Fixes #1286 (Dialogue topic list clips with window frame)

The first problem was with the ScrollView skin, which had a full-sized client area. Since the scrollbar starts out visible, MyGUI expects the client area to be smaller to accomodate for the scrollbar width. As a result, the starting canvas size becomes bigger than the view size.
Another bug was with the MWList code: reducing the canvas size for the scrollbar is not needed, since MyGUI is already doing that, and attempting to do it manually interferes with the view offset.

apps/openmw/mwgui/list.cpp

@@ -48,7 +48,7 @@ namespace MWGui
 
         void MWList::redraw(bool scrollbarShown)
         {
-            const int _scrollBarWidth = 24; // fetch this from skin?
+            const int _scrollBarWidth = 20; // fetch this from skin?
             const int scrollBarWidth = scrollbarShown ? _scrollBarWidth : 0;
             const int spacing = 3;
             size_t scrollbarPosition = mScrollView->getScrollPosition();
@@ -83,7 +83,7 @@ namespace MWGui
                 else
                 {
                     MyGUI::ImageBox* separator = mScrollView->createWidget<MyGUI::ImageBox>("MW_HLine",
-                        MyGUI::IntCoord(2, mItemHeight, mScrollView->getWidth()-4, 18),
+                        MyGUI::IntCoord(2, mItemHeight, mScrollView->getWidth() - scrollBarWidth - 4, 18),
                         MyGUI::Align::Left | MyGUI::Align::Top | MyGUI::Align::HStretch);
                     separator->setNeedMouseFocus(false);
 
@@ -91,7 +91,7 @@ namespace MWGui
                 }
                 ++i;
             }
-            mScrollView->setCanvasSize(mClient->getSize().width + (_scrollBarWidth-scrollBarWidth), std::max(mItemHeight, mClient->getSize().height));
+            mScrollView->setCanvasSize(mClient->getSize().width, std::max(mItemHeight, mClient->getSize().height));
 
             if (!scrollbarShown && mItemHeight > mClient->getSize().height)
                 redraw(true);

files/mygui/openmw_scroll_skin.xml

@@ -3,12 +3,12 @@
 <MyGUI type="Skin">
 
     <Skin name="MW_ScrollView" size="516 516">
-        <Child type="Widget" skin="" offset="0 0 516 516" align="Stretch" name="Client"/>
+        <Child type="Widget" skin="" offset="0 0 502 516" align="Stretch" name="Client"/>
         <Child type="MWScrollBar" skin="MW_VScroll" offset="498 3 14 509" align="Right Top VStretch" name="VScroll"/>
     </Skin>
 
     <Skin name="MW_ScrollViewH" size="516 516">
-        <Child type="Widget" skin="" offset="0 0 516 516" align="Stretch" name="Client"/>
+        <Child type="Widget" skin="" offset="0 0 516 502" align="Stretch" name="Client"/>
         <Child type="MWScrollBar" skin="MW_HScroll" offset="3 498 509 14" align="Left Bottom HStretch" name="HScroll"/>
     </Skin>