Merge remote-tracking branch 'origin/master' into temp-lanpr-review

1 files changed, 414 insertions, 470 deletions

diff --git a/release/scripts/startup/bl_ui/space_userpref.py b/release/scripts/startup/bl_ui/space_userpref.py
index bf39cbda391..9527c7f4de8 100644
--- a/release/scripts/startup/bl_ui/space_userpref.py
+++ b/release/scripts/startup/bl_ui/space_userpref.py
@@ -27,6 +27,9 @@ from bpy.app.translations import pgettext_iface as iface_
 from bpy.app.translations import contexts as i18n_contexts
 
 
+# -----------------------------------------------------------------------------
+# Main Header
+
 class USERPREF_HT_header(Header):
     bl_space_type = 'PREFERENCES'
 
@@ -60,6 +63,9 @@ class USERPREF_HT_header(Header):
         self.draw_buttons(layout, context)
 
 
+# -----------------------------------------------------------------------------
+# Main Navigation Bar
+
 class USERPREF_PT_navigation_bar(Panel):
     bl_label = "Preferences Navigation"
     bl_space_type = 'PREFERENCES'
@@ -128,47 +134,53 @@ class USERPREF_PT_save_preferences(Panel):
         USERPREF_HT_header.draw_buttons(layout, context)
 
 
+# -----------------------------------------------------------------------------
+# Min-In Helpers
+
 # Panel mix-in.
-class PreferencePanel:
+class CenterAlignMixIn:
     """
     Base class for panels to center align contents with some horizontal margin.
-    Deriving classes need to implement a ``draw_props(context, layout)`` function.
+    Deriving classes need to implement a ``draw_centered(context, layout)`` function.
     """
 
-    bl_space_type = 'PREFERENCES'
-    bl_region_type = 'WINDOW'
-
     def draw(self, context):
         layout = self.layout
         width = context.region.width
         ui_scale = context.preferences.system.ui_scale
+        # No horizontal margin if region is rather small.
+        is_wide = width > (350 * ui_scale)
 
         layout.use_property_split = True
         layout.use_property_decorate = False  # No animation.
 
         row = layout.row()
-        if width > (350 * ui_scale):  # No horizontal margin if region is rather small.
+        if is_wide:
             row.label()  # Needed so col below is centered.
 
         col = row.column()
         col.ui_units_x = 50
 
-        # draw_props implemented by deriving classes.
-        self.draw_props(context, col)
+        # Implemented by sub-classes.
+        self.draw_centered(context, col)
 
-        if width > (350 * ui_scale):  # No horizontal margin if region is rather small.
+        if is_wide:
             row.label()  # Needed so col above is centered.
 
 
-class USERPREF_PT_interface_display(PreferencePanel, Panel):
-    bl_label = "Display"
+# -----------------------------------------------------------------------------
+# Interface Panels
+
+class InterfacePanel:
+    bl_space_type = 'PREFERENCES'
+    bl_region_type = 'WINDOW'
+    bl_context = "interface"
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'INTERFACE')
 
-    def draw_props(self, context, layout):
+class USERPREF_PT_interface_display(InterfacePanel, CenterAlignMixIn, Panel):
+    bl_label = "Display"
+
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         view = prefs.view
 
@@ -188,16 +200,11 @@ class USERPREF_PT_interface_display(PreferencePanel, Panel):
         flow.prop(view, "show_large_cursors")
 
 
-class USERPREF_PT_interface_text(PreferencePanel, Panel):
+class USERPREF_PT_interface_text(InterfacePanel, CenterAlignMixIn, Panel):
     bl_label = "Text Rendering"
     bl_options = {'DEFAULT_CLOSED'}
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'INTERFACE')
-
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         view = prefs.view
 
@@ -212,14 +219,13 @@ class USERPREF_PT_interface_text(PreferencePanel, Panel):
         flow.prop(view, "font_path_ui_mono")
 
 
-class USERPREF_PT_interface_translation(PreferencePanel, Panel):
+class USERPREF_PT_interface_translation(InterfacePanel, CenterAlignMixIn, Panel):
     bl_label = "Translation"
     bl_translation_context = i18n_contexts.id_windowmanager
 
     @classmethod
     def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'INTERFACE') and bpy.app.build_options.international
+        return bpy.app.build_options.international
 
     def draw_header(self, context):
         prefs = context.preferences
@@ -227,7 +233,7 @@ class USERPREF_PT_interface_translation(PreferencePanel, Panel):
 
         self.layout.prop(view, "use_international_fonts", text="")
 
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         view = prefs.view
 
@@ -242,15 +248,10 @@ class USERPREF_PT_interface_translation(PreferencePanel, Panel):
         flow.prop(view, "use_translate_new_dataname", text="New Data")
 
 
-class USERPREF_PT_interface_editors(PreferencePanel, Panel):
+class USERPREF_PT_interface_editors(InterfacePanel, CenterAlignMixIn, Panel):
     bl_label = "Editors"
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'INTERFACE')
-
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         view = prefs.view
         system = prefs.system
@@ -265,17 +266,12 @@ class USERPREF_PT_interface_editors(PreferencePanel, Panel):
         flow.prop(view, "factor_display_type")
 
 
-class USERPREF_PT_interface_temporary_windows(PreferencePanel, Panel):
+class USERPREF_PT_interface_temporary_windows(InterfacePanel, CenterAlignMixIn, Panel):
     bl_label = "Temporary Windows"
     bl_parent_id = "USERPREF_PT_interface_editors"
     bl_options = {'DEFAULT_CLOSED'}
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'INTERFACE')
-
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         view = prefs.view
 
@@ -285,22 +281,15 @@ class USERPREF_PT_interface_temporary_windows(PreferencePanel, Panel):
         flow.prop(view, "filebrowser_display_type", text="File Browser")
 
 
-class USERPREF_PT_interface_menus(Panel):
-    bl_space_type = 'PREFERENCES'
-    bl_region_type = 'WINDOW'
+class USERPREF_PT_interface_menus(InterfacePanel, Panel):
     bl_label = "Menus"
     bl_options = {'DEFAULT_CLOSED'}
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'INTERFACE')
-
     def draw(self, context):
         pass
 
 
-class USERPREF_PT_interface_menus_mouse_over(PreferencePanel, Panel):
+class USERPREF_PT_interface_menus_mouse_over(InterfacePanel, CenterAlignMixIn, Panel):
     bl_label = "Open on Mouse Over"
     bl_parent_id = "USERPREF_PT_interface_menus"
 
@@ -310,7 +299,7 @@ class USERPREF_PT_interface_menus_mouse_over(PreferencePanel, Panel):
 
         self.layout.prop(view, "use_mouse_over_open", text="")
 
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         view = prefs.view
 
@@ -322,11 +311,11 @@ class USERPREF_PT_interface_menus_mouse_over(PreferencePanel, Panel):
         flow.prop(view, "open_sublevel_delay", text="Sub Level")
 
