CanvasX11GLX: Updates to handle the API change for GLX_EXT_swap_control

(The spec always had a void return value for glXSwapIntervalEXT, however, the
original example and protocol had a return value of int.  To make matters worse,
the header files in mesa were updated a year after the spec.).  Also, make the
GLX_MESA_swap_control initialization match the new logic for GLX_EXT_swap_control.

1 files changed, 23 insertions, 4 deletions

diff --git a/src/canvas-x11-glx.cpp b/src/canvas-x11-glx.cpp
index 01d71cc..db3ac70 100644
--- a/src/canvas-x11-glx.cpp
+++ b/src/canvas-x11-glx.cpp
@@ -28,6 +28,7 @@
 
 static PFNGLXSWAPINTERVALEXTPROC glXSwapIntervalEXT_;
 static PFNGLXSWAPINTERVALMESAPROC glXSwapIntervalMESA_;
+static PFNGLXGETSWAPINTERVALMESAPROC glXGetSwapIntervalMESA_;
 
 /*********************
  * Protected methods *
@@ -60,12 +61,24 @@ CanvasX11GLX::make_current()
         return false;
     }
 
-    if ((!glXSwapIntervalEXT_ || glXSwapIntervalEXT_(xdpy_, xwin_, 0)) &&
-        (!glXSwapIntervalMESA_ || glXSwapIntervalMESA_(0)))
-    {
-        Log::info("** Failed to set swap interval. Results may be bounded above by refresh rate.\n");
+    unsigned int desired_swap(0);
+    unsigned int actual_swap(-1);
+    if (glXSwapIntervalEXT_) {
+        glXSwapIntervalEXT_(xdpy_, xwin_, desired_swap);
+        glXQueryDrawable(xdpy_, xwin_, GLX_SWAP_INTERVAL_EXT, &actual_swap);
+        if (actual_swap == desired_swap)
+            return true;
+    }
+
+    if (glXSwapIntervalMESA_) {
+        glXSwapIntervalMESA_(desired_swap);
+        actual_swap = glXGetSwapIntervalMESA_();
+        if (actual_swap == desired_swap)
+            return true;
     }
 
+    Log::info("** Failed to set swap interval. Results may be bounded above by refresh rate.\n");
+
     return true;
 }
 
@@ -131,6 +144,12 @@ CanvasX11GLX::init_extensions()
                     reinterpret_cast<const GLubyte *>("glXSwapIntervalMESA")
                 )
             );
+        glXGetSwapIntervalMESA_ =
+            reinterpret_cast<PFNGLXGETSWAPINTERVALMESAPROC>(
+                glXGetProcAddress(
+                    reinterpret_cast<const GLubyte *>("glXGetSwapIntervalMESA")
+                )
+            );
     }