Refactor: move Paint .blend I/O to blenkernel

Ref T76372.

source/blender/blenkernel/BKE_paint.h

@@ -66,6 +66,8 @@ struct ViewLayer;
 struct bContext;
 struct bToolRef;
 struct tPaletteColorHSV;
+struct BlendWriter;
+struct BlendDataReader;
 
 enum eOverlayFlags;
 
@@ -217,6 +219,12 @@ void BKE_paint_toolslots_brush_update(struct Paint *paint);
 void BKE_paint_toolslots_brush_validate(struct Main *bmain, struct Paint *paint);
 struct Brush *BKE_paint_toolslots_brush_get(struct Paint *paint, int slot_index);
 
+/* .blend I/O */
+void BKE_paint_blend_write(struct BlendWriter *writer, struct Paint *paint);
+void BKE_paint_blend_read_data(struct BlendDataReader *reader,
+                               const struct Scene *scene,
+                               struct Paint *paint);
+
 #define SCULPT_FACE_SET_NONE 0
 
 /* Used for both vertex color and weight paint */

source/blender/blenkernel/intern/paint.c

@@ -1176,6 +1176,40 @@ void BKE_paint_stroke_get_average(Scene *scene, Object *ob, float stroke[3])
   }
 }
 
+void BKE_paint_blend_write(BlendWriter *writer, Paint *p)
+{
+  if (p->cavity_curve) {
+    BKE_curvemapping_blend_write(writer, p->cavity_curve);
+  }
+  BLO_write_struct_array(writer, PaintToolSlot, p->tool_slots_len, p->tool_slots);
+}
+
+void BKE_paint_blend_read_data(BlendDataReader *reader, const Scene *scene, Paint *p)
+{
+  if (p->num_input_samples < 1) {
+    p->num_input_samples = 1;
+  }
+
+  BLO_read_data_address(reader, &p->cavity_curve);
+  if (p->cavity_curve) {
+    BKE_curvemapping_blend_read(reader, p->cavity_curve);
+  }
+  else {
+    BKE_paint_cavity_curve_preset(p, CURVE_PRESET_LINE);
+  }
+
+  BLO_read_data_address(reader, &p->tool_slots);
+
+  /* Workaround for invalid data written in older versions. */
+  const size_t expected_size = sizeof(PaintToolSlot) * p->tool_slots_len;
+  if (p->tool_slots && MEM_allocN_len(p->tool_slots) < expected_size) {
+    MEM_freeN(p->tool_slots);
+    p->tool_slots = MEM_callocN(expected_size, "PaintToolSlot");
+  }
+
+  BKE_paint_runtime_init(scene->toolsettings, p);
+}
+
 /* returns non-zero if any of the face's vertices
  * are hidden, zero otherwise */
 bool paint_is_face_hidden(const MLoopTri *lt, const MVert *mvert, const MLoop *mloop)

source/blender/blenloader/intern/readfile.c

@@ -4181,39 +4181,13 @@ static void link_recurs_seq(BlendDataReader *reader, ListBase *lb)
   }
 }
 
-static void direct_link_paint(BlendDataReader *reader, const Scene *scene, Paint *p)
-{
-  if (p->num_input_samples < 1) {
-    p->num_input_samples = 1;
-  }
-
-  BLO_read_data_address(reader, &p->cavity_curve);
-  if (p->cavity_curve) {
-    BKE_curvemapping_blend_read(reader, p->cavity_curve);
-  }
-  else {
-    BKE_paint_cavity_curve_preset(p, CURVE_PRESET_LINE);
-  }
-
-  BLO_read_data_address(reader, &p->tool_slots);
-
-  /* Workaround for invalid data written in older versions. */
-  const size_t expected_size = sizeof(PaintToolSlot) * p->tool_slots_len;
-  if (p->tool_slots && MEM_allocN_len(p->tool_slots) < expected_size) {
-    MEM_freeN(p->tool_slots);
-    p->tool_slots = MEM_callocN(expected_size, "PaintToolSlot");
-  }
-
-  BKE_paint_runtime_init(scene->toolsettings, p);
-}
-
 static void direct_link_paint_helper(BlendDataReader *reader, const Scene *scene, Paint **paint)
 {
   /* TODO. is this needed */
   BLO_read_data_address(reader, paint);
 
   if (*paint) {
-    direct_link_paint(reader, scene, *paint);
+    BKE_paint_blend_read_data(reader, scene, *paint);
   }
 }
 
@@ -4280,7 +4254,7 @@ static void direct_link_scene(BlendDataReader *reader, Scene *sce)
     direct_link_paint_helper(reader, sce, (Paint **)&sce->toolsettings->gp_sculptpaint);
     direct_link_paint_helper(reader, sce, (Paint **)&sce->toolsettings->gp_weightpaint);
 
-    direct_link_paint(reader, sce, &sce->toolsettings->imapaint.paint);
+    BKE_paint_blend_read_data(reader, sce, &sce->toolsettings->imapaint.paint);
 
     sce->toolsettings->particle.paintcursor = NULL;
     sce->toolsettings->particle.scene = NULL;

source/blender/blenloader/intern/writefile.c

@@ -153,6 +153,7 @@
 #include "BKE_node.h"
 #include "BKE_object.h"
 #include "BKE_packedFile.h"
+#include "BKE_paint.h"
 #include "BKE_pointcache.h"
 #include "BKE_report.h"
 #include "BKE_screen.h"
@@ -1323,10 +1324,7 @@ static void write_view_settings(BlendWriter *writer, ColorManagedViewSettings *v
 
 static void write_paint(BlendWriter *writer, Paint *p)
 {
-  if (p->cavity_curve) {
-    BKE_curvemapping_blend_write(writer, p->cavity_curve);
-  }
-  BLO_write_struct_array(writer, PaintToolSlot, p->tool_slots_len, p->tool_slots);
+  BKE_paint_blend_write(writer, p);
 }
 
 static void write_layer_collections(BlendWriter *writer, ListBase *lb)