[Gambas-user] gb3 (rev. 3641) and SDL surfaces

[Kevin Fishburne]

I've been experimenting with gb.sdl and found that I could achieve frame 
rates higher than 380 fps at 1920x1080, including alpha channel. This 
involves writing directly to the SDL window/surface with a 1920x1080 
image loaded from a file, for example:

Public Screen As New Window As "Screen"
Public SomeImage As Image = Image.Load("someimage.png")

Public Sub Main()

   ' Create screen.
   With Screen
     .Width = 1920
     .Height = 1080
     .Framerate = 1000
     .FullScreen = True
     .Show()
   End With

End

Public Sub Screen_Draw()

   Draw.Image(SomeImage, 0, 0)
   Draw.Text(Screen.Framerate & " FPS", 0, 0)

End

While this is awesome, there is a problem if images need to be 
composited before being written to the SDL surface. For example, if I 
wanted to do something like this:

Water.Draw(WaterRipples, 0, 0)
Water.Draw(SkyReflection, 0, 0)
Water.DrawAlpha(WaterDepth, 0, 0)

and then draw Water to the SDL window, not only is the imlib2 component 
required (otherwise it states the .Draw method is unknown), it kills the 
frame rate because the Draw method is done in software (imlib2) and only 
the writes done directly to the SDL window are hardware accelerated.

Attempting to circumvent this I created a second SDL window, hoping I 
could write the contents of window B to window A. The idea was to create 
multiple secondary SDL windows, using them as image buffers, then write 
the buffers as necessary to the main SDL window when its Draw event was 
called. This didn't work at all and I don't think it's supported.

Is there a way to use the Draw method, or an equivalent, so that 
image-to-image writes can be done entirely in SDL? I've already 
converted my app to use the SDL component but too much of it currently 
uses the .Draw and .DrawAlpha methods which bring the framerate to 21 
fps at 1280x720. The framerate is only going to get worse from here, as 
I'm just getting started.

-- 
Kevin Fishburne
Eight Virtues
www: http://sales.eightvirtues.com
e-mail: sales at ...1887...
phone: (770) 853-6271