wxGUI/gui_core: fix change opacity level dialog min/max size (#2067)

Widgets expand horizontally.

gui/wxpython/gui_core/dialogs.py

@@ -1802,15 +1802,16 @@ class SetOpacityDialog(wx.Dialog):
         sizer = wx.BoxSizer(wx.VERTICAL)
 
         box = wx.GridBagSizer(vgap=5, hgap=5)
+        box.AddGrowableCol(0)
         self.value = Slider(
             panel,
             id=wx.ID_ANY,
             value=int(self.opacity * 100),
             style=wx.SL_HORIZONTAL | wx.SL_AUTOTICKS | wx.SL_TOP | wx.SL_LABELS,
-            minValue=0, maxValue=100, size=(350, -1))
+            minValue=0, maxValue=100)
 
         box.Add(self.value,
-                flag=wx.ALIGN_CENTRE, pos=(0, 0), span=(1, 2))
+                flag=wx.EXPAND, pos=(0, 0), span=(1, 2))
         box.Add(StaticText(parent=panel, id=wx.ID_ANY,
                            label=_("transparent")),
                 pos=(1, 0))
@@ -1848,7 +1849,10 @@ class SetOpacityDialog(wx.Dialog):
         panel.SetSizer(sizer)
         sizer.Fit(panel)
 
-        self.SetSize(self.GetBestSize())
+        w, h = self.GetBestSize()
+        self.SetSize(wx.Size(w, h))
+        self.SetMaxSize(wx.Size(-1, h))
+        self.SetMinSize(wx.Size(w, h))
 
         self.Layout()