refactor: Extracted logic of enumerating child windows in WindowEnumerator

Chameleon.lpi

@@ -45,7 +45,7 @@
         <PackageName Value="LCL"/>
       </Item1>
     </RequiredPackages>
-    <Units Count="7">
+    <Units Count="8">
       <Unit0>
         <Filename Value="Chameleon.lpr"/>
         <IsPartOfProject Value="True"/>
@@ -83,6 +83,11 @@
         <HasResources Value="True"/>
         <ResourceBaseClass Value="Form"/>
       </Unit6>
+      <Unit7>
+        <Filename Value="windowenumerator.pas"/>
+        <IsPartOfProject Value="True"/>
+        <UnitName Value="WindowEnumerator"/>
+      </Unit7>
     </Units>
   </ProjectOptions>
   <CompilerOptions>

DfmEngine.pas

@@ -8,13 +8,6 @@ uses Windows, Messages, SysUtils, Classes, Forms, Graphics,
   Writers;
 
 type
-  PEnumParams = ^TEnumParams;
-
-  TEnumParams = record
-    List: TList;
-    ParentWnd: HWND;
-  end;
-
   TKnownControl = (
     kcUnknown, kcButton, kcCheckBox, kcComboBox, kcEdit,
     kcGroupBox, kcImage, kcLabel, kcListBox, kcListView,
@@ -66,7 +59,6 @@ const
 
 function BitTest(Value, Mask: integer): boolean;
 function GetWndText(wnd: HWND): string;
-function EnumChildrenProc(wnd: HWND; lp: LPARAM): BOOL; stdcall;
 procedure WriteBitmapData(dfm1: TDfmWriter; bmp: HBITMAP;
   BelongsToPicture: boolean; const Name: string);
 procedure WriteIconData(dfm1: TDfmWriter; icon: HICON; BelongsToPicture: boolean;
@@ -74,6 +66,8 @@ procedure WriteIconData(dfm1: TDfmWriter; icon: HICON; BelongsToPicture: boolean
 
 implementation
 
+uses WindowEnumerator;
+
 function BitTest(Value, Mask: integer): boolean;
 begin
   Result := (Value and Mask) = Mask;
@@ -88,16 +82,6 @@ begin
   GetWindowText(wnd, PChar(Result), len + 1);
 end;
 
-function EnumChildrenProc(wnd: HWND; lp: LPARAM): BOOL; stdcall;
-var
-  p: PEnumParams;
-begin
-  p := PEnumParams(lp);
-  if GetParent(wnd) = p^.ParentWnd then
-    p^.List.Add(Pointer(wnd));
-  Result := True;
-end;
-
 function GetBorderIconsStr(ABorderIcons: TBorderIcons): string;
 const
   biStr: array [TBorderIcon] of string = (
@@ -127,11 +111,9 @@ end;
 procedure TDfmBuilder.Build(OutStream: TStream; const frmName: string; wnd: HWND);
 var
   InStream: TMemoryStream;
-  childlist: TList;
   i: integer;
   style, exstyle: longint;
   wndX: HWND;
-  EnumParams: TEnumParams;
 
   procedure WriteBorderIcons;
   var
@@ -156,7 +138,6 @@ begin
   FillChar(Counts, sizeof(Counts), #0);
   InStream := TMemoryStream.Create;
   Dfm1 := TDfmWriter.Create(InStream);
-  childlist := TList.Create;
 
   dfm1.WriteLn('object ' + frmName + ': T' + frmName);
   style := GetWindowLong(wnd, GWL_EXSTYLE);
@@ -175,14 +156,7 @@ begin
   dfm1.WriteIntProp('TextHeight', 13);
 
   // write the children
-  EnumParams.List := childlist;
-  EnumParams.ParentWnd := wnd;
-  EnumChildWindows(wnd, @EnumChildrenProc, integer(@EnumParams));
-  for i := 0 to childlist.Count - 1 do
-  begin
-    wndX := HWND(childlist[i]);
-    PreHandleCtl(wndX);
-  end;
+  EnumerateChildWindows(wnd, Self.PreHandleCtl);
   dfm1.Ident := 0;
   dfm1.WriteLn('end');
   InStream.Position := 0;
@@ -190,29 +164,18 @@ begin
   ObjectTextToResource(InStream, OutStream);
 
   // finalization
-  childlist.Free;
   DFM1.Free;
 end;
 
 procedure TDfmBuilder.HandleUnknown(wnd: HWND; style: integer);
 var
   class_name: array [0..100] of char;
-  childlist: TList;
-  EnumParams: TEnumParams;
   i: integer;
 begin
   // since we don't know what window we're after write the class name
   GetClassName(wnd, class_name, 100);
   dfm1.WriteStringProp('Caption', class_name);
-  childlist := TList.Create;
-  EnumParams.List := childlist;
-  EnumParams.ParentWnd := wnd;
-  EnumChildWindows(wnd, @EnumChildrenProc, integer(@EnumParams));
-  for i := 0 to childlist.Count - 1 do
-  begin
-    PreHandleCtl(HWND(childlist[i]));
-  end;
-  childlist.Free;
+  EnumerateChildWindows(wnd, Self.PreHandleCtl);
 end;
 
 procedure TDfmBuilder.HandleButton(wnd: HWND; style: integer);