 
-class USERPREF_PT_interface_menus_pie(PreferencePanel, Panel):
+class USERPREF_PT_interface_menus_pie(InterfacePanel, CenterAlignMixIn, Panel):
     bl_label = "Pie Menus"
     bl_parent_id = "USERPREF_PT_interface_menus"
 
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         view = prefs.view
 
@@ -340,25 +329,27 @@ class USERPREF_PT_interface_menus_pie(PreferencePanel, Panel):
         flow.prop(view, "pie_menu_confirm")
 
 
-class USERPREF_PT_edit_objects(Panel):
-    bl_label = "Objects"
+# -----------------------------------------------------------------------------
+# Editing Panels
+
+class EditingPanel:
     bl_space_type = 'PREFERENCES'
     bl_region_type = 'WINDOW'
+    bl_context = "editing"
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'EDITING')
+
+class USERPREF_PT_edit_objects(EditingPanel, Panel):
+    bl_label = "Objects"
 
     def draw(self, context):
         pass
 
 
-class USERPREF_PT_edit_objects_new(PreferencePanel, Panel):
+class USERPREF_PT_edit_objects_new(EditingPanel, CenterAlignMixIn, Panel):
     bl_label = "New Objects"
     bl_parent_id = "USERPREF_PT_edit_objects"
 
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         edit = prefs.edit
 
@@ -369,11 +360,11 @@ class USERPREF_PT_edit_objects_new(PreferencePanel, Panel):
         flow.prop(edit, "use_enter_edit_mode", text="Enter Edit Mode")
 
 
-class USERPREF_PT_edit_objects_duplicate_data(PreferencePanel, Panel):
+class USERPREF_PT_edit_objects_duplicate_data(EditingPanel, CenterAlignMixIn, Panel):
     bl_label = "Duplicate Data"
     bl_parent_id = "USERPREF_PT_edit_objects"
 
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         edit = prefs.edit
 
@@ -398,15 +389,10 @@ class USERPREF_PT_edit_objects_duplicate_data(PreferencePanel, Panel):
         col.prop(edit, "use_duplicate_grease_pencil", text="Grease Pencil")
 
 
-class USERPREF_PT_edit_cursor(PreferencePanel, Panel):
+class USERPREF_PT_edit_cursor(EditingPanel, CenterAlignMixIn, Panel):
     bl_label = "3D Cursor"
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'EDITING')
-
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         edit = prefs.edit
 
@@ -416,16 +402,11 @@ class USERPREF_PT_edit_cursor(PreferencePanel, Panel):
         flow.prop(edit, "use_cursor_lock_adjust")
 
 
-class USERPREF_PT_edit_gpencil(PreferencePanel, Panel):
+class USERPREF_PT_edit_gpencil(EditingPanel, CenterAlignMixIn, Panel):
     bl_label = "Grease Pencil"
     bl_options = {'DEFAULT_CLOSED'}
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'EDITING')
-
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         edit = prefs.edit
 
@@ -435,15 +416,10 @@ class USERPREF_PT_edit_gpencil(PreferencePanel, Panel):
         flow.prop(edit, "grease_pencil_euclidean_distance", text="Euclidean Distance")
 
 
-class USERPREF_PT_edit_annotations(PreferencePanel, Panel):
+class USERPREF_PT_edit_annotations(EditingPanel, CenterAlignMixIn, Panel):
     bl_label = "Annotations"
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'EDITING')
-
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         edit = prefs.edit
 
@@ -453,16 +429,11 @@ class USERPREF_PT_edit_annotations(PreferencePanel, Panel):
         flow.prop(edit, "grease_pencil_eraser_radius", text="Eraser Radius")
 
 
-class USERPREF_PT_edit_weight_paint(PreferencePanel, Panel):
+class USERPREF_PT_edit_weight_paint(EditingPanel, CenterAlignMixIn, Panel):
     bl_label = "Weight Paint"
     bl_options = {'DEFAULT_CLOSED'}
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'EDITING')
-
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         view = prefs.view
 
@@ -473,16 +444,11 @@ class USERPREF_PT_edit_weight_paint(PreferencePanel, Panel):
         col.template_color_ramp(view, "weight_color_range", expand=True)
 
 
-class USERPREF_PT_edit_misc(PreferencePanel, Panel):
+class USERPREF_PT_edit_misc(EditingPanel, CenterAlignMixIn, Panel):
     bl_label = "Miscellaneous"
     bl_options = {'DEFAULT_CLOSED'}
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'EDITING')
-
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         edit = prefs.edit
 
@@ -492,15 +458,19 @@ class USERPREF_PT_edit_misc(PreferencePanel, Panel):
         flow.prop(edit, "node_margin", text="Node Auto-offset Margin")
 
 
-class USERPREF_PT_animation_timeline(PreferencePanel, Panel):
-    bl_label = "Timeline"
+# -----------------------------------------------------------------------------
+# Animation Panels
+
+class AnimationPanel:
+    bl_space_type = 'PREFERENCES'
+    bl_region_type = 'WINDOW'
+    bl_context = "animation"
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'ANIMATION')
 
-    def draw_props(self, context, layout):
+class USERPREF_PT_animation_timeline(AnimationPanel, CenterAlignMixIn, Panel):
+    bl_label = "Timeline"
+
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         view = prefs.view
         edit = prefs.edit
@@ -521,15 +491,10 @@ class USERPREF_PT_animation_timeline(PreferencePanel, Panel):
             flow.prop(view, "view_frame_keyframes")
 
 
-class USERPREF_PT_animation_keyframes(PreferencePanel, Panel):
+class USERPREF_PT_animation_keyframes(AnimationPanel, CenterAlignMixIn, Panel):
     bl_label = "Keyframes"
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'ANIMATION')
-
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         edit = prefs.edit
 
@@ -539,11 +504,11 @@ class USERPREF_PT_animation_keyframes(PreferencePanel, Panel):
         flow.prop(edit, "use_keyframe_insert_needed", text="Only Insert Needed")
 
 
-class USERPREF_PT_animation_autokey(PreferencePanel, Panel):
+class USERPREF_PT_animation_autokey(AnimationPanel, CenterAlignMixIn, Panel):
     bl_label = "Auto-Keyframing"
     bl_parent_id = "USERPREF_PT_animation_keyframes"
 
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         edit = prefs.edit
 
@@ -554,15 +519,10 @@ class USERPREF_PT_animation_autokey(PreferencePanel, Panel):
         flow.prop(edit, "use_auto_keying", text="Enable in New Scenes")
 
 
-class USERPREF_PT_animation_fcurves(PreferencePanel, Panel):
+class USERPREF_PT_animation_fcurves(AnimationPanel, CenterAlignMixIn, Panel):
     bl_label = "F-Curves"
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'ANIMATION')
-
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         edit = prefs.edit
 
@@ -575,15 +535,19 @@ class USERPREF_PT_animation_fcurves(PreferencePanel, Panel):
         flow.prop(edit, "use_insertkey_xyz_to_rgb", text="XYZ to RGB")
 
