From b01341302fe6fee2dc0dc83df23fa4cccccc8db1 Mon Sep 17 00:00:00 2001
From: wp_xxyyzz <wp_xxyyzz@8e941d3f-bd1b-0410-a28a-d453659cc2b4>
Date: Sun, 15 Jan 2023 17:18:52 +0000
Subject: [PATCH] ExCtrls: Fix CheckComboboxEx having a zero-height dropdown
 after Laz commit e4043024. Minor optimization in MeasureItem.

git-svn-id: https://svn.code.sf.net/p/lazarus-ccr/svn@8679 8e941d3f-bd1b-0410-a28a-d453659cc2b4
---
 components/exctrls/source/excheckcombo.pas | 36 ++++++++++++++++------
 1 file changed, 27 insertions(+), 9 deletions(-)

diff --git a/components/exctrls/source/excheckcombo.pas b/components/exctrls/source/excheckcombo.pas
index 4ebae80a1..9cc6d0abd 100644
--- a/components/exctrls/source/excheckcombo.pas
+++ b/components/exctrls/source/excheckcombo.pas
@@ -5,7 +5,8 @@ unit ExCheckCombo;
 interface
 
 uses
-  LCLIntf, LCLType, Classes, SysUtils, Controls, StdCtrls, ImgList,
+  LCLIntf, LCLType,
+  Classes, SysUtils, Controls, StdCtrls, ImgList,
   GroupedEdit, EditBtn, CheckLst, Forms;
 
 type
@@ -215,6 +216,17 @@ implementation
 uses
   Buttons, Themes, WSForms;
 
+type
+  TCustomListboxHelper = class helper for TCustomListbox
+  public
+    function CalculateStandardItemHeight: Integer;
+  end;
+
+function TCustomListboxHelper.CalculateStandardItemHeight: Integer;
+begin
+  Result := inherited;
+end;
+
 { TCCBItem }     // CCB = CheckComboBox
 type
   TCCBItem = class
@@ -481,6 +493,7 @@ type
     FCaller: TControl;
     FCheckListBox: TCheckListBox;
     FDropDownCount: Integer;
+    FStdItemHeight: Integer;
   protected
     procedure ActivateDoubleBuffered;
     procedure DblClickHandler(Sender: TObject);
@@ -503,6 +516,7 @@ begin
   FCheckListbox.OnDblClick := @DblClickHandler;
   FCheckListbox.OnKeyDown := @KeyDownHandler;
   FDropDownCount := 8;
+  FStdItemHeight := FCheckListbox.CalculateStandardItemHeight;
 end;
   
 procedure TCheckComboBoxForm.ActivateDoubleBuffered;
@@ -578,16 +592,20 @@ end;
 
 procedure TCheckComboBoxForm.MeasureHeight(out AHeight: Integer);
 var
-  i: Integer;
-  h: Integer = 0;
+  i, h, n: Integer;
 begin
   AHeight := 0;
-  for i := 0 to FCheckListbox.Items.Count-1 do
-    if i < FDropDownCount then
-    begin
-      FCheckListbox.MeasureItem(i, h);
-      inc(AHeight,h);
-    end;
+  n := FCheckListbox.Items.Count;
+  if FDropDownCount < n then
+    n := FDropDownCount;
+  for i := 0 to n-1 do
+  begin
+    h := -1;
+    FCheckListbox.MeasureItem(i, h);
+    if h = -1 then
+      h := FStdItemHeight;
+    inc(AHeight, h);
+  end;
   inc(AHeight, 6);
 end;