UV Editor: Grid and snapping improvements

Implements T89789, T89792, custom grid (described as dynamic grid in
T78389) and UV grid snapping (T78391)
Replaces the default UV editor grid with 2 new types of grid :

* Custom grid: Allows the user to create an NxN grid, where the value
  of N is specified by the user.
* Subdividing grid: Subdivides the UV editor grid when the user
  zooms in the viewport and vice versa when zooming out.

UV snapping improvements :
* Increment snapping: Increment values for snapping are calculated based
  on which grid type is being used in the UV editor
  (subdividing or custom). In general the increment value is equal to
  the distance between 2 visible grid lines.
* Absolute grid snap: New toggle added to increment snapping option in
  the UV editor, allows UV grid snapping during translation.

Reviewed By: campbellbarton

Ref D12684

1 files changed, 10 insertions, 0 deletions

diff --git a/source/blender/editors/include/ED_image.h b/source/blender/editors/include/ED_image.h
index 6b0b9f4a27c..9532035a1cd 100644
--- a/source/blender/editors/include/ED_image.h
+++ b/source/blender/editors/include/ED_image.h
@@ -41,6 +41,16 @@ struct SpaceImage;
 struct bContext;
 struct wmOperator;
 struct wmWindowManager;
+struct View2D;
+
+/* image_draw.c */
+float ED_space_image_zoom_level(const struct View2D *v2d, const int grid_dimension);
+void ED_space_image_grid_steps(struct SpaceImage *sima,
+                               float grid_steps[SI_GRID_STEPS_LEN],
+                               const int grid_dimension);
+float ED_space_image_increment_snap_value(const int grid_dimesnions,
+                                          const float grid_steps[SI_GRID_STEPS_LEN],
+                                          const float zoom_factor);
 
 /* image_edit.c, exported for transform */
 struct Image *ED_space_image(struct SpaceImage *sima);