WindowEnumerator.pas

@@ -0,0 +1,66 @@
+unit WindowEnumerator;
+
+{$mode Delphi}
+
+interface
+
+uses
+  Windows;
+
+type
+  TWndConsumer = procedure (wnd: HWND) of object;
+
+procedure EnumerateChildWindows(wnd: HWND; consumer: TWndConsumer);
+
+implementation
+
+type
+  TWindowEnumerator = class
+  private
+    wnd: HWND;
+    consumer: TWndConsumer;
+    class function MyEnumChildrenProc(wnd: HWND; lp: LPARAM): BOOL; static; stdcall;
+    procedure Add(wnd: HWND);
+  public
+    constructor Create(wnd: HWND; consumer: TWndConsumer);
+    procedure Run;
+  end;
+
+procedure EnumerateChildWindows(wnd: HWND; consumer: TWndConsumer);
+var
+  enumerator: TWindowEnumerator;
+begin
+  enumerator := TWindowEnumerator.Create(wnd, consumer);
+  try
+    enumerator.Run;
+  finally
+    enumerator.Free;
+  end;
+end;
+
+constructor TWindowEnumerator.Create(wnd: HWND; consumer: TWndConsumer);
+begin
+  Self.wnd := wnd;
+  Self.consumer := consumer;
+end;
+
+procedure TWindowEnumerator.Run;
+begin
+  EnumChildWindows(wnd, @TWindowEnumerator.MyEnumChildrenProc, LPARAM(Self));
+end;
+
+class function TWindowEnumerator.MyEnumChildrenProc(wnd: HWND; lp: LPARAM): BOOL; static; stdcall;
+var
+  me: TWindowEnumerator;
+begin
+  me := TWindowEnumerator(lp);
+  me.Add(wnd);
+  Result := True;
+end;
+
+procedure TWindowEnumerator.Add(wnd: HWND);
+begin
+  consumer(wnd);
+end;
+
+end.

frmResults.pas

@@ -32,7 +32,7 @@ var
 
 implementation
 
-uses DfmEngine, StyleNames;
+uses StyleNames, WindowEnumerator;
 
 {$R *.lfm}
 
@@ -208,33 +208,44 @@ begin
   end;
 end;
 
+type
+  TTreeNodeChildConsumer = class
+  private
+    ParentNode: TTreeNode;
+    ChildrenRootNode: TTreeNode;
+    ChildCount: Integer;
+    Form: TResults;
+  public
+    constructor Create(Form: TResults; ParentNode: TTreeNode);
+    procedure Consume(wnd: HWND);
+  end;
+
+constructor TTreeNodeChildConsumer.Create(Form: TResults; ParentNode: TTreeNode);
+begin
+  Self.Form := Form;
+  Self.ParentNode := ParentNode;
+  Self.ChildrenRootNode := nil;
+  Self.ChildCount := 0;
+end;
+
+procedure TTreeNodeChildConsumer.Consume(wnd: HWND);
+var
+  node2: TTreeNode;
+begin
+  if not Assigned(ChildrenRootNode) then
+    ChildrenRootNode := Form.TreeView1.Items.AddChild(ParentNode, 'Children information');
+  Inc(ChildCount);
+  node2 := Form.TreeView1.Items.AddChild(ChildrenRootNode, 'Child #' + IntToStr(ChildCount));
+  Form.GetWinInfo(integer(wnd), node2);
+end;
+
 procedure TResults.GetWinInfoChildren(wnd: HWND; ParentNode: TTreeNode);
 var
-  i: integer;
-  node1, node2: TTreeNode;
-  childlist: TList;
-  EnumParams: TEnumParams;
-  class_name: String;
+  consumer: TTreeNodeChildConsumer;
 begin
-  childlist := TList.Create;
-
-  EnumParams.List := childlist;
-  EnumParams.ParentWnd := wnd;
-  EnumChildWindows(wnd, @EnumChildrenProc, integer(@EnumParams));
-
-  with TreeView1.Items do
-  begin
-    if childlist.Count > 0 then
-    begin
-      node1 := AddChild(ParentNode, 'Children information');
-      for i := 1 to childlist.Count do
-      begin
-        node2 := AddChild(node1, 'Child #' + IntToStr(i));
-        GetWinInfo(integer(childlist[i - 1]), node2);
-      end;
-    end;
-  end;
-  childlist.Free;
+  consumer := TTreeNodeChildConsumer.Create(Self, ParentNode);
+  EnumerateChildWindows(wnd, consumer.Consume);
+  consumer.Free;
 end;
 
 end.