 
-class USERPREF_PT_system_sound(PreferencePanel, Panel):
-    bl_label = "Sound"
+# -----------------------------------------------------------------------------
+# System Panels
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'SYSTEM')
+class SystemPanel:
+    bl_space_type = 'PREFERENCES'
+    bl_region_type = 'WINDOW'
+    bl_context = "system"
+
+
+class USERPREF_PT_system_sound(SystemPanel, CenterAlignMixIn, Panel):
+    bl_label = "Sound"
 
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         system = prefs.system
 
@@ -597,15 +561,10 @@ class USERPREF_PT_system_sound(PreferencePanel, Panel):
         sub.prop(system, "audio_sample_format", text="Sample Format")
 
 
-class USERPREF_PT_system_cycles_devices(PreferencePanel, Panel):
+class USERPREF_PT_system_cycles_devices(SystemPanel, CenterAlignMixIn, Panel):
     bl_label = "Cycles Render Devices"
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'SYSTEM')
-
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
 
         col = layout.column()
@@ -624,15 +583,55 @@ class USERPREF_PT_system_cycles_devices(PreferencePanel, Panel):
         #     col.row().prop(system, "opensubdiv_compute_type", text="")
 
 
-class USERPREF_PT_viewport_display(PreferencePanel, Panel):
-    bl_label = "Display"
+class USERPREF_PT_system_memory(SystemPanel, CenterAlignMixIn, Panel):
+    bl_label = "Memory & Limits"
 
-    @classmethod
-    def poll(cls, context):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
-        return (prefs.active_section == 'VIEWPORT')
+        system = prefs.system
+        edit = prefs.edit
+
+        flow = layout.grid_flow(row_major=False, columns=0, even_columns=True, even_rows=False, align=False)
+
+        flow.prop(edit, "undo_steps", text="Undo Steps")
+        flow.prop(edit, "undo_memory_limit", text="Undo Memory Limit")
+        flow.prop(edit, "use_global_undo")
+
+        layout.separator()
+
+        flow = layout.grid_flow(row_major=False, columns=0, even_columns=True, even_rows=False, align=False)
+
+        flow.prop(system, "memory_cache_limit", text="Sequencer Cache Limit")
+        flow.prop(system, "scrollback", text="Console Scrollback Lines")
+
+        layout.separator()
+
+        flow = layout.grid_flow(row_major=False, columns=0, even_columns=True, even_rows=False, align=False)
+
+        flow.prop(system, "texture_time_out", text="Texture Time Out")
+        flow.prop(system, "texture_collection_rate", text="Garbage Collection Rate")
+
+        layout.separator()
+
+        flow = layout.grid_flow(row_major=False, columns=0, even_columns=True, even_rows=False, align=False)
+
+        flow.prop(system, "vbo_time_out", text="Vbo Time Out")
+        flow.prop(system, "vbo_collection_rate", text="Garbage Collection Rate")
+
+
+# -----------------------------------------------------------------------------
+# Viewport Panels
+
+class ViewportPanel:
+    bl_space_type = 'PREFERENCES'
+    bl_region_type = 'WINDOW'
+    bl_context = "viewport"
+
+
+class USERPREF_PT_viewport_display(ViewportPanel, CenterAlignMixIn, Panel):
+    bl_label = "Display"
 
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         view = prefs.view
 
@@ -660,15 +659,10 @@ class USERPREF_PT_viewport_display(PreferencePanel, Panel):
             col.prop(view, "mini_axis_brightness", text="Brightness")
 
 
-class USERPREF_PT_viewport_quality(PreferencePanel, Panel):
+class USERPREF_PT_viewport_quality(ViewportPanel, CenterAlignMixIn, Panel):
     bl_label = "Quality"
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'VIEWPORT')
-
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         system = prefs.system
 
@@ -680,15 +674,10 @@ class USERPREF_PT_viewport_quality(PreferencePanel, Panel):
         flow.prop(system, "use_edit_mode_smooth_wire")
 
 
-class USERPREF_PT_viewport_textures(PreferencePanel, Panel):
+class USERPREF_PT_viewport_textures(ViewportPanel, CenterAlignMixIn, Panel):
     bl_label = "Textures"
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'VIEWPORT')
-
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         system = prefs.system
 
@@ -700,16 +689,11 @@ class USERPREF_PT_viewport_textures(PreferencePanel, Panel):
         flow.prop(system, "image_draw_method", text="Image Display Method")
 
 
-class USERPREF_PT_viewport_selection(PreferencePanel, Panel):
+class USERPREF_PT_viewport_selection(ViewportPanel, CenterAlignMixIn, Panel):
     bl_label = "Selection"
     bl_options = {'DEFAULT_CLOSED'}
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'VIEWPORT')
-
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         system = prefs.system
 
@@ -718,45 +702,13 @@ class USERPREF_PT_viewport_selection(PreferencePanel, Panel):
         flow.prop(system, "use_select_pick_depth")
 
 
-class USERPREF_PT_system_memory(PreferencePanel, Panel):
-    bl_label = "Memory & Limits"
-
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'SYSTEM')
-
-    def draw_props(self, context, layout):
-        prefs = context.preferences
-        system = prefs.system
-        edit = prefs.edit
-
-        flow = layout.grid_flow(row_major=False, columns=0, even_columns=True, even_rows=False, align=False)
-
-        flow.prop(edit, "undo_steps", text="Undo Steps")
-        flow.prop(edit, "undo_memory_limit", text="Undo Memory Limit")
-        flow.prop(edit, "use_global_undo")
-
-        layout.separator()
-
-        flow = layout.grid_flow(row_major=False, columns=0, even_columns=True, even_rows=False, align=False)
-
-        flow.prop(system, "memory_cache_limit", text="Sequencer Cache Limit")
-        flow.prop(system, "scrollback", text="Console Scrollback Lines")
-
-        layout.separator()
-
-        flow = layout.grid_flow(row_major=False, columns=0, even_columns=True, even_rows=False, align=False)
+# -----------------------------------------------------------------------------
+# Theme Panels
 
-        flow.prop(system, "texture_time_out", text="Texture Time Out")
-        flow.prop(system, "texture_collection_rate", text="Garbage Collection Rate")
-
-        layout.separator()
-
-        flow = layout.grid_flow(row_major=False, columns=0, even_columns=True, even_rows=False, align=False)
-
-        flow.prop(system, "vbo_time_out", text="Vbo Time Out")
-        flow.prop(system, "vbo_collection_rate", text="Garbage Collection Rate")
+class ThemePanel:
+    bl_space_type = 'PREFERENCES'
+    bl_region_type = 'WINDOW'
+    bl_context = "themes"
 
 
 class USERPREF_MT_interface_theme_presets(Menu):
@@ -775,17 +727,10 @@ class USERPREF_MT_interface_theme_presets(Menu):
         bpy.ops.preferences.reset_default_theme()
 
