BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Component needs to confirm parent before showing          BorlandTalk.com Forum Index -> comp.lang.pascal.delphi.components.writing View previous topic :: View next topic   Author Message Bill Bateman Guest Posted: Thu Apr 07, 2005 7:18 am    Post subject: Component needs to confirm parent before showing Hello all, I am attempting to create some CustomControls that only drop on a TPanel. However, in order to do this, I need to check the Parent.Classtype for a match to TPanel. I cannot get access to Parent in the constructor and the loaded procedure doesn't get fired. I cannot use AOwner in the constructor because it always references Tform. Has anyone done this before that can help? Bill Back to top Bruce Roberts Guest Posted: Thu Apr 07, 2005 3:32 pm    Post subject: Re: Component needs to confirm parent before showing "Bill Bateman" <bbateman (AT) gmail (DOT) com> wrote Quote: I am attempting to create some CustomControls that only drop on a TPanel. However, in order to do this, I need to check the Parent.Classtype for a match to TPanel. I cannot get access to Parent in the constructor and the loaded procedure doesn't get fired. I cannot use AOwner in the constructor because it always references Tform. Parent isn't known until after component construction. You'll need to override the SetParent method to prevent the assignement of anything but a tCustomPanel, or whatever. IIRC something like the following should do it procedure tSomeControl.SetParent (aParent : tWinControl); begin if not (aParent is tCustomPanel) then raise exception.Create ('Drop me only on a panel'); inherited; end; Back to top dhamdon@gmail.com Guest Posted: Thu Apr 07, 2005 4:19 pm    Post subject: Re: Component needs to confirm parent before showing I have attempted this solution. At first it appears to work but then you quickly find out that, even though the exception was thrown, the Object is still written to the .DFM file. Which, I guess, means that the streaming mechanism still writes the object definition even if you throw an exception in the SetParent before or after the Inherited call. This seems to be so difficult to implement cleaning. Does this mean we have the wrong solution to the problem? Did Borland intend for us to do this in a different way? Like the TToolButton & TToolbar for example. There you have to right-click to add a TToolbar. You cannot drag one off the Component Palette. TToolbar isn't there. Back to top Bill Bateman Guest Posted: Thu Apr 07, 2005 4:23 pm    Post subject: Re: Component needs to confirm parent before showing I saw how the toolbar was implemented, however, that control only allows for the layout IT designates, not custom layouts that would be able to mimic, say, Microsoft interfaces. This way, I can drop combos, buttons, etc on the panel/toolbar, in any layout, but they need only to work on that panel I created because the paint needs to know information from that specific parent. Bill Back to top Bruce Roberts Guest Posted: Thu Apr 07, 2005 8:18 pm    Post subject: Re: Component needs to confirm parent before showing <dhamdon (AT) gmail (DOT) com> wrote Quote: I have attempted this solution. At first it appears to work but then you quickly find out that, even though the exception was thrown, the Object is still written to the .DFM file. Which, I guess, means that the streaming mechanism still writes the object definition even if you throw an exception in the SetParent before or after the Inherited call. At the time Parent is set, Owner already has a value - typically the form. Owner is responsible for streaming, so I'm not sure that there is a clean way to get rid of the thing. You might consider, instead, simply having your controls not function if Parent isn't a valid control. Back to top Bill Bateman Guest Posted: Sat Apr 09, 2005 5:21 am    Post subject: Re: Component needs to confirm parent before showing Still not the cleanest or most complete solution. I am quite surprised