From 258e60f1b76fad21aec9dd412b451da2aa554d7c Mon Sep 17 00:00:00 2001
From: Ell <ell_se@yahoo.com>
Date: Sun, 28 Jan 2018 15:21:33 -0500
Subject: [PATCH] app: use gimp_transform_polygon() in GimpCanvasBoundary

... so that clipping is done properly.
---
 app/display/gimpcanvasboundary.c | 65 +++++++++++++++++++++-----------
 1 file changed, 43 insertions(+), 22 deletions(-)

diff --git a/app/display/gimpcanvasboundary.c b/app/display/gimpcanvasboundary.c
index 272308a16b..28b1da992e 100644
--- a/app/display/gimpcanvasboundary.c
+++ b/app/display/gimpcanvasboundary.c
@@ -29,6 +29,7 @@
 #include "display-types.h"
 
 #include "core/gimp-cairo.h"
+#include "core/gimp-transform-utils.h"
 #include "core/gimpboundary.h"
 #include "core/gimpparamspecs.h"
 
@@ -219,35 +220,44 @@ gimp_canvas_boundary_get_property (GObject    *object,
 
 static void
 gimp_canvas_boundary_transform (GimpCanvasItem *item,
-                                GimpSegment    *segs)
+                                GimpSegment    *segs,
+                                gint           *n_segs)
 {
   GimpCanvasBoundaryPrivate *private = GET_PRIVATE (item);
   gint                       i;
 
   if (private->transform)
     {
+      gint n = 0;
+
       for (i = 0; i < private->n_segs; i++)
         {
-          gdouble tx, ty;
+          GimpVector2 vertices[2];
+          GimpVector2 t_vertices[2];
+          gint        n_t_vertices;
 
-          gimp_matrix3_transform_point (private->transform,
-                                        private->segs[i].x1,
-                                        private->segs[i].y1,
-                                        &tx, &ty);
-          gimp_canvas_item_transform_xy (item,
-                                         tx + private->offset_x,
-                                         ty + private->offset_y,
-                                         &segs[i].x1, &segs[i].y1);
+          vertices[0] = (GimpVector2) { private->segs[i].x1, private->segs[i].y1 };
+          vertices[1] = (GimpVector2) { private->segs[i].x2, private->segs[i].y2 };
 
-          gimp_matrix3_transform_point (private->transform,
-                                        private->segs[i].x2,
-                                        private->segs[i].y2,
-                                        &tx, &ty);
-          gimp_canvas_item_transform_xy (item,
-                                         tx + private->offset_x,
-                                         ty + private->offset_y,
-                                         &segs[i].x2, &segs[i].y2);
+          gimp_transform_polygon (private->transform, vertices, 2, FALSE,
+                                  t_vertices, &n_t_vertices);
+
+          if (n_t_vertices == 2)
+            {
+              gimp_canvas_item_transform_xy (item,
+                                             t_vertices[0].x + private->offset_x,
+                                             t_vertices[0].y + private->offset_y,
+                                             &segs[n].x1, &segs[n].y1);
+              gimp_canvas_item_transform_xy (item,
+                                             t_vertices[1].x + private->offset_x,
+                                             t_vertices[1].y + private->offset_y,
+                                             &segs[n].x2, &segs[n].y2);
+
+              n++;
+            }
         }
+
+      *n_segs = n;
     }
   else
     {
@@ -284,6 +294,8 @@ gimp_canvas_boundary_transform (GimpCanvasItem *item,
                 }
             }
         }
+
+      *n_segs = private->n_segs;
     }
 }
 
@@ -293,12 +305,13 @@ gimp_canvas_boundary_draw (GimpCanvasItem *item,
 {
   GimpCanvasBoundaryPrivate *private = GET_PRIVATE (item);
   GimpSegment               *segs;
+  gint                       n_segs;
 
   segs = g_new0 (GimpSegment, private->n_segs);
 
-  gimp_canvas_boundary_transform (item, segs);
+  gimp_canvas_boundary_transform (item, segs, &n_segs);
 
-  gimp_cairo_add_segments (cr, segs, private->n_segs);
+  gimp_cairo_add_segments (cr, segs, n_segs);
 
   _gimp_canvas_item_stroke (item, cr);
 
@@ -311,19 +324,27 @@ gimp_canvas_boundary_get_extents (GimpCanvasItem *item)
   GimpCanvasBoundaryPrivate *private = GET_PRIVATE (item);
   cairo_rectangle_int_t      rectangle;
   GimpSegment               *segs;
+  gint                       n_segs;
   gint                       x1, y1, x2, y2;
   gint                       i;
 
   segs = g_new0 (GimpSegment, private->n_segs);
 
-  gimp_canvas_boundary_transform (item, segs);
+  gimp_canvas_boundary_transform (item, segs, &n_segs);
+
+  if (n_segs == 0)
+    {
+      g_free (segs);
+
+      return cairo_region_create ();
+    }
 
   x1 = MIN (segs[0].x1, segs[0].x2);
   y1 = MIN (segs[0].y1, segs[0].y2);
   x2 = MAX (segs[0].x1, segs[0].x2);
   y2 = MAX (segs[0].y1, segs[0].y2);
 
-  for (i = 1; i < private->n_segs; i++)
+  for (i = 1; i < n_segs; i++)
     {
       gint x3 = MIN (segs[i].x1, segs[i].x2);
       gint y3 = MIN (segs[i].y1, segs[i].y2);