 
-class USERPREF_PT_theme(Panel):
-    bl_space_type = 'PREFERENCES'
+class USERPREF_PT_theme(ThemePanel, Panel):
     bl_label = "Themes"
-    bl_region_type = 'WINDOW'
     bl_options = {'HIDE_HEADER'}
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'THEMES')
-
     def draw(self, _context):
         layout = self.layout
 
@@ -801,17 +746,10 @@ class USERPREF_PT_theme(Panel):
         row.operator("preferences.reset_default_theme", text="Reset", icon='LOOP_BACK')
 
 
-class USERPREF_PT_theme_user_interface(PreferencePanel, Panel):
-    bl_space_type = 'PREFERENCES'
-    bl_region_type = 'WINDOW'
+class USERPREF_PT_theme_user_interface(ThemePanel, CenterAlignMixIn, Panel):
     bl_label = "User Interface"
     bl_options = {'DEFAULT_CLOSED'}
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'THEMES')
-
     def draw_header(self, _context):
         layout = self.layout
 
@@ -822,9 +760,8 @@ class USERPREF_PT_theme_user_interface(PreferencePanel, Panel):
 
 
 # Base class for dynamically defined widget color panels.
+# This is not registered.
 class PreferenceThemeWidgetColorPanel:
-    bl_space_type = 'PREFERENCES'
-    bl_region_type = 'WINDOW'
     bl_parent_id = "USERPREF_PT_theme_user_interface"
 
     def draw(self, context):
@@ -851,15 +788,10 @@ class PreferenceThemeWidgetColorPanel:
 
         col.prop(widget_style, "roundness")
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'THEMES')
-
 
+# Base class for dynamically defined widget color panels.
+# This is not registered.
 class PreferenceThemeWidgetShadePanel:
-    bl_space_type = 'PREFERENCES'
-    bl_region_type = 'WINDOW'
 
     def draw(self, context):
         theme = context.preferences.themes[0]
@@ -882,12 +814,12 @@ class PreferenceThemeWidgetShadePanel:
         self.layout.prop(widget_style, "show_shaded", text="")
 
 
-class USERPREF_PT_theme_interface_state(PreferencePanel, Panel):
+class USERPREF_PT_theme_interface_state(ThemePanel, CenterAlignMixIn, Panel):
     bl_label = "State"
     bl_options = {'DEFAULT_CLOSED'}
     bl_parent_id = "USERPREF_PT_theme_user_interface"
 
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         theme = context.preferences.themes[0]
         ui_state = theme.user_interface.wcol_state
 
@@ -917,12 +849,12 @@ class USERPREF_PT_theme_interface_state(PreferencePanel, Panel):
         col.prop(ui_state, "blend")
 
 
-class USERPREF_PT_theme_interface_styles(PreferencePanel, Panel):
+class USERPREF_PT_theme_interface_styles(ThemePanel, CenterAlignMixIn, Panel):
     bl_label = "Styles"
     bl_options = {'DEFAULT_CLOSED'}
     bl_parent_id = "USERPREF_PT_theme_user_interface"
 
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         theme = context.preferences.themes[0]
         ui = theme.user_interface
 
@@ -937,12 +869,12 @@ class USERPREF_PT_theme_interface_styles(PreferencePanel, Panel):
         flow.prop(ui, "widget_emboss")
 
 
-class USERPREF_PT_theme_interface_gizmos(PreferencePanel, Panel):
+class USERPREF_PT_theme_interface_gizmos(ThemePanel, CenterAlignMixIn, Panel):
     bl_label = "Axis & Gizmo Colors"
     bl_options = {'DEFAULT_CLOSED'}
     bl_parent_id = "USERPREF_PT_theme_user_interface"
 
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         theme = context.preferences.themes[0]
         ui = theme.user_interface
 
@@ -962,12 +894,12 @@ class USERPREF_PT_theme_interface_gizmos(PreferencePanel, Panel):
         col.prop(ui, "gizmo_b")
 
 
-class USERPREF_PT_theme_interface_icons(PreferencePanel, Panel):
+class USERPREF_PT_theme_interface_icons(ThemePanel, CenterAlignMixIn, Panel):
     bl_label = "Icon Colors"
     bl_options = {'DEFAULT_CLOSED'}
     bl_parent_id = "USERPREF_PT_theme_user_interface"
 
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         theme = context.preferences.themes[0]
         ui = theme.user_interface
 
@@ -983,15 +915,10 @@ class USERPREF_PT_theme_interface_icons(PreferencePanel, Panel):
         flow.prop(ui, "icon_border_intensity")
 
 
-class USERPREF_PT_theme_text_style(PreferencePanel, Panel):
+class USERPREF_PT_theme_text_style(ThemePanel, CenterAlignMixIn, Panel):
     bl_label = "Text Style"
     bl_options = {'DEFAULT_CLOSED'}
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'THEMES')
-
     @staticmethod
     def _ui_font_style(layout, font_style):
         layout.use_property_split = True
@@ -1015,7 +942,7 @@ class USERPREF_PT_theme_text_style(PreferencePanel, Panel):
 
         layout.label(icon='FONTPREVIEW')
 
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         style = context.preferences.ui_styles[0]
 
         layout.label(text="Panel Title")
@@ -1032,21 +959,16 @@ class USERPREF_PT_theme_text_style(PreferencePanel, Panel):
         self._ui_font_style(layout, style.widget_label)
 
 
-class USERPREF_PT_theme_bone_color_sets(PreferencePanel, Panel):
+class USERPREF_PT_theme_bone_color_sets(ThemePanel, CenterAlignMixIn, Panel):
     bl_label = "Bone Color Sets"
     bl_options = {'DEFAULT_CLOSED'}
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'THEMES')
-
     def draw_header(self, _context):
         layout = self.layout
 
         layout.label(icon='COLOR')
 
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         theme = context.preferences.themes[0]
 
         layout.use_property_split = True
@@ -1063,9 +985,8 @@ class USERPREF_PT_theme_bone_color_sets(PreferencePanel, Panel):
 
 
 # Base class for dynamically defined theme-space panels.
+# This is not registered.
 class PreferenceThemeSpacePanel:
-    bl_space_type = 'PREFERENCES'
-    bl_region_type = 'WINDOW'
 
     # not essential, hard-coded UI delimiters for the theme layout
     ui_delimiters = {
@@ -1137,11 +1058,6 @@ class PreferenceThemeSpacePanel:
             data = getattr(data, datapath_item)
         PreferenceThemeSpacePanel._theme_generic(layout, data, self.theme_area)
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'THEMES')
-
 
 class ThemeGenericClassGenerator():
 
