add limit_width and limit_height virtual constraints

enaml/qt/qt_constraints_widget.py

@@ -77,11 +77,15 @@ def _default_size_hint_cns(self):
                     cns.append((d.width == width_hint) | d.hug_width)
                 if d.resist_width != 'ignore':
                     cns.append((d.width >= width_hint) | d.resist_width)
+                if d.limit_width != 'ignore':
+                    cns.append((d.width <= width_hint) | d.limit_width)
             if height_hint >= 0:
                 if d.hug_height != 'ignore':
                     cns.append((d.height == height_hint) | d.hug_height)
                 if d.resist_height != 'ignore':
                     cns.append((d.height >= height_hint) | d.resist_height)
+                if d.limit_height != 'ignore':
+                    cns.append((d.height <= height_hint) | d.limit_height)
         return cns
 
     #--------------------------------------------------------------------------

enaml/qt/qt_container.py

@@ -74,6 +74,22 @@ def hard_constraints(d):
     return [d.left >= 0, d.top >= 0, d.width >= 0, d.height >= 0]
 
 
+def can_expand_in_width(d):
+    """ Get whether a declarative container can expand in width.
+
+    """
+    expand = ('ignore', 'weak')
+    return d.hug_width in expand and d.limit_width in expand
+
+
+def can_expand_in_height(d):
+    """ Get whether a declarative container can expand in height.
+
+    """
+    expand = ('ignore', 'weak')
+    return d.hug_height in expand and d.limit_height in expand
+
+
 class QtContainer(QtFrame, ProxyContainer):
     """ A Qt implementation of an Enaml ProxyContainer.
 
@@ -574,14 +590,15 @@ def compute_max_size(self):
 
         """
         d = self.declaration
-        expanding = ('ignore', 'weak')
-        if d.hug_width in expanding and d.hug_height in expanding:
+        expand_w = can_expand_in_width(d)
+        expand_h = can_expand_in_height(d)
+        if expand_w and expand_h:
             return QSize(16777215, 16777215)
         if self._owns_layout and self._layout_manager is not None:
             w, h = self._layout_manager.get_max_size(d.width, d.height)
-            if w < 0 or d.hug_width in expanding:
+            if w < 0 or expand_w:
                 w = 16777215
-            if h < 0 or d.hug_height in expanding:
+            if h < 0 or expand_h:
                 h = 16777215
             return QSize(w, h)
         return QSize(16777215, 16777215)

enaml/widgets/constraints_widget.py

@@ -115,27 +115,53 @@ def _default_h_center(self):
         return self.left + self.width / 2.0
 
     #: How strongly a component hugs it's width hint. Valid strengths
-    #: are 'weak', 'medium', 'strong', 'required' and 'ignore'. Default
-    #: is 'strong'. This can be overridden on a per-control basis to
-    #: specify a logical default for the given control.
+    #: are 'weak', 'medium', 'strong', 'required' and 'ignore'. The
+    #: default is 'strong'. This can be overridden on a per-control
+    #: basis to specify a logical default for the given control. This
+    #: is equivalent to the following constraint:
+    #:     (width == hint) | hug_width
     hug_width = d_(PolicyEnum('strong'))
 
     #: How strongly a component hugs it's height hint. Valid strengths
-    #: are 'weak', 'medium', 'strong', 'required' and 'ignore'. Default
-    #: is 'strong'. This can be overridden on a per-control basis to
-    #: specify a logical default for the given control.
+    #: are 'weak', 'medium', 'strong', 'required' and 'ignore'. The
+    #: default is 'strong'. This can be overridden on a per-control
+    #: basis to specify a logical default for the given control. This
+    #: is equivalent to the following constraint:
+    #:     (height == hint) | hug_height
     hug_height = d_(PolicyEnum('strong'))
 
-    #: How strongly a component resists clipping its contents. Valid
+    #: How strongly a component resists clipping its width hint. Valid
     #: strengths are 'weak', 'medium', 'strong', 'required' and 'ignore'.
-    #: The default is 'strong' for width.
+    #: The default is 'strong'. This can be overridden on a per-control
+    #: basis to specify a logical default for the given control. This
+    #: is equivalent to the following constraint:
+    #:     (width >= hint) | resist_width
     resist_width = d_(PolicyEnum('strong'))
 
