlay is drawn.
> I really don't understand where the problem is.

> I edited the glcanvas demo:

> class MyCanvasBase(glcanvas.GLCanvas):
> def __init__(self, parent):
> ...
> self.pdc = wx.PseudoDC()
> self.pdc.BeginDrawing()
> pen = wx.GREEN_PEN
> self.pdc.SetPen(pen)
> self.pdc.DrawLine(20,20,200,200)
> self.pdc.EndDrawing()

> def OnPaint(self, event):
> dc = wx.PaintDC(self)
> self.SetCurrent()
> if not self.init:
> self.InitGL()
> self.init = True
> self.OnDraw()
> self.PrepareDC(dc)
> self.pdc.DrawToDC(dc)

> I can see both the line and the cube/cone. On Mac only the cone/cube
> is visible.

My guess is that since the OSX UI is based on OpenGL that probably there
is some additional or out of order buffering, refreshing and/or context
swapping that OSX is doing for the GL canvas, and so your DC operations
are getting drawn over by GL. You might try using a wx.Overlay, at
least on Mac. On the Mac it is a native UI tool that allows you to draw
over some other widgets without actually blending the foreground and
background drawing. You can think of the overlay as an extra piece of
glass laid on top of your window, and any drawing you do on the overlay
is kept separate. On MSW and GTK the overlay is just a simple
simulation using a wx.ClientDC, so if you current approach works ok on
those platforms then you will probably want to avoid it there and just
leave them as-is.

Unfortunately the wx.Overlay classes are not documented, but I've
attached a sample that I've used in the past for testing overlays that
should help you figure it out. The example uses the overlay in some
mouse event handlers, so as you can see it doesn't have to be done in
the paint event handler. If you're pseudo dc drawing is constant (or
mostly) then you can probably do it once and forget about it (until it
needs to change) and then just do nothing except the GL stuff in the
paint handler.

I forgot to ask which version of wxPython is it available for? I
couldn't
find it anywhere and it's quite important for me.

Thanks

Anna

···

On 27 čnc, 22:51, Robin Dunn <ro...@alldunn.com> wrote:

On 7/27/11 12:16 PM, annakrat wrote:

--
Robin Dunn
Software Craftsmanhttp://wxPython.org

test_Overlay.py
2KZobrazitStáhnout

Robin · July 28, 2011, 8:15pm

I think it was added sometime in the 2.8 series. Try running the sample code I included with my last message. If it works then you have wx.Overlay. If not then you need a newer version.

···

On 7/27/11 11:32 PM, annakrat wrote:

On 27 ďż˝nc, 22:51, Robin Dunn<ro...@alldunn.com> wrote:

I can see both the line and the cube/cone. On Mac only the cone/cube
is visible.

My guess is that since the OSX UI is based on OpenGL that probably there
is some additional or out of order buffering, refreshing and/or context
swapping that OSX is doing for the GL canvas, and so your DC operations
are getting drawn over by GL. You might try using a wx.Overlay, at
least on Mac. On the Mac it is a native UI tool that allows you to draw
over some other widgets without actually blending the foreground and
background drawing. You can think of the overlay as an extra piece of
glass laid on top of your window, and any drawing you do on the overlay
is kept separate. On MSW and GTK the overlay is just a simple
simulation using a wx.ClientDC, so if you current approach works ok on
those platforms then you will probably want to avoid it there and just
leave them as-is.

Unfortunately the wx.Overlay classes are not documented, but I've
attached a sample that I've used in the past for testing overlays that
should help you figure it out. The example uses the overlay in some
mouse event handlers, so as you can see it doesn't have to be done in
the paint event handler. If you're pseudo dc drawing is constant (or
mostly) then you can probably do it once and forget about it (until it
needs to change) and then just do nothing except the GL stuff in the
paint handler.

I forgot to ask which version of wxPython is it available for? I
couldn't
find it anywhere and it's quite important for me.

--
Robin Dunn
Software Craftsman

petrasovaa · July 29, 2011, 5:59am

>>> I can see both the line and the cube/cone. On Mac only the cone/cube
>>> is visible.

>> My guess is that since the OSX UI is based on OpenGL that probably there
>> is some additional or out of order buffering, refreshing and/or context
>> swapping that OSX is doing for the GL canvas, and so your DC operations
>> are getting drawn over by GL. You might try using a wx.Overlay, at
>> least on Mac. On the Mac it is a native UI tool that allows you to draw
>> over some other widgets without actually blending the foreground and
>> background drawing. You can think of the overlay as an extra piece of
>> glass laid on top of your window, and any drawing you do on the overlay
>> is kept separate. On MSW and GTK the overlay is just a simple
>> simulation using a wx.ClientDC, so if you current approach works ok on
>> those platforms then you will probably want to avoid it there and just
>> leave them as-is.

>> Unfortunately the wx.Overlay classes are not documented, but I've
>> attached a sample that I've used in the past for testing overlays that
>> should help you figure it out. The example uses the overlay in some
>> mouse event handlers, so as you can see it doesn't have to be done in
>> the paint event handler. If you're pseudo dc drawing is constant (or
>> mostly) then you can probably do it once and forget about it (until it
>> needs to change) and then just do nothing except the GL stuff in the
>> paint handler.

> I forgot to ask which version of wxPython is it available for? I
> couldn't
> find it anywhere and it's quite important for me.

I think it was added sometime in the 2.8 series. Try running the sample
code I included with my last message. If it works then you have
wx.Overlay. If not then you need a newer version.

The program I contribute to has requirements on wxPython version >=
2.8.1.1 .
So it should be OK. wx.Overlay seems to work together with glCanvas on
Mac
so I'm going to use it.

Thanks very much for your advice, it was very helpful.

Anna

···

On 28 čnc, 22:15, Robin Dunn <ro...@alldunn.com> wrote:

On 7/27/11 11:32 PM, annakrat wrote:
> On 27 nc, 22:51, Robin Dunn<ro...@alldunn.com> wrote:

--
Robin Dunn
Software Craftsmanhttp://wxPython.org