Roku Developer Program

[jbrave]

So I tried to throw together a little app to plot points on the screen, using 1 pixel .png images, of red green and blue. Not working. Background display is working. Any suggestions as to why nothing is showing up? The idea was to plot a point and leave it up, plot another in 3 colors, just an experiment. Nothing is happening except if I set the background, which I have commented out in case it was overlaying the points. Heres the code, based off a screensaver test TheEndless posted a while back.

sub main()
   backgroundHD = {
      Color: "#000000",
      TargetRect: { x: 0, y: 0, w: 1280, h: 720 }
   }
   
      
   rx=640 
   ry=360
   gx=640 
   gy=360
   bx=640 
   by=360
   
   gpix={url:"pkg:/green.png" 
   		TargetRect:{x:gx,y:gy,w:10,h:10}}
   bpix={url:"pkg:/blue.png" 
   		TargetRect:{x:bx,y:by,w:10,h:10}}
   rpix={url:"pkg:/red.png" 
   		TargetRect:{x:rx,y:ry,w:10,h:10}}
   
   port = CreateObject( "roMessagePort" )
   canvas = CreateObject( "roImageCanvas" )
   canvas.SetMessagePort(port)
   canvas.SetRequireAllImagesToDraw( false )
   'canvas.SetLayer( 1, backgroundHD)   
   canvas.Show()
   canvas.SetRequireAllImagesToDraw(false)
   While true
      msg = Wait(10, port )
      if Type(msg)="roImageCanvasEvent" then
      ?msg.GetMessage()
      If msg.isRemoteKeyPressed() Then
         canvas.Close()
         Return
      End If
      end if


      rx=rx+rnd(3)-2  
      ry=ry+rnd(3)-2
      gx=gx+rnd(3)-2
      gy=gy+rnd(3)-2
      bx=bx+rnd(3)-2
      by=by+rnd(3)-2
      canvas.SetLayer( 2, gpix)
      canvas.SetLayer( 3, bpix)
      canvas.SetLayer( 4, rpix)
      canvas.show()
      ?rx,ry,gx,gy,bx,by
      
   End While   
End Sub

[TheEndless]

First problem I see is that you're never updating the TargetRects for your pixel PNGs. rx, ry, gx, gy, bx, and by are all integers, so changing them won't automatically update the TargetRects. You'll need to explicitly update those.
Second, 10 milliseconds is probably too fast for the screen to refresh. I'd try bumping that up to 100 or so until you get the screen drawing correctly.
Otherwise, it looks ok. Are your images actually in the root of your package, or are they in an images subfolder? If in an images subfolder, then your URLs are wrong, which could be your problem.

[jbrave]

Yep, you are correct about the path...

So if I use floats instead of integers, it will auto-update?

- Joel

[TheEndless]

"jbrave" wrote:
Yep, you are correct about the path...

So if I use floats instead of integers, it will auto-update?

- Joel

No, only objects are updated by reference, so you'll need to change the target rects directly:

      rx=rx+rnd(3)-2 
      ry=ry+rnd(3)-2
      gx=gx+rnd(3)-2
      gy=gy+rnd(3)-2
      bx=bx+rnd(3)-2
      by=by+rnd(3)-2

      rpix.TargetRect.x = rx
      rpix.TargetRecy.y = ry
      gpix.TargetRect.x = gx
      gpix.TargetRect.y = gy
      bpix.TargetRect.x = bx
      bpix.TargetRect.y = by

[jbrave]

interestingly, nothing happened until I added:

rpix.CompositionMode="Source_Over"
 

to each line

[retrotom]

"TheEndless" wrote:
First problem I see is that you're never updating the TargetRects for your pixel PNGs. rx, ry, gx, gy, bx, and by are all integers, so changing them won't automatically update the TargetRects. You'll need to explicitly update those.
Second, 10 milliseconds is probably too fast for the screen to refresh. I'd try bumping that up to 100 or so until you get the screen drawing correctly.
Otherwise, it looks ok. Are your images actually in the root of your package, or are they in an images subfolder? If in an images subfolder, then your URLs are wrong, which could be your problem.

I'd like to mirror what TheEndless says about the update frequency. In my testing you can TRY to update at a really high frequency like that -- but nine times out of ten my roku would crash with anything "sizable" being rendered in under 100ms.

[jbrave]

I figured out I don't need my 1pix png, I can just set a color for the targetRect and draw a dot or a square with no .png.

Other weird things: drawing to layer 1 2 or 3 results in a moving image. Drawing to layer 0 results in a line that follows the draw position.
Drawing three colors to layer 0 results in only the last draw appearing - unless a delay is put in after each draw. So as both of you mentioned, there is definitely some timing related weirdness. a 15ms wait between each color draw seems to work, don't know what the minimum is yet.

- Joel

[kbenson]

Here's some general tips from other threads about using roImageCanvas, and our own experience:

• Whenever changing a canvas in any way, the call to .show() will take a while. Anywhere from a little less than 100ms to well over 10 seconds, depending on complexity.


• After you've called .show() on a canvas (and it was given enough time to display), subsequent calls to .show() are very fast, generally displaying in less than 20ms until the next change.


• Creating a new roImageCanvas object anywhere causes all current canvas objects to recomposite (take a long time) on the next call to .show().


• Using TargetRect for simple squares is fine, just don't try to rotate them (unless that's fixed now?)


• Scaling an image causes automatic gradients. A two pixel image with one pixel red and the other green, when scaled will automatically fill in the pixels between the colors with a gradient.

Also, be careful with floats and integers. In many places using a float instead of an integer in components yields silent but wrong behavior (such as automatically being evaluated as zero). Most places it just blows up though. 😉

[jbrave]

Thanks. I'm still pretty confused about how all this works. For instance:

If I plot a bunch of squares on layer 0 they all stay on the screen.
If I plot on layer 1, 2 ,3 then each new call erases the previous and draws a new square.

Also, discovered that the transparancy byte documented for text also works for graphics even though it is not documented:

#ff00F00C0 (where C0 is the transparancy)

Rotation is completely inaccurate, but could be used creatively.

- Joel

[TheEndless]

Calling SetLayer on any layer should replace all of the content on that layer, even 0. What you may be seeing is left over from the screen behind your ImageCanvas not redrawing.

#ff00F00C0 (where C0 is the transparancy)

Actually ff is the transparency in that string (though technically not transparent at FF). Either the trailing 0 or the leading f is likely being ignored, since there are only 4 bytes to a color string, and yours seems to have 4 and a half..