@@ -1172,7 +1088,7 @@ class ThemeGenericClassGenerator():
 
         for (name, wcol) in wcols:
             panel_id = "USERPREF_PT_theme_interface_" + wcol
-            yield type(panel_id, (PreferenceThemeWidgetColorPanel, Panel), {
+            yield type(panel_id, (PreferenceThemeWidgetColorPanel, ThemePanel, Panel), {
                 "bl_label": name,
                 "bl_options": {'DEFAULT_CLOSED'},
                 "draw": PreferenceThemeWidgetColorPanel.draw,
@@ -1180,7 +1096,7 @@ class ThemeGenericClassGenerator():
             })
 
             panel_shade_id = "USERPREF_PT_theme_interface_shade_" + wcol
-            yield type(panel_shade_id, (PreferenceThemeWidgetShadePanel, Panel), {
+            yield type(panel_shade_id, (PreferenceThemeWidgetShadePanel, ThemePanel, Panel), {
                 "bl_label": "Shaded",
                 "bl_options": {'DEFAULT_CLOSED'},
                 "bl_parent_id": panel_id,
@@ -1204,7 +1120,7 @@ class ThemeGenericClassGenerator():
                     for prop in props_ls:
                         new_datapath = datapath + "." + prop.identifier if datapath else prop.identifier
                         panel_id = parent_id + "_" + prop.identifier
-                        yield type(panel_id, (PreferenceThemeSpacePanel, Panel), {
+                        yield type(panel_id, (PreferenceThemeSpacePanel, ThemePanel, Panel), {
                             "bl_label": rna_type.properties[prop.identifier].name,
                             "bl_parent_id": parent_id,
                             "bl_options": {'DEFAULT_CLOSED'},
@@ -1213,7 +1129,12 @@ class ThemeGenericClassGenerator():
                             "datapath": new_datapath,
                         })
 
-                        yield from generate_child_panel_classes_recurse(panel_id, prop.fixed_type, theme_area, new_datapath)
+                        yield from generate_child_panel_classes_recurse(
+                            panel_id,
+                            prop.fixed_type,
+                            theme_area,
+                            new_datapath,
+                        )
 
         yield from generate_child_panel_classes_recurse(parent_id, rna_type, theme_area, datapath)
 
@@ -1227,7 +1148,7 @@ class ThemeGenericClassGenerator():
 
             panel_id = "USERPREF_PT_theme_" + theme_area.identifier.lower()
             # Generate panel-class from theme_area
-            yield type(panel_id, (PreferenceThemeSpacePanel, Panel), {
+            yield type(panel_id, (PreferenceThemeSpacePanel, ThemePanel, Panel), {
                 "bl_label": theme_area.name,
                 "bl_options": {'DEFAULT_CLOSED'},
                 "draw_header": PreferenceThemeSpacePanel.draw_header,
@@ -1242,29 +1163,24 @@ class ThemeGenericClassGenerator():
                 theme_area, theme_area.identifier.lower())
 
 
+# -----------------------------------------------------------------------------
+# File Paths Panels
+
 # Panel mix-in.
 class FilePathsPanel:
     bl_space_type = 'PREFERENCES'
     bl_region_type = 'WINDOW'
+    bl_context = "file_paths"
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'FILE_PATHS')
+
+class USERPREF_PT_file_paths_data(FilePathsPanel, Panel):
+    bl_label = "Data"
 
     def draw(self, context):
         layout = self.layout
-
         layout.use_property_split = True
         layout.use_property_decorate = False
 
-        self.draw_props(context, layout)
-
-
-class USERPREF_PT_file_paths_data(FilePathsPanel, Panel):
-    bl_label = "Data"
-
-    def draw_props(self, context, _layout):
         paths = context.preferences.filepaths
 
         col = self.layout.column()
@@ -1278,7 +1194,11 @@ class USERPREF_PT_file_paths_data(FilePathsPanel, Panel):
 class USERPREF_PT_file_paths_render(FilePathsPanel, Panel):
     bl_label = "Render"
 
-    def draw_props(self, context, _layout):
+    def draw(self, context):
+        layout = self.layout
+        layout.use_property_split = True
+        layout.use_property_decorate = False
+
         paths = context.preferences.filepaths
 
         col = self.layout.column()
@@ -1289,7 +1209,11 @@ class USERPREF_PT_file_paths_render(FilePathsPanel, Panel):
 class USERPREF_PT_file_paths_applications(FilePathsPanel, Panel):
     bl_label = "Applications"
 
-    def draw_props(self, context, layout):
+    def draw(self, context):
+        layout = self.layout
+        layout.use_property_split = True
+        layout.use_property_decorate = False
+
         paths = context.preferences.filepaths
 
         col = layout.column()
@@ -1305,14 +1229,18 @@ class USERPREF_PT_file_paths_development(FilePathsPanel, Panel):
     @classmethod
     def poll(cls, context):
         prefs = context.preferences
-        return (prefs.active_section == 'FILE_PATHS') and prefs.view.show_developer_ui
+        return prefs.view.show_developer_ui
+
+    def draw(self, context):
+        layout = self.layout
+        layout.use_property_split = True
+        layout.use_property_decorate = False
 
-    def draw_props(self, context, layout):
         paths = context.preferences.filepaths
         layout.prop(paths, "i18n_branches_directory", text="I18n Branches")
 
 
-class USERPREF_PT_saveload_autorun(PreferencePanel, Panel):
+class USERPREF_PT_saveload_autorun(FilePathsPanel, Panel):
     bl_label = "Auto Run Python Scripts"
     bl_parent_id = "USERPREF_PT_saveload_blend"
 
@@ -1343,15 +1271,19 @@ class USERPREF_PT_saveload_autorun(PreferencePanel, Panel):
             row.operator("wm.userpref_autoexec_path_remove", text="", icon='X', emboss=False).index = i
 
 
-class USERPREF_PT_saveload_blend(PreferencePanel, Panel):
-    bl_label = "Blend Files"
+# -----------------------------------------------------------------------------
+# Save/Load Panels
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'SAVE_LOAD')
+class SaveLoadPanel:
+    bl_space_type = 'PREFERENCES'
+    bl_region_type = 'WINDOW'
+    bl_context = "save_load"
+
+
+class USERPREF_PT_saveload_blend(SaveLoadPanel, CenterAlignMixIn, Panel):
+    bl_label = "Blend Files"
 
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         paths = prefs.filepaths
         view = prefs.view
@@ -1373,11 +1305,11 @@ class USERPREF_PT_saveload_blend(PreferencePanel, Panel):
         flow.prop(paths, "recent_files")
 
 
-class USERPREF_PT_saveload_blend_autosave(PreferencePanel, Panel):
+class USERPREF_PT_saveload_blend_autosave(SaveLoadPanel, CenterAlignMixIn, Panel):
     bl_label = "Auto Save"
     bl_parent_id = "USERPREF_PT_saveload_blend"
 
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         paths = prefs.filepaths
 
@@ -1389,15 +1321,10 @@ class USERPREF_PT_saveload_blend_autosave(PreferencePanel, Panel):
         sub.prop(paths, "auto_save_time", text="Timer (mins)")
 
 
-class USERPREF_PT_saveload_file_browser(PreferencePanel, Panel):
+class USERPREF_PT_saveload_file_browser(SaveLoadPanel, CenterAlignMixIn, Panel):
     bl_label = "File Browser"
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'SAVE_LOAD')
-
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         paths = prefs.filepaths
 
