Timeline: add support to move/copy ranges (multiple cels/frames/layers)

- Merge Timeline::STATE_MOVING_LAYER/CEL/FRAME to STATE_MOVING_RANGE.
- Remove celmove.h/cpp and move_cel/copy_cel functions. Now they are
  in the Timeline as dropRange/Cels/Frames/Layers member functions.
- Add DocumentApi::copyFrame/moveCel/copyCel member functions.
- Add timeline_drop_layer_deco and timeline_drop_frame_deco skin parts.
- Move code from DuplicateLayerCommand::onExecute() to new member
  function DocumentApi::duplicateLayer().
- Fix a bug changing Cel's frame number: we weren't updating the Cel
  position properly inside the LayerImage::m_cels collection. Now we use
  LayerImage::moveCel() to change the Cel frame number.
- Other fixes to DocumentApi: Change bgcolor from int to color_t.

data/skins/default/skin.xml

@@ -310,6 +310,8 @@
     <part id="timeline_padding_tr"              x="288" y="12" w1="1" w2="10" w3="1" h1="1" h2="10" h3="1" />
     <part id="timeline_padding_bl"              x="276" y="24" w1="1" w2="10" w3="1" h1="1" h2="10" h3="1" />
     <part id="timeline_padding_br"              x="288" y="24" w1="1" w2="10" w3="1" h1="1" h2="10" h3="1" />
+    <part id="timeline_drop_layer_deco"         x="252" y="127" w1="3" w2="1" w3="3" h1="2" h2="1" h3="2" />
+    <part id="timeline_drop_frame_deco"         x="252" y="120" w1="2" w2="1" w3="2" h1="3" h2="1" h3="3" />
   </parts>
 
   <stylesheet>
@@ -502,6 +504,16 @@
       <background part="colorbar_border_fg" />
     </style>
 
+    <!-- timeline_drop_layer_deco -->
+    <style id="timeline_drop_layer_deco">
+      <background part="timeline_drop_layer_deco" />
+    </style>
+
+    <!-- timeline_drop_frame_deco -->
+    <style id="timeline_drop_frame_deco">
+      <background part="timeline_drop_frame_deco" />
+    </style>
+
   </stylesheet>
 
 </skin>

src/app/CMakeLists.txt

@@ -227,7 +227,6 @@ add_library(app-lib
   undoers/set_total_frames.cpp
   util/autocrop.cpp
   util/boundary.cpp
-  util/celmove.cpp
   util/clipboard.cpp
   util/expand_cel_canvas.cpp
   util/filetoks.cpp

src/app/commands/cmd_copy_cel.cpp

@@ -25,7 +25,6 @@
 #include "app/context_access.h"
 #include "app/ui/timeline.h"
 #include "app/ui/main_window.h"
-#include "app/util/celmove.h"
 #include "ui/base.h"
 
 namespace app {
@@ -54,8 +53,7 @@ bool CopyCelCommand::onEnabled(Context* context)
 
 void CopyCelCommand::onExecute(Context* context)
 {
-  ContextWriter writer(context);
-  copy_cel(writer);
+  App::instance()->getMainWindow()->getTimeline()->dropRange(Timeline::kCopy);
 }
 
 Command* CommandFactory::createCopyCelCommand()

src/app/commands/cmd_duplicate_layer.cpp

@@ -66,33 +66,14 @@ void DuplicateLayerCommand::onExecute(Context* context)
 {
   ContextWriter writer(context);
   Document* document = writer.document();
-  Sprite* sprite = writer.sprite();
-  UndoTransaction undo(writer.context(), "Layer Duplication");
-  LayerImage* sourceLayer = static_cast<LayerImage*>(writer.layer());
-
-  // Create a new layer
-  base::UniquePtr<LayerImage> newLayerPtr(new LayerImage(sprite));
-
-  // Disable undo because the layer content is added as a whole with
-  // AddLayer() undoer.
-  document->getUndo()->setEnabled(false);
-
-  // Copy the layer content (cels + images)
-  document->copyLayerContent(sourceLayer, document, newLayerPtr);
-
-  // Restore enabled status.
-  document->getUndo()->setEnabled(undo.isEnabled());
-
-  // Copy the layer name
-  newLayerPtr->setName(newLayerPtr->getName() + " Copy");
-
-  // Add the new layer in the sprite.
-  document->getApi().addLayer(sourceLayer->getParent(), newLayerPtr, sourceLayer);
-
-  // Release the pointer as it is owned by the sprite now
-  Layer* newLayer = newLayerPtr.release();
-
-  undo.commit();
+  DocumentApi api = document->getApi();
+
+  {
+    UndoTransaction undo(writer.context(), "Layer Duplication");
+    LayerImage* sourceLayer = static_cast<LayerImage*>(writer.layer());
+    api.duplicateLayer(sourceLayer, sourceLayer);
+    undo.commit();
+  }
 
   update_screen_for_document(document);
 }

src/app/commands/cmd_move_cel.cpp

@@ -25,7 +25,6 @@
 #include "app/context_access.h"
 #include "app/ui/main_window.h"
 #include "app/ui/timeline.h"
-#include "app/util/celmove.h"
 #include "ui/base.h"
 
 namespace app {
@@ -54,8 +53,7 @@ bool MoveCelCommand::onEnabled(Context* context)
 
 void MoveCelCommand::onExecute(Context* context)
 {
-  ContextWriter writer(context);
-  move_cel(writer);
+  App::instance()->getMainWindow()->getTimeline()->dropRange(Timeline::kMove);
 }
 
 Command* CommandFactory::createMoveCelCommand()

src/app/document.cpp

@@ -360,8 +360,6 @@ void Document::resetTransformation()
 
 void Document::copyLayerContent(const Layer* sourceLayer0, Document* destDoc, Layer* destLayer0) const
 {
-  DocumentUndo* undo = destDoc->getUndo();
-
   // Copy the layer name
   destLayer0->setName(sourceLayer0->getName());
 
@@ -386,12 +384,6 @@ void Document::copyLayerContent(const Layer* sourceLayer0, Document* destDoc, La
       Image* newImage = Image::createCopy(sourceImage);
       newCel->setImage(destLayer->getSprite()->getStock()->addImage(newImage));
 
-      if (undo->isEnabled()) {
-        undo->pushUndoer(new undoers::AddImage(undo->getObjects(),
-            destLayer->getSprite()->getStock(),
-            newCel->getImage()));
-      }
-
       destLayer->addCel(newCel);
       newCel.release();
     }
@@ -422,9 +414,14 @@ void Document::copyLayerContent(const Layer* sourceLayer0, Document* destDoc, La
       ASSERT(destChild != NULL);
 
       // Add the new layer in the sprite.
-      destDoc->getApi().addLayer(destLayer,
-                                 destChild.release(),
-                                 destLayer->getLastLayer());
+
+      Layer* newLayer = destChild.release();
+      Layer* afterThis = destLayer->getLastLayer();
+
+      destLayer->addLayer(newLayer);
+      destChild.release();
+
+      destLayer->stackLayer(newLayer, afterThis);
     }
   }
   else  {
@@ -461,14 +458,8 @@ Document* Document::duplicate(DuplicateType type) const
   switch (type) {
 
     case DuplicateExactCopy:
-      // Disable the undo
-      documentCopy->getUndo()->setEnabled(false);
-
       // Copy the layer folder
       copyLayerContent(getSprite()->getFolder(), documentCopy, spriteCopy->getFolder());
-
-      // Re-enable the undo
-      documentCopy->getUndo()->setEnabled(true);
       break;
 
     case DuplicateWithFlattenLayers: