# HG changeset patch
# User John Tsiombikas <nuclear@member.fsf.org>
# Date 1446178368 -7200
# Node ID 7eea82cea9d27e777b7e625e32a247a376193d59
# Parent  ec6edfe7774c66ae8a6c6c0609145bf47317eafa
added preliminary support for quad-buffer stereo fallback drawing

diff -r ec6edfe7774c -r 7eea82cea9d2 src/vr.c
--- a/src/vr.c	Sun Apr 12 02:02:04 2015 +0300
+++ b/src/vr.c	Fri Oct 30 06:12:48 2015 +0200
@@ -43,10 +43,15 @@
 		set_option_vec3f(defopt, VR_LEYE_OFFSET, -DEF_IPD * 0.5f, 0.0f, 0.0f);
 		set_option_vec3f(defopt, VR_REYE_OFFSET, DEF_IPD * 0.5f, 0.0f, 0.0f);
 
-		if((env = getenv("VR_NULL_STEREO")) && atoi(env)) {
-			set_option_int(defopt, VR_NULL_STEREO, 1);
+		if((env = getenv("VR_NULL_STEREO_SBS")) && atoi(env)) {
+			set_option_int(defopt, VR_NULL_STEREO_SBS, 1);
 		} else {
-			set_option_int(defopt, VR_NULL_STEREO, 0);
+			set_option_int(defopt, VR_NULL_STEREO_SBS, 0);
+		}
+		if((env = getenv("VR_NULL_STEREO_GL")) && atoi(env)) {
+			set_option_int(defopt, VR_NULL_STEREO_GL, 1);
+		} else {
+			set_option_int(defopt, VR_NULL_STEREO_GL, 0);
 		}
 	}
 
@@ -364,7 +369,8 @@
 
 static void fallback_present(void)
 {
-	int i, show_both = vr_geti(VR_NULL_STEREO);
+	int i, show_sbs = vr_geti(VR_NULL_STEREO_SBS);
+	int use_quadbuf = vr_geti(VR_NULL_STEREO_GL);
 
 	glPushAttrib(GL_ENABLE_BIT | GL_TRANSFORM_BIT);
 
@@ -386,7 +392,7 @@
 	for(i=0; i<2; i++) {
 		float x0, x1;
 
-		if(show_both) {
+		if(show_sbs && !use_quadbuf) {
 			x0 = i == 0 ? -1 : 0;
 			x1 = i == 0 ? 0 : 1;
 		} else {
@@ -396,6 +402,10 @@
 
 		glBindTexture(GL_TEXTURE_2D, rtarg[i].tex);
 
+		if(use_quadbuf) {
+			glDrawBuffer(GL_BACK_LEFT + i);
+		}
+
 		glBegin(GL_QUADS);
 		glTexCoord2f(rtarg[i].umin, rtarg[i].vmin);
 		glVertex2f(x0, -1);
@@ -407,7 +417,11 @@
 		glVertex2f(x0, 1);
 		glEnd();
 
-		if(!show_both) break;
+		if(!show_sbs && !use_quadbuf) break;
+	}
+
+	if(use_quadbuf) {
+		glDrawBuffer(GL_BACK);
 	}
 
 	glPopMatrix();
diff -r ec6edfe7774c -r 7eea82cea9d2 src/vr.h
--- a/src/vr.h	Sun Apr 12 02:02:04 2015 +0300
+++ b/src/vr.h	Fri Oct 30 06:12:48 2015 +0200
@@ -19,7 +19,8 @@
 #define VR_LEYE_OFFSET		"left-eye-offset"	/* stereo offset from center of the head */
 #define VR_REYE_OFFSET		"right-eye-offset"	/* stereo offset from center of the head */
 /* misc options */
-#define VR_NULL_STEREO		"null-stereo"	/* bool, default 0 */
+#define VR_NULL_STEREO_SBS	"null-stereo-sbs"	/* bool, default 0: draw side-by-side */
+#define VR_NULL_STEREO_GL	"null-stereo-gl"	/* bool, default 0: use quad-buffer stereo */
 
 enum {
 	VR_EYE_LEFT,