7 files changed, 86 insertions, 12 deletions
diff --git a/src/gallium/state_trackers/wgl/stw_device.c b/src/gallium/state_trackers/wgl/stw_device.c
index b57f96f2e87..42a2f0e82f9 100644
--- a/src/gallium/state_trackers/wgl/stw_device.c
+++ b/src/gallium/state_trackers/wgl/stw_device.c
@@ -63,6 +63,24 @@ stw_get_param(struct st_manager *smapi,
    }
 }
 
+
+/** Get the refresh rate for the monitor, in Hz */
+static int
+get_refresh_rate(void)
+{
+   DEVMODE devModes;
+
+   if (EnumDisplaySettings(NULL, ENUM_CURRENT_SETTINGS, &devModes)) {
+      /* clamp the value, just in case we get garbage */
+      return CLAMP(devModes.dmDisplayFrequency, 30, 120);
+   }
+   else {
+      /* reasonable default */
+      return 60;
+   }
+}
+
+
 boolean
 stw_init(const struct stw_winsys *stw_winsys)
 {
@@ -116,6 +134,13 @@ stw_init(const struct stw_winsys *stw_winsys)
 
    stw_pixelformat_init();
 
+   /* env var override for WGL_EXT_swap_control, useful for testing/debugging */
+   const char *s = os_get_option("SVGA_SWAP_INTERVAL");
+   if (s) {
+      stw_dev->swap_interval = atoi(s);
+   }
+   stw_dev->refresh_rate = get_refresh_rate();
+
    stw_dev->initialized = true;
 
    return TRUE;
diff --git a/src/gallium/state_trackers/wgl/stw_device.h b/src/gallium/state_trackers/wgl/stw_device.h
index ecf212d7cb6..766975c292c 100644
--- a/src/gallium/state_trackers/wgl/stw_device.h
+++ b/src/gallium/state_trackers/wgl/stw_device.h
@@ -78,6 +78,10 @@ struct stw_device
    unsigned long memdbg_no;
 #endif
 
+   /** WGL_EXT_swap_control */
+   int refresh_rate;
+   int swap_interval;
+
    bool initialized;
 };
 
diff --git a/src/gallium/state_trackers/wgl/stw_ext_extensionsstring.c b/src/gallium/state_trackers/wgl/stw_ext_extensionsstring.c
index 06af8b1e994..996eb586d94 100644
--- a/src/gallium/state_trackers/wgl/stw_ext_extensionsstring.c
+++ b/src/gallium/state_trackers/wgl/stw_ext_extensionsstring.c
@@ -45,7 +45,7 @@ static const char *stw_extension_string =
    "WGL_EXT_create_context_es_profile "
    "WGL_EXT_create_context_es2_profile "
    "WGL_ARB_make_current_read "
-/*   "WGL_EXT_swap_interval " */
+   "WGL_EXT_swap_control "
    "WGL_EXT_extensions_string";
 
 
diff --git a/src/gallium/state_trackers/wgl/stw_ext_swapinterval.c b/src/gallium/state_trackers/wgl/stw_ext_swapinterval.c
index b960913ccbb..b2074a73fb7 100644
--- a/src/gallium/state_trackers/wgl/stw_ext_swapinterval.c
+++ b/src/gallium/state_trackers/wgl/stw_ext_swapinterval.c
@@ -33,25 +33,30 @@
 #include <GL/gl.h>
 #include <GL/wglext.h>
 #include "util/u_debug.h"
+#include "stw_device.h"
 
-/* A dummy implementation of this extension.
- *
- * Required as some applications retrieve and call these functions
- * regardless of the fact that we don't advertise the extension and
- * further more the results of wglGetProcAddress are NULL.
+
+/**
+ * Note that our implementation of swap intervals is a bit of a hack.
+ * We implement it based on querying the time and Sleep()'ing.  We don't
+ * sync to the vblank.
  */
 WINGDIAPI BOOL APIENTRY
 wglSwapIntervalEXT(int interval)
 {
-   (void) interval;
-   debug_printf("%s: %d\n", __FUNCTION__, interval);
+   if (interval < 0) {
+      SetLastError(ERROR_INVALID_DATA);
+      return FALSE;
+   }
+   if (stw_dev) {
+      stw_dev->swap_interval = interval;
+   }
    return TRUE;
 }
 
