Fix T98904: GPencil sculpt brushes break after you delete a brush

There were two problems here:

1) Console warnings due to brush was None.
2) It was impossible to recreate a brush.

This patch fixes both issues and it is now possible to recreate any brush.

Differential Revision: https://developer.blender.org/D15213

Reviewed by: @dflelinto

3 files changed, 147 insertions, 14 deletions

diff --git a/release/scripts/startup/bl_ui/properties_paint_common.py b/release/scripts/startup/bl_ui/properties_paint_common.py
index 320b5f60911..e0c5da5ee1a 100644
--- a/release/scripts/startup/bl_ui/properties_paint_common.py
+++ b/release/scripts/startup/bl_ui/properties_paint_common.py
@@ -1295,6 +1295,8 @@ def brush_basic_gpencil_paint_settings(layout, context, brush, *, compact=False)
 
 
 def brush_basic_gpencil_sculpt_settings(layout, _context, brush, *, compact=False):
+    if brush is None:
+        return
     gp_settings = brush.gpencil_settings
     if gp_settings is None:
         return
diff --git a/release/scripts/startup/bl_ui/space_view3d.py b/release/scripts/startup/bl_ui/space_view3d.py
index a8624030564..625ba6016c6 100644
--- a/release/scripts/startup/bl_ui/space_view3d.py
+++ b/release/scripts/startup/bl_ui/space_view3d.py
@@ -97,7 +97,7 @@ class VIEW3D_HT_tool_header(Header):
         elif tool_mode == 'PAINT_GPENCIL':
             if is_valid_context:
                 brush = context.tool_settings.gpencil_paint.brush
-                if brush.gpencil_tool != 'ERASE':
+                if brush and brush.gpencil_tool != 'ERASE':
                     if brush.gpencil_tool != 'TINT':
                         layout.popover("VIEW3D_PT_tools_grease_pencil_brush_advanced")
 
@@ -108,10 +108,11 @@ class VIEW3D_HT_tool_header(Header):
         elif tool_mode == 'SCULPT_GPENCIL':
             if is_valid_context:
                 brush = context.tool_settings.gpencil_sculpt_paint.brush
-                tool = brush.gpencil_sculpt_tool
-                if tool in {'SMOOTH', 'RANDOMIZE'}:
-                    layout.popover("VIEW3D_PT_tools_grease_pencil_sculpt_options")
-                layout.popover("VIEW3D_PT_tools_grease_pencil_sculpt_appearance")
+                if brush:
+                    tool = brush.gpencil_sculpt_tool
+                    if tool in {'SMOOTH', 'RANDOMIZE'}:
+                        layout.popover("VIEW3D_PT_tools_grease_pencil_sculpt_options")
+                    layout.popover("VIEW3D_PT_tools_grease_pencil_sculpt_appearance")
         elif tool_mode == 'WEIGHT_GPENCIL':
             if is_valid_context:
                 layout.popover("VIEW3D_PT_tools_grease_pencil_weight_appearance")
diff --git a/source/blender/editors/sculpt_paint/paint_ops.c b/source/blender/editors/sculpt_paint/paint_ops.c
index 926a564184a..0f2b02ed3ab 100644
--- a/source/blender/editors/sculpt_paint/paint_ops.c
+++ b/source/blender/editors/sculpt_paint/paint_ops.c
@@ -82,11 +82,86 @@ static void BRUSH_OT_add(wmOperatorType *ot)
   ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;
 }
 
