Transform 2D center was using short. Not good enough when it's it's way off screen. Switched to ints, that fixed the bug in the tracker.

Switching to floats would probably be safer in the long term, but too many things to test to do that now.

source/blender/include/BSE_view.h

@@ -50,6 +50,7 @@ void initgrabz(float x, float y, float z);
 void window_to_3d(float *vec, short mx, short my);
 void project_short(float *vec, short *adr);
 void project_short_noclip(float *vec, short *adr);
+void project_int(float *vec, int *adr);
 void project_float(float *vec, float *adr);
 int boundbox_clip(float obmat[][4], struct BoundBox *bb);
 void fdrawline(float x1, float y1, float x2, float y2);

source/blender/include/transform.h

@@ -135,7 +135,7 @@ typedef struct TransInfo {
 	float		propsize;		/* proportional circle radius           */
 	char		proptext[20];	/* proportional falloff text			*/
     float       center[3];      /* center of transformation             */
-    short       center2d[2];    /* center in screen coordinates         */
+    int         center2d[2];    /* center in screen coordinates         */
     short       imval[2];       /* initial mouse position               */
 	short		shiftmval[2];	/* mouse position when shift was pressed */
 	short       idx_max;

source/blender/src/transform_constraints.c

@@ -842,8 +842,8 @@ void setNearestAxis(TransInfo *t)
 	float zfac;
 	float mvec[3], axis[3], proj[3];
 	float len[3];
+	int i, icoord[2];
 	short coord[2];
-	int i;
 
 	t->con.mode &= ~CON_AXIS0;
 	t->con.mode &= ~CON_AXIS1;
@@ -871,10 +871,10 @@ void setNearestAxis(TransInfo *t)
 		VecMulf(axis, zfac);
 		/* now we can project to get window coordinate */
 		VecAddf(axis, axis, t->con.center);
-		project_short_noclip(axis, coord);
+		project_int(axis, icoord);
 		
-		axis[0] = (float)(coord[0] - t->center2d[0]);
+		axis[0] = (float)(icoord[0] - t->center2d[0]);
-		axis[1] = (float)(coord[1] - t->center2d[1]);
+		axis[1] = (float)(icoord[1] - t->center2d[1]);
 		axis[2] = 0.0f;
 
  		if (Normalise(axis) != 0.0f) {

source/blender/src/transform_generics.c

@@ -608,10 +608,10 @@ void calculateCenterCursor(TransInfo *t)
 		
 		VECCOPY(vec, t->center);
 		Mat4MulVecfl(ob->obmat, vec);
-		project_short_noclip(vec, t->center2d);
+		project_int(vec, t->center2d);
 	}
 	else {
-		project_short_noclip(t->center, t->center2d);
+		project_int(t->center, t->center2d);
 	}
 }
 
@@ -640,10 +640,10 @@ void calculateCenterMedian(TransInfo *t)
 		
 		VECCOPY(vec, t->center);
 		Mat4MulVecfl(ob->obmat, vec);
-		project_short_noclip(vec, t->center2d);
+		project_int(vec, t->center2d);
 	}
 	else {
-		project_short_noclip(t->center, t->center2d);
+		project_int(t->center, t->center2d);
 	}
 }
 
@@ -679,10 +679,10 @@ void calculateCenterBound(TransInfo *t)
 		
 		VECCOPY(vec, t->center);
 		Mat4MulVecfl(ob->obmat, vec);
-		project_short_noclip(vec, t->center2d);
+		project_int(vec, t->center2d);
 	}
 	else {
-		project_short_noclip(t->center, t->center2d);
+		project_int(t->center, t->center2d);
 	}
 }
 
@@ -709,7 +709,7 @@ void calculateCenter(TransInfo *t)
 			Object *ob= OBACT;
 			if(ob) {
 				VECCOPY(t->center, ob->obmat[3]);
-				project_short_noclip(t->center, t->center2d);
+				project_int(t->center, t->center2d);
 			}
 		}
 		
@@ -735,7 +735,7 @@ void calculateCenter(TransInfo *t)
 			axis[1]= t->center[1]- 6.0f*axis[1];
 			axis[2]= t->center[2]- 6.0f*axis[2];
 			
-			project_short_noclip(axis, t->center2d);
+			project_int(axis, t->center2d);
 			
 			/* rotate only needs correct 2d center, grab needs initgrabz() value */
 			if(t->mode==TFM_TRANSLATION) VECCOPY(t->center, axis);

source/blender/src/view.c

@@ -192,6 +192,30 @@ void project_short(float *vec, short *adr)	/* clips */
 	}
 }
 
+void project_int(float *vec, int *adr)
+{
+	float fx, fy, vec4[4];
+
+	adr[0]= 2140000000.0f;
+	VECCOPY(vec4, vec);
+	vec4[3]= 1.0;
+	
+	Mat4MulVec4fl(G.vd->persmat, vec4);
+
+	if( vec4[3]>BL_NEAR_CLIP ) {	/* 0.001 is the NEAR clipping cutoff for picking */
+		fx= (curarea->winx/2)*(1 + vec4[0]/vec4[3]);
+		
+		if( fx>-2140000000.0f && fx<2140000000.0f) {
+			fy= (curarea->winy/2)*(1 + vec4[1]/vec4[3]);
+			
+			if(fy>-2140000000.0f && fy<2140000000.0f) {
+				adr[0]= floor(fx); 
+				adr[1]= floor(fy);
+			}
+		}
+	}
+}
+
 void project_short_noclip(float *vec, short *adr)
 {
 	float fx, fy, vec4[4];