Add "cascade" filter run prefix and use it to control view templates (#6168)

* Initial Commit

* Set currentTiddler and ..currentTiddler for filter evaulation

* Precompile the filters for performance

* Add explicit test for empty result when no filter passes

* Use the cascade filter run prefix to choose the view template body template

* Use the cascade mechanism to choose between the edit and view templates

* Simplify cascade filter

Thanks @saqimtiaz

* Add control panel UI for inspecting the template cascades

* Refactor import listing and plugin listing as alternate body templates

As suggested by @pmario

* Refer to $:/core/ui/{View|Edit}Template via their associated config tiddlers

* Fix typo in previous commit

* Add demo of custom story tiddler template

* Tweak control panel wording

* Standardise "Story Tiddler Template" nomenclature

* Add a cascade for the editor template body

* Add a cascade for the view template title

* Avoid unwanted whitespace

* Add a cascade for dynamically choosing tiddler icons

core/ui/EditTemplate/body.tid

@@ -1,56 +1,4 @@
 title: $:/core/ui/EditTemplate/body
 tags: $:/tags/EditTemplate
 
-\define lingo-base() $:/language/EditTemplate/Body/
-\define config-visibility-title()
-$:/config/EditorToolbarButtons/Visibility/$(currentTiddler)$
-\end
-
-\define importFileActions()
-<$action-popup $state=<<importState>> $coords="(0,0,0,0)" $floating="yes"/>
-\end
-
-<$list filter="[all[current]has[_canonical_uri]]">
-
-<div class="tc-message-box">
-
-<<lingo External/Hint>>
-
-<a href={{!!_canonical_uri}}><$text text={{!!_canonical_uri}}/></a>
-
-<$edit-text field="_canonical_uri" class="tc-edit-fields" tabindex={{$:/config/EditTabIndex}} cancelPopups="yes"></$edit-text>
-
-</div>
-
-</$list>
-
-<$set name="edit-preview-state" value={{{ [{$:/config/ShowEditPreview/PerTiddler}!match[yes]then[$:/state/showeditpreview]] :else[<qualify "$:/state/showeditpreview">] }}}>
-<$list filter="[all[current]!has[_canonical_uri]]">
-<$vars importTitle=<<qualify $:/ImportImage>> importState=<<qualify $:/state/ImportImage>> >
-<$dropzone importTitle=<<importTitle>> autoOpenOnImport="no" contentTypesFilter={{$:/config/Editor/ImportContentTypesFilter}} class="tc-dropzone-editor" enable={{{ [{$:/config/DragAndDrop/Enable}match[no]] :else[subfilter{$:/config/Editor/EnableImportFilter}then[yes]else[no]] }}} filesOnly="yes" actions=<<importFileActions>> ><$reveal stateTitle=<<edit-preview-state>> type="match" text="yes">
-<div class="tc-tiddler-preview">
-
-<$transclude tiddler="$:/core/ui/EditTemplate/body/editor" mode="inline"/>
-
-<div class="tc-tiddler-preview-preview">
-
-<$transclude tiddler={{$:/state/editpreviewtype}} mode="inline">
-
-<$transclude tiddler="$:/core/ui/EditTemplate/body/preview/output" mode="inline"/>
-
-</$transclude>
-
-</div>
-
-</div>
-</$reveal>
-
-<$reveal stateTitle=<<edit-preview-state>> type="nomatch" text="yes">
-
-<$transclude tiddler="$:/core/ui/EditTemplate/body/editor" mode="inline"/>
-
-</$reveal>
-</$dropzone>
-</$vars>
-</$list>
-</$set>
+<$transclude tiddler={{{ [<currentTiddler>] :cascade[all[shadows+tiddlers]tag[$:/tags/EditTemplateBodyFilter]get[text]] :and[!is[blank]else[$:/core/ui/EditTemplate/body/default]] }}} />

core/ui/EditTemplate/body/canonical-uri.tid

@@ -0,0 +1,13 @@
+title: $:/core/ui/EditTemplate/body/canonical-uri
+
+\define lingo-base() $:/language/EditTemplate/Body/
+
+<div class="tc-message-box">
+
+<<lingo External/Hint>>
+
+<a href={{!!_canonical_uri}}><$text text={{!!_canonical_uri}}/></a>
+
+<$edit-text field="_canonical_uri" class="tc-edit-fields" tabindex={{$:/config/EditTabIndex}} cancelPopups="yes"></$edit-text>
+
+</div>

core/ui/EditTemplate/body/default.tid

@@ -0,0 +1,38 @@
+title: $:/core/ui/EditTemplate/body/default
+
+\define config-visibility-title()
+$:/config/EditorToolbarButtons/Visibility/$(currentTiddler)$
+\end
+
+\define importFileActions()
+<$action-popup $state=<<importState>> $coords="(0,0,0,0)" $floating="yes"/>
+\end
+
+<$set name="edit-preview-state" value={{{ [{$:/config/ShowEditPreview/PerTiddler}!match[yes]then[$:/state/showeditpreview]] :else[<qualify "$:/state/showeditpreview">] }}}>
+<$vars importTitle=<<qualify $:/ImportImage>> importState=<<qualify $:/state/ImportImage>> >
+<$dropzone importTitle=<<importTitle>> autoOpenOnImport="no" contentTypesFilter={{$:/config/Editor/ImportContentTypesFilter}} class="tc-dropzone-editor" enable={{{ [{$:/config/DragAndDrop/Enable}match[no]] :else[subfilter{$:/config/Editor/EnableImportFilter}then[yes]else[no]] }}} filesOnly="yes" actions=<<importFileActions>> ><$reveal stateTitle=<<edit-preview-state>> type="match" text="yes">
+<div class="tc-tiddler-preview">
+
+<$transclude tiddler="$:/core/ui/EditTemplate/body/editor" mode="inline"/>
+
+<div class="tc-tiddler-preview-preview">
+
+<$transclude tiddler={{$:/state/editpreviewtype}} mode="inline">
+
+<$transclude tiddler="$:/core/ui/EditTemplate/body/preview/output" mode="inline"/>
+
+</$transclude>
+
+</div>
+
+</div>
+</$reveal>
+
+<$reveal stateTitle=<<edit-preview-state>> type="nomatch" text="yes">
+
+<$transclude tiddler="$:/core/ui/EditTemplate/body/editor" mode="inline"/>
+
+</$reveal>
+</$dropzone>
+</$vars>
+</$set>