Fix panning with Lock-to-Selection and no selection in Clip Editor

Rather self-explanatory. Never worked since the initial implementation.
It is possible to preserve lock-to-selection option with no selection
nowadays (since the fix for T84850). So now the Lock-to-Selection option
is fully under user control. Surely, the panning and zooming is also
properly supported now in the described scenario.

Differential Revision: https://developer.blender.org/D10226

source/blender/editors/space_clip/clip_intern.h

@@ -178,6 +178,8 @@ void clip_view_center_to_point(SpaceClip *sc, float x, float y);
 bool clip_view_calculate_view_selection(
     const struct bContext *C, bool fit, float *r_offset_x, float *r_offset_y, float *r_zoom);
 
+bool clip_view_has_locked_selection(const struct bContext *C);
+
 void clip_draw_sfra_efra(struct View2D *v2d, struct Scene *scene);
 
 /* tracking_ops.c */

source/blender/editors/space_clip/clip_ops.c

@@ -125,7 +125,7 @@ static void sclip_zoom_set(const bContext *C,
     dx = ((location[0] - 0.5f) * w - sc->xof) * (sc->zoom - oldzoom) / sc->zoom;
     dy = ((location[1] - 0.5f) * h - sc->yof) * (sc->zoom - oldzoom) / sc->zoom;
 
-    if (sc->flag & SC_LOCK_SELECTION) {
+    if (clip_view_has_locked_selection(C)) {
       sc->xlockof += dx;
       sc->ylockof += dy;
     }
@@ -396,7 +396,7 @@ static void view_pan_init(bContext *C, wmOperator *op, const wmEvent *event)
   vpd->x = event->x;
   vpd->y = event->y;
 
-  if (sc->flag & SC_LOCK_SELECTION) {
+  if (clip_view_has_locked_selection(C)) {
     vpd->vec = &sc->xlockof;
   }
   else {
@@ -434,7 +434,7 @@ static int view_pan_exec(bContext *C, wmOperator *op)
 
   RNA_float_get_array(op->ptr, "offset", offset);
 
-  if (sc->flag & SC_LOCK_SELECTION) {
+  if (clip_view_has_locked_selection(C)) {
     sc->xlockof += offset[0];
     sc->ylockof += offset[1];
   }

source/blender/editors/space_clip/clip_utils.c

@@ -465,6 +465,68 @@ static bool selected_tracking_boundbox(SpaceClip *sc, float min[2], float max[2]
   return ok;
 }
 
+static bool tracking_has_selection(SpaceClip *space_clip)
+{
+  MovieClip *clip = ED_space_clip_get_clip(space_clip);
+  ListBase *tracksbase = BKE_tracking_get_active_tracks(&clip->tracking);
+  const int framenr = ED_space_clip_get_clip_frame_number(space_clip);
+
+  LISTBASE_FOREACH (MovieTrackingTrack *, track, tracksbase) {
+    if (!TRACK_VIEW_SELECTED(space_clip, track)) {
+      continue;
+    }
+    const MovieTrackingMarker *marker = BKE_tracking_marker_get(track, framenr);
+    if (marker != NULL) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+static bool mask_has_selection(const bContext *C, bool include_handles)
+{
+  Mask *mask = CTX_data_edit_mask(C);
+  if (mask == NULL) {
+    return false;
+  }
+
+  LISTBASE_FOREACH (MaskLayer *, mask_layer, &mask->masklayers) {
+    if (mask_layer->restrictflag & (MASK_RESTRICT_VIEW | MASK_RESTRICT_SELECT)) {
+      continue;
+    }
+    LISTBASE_FOREACH (MaskSpline *, spline, &mask_layer->splines) {
+      for (int i = 0; i < spline->tot_point; i++) {
+        const MaskSplinePoint *point = &spline->points[i];
+        const BezTriple *bezt = &point->bezt;
+        if (!MASKPOINT_ISSEL_ANY(point)) {
+          continue;
+        }
+        if (bezt->f2 & SELECT) {
+          return true;
+        }
+
+        if (!include_handles) {
+          /* Ignore handles. */
+        }
+        else if (BKE_mask_point_handles_mode_get(point) == MASK_HANDLE_MODE_STICK) {
+          return true;
+        }
+        else {
+          if ((bezt->f1 & SELECT) && (bezt->h1 != HD_VECT)) {
+            return true;
+          }
+          if ((bezt->f3 & SELECT) && (bezt->h2 != HD_VECT)) {
+            return true;
+          }
+        }
+      }
+    }
+  }
+
+  return false;
+}
+
 static bool selected_boundbox(const bContext *C, float min[2], float max[2], bool include_handles)
 {
   SpaceClip *sc = CTX_wm_space_clip(C);
@@ -546,6 +608,23 @@ bool clip_view_calculate_view_selection(
   return true;
 }
 
+/* Returns truth if lock-to-selection is enabled and possible.
+ * Locking to selection is not possible if there is no selection. */
+bool clip_view_has_locked_selection(const bContext *C)
+{
+  SpaceClip *space_clip = CTX_wm_space_clip(C);
+
+  if ((space_clip->flag & SC_LOCK_SELECTION) == 0) {
+    return false;
+  }
+
+  if (space_clip->mode == SC_MODE_TRACKING) {
+    return tracking_has_selection(space_clip);
+  }
+
+  return mask_has_selection(C, false);
+}
+
 void clip_draw_sfra_efra(View2D *v2d, Scene *scene)
 {
   UI_view2d_view_ortho(v2d);

source/blender/editors/space_clip/tracking_ops.c

@@ -243,8 +243,6 @@ static int delete_track_exec(bContext *C, wmOperator *UNUSED(op))
       changed = true;
     }
   }
-  /* Nothing selected now, unlock view so it can be scrolled nice again. */
-  sc->flag &= ~SC_LOCK_SELECTION;
   if (changed) {
     WM_event_add_notifier(C, NC_MOVIECLIP | NA_EDITED, clip);
   }
@@ -313,11 +311,6 @@ static int delete_marker_exec(bContext *C, wmOperator *UNUSED(op))
     }
   }
 
-  if (!has_selection) {
-    /* Nothing selected now, unlock view so it can be scrolled nice again. */
-    sc->flag &= ~SC_LOCK_SELECTION;
-  }
-
   if (!changed) {
     return OPERATOR_CANCELLED;
   }
@@ -1224,13 +1217,6 @@ static int hide_tracks_exec(bContext *C, wmOperator *op)
     clip->tracking.act_plane_track = NULL;
   }
 
-  if (unselected == 0) {
-    /* No selection on screen now, unlock view so it can be
-     * scrolled nice again.
-     */
-    sc->flag &= ~SC_LOCK_SELECTION;
-  }
-
   BKE_tracking_dopesheet_tag_update(tracking);
   WM_event_add_notifier(C, NC_MOVIECLIP | ND_DISPLAY, NULL);
 

source/blender/editors/space_clip/tracking_select.c

@@ -875,10 +875,7 @@ static int select_all_exec(bContext *C, wmOperator *op)
   bool has_selection = false;
   ED_clip_select_all(sc, action, &has_selection);
 
-  if (!has_selection) {
-    sc->flag &= ~SC_LOCK_SELECTION;
-  }
-  else {
+  if (has_selection) {
     ED_clip_view_lock_state_restore_no_jump(C, &lock_state);
   }