Bug 1202 - Add support of Adaptive Vsync via [GLX|WGL]_EXT_swap_control_tear

[GLX|WGL]_EXT_swap_control_tear extensions support
asynchronous buffer swaps, i.e. adaptive Vsync.

<https://www.opengl.org/wiki/SwapInterval_aka_vsync#Adaptive_Vsync>
<https://www.opengl.org/registry/specs/EXT/wgl_swap_control_tear.txt>
<https://www.opengl.org/registry/specs/EXT/glx_swap_control_tear.txt>

<http://keithp.com/blogs/async_flip/>

The extensions utilizes a negative interval value,
enabling late swaps to occur without synchronization to the video frame.

Hence '-1' has new semantics, previously it was the 'default value'
of 'untouched vsync interval'.

New default is:
  - 0 for unrealized context
  - 1 for realized context

+++

It requires [GLX|WGL]_EXT_swap_control,
hence we shall ensure to use use this extension
in the implementation of GLContext.setSwapInterval(..).

+++

Mesa3D seems to support GLX_SGI_swap_control only.

+++

Implemented on Windows and X11.

+++

On GNU/Linux using NVidia driver w/ my setup(*), sadly the query
  GLX.glXQueryDrawable(displayHandle, drawable.getHandle(), GLX.GLX_LATE_SWAPS_TEAR_EXT, val);
always returns zero here, indicating async vsync is not supported.

(Queried the attribute for every frame in windowed or fullscreen mode)

Fullscreen
(*)
  - Debian 8
  - Kernel 3.16
  - KDE/Kwin
  - GL Version     4.5 (Core profile, arb, compat[ES2, ES3, ES31], FBO, hardware) - 4.5.0 NVIDIA 355.06 [GL 4.5.0, vendor 355.6.0 (NVIDIA 355.06)]
  - GL_RENDERER    GeForce GTX 660/PCIe/SSE2
  - Samsung U28D590 (DFP-4): Internal DisplayPort

+++

1 files changed, 31 insertions, 0 deletions

diff --git a/src/jogl/classes/jogamp/opengl/GLContextImpl.java b/src/jogl/classes/jogamp/opengl/GLContextImpl.java
index fa7aeaff8..39c5796f3 100644
--- a/src/jogl/classes/jogamp/opengl/GLContextImpl.java
+++ b/src/jogl/classes/jogamp/opengl/GLContextImpl.java
@@ -131,6 +131,8 @@ public abstract class GLContextImpl extends GLContext {
   private boolean pixelDataEvaluated;
   private int /* pixelDataInternalFormat, */ pixelDataFormat, pixelDataType;
 
+  private int currentSwapInterval;
+
   protected GL gl;
 
   protected static final Object mappedContextTypeObjectLock;
@@ -209,6 +211,7 @@ public abstract class GLContextImpl extends GLContext {
 
       surfacelessOK = false;
       pixelDataEvaluated = false;
+      currentSwapInterval = 0;
 
       super.resetStates(isInit);
   }
@@ -1110,6 +1113,34 @@ public abstract class GLContextImpl extends GLContext {
     }
   }
 
+  @Override
+  public final boolean setSwapInterval(final int interval) throws GLException {
+    validateCurrent();
+    return setSwapIntervalNC(interval);
+  }
+  protected final boolean setSwapIntervalNC(final int interval) throws GLException {
+    if( drawable.getChosenGLCapabilities().isOnscreen() &&
+        ( !drawableRetargeted || !hasRendererQuirk(GLRendererQuirks.NoSetSwapIntervalPostRetarget) )
+      )
+    {
+        final Integer usedInterval = setSwapIntervalImpl(interval);
+        if( null != usedInterval ) {
+            currentSwapInterval = usedInterval.intValue();
+            return true;
+        }
+    }
+    return false;
+  }
+  protected abstract Integer setSwapIntervalImpl(final int interval);
+
+  public final int getSwapInterval() {
+    return currentSwapInterval;
+  }
+  protected final void setDefaultSwapInterval() {
+    currentSwapInterval = 0;
+    setSwapIntervalNC(1);
+  }
+
   /**
    * Note: Since context creation is temporary, caller need to issue {@link #resetStates(boolean)}, if creation was successful, i.e. returns true.
    * This method does not reset the states, allowing the caller to utilize the state variables.