Fix T71995: Texture Paint workspace crash with new scene

Issue likely caused by 8b31f6fb2169.

With this, initializing the toolsystem (e.g. for a new workspace-scene
combination) would skip the entire create->initialize routine for
image/texture painting settings. Reason being that these are not
allocated, unlike other paint settings. So while correctly skipping the
create part, it also skipped the initialization, which was still needed.

This does further changes in related code to avoid NULL pointer
accesses.

1 files changed, 33 insertions, 15 deletions

diff --git a/source/blender/blenkernel/intern/paint.c b/source/blender/blenkernel/intern/paint.c
index e7c20ca4fb2..584f1ab1b0c 100644
--- a/source/blender/blenkernel/intern/paint.c
+++ b/source/blender/blenkernel/intern/paint.c
@@ -152,6 +152,9 @@ bool BKE_paint_ensure_from_paintmode(Scene *sce, ePaintMode mode)
 {
   ToolSettings *ts = sce->toolsettings;
   Paint **paint_ptr = NULL;
+  /* Some paint modes don't store paint settings as pointer, for these this can be set and
+   * referenced by paint_ptr. */
+  Paint *paint_tmp = NULL;
 
   switch (mode) {
     case PAINT_MODE_SCULPT:
@@ -165,6 +168,8 @@ bool BKE_paint_ensure_from_paintmode(Scene *sce, ePaintMode mode)
       break;
     case PAINT_MODE_TEXTURE_2D:
     case PAINT_MODE_TEXTURE_3D:
+      paint_tmp = (Paint *)&ts->imapaint;
+      paint_ptr = &paint_tmp;
       break;
     case PAINT_MODE_SCULPT_UV:
       paint_ptr = (Paint **)&ts->uvsculpt;
@@ -175,7 +180,7 @@ bool BKE_paint_ensure_from_paintmode(Scene *sce, ePaintMode mode)
     case PAINT_MODE_INVALID:
       break;
   }
-  if (paint_ptr && (*paint_ptr == NULL)) {
+  if (paint_ptr) {
     BKE_paint_ensure(ts, paint_ptr);
     return true;
   }
@@ -693,26 +698,36 @@ eObjectMode BKE_paint_object_mode_from_paintmode(ePaintMode mode)
 /**
  * Call when entering each respective paint mode.
  */
-bool BKE_paint_ensure(const ToolSettings *ts, struct Paint **r_paint)
+bool BKE_paint_ensure(ToolSettings *ts, struct Paint **r_paint)
 {
   Paint *paint = NULL;
   if (*r_paint) {
-    /* Note: 'ts->imapaint' is ignored, it's not allocated. */
-    BLI_assert(ELEM(*r_paint,
-                    &ts->gp_paint->paint,
-                    &ts->sculpt->paint,
-                    &ts->vpaint->paint,
-                    &ts->wpaint->paint,
-                    &ts->uvsculpt->paint));
+    /* Tool offset should never be 0 for initialized paint settings, so it's a reliable way to
+     * check if already initialized. */
+    if ((*r_paint)->runtime.tool_offset == 0) {
+      /* Currently only image painting is initialized this way, others have to be allocated. */
+      BLI_assert(ELEM(*r_paint, (Paint *)&ts->imapaint));
 
+      BKE_paint_runtime_init(ts, *r_paint);
+    }
+    else {
+      BLI_assert(ELEM(*r_paint,
+                      /* Cast is annoying, but prevent NULL-pointer access. */
+                      (Paint *)ts->gp_paint,
+                      (Paint *)ts->sculpt,
+                      (Paint *)ts->vpaint,
+                      (Paint *)ts->wpaint,
+                      (Paint *)ts->uvsculpt,
+                      (Paint *)&ts->imapaint));
 #ifdef DEBUG
-    struct Paint paint_test = **r_paint;
-    BKE_paint_runtime_init(ts, *r_paint);
-    /* Swap so debug doesn't hide errors when release fails. */
-    SWAP(Paint, **r_paint, paint_test);
-    BLI_assert(paint_test.runtime.ob_mode == (*r_paint)->runtime.ob_mode);
-    BLI_assert(paint_test.runtime.tool_offset == (*r_paint)->runtime.tool_offset);
+      struct Paint paint_test = **r_paint;
+      BKE_paint_runtime_init(ts, *r_paint);
+      /* Swap so debug doesn't hide errors when release fails. */
+      SWAP(Paint, **r_paint, paint_test);
+      BLI_assert(paint_test.runtime.ob_mode == (*r_paint)->runtime.ob_mode);
+      BLI_assert(paint_test.runtime.tool_offset == (*r_paint)->runtime.tool_offset);
 #endif
+    }
     return true;
   }
 
@@ -738,6 +753,9 @@ bool BKE_paint_ensure(const ToolSettings *ts, struct Paint **r_paint)
     UvSculpt *data = MEM_callocN(sizeof(*data), __func__);
     paint = &data->paint;
   }
+  else if (*r_paint == &ts->imapaint.paint) {
+    paint = &ts->imapaint.paint;
+  }
 
   paint->flags |= PAINT_SHOW_BRUSH;