From c3e13d5a2b8e9ada467850b4629dc4f228a2b2b8 Mon Sep 17 00:00:00 2001
From: Philipp Oeser <info@graphics-engineer.com>
Date: Fri, 14 May 2021 13:21:10 +0200
Subject: GPencil: fix separate points/strokes freezing with empty selection

Code would still create an object (without setting up materials), code
for removing unused material slots would then freeze.

Now return/cancel early in case of empty selection.

This came up in T88269 [which is still not fully fixed, transforming
curve edit points clear their GP_STROKE_SELECT flag which now results in
the early exit, should be looked at separately]

Maniphest Tasks: T88269

Differential Revision: https://developer.blender.org/D11252
---
 source/blender/editors/gpencil/gpencil_edit.c  | 21 +++++++++++++++--
 source/blender/editors/gpencil/gpencil_utils.c | 32 ++++++++++++++++++++++++++
 2 files changed, 51 insertions(+), 2 deletions(-)

(limited to 'source/blender/editors/gpencil')

diff --git a/source/blender/editors/gpencil/gpencil_edit.c b/source/blender/editors/gpencil/gpencil_edit.c
index d388e11dc8c..66d50e2fd12 100644
--- a/source/blender/editors/gpencil/gpencil_edit.c
+++ b/source/blender/editors/gpencil/gpencil_edit.c
@@ -4520,6 +4520,9 @@ static int gpencil_stroke_separate_exec(bContext *C, wmOperator *op)
 
   eGP_SeparateModes mode = RNA_enum_get(op->ptr, "mode");
 
+  const bool is_multiedit = (bool)GPENCIL_MULTIEDIT_SESSIONS_ON(gpd_src);
+  const bool is_curve_edit = (bool)GPENCIL_CURVE_EDIT_SESSIONS_ON(gpd_src);
+
   /* sanity checks */
   if (ELEM(NULL, gpd_src)) {
     return OPERATOR_CANCELLED;
@@ -4530,8 +4533,22 @@ static int gpencil_stroke_separate_exec(bContext *C, wmOperator *op)
     return OPERATOR_CANCELLED;
   }
 
-  const bool is_multiedit = (bool)GPENCIL_MULTIEDIT_SESSIONS_ON(gpd_src);
-  const bool is_curve_edit = (bool)GPENCIL_CURVE_EDIT_SESSIONS_ON(gpd_src);
+  /* Cancel if nothing selected. */
+  if (ELEM(mode, GP_SEPARATE_POINT, GP_SEPARATE_STROKE)) {
+    bool has_selected = false;
+    CTX_DATA_BEGIN (C, bGPDlayer *, gpl, editable_gpencil_layers) {
+      if (ED_gpencil_layer_has_selected_stroke(gpl, is_multiedit)) {
+        has_selected = true;
+        break;
+      }
+    }
+    CTX_DATA_END;
+
+    if (!has_selected) {
+      BKE_report(op->reports, RPT_ERROR, "Nothing selected");
+      return OPERATOR_CANCELLED;
+    }
+  }
 
   /* Create a new object. */
   /* Take into account user preferences for duplicating actions. */
diff --git a/source/blender/editors/gpencil/gpencil_utils.c b/source/blender/editors/gpencil/gpencil_utils.c
index 8d42024a518..9fba2ce5902 100644
--- a/source/blender/editors/gpencil/gpencil_utils.c
+++ b/source/blender/editors/gpencil/gpencil_utils.c
@@ -542,6 +542,38 @@ bool gpencil_stroke_inside_circle(const float mval[2], int rad, int x0, int y0,
   return false;
 }
 
+/* ******************************************************** */
+/* Selection Validity Testing */
+
+bool ED_gpencil_frame_has_selected_stroke(const bGPDframe *gpf)
+{
+  LISTBASE_FOREACH (bGPDstroke *, gps, &gpf->strokes) {
+    if (gps->flag & GP_STROKE_SELECT) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+bool ED_gpencil_layer_has_selected_stroke(const bGPDlayer *gpl, const bool is_multiedit)
+{
+  bGPDframe *init_gpf = (is_multiedit) ? gpl->frames.first : gpl->actframe;
+  for (bGPDframe *gpf = init_gpf; gpf; gpf = gpf->next) {
+    if ((gpf == gpl->actframe) || ((gpf->flag & GP_FRAME_SELECT) && (is_multiedit))) {
+      if (ED_gpencil_frame_has_selected_stroke(gpf)) {
+        return true;
+      }
+    }
+    /* If not multiedit, exit loop. */
+    if (!is_multiedit) {
+      break;
+    }
+  }
+
+  return false;
+}
+
 /* ******************************************************** */
 /* Stroke Validity Testing */
 
-- 
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