@@ -1409,85 +1336,19 @@ class USERPREF_PT_saveload_file_browser(PreferencePanel, Panel):
         flow.prop(paths, "hide_system_bookmarks")
 
 
-class USERPREF_PT_ndof_settings(Panel):
-    bl_label = "3D Mouse Settings"
-    bl_space_type = 'TOPBAR'  # dummy.
-    bl_region_type = 'HEADER'
-
-    def draw(self, context):
-        layout = self.layout
-        layout.use_property_split = True
-        layout.use_property_decorate = False  # No animation.
-
-        input_prefs = context.preferences.inputs
-
-        is_view3d = context.space_data.type == 'VIEW_3D'
-
-        col = layout.column(align=True)
-        col.prop(input_prefs, "ndof_sensitivity")
-        col.prop(input_prefs, "ndof_orbit_sensitivity")
-        col.prop(input_prefs, "ndof_deadzone")
-
-        if is_view3d:
-            layout.separator()
-            layout.prop(input_prefs, "ndof_show_guide")
-
-            layout.separator()
-            layout.label(text="Orbit Style")
-            layout.row().prop(input_prefs, "ndof_view_navigate_method", text="Navigate")
-            layout.row().prop(input_prefs, "ndof_view_rotate_method", text="Orbit")
-            layout.separator()
-
-            layout.label(text="Orbit Options")
-            split = layout.split(factor=0.6)
-            row = split.row()
-            row.alignment = 'RIGHT'
-            row.label(text="Invert Axis")
-            row = split.row(align=True)
-            for text, attr in (
-                    ("X", "ndof_rotx_invert_axis"),
-                    ("Y", "ndof_roty_invert_axis"),
-                    ("Z", "ndof_rotz_invert_axis"),
-            ):
-                row.prop(input_prefs, attr, text=text, toggle=True)
-
-        # view2d use pan/zoom
-        layout.separator()
-        layout.label(text="Pan Options")
-
-        split = layout.split(factor=0.6)
-        row = split.row()
-        row.alignment = 'RIGHT'
-        row.label(text="Invert Axis")
-        row = split.row(align=True)
-        for text, attr in (
-                ("X", "ndof_panx_invert_axis"),
-                ("Y", "ndof_pany_invert_axis"),
-                ("Z", "ndof_panz_invert_axis"),
-        ):
-            row.prop(input_prefs, attr, text=text, toggle=True)
+# -----------------------------------------------------------------------------
+# Input Panels
 
-        layout.prop(input_prefs, "ndof_pan_yz_swap_axis")
-
-        layout.label(text="Zoom Options")
-        layout.prop(input_prefs, "ndof_zoom_invert")
-
-        if is_view3d:
-            layout.separator()
-            layout.label(text="Fly/Walk Options")
-            layout.prop(input_prefs, "ndof_fly_helicopter")
-            layout.prop(input_prefs, "ndof_lock_horizon")
+class InputPanel:
+    bl_space_type = 'PREFERENCES'
+    bl_region_type = 'WINDOW'
+    bl_context = "input"
 
 
-class USERPREF_PT_input_keyboard(PreferencePanel, Panel):
+class USERPREF_PT_input_keyboard(InputPanel, CenterAlignMixIn, Panel):
     bl_label = "Keyboard"
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'INPUT')
-
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         inputs = prefs.inputs
 
@@ -1495,15 +1356,10 @@ class USERPREF_PT_input_keyboard(PreferencePanel, Panel):
         layout.prop(inputs, "use_numeric_input_advanced")
 
 
-class USERPREF_PT_input_mouse(PreferencePanel, Panel):
+class USERPREF_PT_input_mouse(InputPanel, CenterAlignMixIn, Panel):
     bl_label = "Mouse"
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'INPUT')
-
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         import sys
         prefs = context.preferences
         inputs = prefs.inputs
@@ -1524,15 +1380,63 @@ class USERPREF_PT_input_mouse(PreferencePanel, Panel):
         flow.prop(inputs, "move_threshold")
 
 
-class USERPREF_PT_navigation_orbit(PreferencePanel, Panel):
-    bl_label = "Orbit & Pan"
+class USERPREF_PT_input_tablet(InputPanel, CenterAlignMixIn, Panel):
+    bl_label = "Tablet"
+
+    def draw_centered(self, context, layout):
+        prefs = context.preferences
+        inputs = prefs.inputs
+
+        import sys
+        if sys.platform[:3] == "win":
+            layout.prop(inputs, "tablet_api")
+            layout.separator()
+
+        flow = layout.grid_flow(row_major=False, columns=0, even_columns=True, even_rows=False, align=False)
+
+        flow.prop(inputs, "pressure_threshold_max")
+        flow.prop(inputs, "pressure_softness")
+
+
+class USERPREF_PT_input_ndof(InputPanel, CenterAlignMixIn, Panel):
+    bl_label = "NDOF"
+    bl_options = {'DEFAULT_CLOSED'}
 
     @classmethod
     def poll(cls, context):
         prefs = context.preferences
-        return (prefs.active_section == 'NAVIGATION')
+        inputs = prefs.inputs
+        return inputs.use_ndof
+
+    def draw_centered(self, context, layout):
+        prefs = context.preferences
+        inputs = prefs.inputs
+
+        flow = layout.grid_flow(row_major=False, columns=0, even_columns=True, even_rows=False, align=False)
+
+        flow.prop(inputs, "ndof_sensitivity", text="Pan Sensitivity")
+        flow.prop(inputs, "ndof_orbit_sensitivity", text="Orbit Sensitivity")
+        flow.prop(inputs, "ndof_deadzone", text="Deadzone")
 
-    def draw_props(self, context, layout):
+        layout.separator()
+
+        flow.row().prop(inputs, "ndof_view_navigate_method", expand=True)
+        flow.row().prop(inputs, "ndof_view_rotate_method", expand=True)
+
+
+# -----------------------------------------------------------------------------
+# Navigation Panels
+
+class NavigationPanel:
+    bl_space_type = 'PREFERENCES'
+    bl_region_type = 'WINDOW'
+    bl_context = "navigation"
+
+
+class USERPREF_PT_navigation_orbit(NavigationPanel, CenterAlignMixIn, Panel):
+    bl_label = "Orbit & Pan"
+
+    def draw_centered(self, context, layout):
         import sys
         prefs = context.preferences
         inputs = prefs.inputs
@@ -1558,15 +1462,10 @@ class USERPREF_PT_navigation_orbit(PreferencePanel, Panel):
         flow.prop(view, "rotation_angle")
 
 
-class USERPREF_PT_navigation_zoom(PreferencePanel, Panel):
+class USERPREF_PT_navigation_zoom(NavigationPanel, CenterAlignMixIn, Panel):
     bl_label = "Zoom"
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'NAVIGATION')
-
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         inputs = prefs.inputs
 
@@ -1582,15 +1481,10 @@ class USERPREF_PT_navigation_zoom(PreferencePanel, Panel):
         flow.prop(inputs, "use_zoom_to_mouse")
 