+static eGPBrush_Presets gpencil_get_brush_preset_from_tool(bToolRef *tool,
+                                                           enum eContextObjectMode mode)
+{
+  switch (mode) {
+    case CTX_MODE_PAINT_GPENCIL: {
+      if (STREQ(tool->runtime->data_block, "DRAW")) {
+        return GP_BRUSH_PRESET_PENCIL;
+      }
+      else if (STREQ(tool->runtime->data_block, "FILL")) {
+        return GP_BRUSH_PRESET_FILL_AREA;
+      }
+      else if (STREQ(tool->runtime->data_block, "ERASE")) {
+        return GP_BRUSH_PRESET_ERASER_SOFT;
+      }
+      else if (STREQ(tool->runtime->data_block, "TINT")) {
+        return GP_BRUSH_PRESET_TINT;
+      }
+      break;
+    }
+    case CTX_MODE_SCULPT_GPENCIL: {
+      if (STREQ(tool->runtime->data_block, "SMOOTH")) {
+        return GP_BRUSH_PRESET_SMOOTH_STROKE;
+      }
+      else if (STREQ(tool->runtime->data_block, "STRENGTH")) {
+        return GP_BRUSH_PRESET_STRENGTH_STROKE;
+      }
+      else if (STREQ(tool->runtime->data_block, "THICKNESS")) {
+        return GP_BRUSH_PRESET_THICKNESS_STROKE;
+      }
+      else if (STREQ(tool->runtime->data_block, "GRAB")) {
+        return GP_BRUSH_PRESET_GRAB_STROKE;
+      }
+      else if (STREQ(tool->runtime->data_block, "PUSH")) {
+        return GP_BRUSH_PRESET_PUSH_STROKE;
+      }
+      else if (STREQ(tool->runtime->data_block, "TWIST")) {
+        return GP_BRUSH_PRESET_TWIST_STROKE;
+      }
+      else if (STREQ(tool->runtime->data_block, "PINCH")) {
+        return GP_BRUSH_PRESET_PINCH_STROKE;
+      }
+      else if (STREQ(tool->runtime->data_block, "RANDOMIZE")) {
+        return GP_BRUSH_PRESET_RANDOMIZE_STROKE;
+      }
+      else if (STREQ(tool->runtime->data_block, "CLONE")) {
+        return GP_BRUSH_PRESET_CLONE_STROKE;
+      }
+      break;
+    }
+    case CTX_MODE_WEIGHT_GPENCIL: {
+      return GP_BRUSH_PRESET_DRAW_WEIGHT;
+    }
+    case CTX_MODE_VERTEX_GPENCIL: {
+      if (STREQ(tool->runtime->data_block, "DRAW")) {
+        return GP_BRUSH_PRESET_VERTEX_DRAW;
+      }
+      else if (STREQ(tool->runtime->data_block, "BLUR")) {
+        return GP_BRUSH_PRESET_VERTEX_BLUR;
+      }
+      else if (STREQ(tool->runtime->data_block, "AVERAGE")) {
+        return GP_BRUSH_PRESET_VERTEX_AVERAGE;
+      }
+      else if (STREQ(tool->runtime->data_block, "SMEAR")) {
+        return GP_BRUSH_PRESET_VERTEX_SMEAR;
+      }
+      else if (STREQ(tool->runtime->data_block, "REPLACE")) {
+        return GP_BRUSH_PRESET_VERTEX_REPLACE;
+      }
+      break;
+    }
+    default:
+      return GP_BRUSH_PRESET_UNKNOWN;
+      break;
+  }
+  return GP_BRUSH_PRESET_UNKNOWN;
+}
+
 static int brush_add_gpencil_exec(bContext *C, wmOperator *UNUSED(op))
 {
-  // int type = RNA_enum_get(op->ptr, "type");
-  ToolSettings *ts = CTX_data_tool_settings(C);
-  Paint *paint = &ts->gp_paint->paint;
+  Paint *paint = BKE_paint_get_active_from_context(C);
   Brush *br = BKE_paint_brush(paint);
   Main *bmain = CTX_data_main(C);
 
@@ -94,15 +169,70 @@ static int brush_add_gpencil_exec(bContext *C, wmOperator *UNUSED(op))
     br = (Brush *)BKE_id_copy(bmain, &br->id);
   }
   else {
-    br = BKE_brush_add(bmain, "Brush", OB_MODE_PAINT_GPENCIL);
+    /* Get the active tool to determine what type of brush is active. */
+    bScreen *screen = CTX_wm_screen(C);
+    if (screen == NULL) {
+      return OPERATOR_CANCELLED;
+    }
 
-    /* Init grease pencil specific data. */
-    BKE_brush_init_gpencil_settings(br);
-  }
+    bToolRef *tool = NULL;
+    LISTBASE_FOREACH (ScrArea *, area, &screen->areabase) {
+      if (area->spacetype == SPACE_VIEW3D) {
+        /* Check the current tool is a brush. */
+        bToolRef *tref = area->runtime.tool;
+        if (tref && tref->runtime && tref->runtime->data_block[0]) {
+          tool = tref;
+          break;
+        }
+      }
+    }
 
-  id_us_min(&br->id); /* fake user only */
+    if (tool == NULL) {
+      return OPERATOR_CANCELLED;
+    }
 
-  BKE_paint_brush_set(paint, br);
+    /* Get Brush mode base on context mode. */
+    const enum eContextObjectMode mode = CTX_data_mode_enum(C);
+    eObjectMode obmode = OB_MODE_PAINT_GPENCIL;
+    switch (mode) {
+      case CTX_MODE_PAINT_GPENCIL:
+        obmode = OB_MODE_PAINT_GPENCIL;
+        break;
+      case CTX_MODE_SCULPT_GPENCIL:
+        obmode = OB_MODE_SCULPT_GPENCIL;
+        break;
+      case CTX_MODE_WEIGHT_GPENCIL:
+        obmode = OB_MODE_WEIGHT_GPENCIL;
+        break;
+      case CTX_MODE_VERTEX_GPENCIL:
+        obmode = OB_MODE_VERTEX_GPENCIL;
+        break;
+      default:
+        return OPERATOR_CANCELLED;
+        break;
+    }
+
+    /* Get brush preset using the actual tool. */
+    eGPBrush_Presets preset = gpencil_get_brush_preset_from_tool(tool, mode);
+
+    /* Capitalize Brush name first letter using the tool name. */
+    char name[64];
+    BLI_strncpy(name, tool->runtime->data_block, sizeof(name));
+    BLI_str_tolower_ascii(name, sizeof(name));
+    name[0] = BLI_toupper_ascii(name[0]);
+
+    /* Create the brush and assign default values. */
+    br = BKE_brush_add(bmain, name, obmode);
+    if (br) {
+      BKE_brush_init_gpencil_settings(br);
+      BKE_gpencil_brush_preset_set(bmain, br, preset);
+    }
+  }
+
+  if (br) {
+    id_us_min(&br->id); /* fake user only */
+    BKE_paint_brush_set(paint, br);
+  }
 
   return OPERATOR_FINISHED;
 }