EMSUSD-1984 collection tab look

- Make tabs be themeable by the Theme class.
- Create a MayaTheme to theme the tab to look right in Maya.
- Make the collection widget theme its tab using the Theme class.
- Only inject Host and Theme once.

lib/mayaUsd/resources/ae/usd-shared-components/src/python/usdSharedComponents/collection/widget.py

@@ -50,7 +50,6 @@ def __init__(
             self._tabWidget = QTabWidget()
             self._tabWidget.setTabBar(NonScrollingTabBar(self._tabWidget))
             self._tabWidget.currentChanged.connect(self.onTabChanged)
-            self._tabWidget.setDocumentMode(True)
 
             self._expressionWidget = ExpressionWidget(self._collData, self._tabWidget)
             self._tabWidget.addTab(self._includeExcludeWidget, QIcon(), "Include/Exclude")
@@ -60,8 +59,7 @@ def __init__(
             self._includeExcludeWidget.setContentsMargins(0, offset, 0, 0)
             self._expressionWidget.setContentsMargins(0, offset, 0, 0)
 
-            self._tabWidget.tabBar().setExpanding(True)
-            self._tabWidget.tabBar().setCursor(Qt.ArrowCursor)
+            Theme.instance().themeTab(self._tabWidget)
             mainLayout.addWidget(self._tabWidget)
         else:
             mainLayout.addWidget(self._includeExcludeWidget)

lib/mayaUsd/resources/ae/usd-shared-components/src/python/usdSharedComponents/common/theme.py

@@ -2,12 +2,12 @@
     from PySide6 import QtSvg
     from PySide6.QtCore import QRect, Qt  # type: ignore
     from PySide6.QtGui import QImage, QPixmap, QPalette, QPainter, QColor, QPen, QIcon  # type: ignore
-    from PySide6.QtWidgets import QWidget  # type: ignore
+    from PySide6.QtWidgets import QWidget, QTabWidget  # type: ignore
 except:
     from PySide2 import QtSvg # type: ignore
     from PySide2.QtCore import QRect, Qt  # type: ignore
     from PySide2.QtGui import QImage, QPixmap, QPalette, QPainter, QColor, QPen, QIcon  # type: ignore
-    from PySide2.QtWidgets import QWidget  # type: ignore
+    from PySide2.QtWidgets import QWidget, QTabWidget  # type: ignore
 
 from enum import Flag, auto
 from typing import Union
@@ -102,6 +102,9 @@ def themedIcon(self, name: str, theme: str) -> QIcon:
                 result.addPixmap(pixmap)
 
         return result
+
+    def themeTab(self, tab: QTabWidget):
+        tab.tabBar().setCursor(Qt.ArrowCursor)
 
     @property
     def palette(self) -> Palette:

lib/mayaUsd/resources/ae/usdschemabase/collectionCustomControl.py

@@ -3,8 +3,9 @@
 
 from usd_shared_components.collection.widget import CollectionWidget # type: ignore
 from usd_shared_components.common.host import Host # type: ignore
+from usd_shared_components.common.theme import Theme # type: ignore
 
-from .collectionMayaHost import MayaHost
+from .collectionMayaHost import MayaHost, MayaTheme
 
 class CollectionCustomControl(object):
     '''Custom control for the light linking data we want to display.'''
@@ -65,7 +66,9 @@ def onCreate(self, *args):
             ptr = MQtUtil.findControl(self.parent)
             parentWidget = wrapInstance(int(ptr), QWidget)
 
-            Host.injectInstance(MayaHost())
+            if Host._instance is None:
+                Host.injectInstance(MayaHost())
+                Theme.injectInstance(MayaTheme())
             self.widget = CollectionWidget(self.prim, Usd.CollectionAPI.Get(self.prim, self.instanceName))
             parentWidget.layout().addWidget(self.widget)
 

lib/mayaUsd/resources/ae/usdschemabase/collectionMayaHost.py

@@ -1,5 +1,6 @@
 
 from usd_shared_components.common.host import Host
+from usd_shared_components.common.theme import Theme
 from usd_shared_components.usdData.usdCollectionData import UsdCollectionData
 from usd_shared_components.usdData.usdCollectionStringListData import CollectionStringListData
 
@@ -307,6 +308,15 @@ def removeStrings(self, items: Sequence[AnyStr]):
         with _UsdUndoBlockContext(_RemoveItemsCommand.commandName):
             super().removeStrings(items)
 
+class MayaTheme(Theme):
+    def __init__(self):
+        self._palette = None
+        self._icons = {}
+
+    def themeTab(self, tab):
+        super().themeTab(tab)
+        tab.setDocumentMode(False)
+        tab.tabBar().setExpanding(False)
 
 class MayaHost(Host):
     '''Class to host and override Maya-specific functions for the collection API.'''