[gimp] Bug 756678 - Layer opacities change upon saving and reopening an xcf file

[Michael Natterer <mitch src gnome org>]

commit a2ad257711a312150f923057462b0ce70dbb3d20
Author: Michael Natterer <mitch gimp org>
Date:   Fri Oct 16 21:59:11 2015 +0200

    Bug 756678 - Layer opacities change upon saving and reopening an xcf file
    
    Add new XCF property FLOAT_OPACITY and always save both the old 8-bit
    and the new float opacity of layers and channels. Float opacity is
    saved after the 8-bit one so when loading, it overwrites the limited
    8-bit value with the proper precision. Do not increase the XCF version
    number because old GIMP versions will simply skip the unknown
    FLOAT_OPACITY and keep using the 8-bit value.

 app/xcf/xcf-load.c    |   18 ++++++++++++++++++
 app/xcf/xcf-private.h |    3 ++-
 app/xcf/xcf-save.c    |   17 +++++++++++++++++
 3 files changed, 37 insertions(+), 1 deletions(-)
---
diff --git a/app/xcf/xcf-load.c b/app/xcf/xcf-load.c
index b1c2322..72e45ed 100644
--- a/app/xcf/xcf-load.c
+++ b/app/xcf/xcf-load.c
@@ -981,6 +981,15 @@ xcf_load_layer_props (XcfInfo    *info,
           }
           break;
 
+        case PROP_FLOAT_OPACITY:
+          {
+            gfloat opacity;
+
+            info->cp += xcf_read_float (info->input, &opacity, 1);
+            gimp_layer_set_opacity (*layer, opacity, FALSE);
+          }
+          break;
+
         case PROP_VISIBLE:
           {
             gboolean visible;
@@ -1227,6 +1236,15 @@ xcf_load_channel_props (XcfInfo      *info,
           }
           break;
 
+        case PROP_FLOAT_OPACITY:
+          {
+            gfloat opacity;
+
+            info->cp += xcf_read_float (info->input, &opacity, 1);
+            gimp_channel_set_opacity (*channel, opacity, FALSE);
+          }
+          break;
+
         case PROP_VISIBLE:
           {
             gboolean visible;
diff --git a/app/xcf/xcf-private.h b/app/xcf/xcf-private.h
index 3c3edf6..5653339 100644
--- a/app/xcf/xcf-private.h
+++ b/app/xcf/xcf-private.h
@@ -56,7 +56,8 @@ typedef enum
   PROP_GROUP_ITEM         = 29,
   PROP_ITEM_PATH          = 30,
   PROP_GROUP_ITEM_FLAGS   = 31,
-  PROP_LOCK_POSITION      = 32
+  PROP_LOCK_POSITION      = 32,
+  PROP_FLOAT_OPACITY      = 33
 } PropType;
 
 typedef enum
diff --git a/app/xcf/xcf-save.c b/app/xcf/xcf-save.c
index 514dc13..89460e1 100644
--- a/app/xcf/xcf-save.c
+++ b/app/xcf/xcf-save.c
@@ -491,6 +491,8 @@ xcf_save_layer_props (XcfInfo    *info,
 
   xcf_check_error (xcf_save_prop (info, image, PROP_OPACITY, error,
                                   gimp_layer_get_opacity (layer)));
+  xcf_check_error (xcf_save_prop (info, image, PROP_FLOAT_OPACITY, error,
+                                  gimp_layer_get_opacity (layer)));
   xcf_check_error (xcf_save_prop (info, image, PROP_VISIBLE, error,
                                   gimp_item_get_visible (GIMP_ITEM (layer))));
   xcf_check_error (xcf_save_prop (info, image, PROP_LINKED, error,
@@ -585,6 +587,8 @@ xcf_save_channel_props (XcfInfo      *info,
 
   xcf_check_error (xcf_save_prop (info, image, PROP_OPACITY, error,
                                   gimp_channel_get_opacity (channel)));
+  xcf_check_error (xcf_save_prop (info, image, PROP_FLOAT_OPACITY, error,
+                                  gimp_channel_get_opacity (channel)));
   xcf_check_error (xcf_save_prop (info, image, PROP_VISIBLE, error,
                                   gimp_item_get_visible (GIMP_ITEM (channel))));
   xcf_check_error (xcf_save_prop (info, image, PROP_LINKED, error,
@@ -695,6 +699,19 @@ xcf_save_prop (XcfInfo    *info,
       }
       break;
 
+    case PROP_FLOAT_OPACITY:
+      {
+        gfloat opacity;
+
+        opacity = va_arg (args, gdouble);
+        size = 4;
+
+        xcf_write_prop_type_check_error (info, prop_type);
+        xcf_write_int32_check_error (info, &size, 1);
+        xcf_write_float_check_error (info, &opacity, 1);
+      }
+      break;
+
     case PROP_MODE:
       {
         gint32 mode;