From: Lyle Johnson <lyle@...>
Date: 2003-01-15T02:14:55+09:00
Subject: Re: FXRuby problem on Windows

Daniel P. Zepeda wrote:

> 	I've cut down a larger program to this test case that shows a problem on
> windows. When I run this on my Linux box, I get an application window with
> some colored boxes and the string "Hi There, (I'm on my way, I'm making
> it) in it. When I run this same program on my Windows box, I get Zip,
> nada, at first a gray window, then a transparent one if I minimize
> thenmaximize the window. Some debugging statements show that onPaint *is*
> getting called. Can anyone tell me what the problem is here?

<snip>

I haven't had a chance to look at this under Windows yet, but I think I 
see what's wrong; you need to call FXDC#end to "flush" out the drawing 
commands that you're making. The fact that it *happens* to work under 
Linux is just a coincidence.

Device contexts (i.e. FXDCWindow instances) are just supposed to be 
temporary objects, not things that you hang on to for the life of a 
program. They are most often constructed and torn down within a 
SEL_PAINT handler, although there are some other times you might need to 
use them (for some examples, see the scribble.rb example program).

As an illustration (no pun intended), I'd recommend restructuring the 
test case as follows. First, move the code for setting up the screen 
device context (@sdc) into the SEL_PAINT handler for the canvas widget:

     def onPaint( sender, sel, event )
       sdc = FXDCWindow.new( @canvas )
       sdc.drawImage( @image, 0,0 )
       sdc.end
     end

Note that sdc doesn't need to be (and probably shouldn't be) an instance 
variable, it's just a local. Also note the call to FXDCWindow#end after 
the drawing is complete.

Next, I'd move the code related to drawing the image out into a separate 
routine:

     def setupImage
       @image.resize( @canvas.width, @canvas.height )

       idc = FXDCWindow.new( @image )

       idc.setForeground( FXColor::White )
       idc.fillRectangle( 0,0, @canvas.width, @canvas.height )

       step = 5
       0.step(50, step ) { |y|
         0.step(50, step ) { |x|
	  idc.setForeground(FXRGB( rand(255), rand(255), rand(255)))
           idc.fillRectangle( x,y, x+@canvas.height, y+@canvas.width  )
         }
       }

       idc.fillRectangle( 50,50, @canvas.width, @canvas.height  )
       idc.setForeground(FXColor::Black)
       idc.setTextFont( @font )
       idc.drawText( 60,80, "Hi There, (I'm on my way I'm making it!)")

       idc.end
     end

As with onPaint(), the device context (idc) is now just a local 
variable. I also replaced the instance variables @canvasWidth and 
@canvasHeight with direct calls to the canvas for its width and height, 
but that's less important.

After these changes, the create() method is much simpler:

     def create
       super

       @font.create
       @image.create

       setupImage

       show(PLACEMENT_SCREEN)
     end

As I said, I haven't tried it out on Windows yet, but I think the added 
calls to FXDC#end will probably take care of the problem you were 
seeing. If not, let me know and I'll take a closer look.

Hope this helps,

Lyle