Hi
Thanks for a great GUI toolkit!
I want to draw transparent lines in a Frame. I have the following setup
but my lines are not transparent.
My colour object is created using:
transparent_blue = Colour.new(0,0,255,100)
and I draw lines using a pen with this colour:
@pen = Pen.new(transparent_blue)
In evt_paint of frame I have:
dc.set_pen(@pen)
dc.draw_line(x1,y1,x2,y2)
The line is blue but there is no transparency.
I set the alpha level to 100 where 255 is supposed to be completely
opaque.
I’m on Windows XP SP2 and
C:>ruby --version
ruby 1.8.6 (2007-09-24 patchlevel 111) [i386-mswin32]
Please help!
Regards, Andreas
Andreas W. wrote:
I want to draw transparent lines in a Frame. I have the following setup
but my lines are not transparent.
The standard DC doesn’t support transparency (except on OS X I think).
But you can instead use wxGraphicsContext which fully supports
transparency, antialiasing and other advanced drawing tools like splines
and transforms. You create one from an ordinary DC like this:
paint.do | dc |
gdc = Wx::GraphicsContext.create(dc)
gdc.stroke_line(0, 0, 500, 500)
etc
end
Unfortunately the wxWidgets developers decided to make the API to
GraphicsContext different to DC, but the results are worth it for
graphical apps.
alex
Alex F. wrote:
The standard DC doesn’t support transparency (except on OS X I think).
But you can instead use wxGraphicsContext which fully supports
transparency, antialiasing and other advanced drawing tools like splines
and transforms. You create one from an ordinary DC like this:
paint.do | dc |
gdc = Wx::GraphicsContext.create(dc)
gdc.stroke_line(0, 0, 500, 500)
etc
end
Thanks! I’m having a bit of trouble, though. Here is a small example I
use:
require ‘wx’
include Wx
App.run do
frame = Frame.new(nil, :title => ‘GraphicsContext example’, :width =>
[300,400])
frame.evt_paint do
frame.paint do |dc|
gdc = GraphicsContext.create(dc)
siz = dc.size
h, w = siz.height, siz.width
#dc.draw_line(0,0,w,h)
gdc.stroke_line(0,0,w,h)
end
end
frame.show
end
It should draw / stroke a diagonal line in the frame. This works if I
use draw_line.
What am I missing? 
Andreas
Andreas W. wrote:
frame.evt_paint do
frame.paint do |dc|
gdc = GraphicsContext.create(dc)
siz = dc.size
h, w = siz.height, siz.width
#dc.draw_line(0,0,w,h)
gdc.pen = Wx::Pen.new( Wx::Colour.new(255, 0, 0, 128), 20)
What am I missing?
It seems with GraphicsContext, you need to set some sort of pen before
starting drawing - there is no default pen when it’s first created.
alex