 
-class USERPREF_PT_navigation_fly_walk(PreferencePanel, Panel):
+class USERPREF_PT_navigation_fly_walk(NavigationPanel, CenterAlignMixIn, Panel):
     bl_label = "Fly & Walk"
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'NAVIGATION')
-
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         inputs = prefs.inputs
 
@@ -1600,7 +1494,7 @@ class USERPREF_PT_navigation_fly_walk(PreferencePanel, Panel):
         flow.prop(inputs, "use_camera_lock_parent")
 
 
-class USERPREF_PT_navigation_fly_walk_navigation(PreferencePanel, Panel):
+class USERPREF_PT_navigation_fly_walk_navigation(NavigationPanel, CenterAlignMixIn, Panel):
     bl_label = "Walk"
     bl_parent_id = "USERPREF_PT_navigation_fly_walk"
     bl_options = {'DEFAULT_CLOSED'}
@@ -1610,7 +1504,7 @@ class USERPREF_PT_navigation_fly_walk_navigation(PreferencePanel, Panel):
         prefs = context.preferences
         return prefs.inputs.navigation_mode == 'WALK'
 
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         inputs = prefs.inputs
         walk = inputs.walk_navigation
@@ -1626,7 +1520,7 @@ class USERPREF_PT_navigation_fly_walk_navigation(PreferencePanel, Panel):
         sub.prop(walk, "walk_speed_factor")
 
 
-class USERPREF_PT_navigation_fly_walk_gravity(PreferencePanel, Panel):
+class USERPREF_PT_navigation_fly_walk_gravity(NavigationPanel, CenterAlignMixIn, Panel):
     bl_label = "Gravity"
     bl_parent_id = "USERPREF_PT_navigation_fly_walk"
     bl_options = {'DEFAULT_CLOSED'}
@@ -1643,7 +1537,7 @@ class USERPREF_PT_navigation_fly_walk_gravity(PreferencePanel, Panel):
 
         self.layout.prop(walk, "use_gravity", text="")
 
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         inputs = prefs.inputs
         walk = inputs.walk_navigation
@@ -1656,53 +1550,84 @@ class USERPREF_PT_navigation_fly_walk_gravity(PreferencePanel, Panel):
         flow.prop(walk, "jump_height")
 
 
-class USERPREF_PT_input_tablet(PreferencePanel, Panel):
-    bl_label = "Tablet"
+# Special case, this is only exposed as a popover.
+class USERPREF_PT_ndof_settings(Panel):
+    bl_label = "3D Mouse Settings"
+    bl_space_type = 'TOPBAR'  # dummy.
+    bl_region_type = 'HEADER'
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return prefs.active_section == 'INPUT'
+    def draw(self, context):
+        layout = self.layout
+        layout.use_property_split = True
+        layout.use_property_decorate = False  # No animation.
 
-    def draw_props(self, context, layout):
-        prefs = context.preferences
-        inputs = prefs.inputs
+        input_prefs = context.preferences.inputs
 
-        import sys
-        if sys.platform[:3] == "win":
-            layout.prop(inputs, "tablet_api")
+        is_view3d = context.space_data.type == 'VIEW_3D'
+
+        col = layout.column(align=True)
+        col.prop(input_prefs, "ndof_sensitivity")
+        col.prop(input_prefs, "ndof_orbit_sensitivity")
+        col.prop(input_prefs, "ndof_deadzone")
+
+        if is_view3d:
             layout.separator()
+            layout.prop(input_prefs, "ndof_show_guide")
 
-        flow = layout.grid_flow(row_major=False, columns=0, even_columns=True, even_rows=False, align=False)
+            layout.separator()
+            layout.label(text="Orbit Style")
+            layout.row().prop(input_prefs, "ndof_view_navigate_method", text="Navigate")
+            layout.row().prop(input_prefs, "ndof_view_rotate_method", text="Orbit")
+            layout.separator()
 
-        flow.prop(inputs, "pressure_threshold_max")
-        flow.prop(inputs, "pressure_softness")
+            layout.label(text="Orbit Options")
+            split = layout.split(factor=0.6)
+            row = split.row()
+            row.alignment = 'RIGHT'
+            row.label(text="Invert Axis")
+            row = split.row(align=True)
+            for text, attr in (
+                    ("X", "ndof_rotx_invert_axis"),
+                    ("Y", "ndof_roty_invert_axis"),
+                    ("Z", "ndof_rotz_invert_axis"),
+            ):
+                row.prop(input_prefs, attr, text=text, toggle=True)
 
+        # view2d use pan/zoom
+        layout.separator()
+        layout.label(text="Pan Options")
 
-class USERPREF_PT_input_ndof(PreferencePanel, Panel):
-    bl_label = "NDOF"
-    bl_options = {'DEFAULT_CLOSED'}
+        split = layout.split(factor=0.6)
+        row = split.row()
+        row.alignment = 'RIGHT'
+        row.label(text="Invert Axis")
+        row = split.row(align=True)
+        for text, attr in (
+                ("X", "ndof_panx_invert_axis"),
+                ("Y", "ndof_pany_invert_axis"),
+                ("Z", "ndof_panz_invert_axis"),
+        ):
+            row.prop(input_prefs, attr, text=text, toggle=True)
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        inputs = prefs.inputs
-        return prefs.active_section == 'INPUT' and inputs.use_ndof
+        layout.prop(input_prefs, "ndof_pan_yz_swap_axis")
 
-    def draw_props(self, context, layout):
-        prefs = context.preferences
-        inputs = prefs.inputs
+        layout.label(text="Zoom Options")
+        layout.prop(input_prefs, "ndof_zoom_invert")
 
-        flow = layout.grid_flow(row_major=False, columns=0, even_columns=True, even_rows=False, align=False)
+        if is_view3d:
+            layout.separator()
+            layout.label(text="Fly/Walk Options")
+            layout.prop(input_prefs, "ndof_fly_helicopter")
+            layout.prop(input_prefs, "ndof_lock_horizon")
 
-        flow.prop(inputs, "ndof_sensitivity", text="Pan Sensitivity")
-        flow.prop(inputs, "ndof_orbit_sensitivity", text="Orbit Sensitivity")
-        flow.prop(inputs, "ndof_deadzone", text="Deadzone")
 
-        layout.separator()
+# -----------------------------------------------------------------------------
+# Key-Map Editor Panels
 
-        flow.row().prop(inputs, "ndof_view_navigate_method", expand=True)
-        flow.row().prop(inputs, "ndof_view_rotate_method", expand=True)
+class KeymapPanel:
+    bl_space_type = 'PREFERENCES'
+    bl_region_type = 'WINDOW'
+    bl_context = "keymap"
 
 
 class USERPREF_MT_keyconfigs(Menu):
@@ -1714,17 +1639,10 @@ class USERPREF_MT_keyconfigs(Menu):
         Menu.draw_preset(self, context)
 
