Multi-View: Map cursor coordinates to visual coordinates

When rendering multi-view in side-by-side or top-bottom mode, we squash
the UI to half of its size and draw it twice on screen. That means the
cursor coordinates used for UI interaction don't match what's visible on
screen.
This commit is a little event system hack (tm) to fix this. It has some
small glitches with cursor grabbing, but nothing to bad.
We'll also use it for viewport HMD support.

D1350, thanks for the feedback @dfelinto!

3 files changed, 29 insertions, 0 deletions

diff --git a/source/blender/windowmanager/intern/wm_event_system.c b/source/blender/windowmanager/intern/wm_event_system.c
index d2b0acd836b..eba132062c9 100644
--- a/source/blender/windowmanager/intern/wm_event_system.c
+++ b/source/blender/windowmanager/intern/wm_event_system.c
@@ -3179,6 +3179,8 @@ void wm_event_add_ghostevent(wmWindowManager *wm, wmWindow *win, int type, int U
 			GHOST_TEventCursorData *cd = customdata;
 
 			copy_v2_v2_int(&event.x, &cd->x);
+			wm_stereo3d_mouse_offset_apply(win, &event.x);
+
 			event.type = MOUSEMOVE;
 			wm_event_add_mousemove(win, &event);
 			copy_v2_v2_int(&evt->x, &event.x);
diff --git a/source/blender/windowmanager/intern/wm_stereo.c b/source/blender/windowmanager/intern/wm_stereo.c
index 46cee907991..66ebf18c9e1 100644
--- a/source/blender/windowmanager/intern/wm_stereo.c
+++ b/source/blender/windowmanager/intern/wm_stereo.c
@@ -345,6 +345,32 @@ bool WM_stereo3d_enabled(wmWindow *win, bool skip_stereo3d_check)
 	return true;
 }
 
+/**
+ * If needed, this adjusts \a r_mouse_xy so that drawn cursor and handled mouse position are matching visually.
+*/
+void wm_stereo3d_mouse_offset_apply(wmWindow *win, int *r_mouse_xy)
+{
+	if (!WM_stereo3d_enabled(win, false))
+		return;
+
+	if (win->stereo3d_format->display_mode == S3D_DISPLAY_SIDEBYSIDE) {
+		const int half_x = win->sizex / 2;
+		/* right half of the screen */
+		if (r_mouse_xy[0] > half_x) {
+			r_mouse_xy[0] -= half_x;
+		}
+		r_mouse_xy[0] *= 2;
+	}
+	else if (win->stereo3d_format->display_mode == S3D_DISPLAY_TOPBOTTOM) {
+		const int half_y = win->sizey / 2;
+		/* upper half of the screen */
+		if (r_mouse_xy[1] > half_y) {
+			r_mouse_xy[1] -= half_y;
+		}
+		r_mouse_xy[1] *= 2;
+	}
+}
+
 /************************** Stereo 3D operator **********************************/
 typedef struct Stereo3dData {
 	Stereo3dFormat stereo3d_format;
diff --git a/source/blender/windowmanager/wm.h b/source/blender/windowmanager/wm.h
index 2f06ddab1e8..e8485359490 100644
--- a/source/blender/windowmanager/wm.h
+++ b/source/blender/windowmanager/wm.h
@@ -78,6 +78,7 @@ void wm_autosave_location(char *filepath);
 
 /* wm_stereo.c */
 void wm_method_draw_stereo3d(const bContext *C, wmWindow *win);
+void wm_stereo3d_mouse_offset_apply(wmWindow *win, int *r_mouse_xy);
 int wm_stereo3d_set_exec(bContext *C, wmOperator *op);
 int wm_stereo3d_set_invoke(bContext *C, wmOperator *op, const wmEvent *event);
 void wm_stereo3d_set_draw(bContext *C, wmOperator *op);