glx: Implement GLX_EXT_swap_control for DRI2 and DRI3

This is a slight generalization of the existing SGI and MESA swap
control extensions, and a prerequisite for GLX_EXT_swap_control_tear.

Reviewed-by: Michel Dänzer <mdaenzer@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6671>

docs/relnotes/new_features.txt

@@ -3,3 +3,4 @@ GL_NV_copy_depth_to_color for NIR
 GL_NV_half_float
 EGL_KHR_swap_buffers_with_damage on X11 (DRI3)
 VK_PRESENT_MODE_FIFO_RELAXED on X11
+GLX_EXT_swap_control for DRI2 and DRI3

src/glx/dri2_glx.c

@@ -1109,6 +1109,7 @@ dri2BindExtensions(struct dri2_screen *psc, struct glx_display * priv,
 
    extensions = psc->core->getExtensions(psc->driScreen);
 
+   __glXEnableDirectExtension(&psc->base, "GLX_EXT_swap_control");
    __glXEnableDirectExtension(&psc->base, "GLX_SGI_swap_control");
    __glXEnableDirectExtension(&psc->base, "GLX_MESA_swap_control");
    __glXEnableDirectExtension(&psc->base, "GLX_SGI_make_current_read");

src/glx/dri3_glx.c

@@ -741,6 +741,7 @@ dri3_bind_extensions(struct dri3_screen *psc, struct glx_display * priv,
 
    extensions = psc->core->getExtensions(psc->driScreen);
 
+   __glXEnableDirectExtension(&psc->base, "GLX_EXT_swap_control");
    __glXEnableDirectExtension(&psc->base, "GLX_SGI_swap_control");
    __glXEnableDirectExtension(&psc->base, "GLX_MESA_swap_control");
    __glXEnableDirectExtension(&psc->base, "GLX_SGI_make_current_read");

src/glx/glx_pbuffer.c

@@ -35,6 +35,7 @@
 #include <X11/extensions/Xext.h>
 #include <assert.h>
 #include <string.h>
+#include <limits.h>
 #include "glxextensions.h"
 
 #ifdef GLX_USE_APPLEGL
@@ -343,6 +344,16 @@ __glXGetDrawableAttribute(Display * dpy, GLXDrawable drawable,
 
       return 0;
    }
+
+   if (pdraw) {
+      if (attribute == GLX_SWAP_INTERVAL_EXT) {
+         *value = pdraw->psc->driScreen->getSwapInterval(pdraw);
+         return 0;
+      } else if (attribute == GLX_MAX_SWAP_INTERVAL_EXT) {
+         *value = INT_MAX;
+         return 0;
+      }
+   }
 #endif
 
    LockDisplay(dpy);

src/glx/glxcmds.c

@@ -1845,6 +1845,34 @@ glXGetSwapIntervalMESA(void)
 }
 
 
+/*
+** GLX_EXT_swap_control
+*/
+_X_HIDDEN void
+glXSwapIntervalEXT(Display *dpy, GLXDrawable drawable, int interval)
+{
+#ifdef GLX_DIRECT_RENDERING
+   __GLXDRIdrawable *pdraw = GetGLXDRIDrawable(dpy, drawable);
+
+   /*
+    * Strictly, this should throw an error if drawable is not a Window or
+    * GLXWindow. We don't actually track that, so, oh well.
+    */
+   if (!pdraw) {
+       __glXSendError(dpy, BadWindow, drawable, 0, True);
+      return;
+   }
+
+   if (interval < 0) {
+      __glXSendError(dpy, BadValue, interval, 0, True);
+      return;
+   }
+
+   pdraw->psc->driScreen->setSwapInterval(pdraw, interval);
+#endif
+}
+
+
 /*
 ** GLX_SGI_video_sync
 */
@@ -2530,6 +2558,9 @@ static const struct name_address_pair GLX_functions[] = {
    /*** GLX_EXT_texture_from_pixmap ***/
    GLX_FUNCTION(glXBindTexImageEXT),
    GLX_FUNCTION(glXReleaseTexImageEXT),
+
+   /*** GLX_EXT_swap_control ***/
+   GLX_FUNCTION(glXSwapIntervalEXT),
 #endif
 
 #if defined(GLX_DIRECT_RENDERING) && defined(GLX_USE_DRM)

src/glx/glxextensions.c

@@ -147,6 +147,7 @@ static const struct extension_info known_glx_extensions[] = {
    { GLX(EXT_fbconfig_packed_float),   VER(0,0), Y, Y, N, N },
    { GLX(EXT_framebuffer_sRGB),        VER(0,0), Y, Y, N, N },
    { GLX(EXT_import_context),          VER(0,0), Y, Y, N, N },
+   { GLX(EXT_swap_control),            VER(0,0), Y, N, N, Y },
    { GLX(EXT_texture_from_pixmap),     VER(0,0), Y, N, N, N },
    { GLX(EXT_visual_info),             VER(0,0), Y, Y, N, N },
    { GLX(EXT_visual_rating),           VER(0,0), Y, Y, N, N },

src/glx/glxextensions.h

@@ -51,6 +51,7 @@ enum
    EXT_fbconfig_packed_float_bit,
    EXT_framebuffer_sRGB_bit,
    EXT_import_context_bit,
+   EXT_swap_control_bit,
    EXT_texture_from_pixmap_bit,
    EXT_visual_info_bit,
    EXT_visual_rating_bit,