Painting: Canvas switcher for painting brushes/tools.

This patch adds color attributes to TexPaintSlot. This allows an easier selection
when painting color attributes.

Previously when selecting a paint tool the user had to start a stroke, before the
UI reflected the correct TexPaintSlot. Now when switching the slot the active
tool is checked and immediate the UI is drawn correctly.

In the future the canvas selector will also be used to select an image or image texture node
to paint on. Basic implementation has already been done inside this patch.

A limitation of this patch is that is isn't possible anymore to rename images directly from
the selection panel. This is currently allowed in master. But as CustomDataLayers
aren't ID fields and not owned by the material supporting this wouldn't be easy.

{F12953989}

In the future we should update the create slot operator to also include color attributes.
Sources could also be extended to use other areas of the object that use image textures
(particles, geom nodes, etc... ).

Reviewed By: brecht

Maniphest Tasks: T96709

Differential Revision: https://developer.blender.org/D14455

3 files changed, 39 insertions, 6 deletions

diff --git a/source/blender/makesdna/DNA_material_types.h b/source/blender/makesdna/DNA_material_types.h
index e83e68a091b..b535d3cdb8a 100644
--- a/source/blender/makesdna/DNA_material_types.h
+++ b/source/blender/makesdna/DNA_material_types.h
@@ -27,11 +27,16 @@ struct bNodeTree;
 /* WATCH IT: change type? also make changes in ipo.h */
 
 typedef struct TexPaintSlot {
-  /** Image to be painted on. */
+  /** Image to be painted on. Mutual exclusive with attribute_name. */
   struct Image *ima;
   /** Custom-data index for uv layer, #MAX_NAME. */
   char *uvname;
-  /** Do we have a valid image and UV map. */
+  /**
+   * Color attribute name when painting using color attributes. Mutual exclusive with ima.
+   * Points to the name of a CustomDataLayer.
+   */
+  char *attribute_name;
+  /** Do we have a valid image and UV map or attribute. */
   int valid;
   /** Copy of node interpolation setting. */
   int interp;
diff --git a/source/blender/makesdna/DNA_node_types.h b/source/blender/makesdna/DNA_node_types.h
index ff7686d87af..5f909ea325b 100644
--- a/source/blender/makesdna/DNA_node_types.h
+++ b/source/blender/makesdna/DNA_node_types.h
@@ -397,6 +397,8 @@ typedef struct bNode {
 #define NODE_DO_OUTPUT_RECALC (1 << 17)
 /* A preview for the data in this node can be displayed in the spreadsheet editor. */
 #define __NODE_ACTIVE_PREVIEW (1 << 18) /* deprecated */
+/* Active node that is used to paint on. */
+#define NODE_ACTIVE_PAINT_CANVAS (1 << 19)
 
 /* node->update */
 #define NODE_UPDATE_ID 1       /* associated id data block has changed */
diff --git a/source/blender/makesdna/DNA_scene_types.h b/source/blender/makesdna/DNA_scene_types.h
index fb1ba15a099..9cc4d5ed55b 100644
--- a/source/blender/makesdna/DNA_scene_types.h
+++ b/source/blender/makesdna/DNA_scene_types.h
@@ -930,6 +930,19 @@ typedef struct ImagePaintSettings {
 } ImagePaintSettings;
 
 /* ------------------------------------------- */
+/* Paint mode settings */
+
+typedef struct PaintModeSettings {
+  /** Source to select canvas from to paint on (ePaintCanvasSource) */
+  char canvas_source;
+  char _pad[7];
+
+  /** Selected image when canvas_source=PAINT_CANVAS_SOURCE_IMAGE. */
+  Image *canvas_image;
+
+} PaintModeSettings;
+
+/* ------------------------------------------- */
 /* Particle Edit */
 
 /** Settings for a Particle Editing Brush. */
@@ -1462,6 +1475,9 @@ typedef struct ToolSettings {
   /* Image Paint (8 bytes aligned please!) */
   struct ImagePaintSettings imapaint;
 
+  /** Settings for paint mode. */
+  struct PaintModeSettings paint_mode;
+
   /* Particle Editing */
   struct ParticleEditSettings particle;
 
@@ -2278,11 +2294,21 @@ typedef enum eSculptFlags {
   SCULPT_HIDE_FACE_SETS = (1 << 17),
 } eSculptFlags;
 
+/** PaintModeSettings.mode */
+typedef enum ePaintCanvasSource {
+  /** Paint on the active node of the active material slot. */
+  PAINT_CANVAS_SOURCE_MATERIAL = 0,
+  /** Paint on a selected image. */
+  PAINT_CANVAS_SOURCE_IMAGE = 1,
+  /** Paint on the active color attribute (vertex color) layer. */
+  PAINT_CANVAS_SOURCE_COLOR_ATTRIBUTE = 2,
+} ePaintCanvasSource;
+
 /** #ImagePaintSettings.mode */
-typedef enum eImagePaintMode {
-  IMAGEPAINT_MODE_MATERIAL = 0, /* detect texture paint slots from the material */
-  IMAGEPAINT_MODE_IMAGE = 1,    /* select texture paint image directly */
-} eImagePaintMode;
+/* Defines to let old texture painting use the new enum. */
+/* TODO(jbakker): rename usages. */
+#define IMAGEPAINT_MODE_MATERIAL PAINT_CANVAS_SOURCE_MATERIAL
+#define IMAGEPAINT_MODE_IMAGE PAINT_CANVAS_SOURCE_IMAGE
 
 /** #ImagePaintSettings.interp */
 enum {