ADD: DARWIN: add a WlxPlugin MacPreview (#603)

* ADD: DARWIN: add a WlxPlugin MacPreview, implemented using MacOS Native QuickLook Preview

* UPD: Plugin name modified and authors added in the remarks

plugins/wlx/MacPreview/src/MacPreview.lpi

@@ -0,0 +1,73 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<CONFIG>
+  <ProjectOptions>
+    <Version Value="12"/>
+    <General>
+      <Flags>
+        <MainUnitHasCreateFormStatements Value="False"/>
+        <MainUnitHasTitleStatement Value="False"/>
+        <MainUnitHasScaledStatement Value="False"/>
+      </Flags>
+      <SessionStorage Value="InProjectDir"/>
+      <Title Value="MacPreview"/>
+      <UseAppBundle Value="False"/>
+      <ResourceType Value="res"/>
+    </General>
+    <BuildModes>
+      <Item Name="Default" Default="True"/>
+    </BuildModes>
+    <PublishOptions>
+      <Version Value="2"/>
+      <UseFileFilters Value="True"/>
+    </PublishOptions>
+    <RunParams>
+      <FormatVersion Value="2"/>
+    </RunParams>
+    <Units>
+      <Unit>
+        <Filename Value="MacPreview.lpr"/>
+        <IsPartOfProject Value="True"/>
+      </Unit>
+    </Units>
+  </ProjectOptions>
+  <CompilerOptions>
+    <Version Value="11"/>
+    <Target>
+      <Filename Value="../MacPreview.wlx" ApplyConventions="False"/>
+    </Target>
+    <SearchPaths>
+      <IncludeFiles Value="$(ProjOutDir)"/>
+      <OtherUnitFiles Value="../../../../sdk"/>
+      <UnitOutputDirectory Value="lib/$(TargetCPU)-$(TargetOS)"/>
+    </SearchPaths>
+    <CodeGeneration>
+      <SmartLinkUnit Value="True"/>
+      <RelocatableUnit Value="True"/>
+      <Optimizations>
+        <OptimizationLevel Value="3"/>
+      </Optimizations>
+    </CodeGeneration>
+    <Linking>
+      <Debugging>
+        <GenerateDebugInfo Value="False"/>
+      </Debugging>
+      <LinkSmart Value="True"/>
+      <Options>
+        <ExecutableType Value="Library"/>
+      </Options>
+    </Linking>
+  </CompilerOptions>
+  <Debugging>
+    <Exceptions>
+      <Item>
+        <Name Value="EAbort"/>
+      </Item>
+      <Item>
+        <Name Value="ECodetoolError"/>
+      </Item>
+      <Item>
+        <Name Value="EFOpenError"/>
+      </Item>
+    </Exceptions>
+  </Debugging>
+</CONFIG>

plugins/wlx/MacPreview/src/MacPreview.lpr

@@ -0,0 +1,95 @@
+{
+   Double commander
+   -------------------------------------------------------------------------
+   MacOS preview plugin
+
+   Copyright (C) 2022 Alexander Koblov (alexx2000@mail.ru)
+   Copyright (C) 2022 Rich Chang (rich2014.git@outlook.com)
+
+   This library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program. If not, see <http://www.gnu.org/licenses/>.
+}
+
+library MacPreview;
+
+{$mode objfpc}{$H+}
+{$modeswitch objectivec1}
+
+uses
+  SysUtils, WlxPlugin, CocoaAll, QuickLookUI;
+
+type
+  TQLPItem = objcclass(NSObject, QLPreviewItemProtocol)
+    url: NSURL;
+    function previewItemURL: NSURL;
+  end;
+
+function TQLPItem.previewItemURL: NSURL;
+begin
+  Result:= url;
+end;
+
+function StringToNSString(const S: String): NSString;
+begin
+  Result:= NSString(NSString.stringWithUTF8String(PAnsiChar(S)));
+end;
+
+procedure setFilepath( view:QLPreviewView; filepath:String );
+var
+  item: TQLPItem;
+begin
+  if filepath=EmptyStr then begin
+    item:= nil;
+  end else begin
+    item:= TQLPItem.alloc.init;
+    item.url:= NSURL.fileURLWithPath( StringToNSString(filepath) );
+  end;
+  view.setPreviewItem( item );
+end;
+
+function ListLoad( ParentWin:THandle; FileToLoad:pchar; {%H-}ShowFlags{%H+}:integer):THandle; cdecl;
+var
+  view: QLPreviewView;
+begin
+  view:= QLPreviewView.alloc.init;
+  view.setShouldCloseWithWindow( false );
+  NSView(ParentWin).addSubview( view );
+  setFilepath( view, FileToLoad );
+  Result:= THandle(view);
+end;
+
+function ListLoadNext( {%H-}ParentWin{%H+},PluginWin:THandle; FileToLoad:pchar; {%H-}ShowFlags{%H+}:integer):integer; cdecl;
+begin
+  setFilepath( QLPreviewView(PluginWin), FileToLoad );
+  Result:= LISTPLUGIN_OK;
+end;
+
+procedure ListCloseWindow(ListWin:THandle); cdecl;
+begin
+  QLPreviewView(ListWin).close;
+  QLPreviewView(ListWin).removeFromSuperview;
+end;
+
+procedure ListGetDetectString(DetectString:pchar;maxlen:integer); cdecl;
+begin
+  StrLCopy(DetectString, '(EXT!="")', MaxLen);
+end;
+
+exports
+  ListLoad,
+  ListLoadNext,
+  ListCloseWindow,
+  ListGetDetectString;
+
+end.
+