[gimp] app: improve gimp_eraser_tool_is_alpha_only()

[N/A <ell src gnome org>]

commit 3d9bc964233e8b5ce7a79e7c59d2ff0552bcadd2
Author: Ell <ell_se yahoo com>
Date:   Tue May 8 10:47:31 2018 -0400

    app: improve gimp_eraser_tool_is_alpha_only()
    
    When in anti-erase mode, always return TRUE, since it's only
    effective when the drawable has an alpha channel.
    
    Also, remove an unnecessary #include in gimp_ink_tool.c.

 app/tools/gimperasertool.c |    7 ++++++-
 app/tools/gimpinktool.c    |    2 --
 2 files changed, 6 insertions(+), 3 deletions(-)
---
diff --git a/app/tools/gimperasertool.c b/app/tools/gimperasertool.c
index bfe2cb8..0b3a438 100644
--- a/app/tools/gimperasertool.c
+++ b/app/tools/gimperasertool.c
@@ -143,7 +143,12 @@ static gboolean
 gimp_eraser_tool_is_alpha_only (GimpPaintTool *paint_tool,
                                 GimpDrawable  *drawable)
 {
-  return gimp_drawable_has_alpha (drawable);
+  GimpEraserOptions *options = GIMP_ERASER_TOOL_GET_OPTIONS (paint_tool);
+
+  if (! options->anti_erase)
+    return gimp_drawable_has_alpha (drawable);
+  else
+    return TRUE;
 }
 
 
diff --git a/app/tools/gimpinktool.c b/app/tools/gimpinktool.c
index fa4ee3f..6cbdd71 100644
--- a/app/tools/gimpinktool.c
+++ b/app/tools/gimpinktool.c
@@ -24,8 +24,6 @@
 
 #include "tools-types.h"
 
-#include "core/gimpdrawable.h"
-
 #include "operations/layer-modes/gimp-layer-modes.h"
 
 #include "paint/gimpinkoptions.h"