-    #: How strongly a component resists clipping its contents. Valid
+    #: How strongly a component resists clipping its height hint. Valid
     #: strengths are 'weak', 'medium', 'strong', 'required' and 'ignore'.
-    #: The default is 'strong' for height.
+    #: The default is 'strong'. This can be overridden on a per-control
+    #: basis to specify a logical default for the given control. This
+    #: is equivalent to the following constraint:
+    #:     (height >= hint) | resist_height
     resist_height = d_(PolicyEnum('strong'))
 
+    #: How strongly a component resists expanding its width hint. Valid
+    #: strengths are 'weak', 'medium', 'strong', 'required' and 'ignore'.
+    #: The default is 'ignore'. This can be overridden on a per-control
+    #: basis to specify a logical default for the given control. This
+    #: is equivalent to the following constraint:
+    #:     (width <= hint) | limit_width
+    limit_width = d_(PolicyEnum('ignore'))
+
+    #: How strongly a component resists expanding its height hint. Valid
+    #: strengths are 'weak', 'medium', 'strong', 'required' and 'ignore'.
+    #: The default is 'strong'. This can be overridden on a per-control
+    #: basis to specify a logical default for the given control. This
+    #: is equivalent to the following constraint:
+    #:     (height <= hint) | limit_height
+    limit_height = d_(PolicyEnum('ignore'))
+
     #: A reference to the ProxyConstraintsWidget object.
     proxy = Typed(ProxyConstraintsWidget)
 

enaml/wx/wx_constraints_widget.py

@@ -92,11 +92,15 @@ def _default_size_hint_cns(self):
                     cns.append((d.width == width_hint) | d.hug_width)
                 if d.resist_width != 'ignore':
                     cns.append((d.width >= width_hint) | d.resist_width)
+                if d.limit_width != 'ignore':
+                    cns.append((d.width <= width_hint) | d.limit_width)
             if height_hint >= 0:
                 if d.hug_height != 'ignore':
                     cns.append((d.height == height_hint) | d.hug_height)
                 if d.resist_height != 'ignore':
                     cns.append((d.height >= height_hint) | d.resist_height)
+                if d.limit_height != 'ignore':
+                    cns.append((d.height <= height_hint) | d.limit_height)
         return cns
 
     #--------------------------------------------------------------------------

enaml/wx/wx_container.py

@@ -61,6 +61,22 @@ def hard_constraints(d):
     return [d.left >= 0, d.top >= 0, d.width >= 0, d.height >= 0]
 
 
+def can_expand_in_width(d):
+    """ Get whether a declarative container can expand in width.
+
+    """
+    expand = ('ignore', 'weak')
+    return d.hug_width in expand and d.limit_width in expand
+
+
+def can_expand_in_height(d):
+    """ Get whether a declarative container can expand in height.
+
+    """
+    expand = ('ignore', 'weak')
+    return d.hug_height in expand and d.limit_height in expand
+
+
 class WxContainer(WxFrame, ProxyContainer):
     """ A Wx implementation of an Enaml ProxyContainer.
 
@@ -560,14 +576,15 @@ def compute_max_size(self):
 
         """
         d = self.declaration
-        expanding = ('ignore', 'weak')
-        if d.hug_width in expanding and d.hug_height in expanding:
+        expand_w = can_expand_in_width(d)
+        expand_h = can_expand_in_height(d)
+        if expand_w and expand_h:
             return wx.Size(-1, -1)
         if self._owns_layout and self._layout_manager is not None:
             w, h = self._layout_manager.get_max_size(d.width, d.height)
-            if w < 0 or d.hug_width in expanding:
+            if w < 0 or expand_w:
                 w = -1
-            if h < 0 or d.hug_height in expanding:
+            if h < 0 or expand_h:
                 h = -1
             return wx.Size(w, h)
         return wx.Size(-1, -1)