+
 WINGDIAPI int APIENTRY
 wglGetSwapIntervalEXT(void)
 {
-   return 0;
+   return stw_dev ? stw_dev->swap_interval : 0;
 }
-
-
diff --git a/src/gallium/state_trackers/wgl/stw_framebuffer.c b/src/gallium/state_trackers/wgl/stw_framebuffer.c
index 09b57766dc0..321fbb6ea77 100644
--- a/src/gallium/state_trackers/wgl/stw_framebuffer.c
+++ b/src/gallium/state_trackers/wgl/stw_framebuffer.c
@@ -30,6 +30,7 @@
 #include "pipe/p_screen.h"
 #include "util/u_memory.h"
 #include "hud/hud_context.h"
+#include "os/os_time.h"
 #include "state_tracker/st_api.h"
 
 #include "stw_icd.h"
@@ -580,6 +581,38 @@ stw_framebuffer_present_locked(HDC hdc,
 }
 
 
+/**
+ * This is called just before issuing the buffer swap/present.
+ * We query the current time and determine if we should sleep before
+ * issuing the swap/present.
+ * This is a bit of a hack and is certainly not very accurate but it
+ * basically works.
+ * This is for the WGL_ARB_swap_interval extension.
+ */
+static void
+wait_swap_interval(struct stw_framebuffer *fb)
+{
+   /* Note: all time variables here are in units of microseconds */
+   int64_t cur_time = os_time_get_nano() / 1000;
+
+   if (fb->prev_swap_time != 0) {
+      /* Compute time since previous swap */
+      int64_t delta = cur_time - fb->prev_swap_time;
+      int64_t min_swap_period =
+         1.0e6 / stw_dev->refresh_rate * stw_dev->swap_interval;
+
+      /* if time since last swap is less than wait period, wait */
+      if (delta < min_swap_period) {
+         float fudge = 1.75f;  /* emperical fudge factor */
+         int64_t wait = (min_swap_period - delta) * fudge;
+         os_time_sleep(wait);
+      }
+   }
+
+   fb->prev_swap_time = cur_time;
+}
+
+
 BOOL APIENTRY
 DrvSwapBuffers(HDC hdc)
 {
@@ -615,6 +648,10 @@ DrvSwapBuffers(HDC hdc)
       }
    }
 
+   if (stw_dev->swap_interval != 0) {
+      wait_swap_interval(fb);
+   }
+
    return stw_st_swap_framebuffer_locked(hdc, fb->stfb);
 }
 
diff --git a/src/gallium/state_trackers/wgl/stw_framebuffer.h b/src/gallium/state_trackers/wgl/stw_framebuffer.h
index 029fb9ffa34..d44c3a6634a 100644
--- a/src/gallium/state_trackers/wgl/stw_framebuffer.h
+++ b/src/gallium/state_trackers/wgl/stw_framebuffer.h
@@ -108,6 +108,9 @@ struct stw_framebuffer
    HANDLE hSharedSurface;
    struct stw_shared_surface *shared_surface;
 
+   /* For WGL_EXT_swap_control */
+   int64_t prev_swap_time;
+
    /** 
     * This is protected by stw_device::fb_mutex, not the mutex above.
     * 
diff --git a/src/gallium/state_trackers/wgl/stw_getprocaddress.c b/src/gallium/state_trackers/wgl/stw_getprocaddress.c
index 9273d103310..c8138f61fa4 100644
--- a/src/gallium/state_trackers/wgl/stw_getprocaddress.c
+++ b/src/gallium/state_trackers/wgl/stw_getprocaddress.c
@@ -67,7 +67,7 @@ static const struct stw_extension_entry stw_extension_entries[] = {
    /* WGL_EXT_extensions_string */
    STW_EXTENSION_ENTRY( wglGetExtensionsStringEXT ),
 
-   /* WGL_EXT_swap_interval */
+   /* WGL_EXT_swap_control */
    STW_EXTENSION_ENTRY( wglGetSwapIntervalEXT ),
    STW_EXTENSION_ENTRY( wglSwapIntervalEXT ),