Request frame duration when opening sequences

data/strings/en.ini

@@ -1033,6 +1033,7 @@ double_high = Double-high Pixels (1:2)
 title = Notice
 description = Do you want to load the following files as an animation?
 repeat = Do the same for other files
+duration = Duration
 agree = &Agree
 skip = &Skip
 

data/widgets/open_sequence.xml

@@ -8,6 +8,10 @@
     <view expansive="true" id="view" minwidth="128" minheight="64">
       <listbox id="files" multiselect="true" />
     </view>
+    <hbox>
+      <label text="@.duration" />
+      <expr text="0" id="duration" suffix="ms" />
+    </hbox>
     <separator horizontal="true" />
     <check id="repeat" text="@.repeat" />
     <check id="dont_show" text="@general.dont_show" />

src/app/file/file.cpp

@@ -385,6 +385,10 @@ FileOp* FileOp::createLoadDocumentOperation(Context* context,
               window.files()->getSelectedChild() != nullptr);
           });
 
+        window.duration()->setTextf("%d", fop->m_seq.duration);
+        window.duration()->Change.connect(
+          [&]() { fop->m_seq.duration = window.duration()->textInt(); });
+
         window.openWindowInForeground();
 
         // Don't show this alert again.
@@ -832,6 +836,8 @@ void FileOp::operate(IFileOpProgress* progress)
 #endif
         }
 
+        m_document->sprite()->setFrameDuration(frame, m_seq.duration);
+
         ++frame;
         m_seq.progress_offset += m_seq.progress_fraction;
       }
@@ -1395,6 +1401,7 @@ FileOp::FileOp(FileOpType type,
   m_seq.frame = frame_t(0);
   m_seq.layer = nullptr;
   m_seq.last_cel = nullptr;
+  m_seq.duration = 100;
   m_seq.flags = 0;
 }
 

src/app/file/file.h

@@ -311,6 +311,7 @@ namespace app {
       bool has_alpha;
       LayerImage* layer;
       Cel* last_cel;
+      int duration;
       // Flags after the user choose what to do with the sequence.
       int flags;
     } m_seq;