Compositor: Support backdrop offset for the Viewer node

This is only part of the experimental "Full Frame" mode (disabled
by default). See T88150.

Currently the viewer node uses buffer paddings to display image offset
in the backdrop as a temporal solution implemented for {D12466}.
This solution is inefficient memory and performance-wise. Another
issue is that the paddings are part the image when saved.

This patch instead sets the offset in the Viewer node image
as variables and makes the backdrop take it into account
when drawing the image or any related gizmo.

Reviewed By: jbakker

Differential Revision: https://developer.blender.org/D12750

3 files changed, 43 insertions, 13 deletions

diff --git a/source/blender/editors/space_node/drawnode.cc b/source/blender/editors/space_node/drawnode.cc
index 365a17c0a04..ad647cf019d 100644
--- a/source/blender/editors/space_node/drawnode.cc
+++ b/source/blender/editors/space_node/drawnode.cc
@@ -1499,8 +1499,10 @@ void draw_nodespace_back_pix(const bContext &C,
   if (ibuf) {
     /* somehow the offset has to be calculated inverse */
     wmOrtho2_region_pixelspace(&region);
-    const float x = (region.winx - snode.zoom * ibuf->x) / 2 + snode.xof;
-    const float y = (region.winy - snode.zoom * ibuf->y) / 2 + snode.yof;
+    const float offset_x = snode.xof + ima->display_offset_x;
+    const float offset_y = snode.yof + ima->display_offset_y;
+    const float x = (region.winx - snode.zoom * ibuf->x) / 2 + offset_x;
+    const float y = (region.winy - snode.zoom * ibuf->y) / 2 + offset_y;
 
     /** \note draw selected info on backdrop */
     if (snode.edittree) {
diff --git a/source/blender/editors/space_node/node_gizmo.cc b/source/blender/editors/space_node/node_gizmo.cc
index 4f27f9baabc..832ec36ab34 100644
--- a/source/blender/editors/space_node/node_gizmo.cc
+++ b/source/blender/editors/space_node/node_gizmo.cc
@@ -38,25 +38,39 @@ namespace blender::ed::space_node {
 
 static void node_gizmo_calc_matrix_space(const SpaceNode *snode,
                                          const ARegion *region,
+                                         const float image_offset[2],
                                          float matrix_space[4][4])
 {
   unit_m4(matrix_space);
   mul_v3_fl(matrix_space[0], snode->zoom);
   mul_v3_fl(matrix_space[1], snode->zoom);
-  matrix_space[3][0] = (region->winx / 2) + snode->xof;
-  matrix_space[3][1] = (region->winy / 2) + snode->yof;
+  const float offset_x = snode->xof + image_offset[0];
+  const float offset_y = snode->yof + image_offset[1];
+  matrix_space[3][0] = (region->winx / 2) + offset_x;
+  matrix_space[3][1] = (region->winy / 2) + offset_y;
 }
 
 static void node_gizmo_calc_matrix_space_with_image_dims(const SpaceNode *snode,
                                                          const ARegion *region,
+                                                         const float image_offset[2],
                                                          const float image_dims[2],
                                                          float matrix_space[4][4])
 {
   unit_m4(matrix_space);
   mul_v3_fl(matrix_space[0], snode->zoom * image_dims[0]);
   mul_v3_fl(matrix_space[1], snode->zoom * image_dims[1]);
-  matrix_space[3][0] = ((region->winx / 2) + snode->xof) - ((image_dims[0] / 2.0f) * snode->zoom);
-  matrix_space[3][1] = ((region->winy / 2) + snode->yof) - ((image_dims[1] / 2.0f) * snode->zoom);
+  const float offset_x = snode->xof + image_offset[0];
+  const float offset_y = snode->yof + image_offset[1];
+  matrix_space[3][0] = ((region->winx / 2) + offset_x) - ((image_dims[0] / 2.0f) * snode->zoom);
+  matrix_space[3][1] = ((region->winy / 2) + offset_y) - ((image_dims[1] / 2.0f) * snode->zoom);
+}
+
+static void get_viewer_image_offset(const bContext *C, float r_offset[2])
+{
+  Main *bmain = CTX_data_main(C);
+  const Image *image = BKE_image_ensure_viewer(bmain, IMA_TYPE_COMPOSITE, "Viewer Node");
+  r_offset[0] = image->display_offset_x;
+  r_offset[1] = image->display_offset_y;
 }
 
 /** \} */
@@ -127,11 +141,13 @@ static void WIDGETGROUP_node_transform_refresh(const bContext *C, wmGizmoGroup *
   Main *bmain = CTX_data_main(C);
   wmGizmo *cage = ((wmGizmoWrapper *)gzgroup->customdata)->gizmo;
   const ARegion *region = CTX_wm_region(C);
-  /* center is always at the origin */
-  const float origin[3] = {float(region->winx / 2), float(region->winy / 2), 0.0f};
 
-  void *lock;
   Image *ima = BKE_image_ensure_viewer(bmain, IMA_TYPE_COMPOSITE, "Viewer Node");
+  /* Center is always at the origin. */
+  const float origin[3] ={ (region->winx / 2) + (float)ima->display_offset_x,
+                           (region->winy / 2) + (float)ima->display_offset_y};
+
+  void *lock;
   ImBuf *ibuf = BKE_image_acquire_ibuf(ima, nullptr, &lock);
 
   if (ibuf) {
@@ -340,7 +356,9 @@ static void WIDGETGROUP_node_crop_draw_prepare(const bContext *C, wmGizmoGroup *
 
   SpaceNode *snode = CTX_wm_space_node(C);
 
-  node_gizmo_calc_matrix_space(snode, region, gz->matrix_space);
+  float image_offset[2];
+  get_viewer_image_offset(C, image_offset);
+  node_gizmo_calc_matrix_space(snode, region, image_offset, gz->matrix_space);
 }
 
 static void WIDGETGROUP_node_crop_refresh(const bContext *C, wmGizmoGroup *gzgroup)
@@ -453,8 +471,10 @@ static void WIDGETGROUP_node_sbeam_draw_prepare(const bContext *C, wmGizmoGroup
 
   SpaceNode *snode = CTX_wm_space_node(C);
 
+  float image_offset[2];
+  get_viewer_image_offset(C, image_offset);
   node_gizmo_calc_matrix_space_with_image_dims(
-      snode, region, sbeam_group->state.dims, gz->matrix_space);
+      snode, region, image_offset, sbeam_group->state.dims, gz->matrix_space);
 }
 
 static void WIDGETGROUP_node_sbeam_refresh(const bContext *C, wmGizmoGroup *gzgroup)
@@ -560,9 +580,12 @@ static void WIDGETGROUP_node_corner_pin_draw_prepare(const bContext *C, wmGizmoG
 
   SpaceNode *snode = CTX_wm_space_node(C);
 
+  float image_offset[2];
+  get_viewer_image_offset(C, image_offset);
+
   float matrix_space[4][4];
   node_gizmo_calc_matrix_space_with_image_dims(
-      snode, region, cpin_group->state.dims, matrix_space);
+      snode, region, image_offset, cpin_group->state.dims, matrix_space);
 
   for (int i = 0; i < 4; i++) {
     wmGizmo *gz = cpin_group->gizmos[i];
diff --git a/source/blender/editors/space_node/space_node.cc b/source/blender/editors/space_node/space_node.cc
index 82b850653be..af93c4d823c 100644
--- a/source/blender/editors/space_node/space_node.cc
+++ b/source/blender/editors/space_node/space_node.cc
@@ -352,9 +352,14 @@ static void node_area_listener(const wmSpaceTypeListenerParams *params)
         case ND_FRAME:
           ED_area_tag_refresh(area);
           break;
-        case ND_COMPO_RESULT:
+        case ND_COMPO_RESULT: {
           ED_area_tag_redraw(area);
+          /* Backdrop image offset is calculated during compositing so gizmos need to be updated
+           * afterwards. */
+          const ARegion *region = BKE_area_find_region_type(area, RGN_TYPE_WINDOW);
+          WM_gizmomap_tag_refresh(region->gizmo_map);
           break;
+        }
         case ND_TRANSFORM_DONE:
           if (ED_node_is_compositor(snode)) {
             if (snode->flag & SNODE_AUTO_RENDER) {