Implement offset_rect property to MobileVRInterface to allow changing screen area.

modules/mobile_vr/doc_classes/MobileVRInterface.xml

@@ -34,6 +34,9 @@
 		<member name="k2" type="float" setter="set_k2" getter="get_k2" default="0.215">
 			The k2 lens factor, see k1.
 		</member>
+		<member name="offset_rect" type="Rect2" setter="set_offset_rect" getter="get_offset_rect" default="Rect2(0, 0, 1, 1)">
+			Set the offset rect relative to the area being rendered. A length of 1 represents the whole rendering area on that axis.
+		</member>
 		<member name="oversample" type="float" setter="set_oversample" getter="get_oversample" default="1.5">
 			The oversample setting. Because of the lens distortion we have to render our buffers at a higher resolution then the screen can natively handle. A value between 1.5 and 2.0 often provides good results but at the cost of performance.
 		</member>

modules/mobile_vr/mobile_vr_interface.cpp

@@ -230,6 +230,9 @@ void MobileVRInterface::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("set_display_to_lens", "display_to_lens"), &MobileVRInterface::set_display_to_lens);
 	ClassDB::bind_method(D_METHOD("get_display_to_lens"), &MobileVRInterface::get_display_to_lens);
 
+	ClassDB::bind_method(D_METHOD("set_offset_rect", "offset_rect"), &MobileVRInterface::set_offset_rect);
+	ClassDB::bind_method(D_METHOD("get_offset_rect"), &MobileVRInterface::get_offset_rect);
+
 	ClassDB::bind_method(D_METHOD("set_oversample", "oversample"), &MobileVRInterface::set_oversample);
 	ClassDB::bind_method(D_METHOD("get_oversample"), &MobileVRInterface::get_oversample);
 
@@ -243,6 +246,7 @@ void MobileVRInterface::_bind_methods() {
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "iod", PROPERTY_HINT_RANGE, "4.0,10.0,0.1"), "set_iod", "get_iod");
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "display_width", PROPERTY_HINT_RANGE, "5.0,25.0,0.1"), "set_display_width", "get_display_width");
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "display_to_lens", PROPERTY_HINT_RANGE, "5.0,25.0,0.1"), "set_display_to_lens", "get_display_to_lens");
+	ADD_PROPERTY(PropertyInfo(Variant::RECT2, "offset_rect"), "set_offset_rect", "get_offset_rect");
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "oversample", PROPERTY_HINT_RANGE, "1.0,2.0,0.1"), "set_oversample", "get_oversample");
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "k1", PROPERTY_HINT_RANGE, "0.1,10.0,0.0001"), "set_k1", "get_k1");
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "k2", PROPERTY_HINT_RANGE, "0.1,10.0,0.0001"), "set_k2", "get_k2");
@@ -256,6 +260,14 @@ double MobileVRInterface::get_eye_height() const {
 	return eye_height;
 }
 
+void MobileVRInterface::set_offset_rect(const Rect2 &p_offset_rect) {
+	offset_rect = p_offset_rect;
+}
+
+Rect2 MobileVRInterface::get_offset_rect() const {
+	return offset_rect;
+}
+
 void MobileVRInterface::set_iod(const double p_iod) {
 	intraocular_dist = p_iod;
 };
@@ -483,6 +495,8 @@ Vector<BlitToScreen> MobileVRInterface::post_draw_viewport(RID p_render_target,
 	// Because we are rendering to our device we must use our main viewport!
 	ERR_FAIL_COND_V(p_screen_rect == Rect2(), blit_to_screen);
 
+	Rect2 modified_screen_rect = Rect2(p_screen_rect.position + offset_rect.position * p_screen_rect.size, p_screen_rect.size * offset_rect.size);
+
 	// and add our blits
 	BlitToScreen blit;
 	blit.render_target = p_render_target;
@@ -494,16 +508,16 @@ Vector<BlitToScreen> MobileVRInterface::post_draw_viewport(RID p_render_target,
 	blit.lens_distortion.aspect_ratio = aspect;
 
 	// left eye
-	blit.dst_rect = p_screen_rect;
+	blit.dst_rect = modified_screen_rect;
 	blit.dst_rect.size.width *= 0.5;
 	blit.multi_view.layer = 0;
 	blit.lens_distortion.eye_center.x = ((-intraocular_dist / 2.0) + (display_width / 4.0)) / (display_width / 2.0);
 	blit_to_screen.push_back(blit);
 
 	// right eye
-	blit.dst_rect = p_screen_rect;
+	blit.dst_rect = modified_screen_rect;
 	blit.dst_rect.size.width *= 0.5;
-	blit.dst_rect.position.x = blit.dst_rect.size.width;
+	blit.dst_rect.position.x += blit.dst_rect.size.width;
 	blit.multi_view.layer = 1;
 	blit.lens_distortion.eye_center.x = ((intraocular_dist / 2.0) - (display_width / 4.0)) / (display_width / 2.0);
 	blit_to_screen.push_back(blit);

modules/mobile_vr/mobile_vr_interface.h

@@ -62,6 +62,8 @@ private:
 	double display_to_lens = 4.0;
 	double oversample = 1.5;
 
+	Rect2 offset_rect = Rect2(0, 0, 1, 1); // Full screen rect.
+
 	double k1 = 0.215;
 	double k2 = 0.215;
 	double aspect = 1.0;
@@ -121,6 +123,9 @@ public:
 	void set_display_width(const double p_display_width);
 	double get_display_width() const;
 
+	void set_offset_rect(const Rect2 &p_offset_rect);
+	Rect2 get_offset_rect() const;
+
 	void set_display_to_lens(const double p_display_to_lens);
 	double get_display_to_lens() const;