 
-class USERPREF_PT_keymap(Panel):
-    bl_space_type = 'PREFERENCES'
+class USERPREF_PT_keymap(KeymapPanel, Panel):
     bl_label = "Keymap"
-    bl_region_type = 'WINDOW'
     bl_options = {'HIDE_HEADER'}
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'KEYMAP')
-
     def draw(self, context):
         from rna_keymap_ui import draw_keymaps
 
@@ -1740,10 +1658,17 @@ class USERPREF_PT_keymap(Panel):
         # print("runtime", time.time() - start)
 
 
-class USERPREF_PT_addons(Panel):
+# -----------------------------------------------------------------------------
+# Add-On Panels
+
+class AddOnPanel:
     bl_space_type = 'PREFERENCES'
-    bl_label = "Add-ons"
     bl_region_type = 'WINDOW'
+    bl_context = "addons"
+
+
+class USERPREF_PT_addons(AddOnPanel, Panel):
+    bl_label = "Add-ons"
     bl_options = {'HIDE_HEADER'}
 
     _support_icon_mapping = {
@@ -1752,11 +1677,6 @@ class USERPREF_PT_addons(Panel):
         'TESTING': 'EXPERIMENTAL',
     }
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'ADDONS')
-
     @staticmethod
     def is_user_addon(mod, user_addon_paths):
         import os
@@ -2027,14 +1947,16 @@ class USERPREF_PT_addons(Panel):
                 row.label(text=module_name, translate=False)
 
 
-class StudioLightPanelMixin():
+# -----------------------------------------------------------------------------
+# Studio Light Panels
+
+class StudioLightPanel:
     bl_space_type = 'PREFERENCES'
     bl_region_type = 'WINDOW'
+    bl_context = "lights"
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'LIGHTS')
+
+class StudioLightPanelMixin:
 
     def _get_lights(self, prefs):
         return [light for light in prefs.studio_lights if light.is_user_defined and light.type == self.sl_type]
@@ -2070,7 +1992,7 @@ class StudioLightPanelMixin():
         box.label(text=studio_light.name)
 
 
-class USERPREF_PT_studiolight_matcaps(Panel, StudioLightPanelMixin):
+class USERPREF_PT_studiolight_matcaps(StudioLightPanel, StudioLightPanelMixin, Panel):
     bl_label = "MatCaps"
     sl_type = 'MATCAP'
 
@@ -2080,7 +2002,7 @@ class USERPREF_PT_studiolight_matcaps(Panel, StudioLightPanelMixin):
         layout.separator()
 
 
-class USERPREF_PT_studiolight_world(Panel, StudioLightPanelMixin):
+class USERPREF_PT_studiolight_world(StudioLightPanel, StudioLightPanelMixin, Panel):
     bl_label = "LookDev HDRIs"
     sl_type = 'WORLD'
 
@@ -2090,7 +2012,7 @@ class USERPREF_PT_studiolight_world(Panel, StudioLightPanelMixin):
         layout.separator()
 
 
-class USERPREF_PT_studiolight_lights(Panel, StudioLightPanelMixin):
+class USERPREF_PT_studiolight_lights(StudioLightPanel, StudioLightPanelMixin, Panel):
     bl_label = "Studio Lights"
     sl_type = 'STUDIO'
 
@@ -2102,14 +2024,13 @@ class USERPREF_PT_studiolight_lights(Panel, StudioLightPanelMixin):
         layout.separator()
 
 
-class USERPREF_PT_studiolight_light_editor(Panel):
+class USERPREF_PT_studiolight_light_editor(StudioLightPanel, Panel):
     bl_label = "Editor"
     bl_parent_id = "USERPREF_PT_studiolight_lights"
-    bl_space_type = 'PREFERENCES'
-    bl_region_type = 'WINDOW'
     bl_options = {'DEFAULT_CLOSED'}
 
-    def opengl_light_buttons(self, layout, light):
+    @staticmethod
+    def opengl_light_buttons(layout, light):
 
         col = layout.column()
         col.active = light.use
@@ -2156,33 +2077,28 @@ class USERPREF_PT_studiolight_light_editor(Panel):
         layout.prop(system, "light_ambient")
 
 
+# -----------------------------------------------------------------------------
+# Experimental Panels
+
 class ExperimentalPanel:
     bl_space_type = 'PREFERENCES'
     bl_region_type = 'WINDOW'
+    bl_context = "experimental"
 
     url_prefix = "https://developer.blender.org/"
 
-    @classmethod
-    def poll(cls, context):
-        prefs = context.preferences
-        return (prefs.active_section == 'EXPERIMENTAL')
-
-    def draw(self, context):
-        layout = self.layout
-
-        layout.use_property_split = True
-        layout.use_property_decorate = False
-
-        self.draw_props(context, layout)
-
 
 class USERPREF_PT_experimental_ui(ExperimentalPanel, Panel):
     bl_label = "User Interface"
 
-    def draw_props(self, context, layout):
+    def draw(self, context):
         prefs = context.preferences
         experimental = prefs.experimental
 
+        layout = self.layout
+        layout.use_property_split = True
+        layout.use_property_decorate = False
+
         task = "T66304"
         split = layout.split(factor=0.66)
         col = split.column()
@@ -2198,7 +2114,7 @@ class USERPREF_PT_experimental_ui(ExperimentalPanel, Panel):
 class USERPREF_PT_experimental_virtual_reality(ExperimentalPanel, Panel):
     bl_label = "Virtual Reality"
 
-    def draw_props(self, context, layout):
+    def draw_centered(self, context, layout):
         prefs = context.preferences
         experimental = prefs.experimental
 
@@ -2218,6 +2134,33 @@ class USERPREF_PT_experimental_virtual_reality(ExperimentalPanel, Panel):
 """
 
 
+class USERPREF_PT_experimental_usd(ExperimentalPanel, Panel):
+    bl_label = "Universal Scene Description"
+
+    @classmethod
+    def poll(cls, context):
+        # Only show the panel if Blender was actually built with USD support.
+        return getattr(bpy.app.build_options, "usd", False)
+
+    def draw(self, context):
+        prefs = context.preferences
+        experimental = prefs.experimental
+
+        layout = self.layout
+        layout.use_property_split = True
+        layout.use_property_decorate = False
+
+        split = layout.split(factor=0.66)
+        col = split.split()
+        col.prop(experimental, "use_usd_exporter", text="USD Exporter")
+        col = split.split()
+        url = "https://devtalk.blender.org/t/universal-scene-description-usd-exporter-feedback/10920"
+        col.operator("wm.url_open", text='Give Feedback', icon='URL').url = url
+
+
+# -----------------------------------------------------------------------------
+# Class Registration
+
 # Order of registration defines order in UI,
 # so dynamically generated classes are 'injected' in the intended order.
 classes = (
@@ -2300,6 +2243,7 @@ classes = (
     USERPREF_PT_studiolight_world,
 
     USERPREF_PT_experimental_ui,
+    USERPREF_PT_experimental_usd,
 
     # Popovers.
     USERPREF_PT_ndof_settings,