Fix T45771: Walk mode fails on OSX

source/blender/editors/space_view3d/view3d_walk.c

@@ -62,6 +62,9 @@
 
 #define USE_TABLET_SUPPORT
 
+/* ensure the target position is one we can reach, see: T45771 */
+#define USE_PIXELSIZE_NATIVE_SUPPORT
+
 /* prototypes */
 static float getVelocityZeroTime(const float gravity, const float velocity);
 
@@ -578,6 +581,16 @@ static bool initWalkInfo(bContext *C, WalkInfo *walk, wmOperator *op)
 	walk->center_mval[0] = walk->ar->winx * 0.5f;
 	walk->center_mval[1] = walk->ar->winy * 0.5f;
 
+#ifdef USE_PIXELSIZE_NATIVE_SUPPORT
+	walk->center_mval[0] += walk->ar->winrct.xmin;
+	walk->center_mval[1] += walk->ar->winrct.ymin;
+
+	WM_cursor_comaptible_xy(win, &walk->center_mval[0], &walk->center_mval[1]);
+
+	walk->center_mval[0] -= walk->ar->winrct.xmin;
+	walk->center_mval[1] -= walk->ar->winrct.ymin;
+#endif
+
 	copy_v2_v2_int(walk->prev_mval, walk->center_mval);
 
 	WM_cursor_warp(win,

source/blender/windowmanager/WM_api.h

@@ -130,6 +130,7 @@ void		WM_paint_cursor_end(struct wmWindowManager *wm, void *handle);
 void		WM_paint_cursor_tag_redraw(struct wmWindow *win, struct ARegion *ar);
 
 void		WM_cursor_warp		(struct wmWindow *win, int x, int y);
+void		WM_cursor_comaptible_xy(wmWindow *win, int *x, int *y);
 float		WM_cursor_pressure	(const struct wmWindow *win);
 
 			/* event map */

source/blender/windowmanager/intern/wm_window.c

@@ -1556,6 +1556,18 @@ void WM_cursor_warp(wmWindow *win, int x, int y)
 	}
 }
 
+/**
+ * Set x, y to values we can actually position the cursor to.
+ */
+void WM_cursor_comaptible_xy(wmWindow *win, int *x, int *y)
+{
+	float f = GHOST_GetNativePixelSize(win->ghostwin);
+	if (f != 1.0f) {
+		*x = (int)(*x / f) * f;
+		*y = (int)(*y / f) * f;
+	}
+}
+
 /**
  * Get the cursor pressure, in most cases you'll want to use wmTabletData from the event
  */