Fix T84850: "Lock to Selection" causes unwanted jumps

Adding new tracks, mask points, mask primitives, changing selection was
causing an unwanted jumps in the view.

This change makes it so those operations are preserving view offset.

Differential Revision: https://developer.blender.org/D10146

1 files changed, 38 insertions, 1 deletions

diff --git a/source/blender/editors/mask/mask_ops.c b/source/blender/editors/mask/mask_ops.c
index 25cc39bf9a0..00a1dfb7d87 100644
--- a/source/blender/editors/mask/mask_ops.c
+++ b/source/blender/editors/mask/mask_ops.c
@@ -226,6 +226,12 @@ typedef struct SlidePointData {
   int width, height;
 
   float prev_mouse_coord[2];
+
+  /* Previous clip coordinate which was resolved from mouse position (0, 0).
+   * Is used to compansate for view offste moving in-between of mouse events when
+   * lock-to-selection is enabled. */
+  float prev_zero_coord[2];
+
   float no[2];
 
   bool is_curvature_only, is_accurate, is_initial_feather, is_overall_feather;
@@ -431,6 +437,9 @@ static void *slide_point_customdata(bContext *C, wmOperator *op, const wmEvent *
   const float threshold = 19;
   eMaskWhichHandle which_handle;
 
+  MaskViewLockState lock_state;
+  ED_mask_view_lock_state_store(C, &lock_state);
+
   ED_mask_mouse_pos(area, region, event->mval, co);
   ED_mask_get_size(area, &width, &height);
 
@@ -530,7 +539,15 @@ static void *slide_point_customdata(bContext *C, wmOperator *op, const wmEvent *
     }
     customdata->which_handle = which_handle;
 
+    {
+      WM_event_add_notifier(C, NC_MASK | NA_EDITED, mask);
+      DEG_id_tag_update(&mask->id, 0);
+
+      ED_mask_view_lock_state_restore_no_jump(C, &lock_state);
+    }
+
     ED_mask_mouse_pos(area, region, event->mval, customdata->prev_mouse_coord);
+    ED_mask_mouse_pos(area, region, (int[2]){0, 0}, customdata->prev_zero_coord);
   }
 
   return customdata;
@@ -655,10 +672,24 @@ static int slide_point_modal(bContext *C, wmOperator *op, const wmEvent *event)
 
       ED_mask_mouse_pos(area, region, event->mval, co);
       sub_v2_v2v2(delta, co, data->prev_mouse_coord);
+      copy_v2_v2(data->prev_mouse_coord, co);
+
+      /* Compensate for possibly moved view offset since the last event.
+       * The idea is to see how mapping of a fixed and known position did change. */
+      {
+        float zero_coord[2];
+        ED_mask_mouse_pos(area, region, (int[2]){0, 0}, zero_coord);
+
+        float zero_delta[2];
+        sub_v2_v2v2(zero_delta, zero_coord, data->prev_zero_coord);
+        sub_v2_v2(delta, zero_delta);
+
+        copy_v2_v2(data->prev_zero_coord, zero_coord);
+      }
+
       if (data->is_accurate) {
         mul_v2_fl(delta, 0.2f);
       }
-      copy_v2_v2(data->prev_mouse_coord, co);
 
       if (data->action == SLIDE_ACTION_HANDLE) {
         float new_handle[2];
@@ -966,6 +997,9 @@ static SlideSplineCurvatureData *slide_spline_curvature_customdata(bContext *C,
   float u, co[2];
   BezTriple *next_bezt;
 
+  MaskViewLockState lock_state;
+  ED_mask_view_lock_state_store(C, &lock_state);
+
   ED_mask_mouse_pos(CTX_wm_area(C), CTX_wm_region(C), event->mval, co);
 
   if (!ED_mask_find_nearest_diff_point(C,
@@ -1047,6 +1081,9 @@ static SlideSplineCurvatureData *slide_spline_curvature_customdata(bContext *C,
   mask_layer->act_point = point;
   ED_mask_select_flush_all(mask);
 
+  DEG_id_tag_update(&mask->id, 0);
+  ED_mask_view_lock_state_restore_no_jump(C, &lock_state);
+
   return slide_data;
 }