that this is not possible. I am posting this in a yahoo group to see if I can get any other answers. I will post any 'good' responses here if i get them. Bill Back to top Bruce Roberts Guest Posted: Mon Apr 11, 2005 1:57 pm    Post subject: Re: Component needs to confirm parent before showing "Bill Bateman" <bbateman (AT) gmail (DOT) com> wrote Quote: Still not the cleanest or most complete solution. I am quite surprised that this is not possible. I am posting this in a yahoo group to see if I can get any other answers. I will post any 'good' responses here if i get them. I don't see why its so surprising. If you want a panel to only host a few types of controls, rather than any hostable control, the panel should be the one making the decision, not the sub-control. You might want to take a look at tPageControl to see how it manages the feat. Back to top Bill Bateman Guest Posted: Tue Apr 12, 2005 3:19 am    Post subject: Re: Component needs to confirm parent before showing OK, here is the working code thanks to the Calgary Delphi Users Group: What is needed is handling both cases; designtime and runtime. Here is a small example: type TTestLabel = class(TLabel) private procedure CheckParent(AParent: TComponent); protected procedure ValidateContainer(AComponent: TComponent); override; procedure SetParent(AParent: TWinControl); override; end; procedure TTestLabel.CheckParent(AParent: TComponent); begin if Assigned(AParent) and not (AParent is TCustomPanel) then raise Exception.Create('TTestLabel requires a TCustomPanel parent'); end; procedure TTestLabel.SetParent(AParent: TWinControl); begin if not (csDesigning in ComponentState) then CheckParent(AParent); inherited SetParent(AParent); end; procedure TTestLabel.ValidateContainer(AComponent: TComponent); begin inherited ValidateContainer(AComponent); if csDesigning in ComponentState then CheckParent(AComponent); end; Bill Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         BorlandTalk.com Forum Index -> comp.lang.pascal.delphi.components.writing All times are GMT Page 1 of 1   Jump to: Select a forum C++ Builder Newsgroups----------------C++ BuilderC++ Builder (ActiveX)C++ Builder (Announcements)C++ Builder (Command Line Tools)C++ Builder DatabasesC++ Builder Databases (ADO)C++ Builder Databases (Desktop)C++ Builder Databases (InterBase Express)C++ Builder Databases (Multi-Tier)C++ Builder Databases (SQL Servers)C++ Builder (Graphics)C++ Builder (IDE)C++ Builder (Internet)C++ Builder (Internet Socket)C++ Builder (Internet Web)C++ Builder (Jobs)C++ Builder (Language)C++ Builder (Language C++)C++ Builder (Compatibility with MFC)C++ Builder (Native API)C++ Builder (Non-Technical)C++ Builder (Students)C++ Builder (Third Party Tools)C++ Builder (Upgrade)C++ Builder (VCL)C++ Builder (VCL Components Usage)C++ Builder (VCL Components Development)C++ Builder (VCL Usage)C++ Builder (WinAPI)C++ Builder Installation Delphi Newsgroups----------------Delphi (General)Delphi ActiveX Controls UsageDelphi ActiveX Controls DevelopmentDelphi As400Delphi DatabasesDelphi Databases (ADO)Delphi Databases (dbExpress)Delphi Databases (Desktop)Delphi Databases (InterBase Express)Delphi Databases (Multi-Tier)Delphi Databases (SQL Servers)Delphi DeploymentDelphi GraphicsDelphi IDEDelphi InternationalizationDelphi InternetDelphi Internet Isapi-WebBrokerDelphi Internet WebSnapDelphi Internet WinsockDelphi JobsDelphi Language BASMDelphi Language ObjectPascalDelphi Model Driven Architecture (General)Delphi Model Driven Architecture (Third Party)Delphi MultimediaDelphi Native APIDelphi Non-TechnicalDelphi ObjectPascalDelphi OLE AutomationDelphi OO designDelphi OpenToolsAPIDelphi Reporting-ChartingDelphi RTLDelphi StudentsDelphi TeamSourceDelphi Thirdparty ToolsDelphi Thirdparty Tools (General)Delphi Thirdparty Tools (IntraWeb)Delphi Thirdparty Tools (RaveReports)Delphi UpgradeDelphi VCLDelphi VCL ComponentsDelphi VCL Components UsingDelphi VCL Components WritingDelphi WebServices SOAPDelphi WinAPIDelphi XMLDelphi Installationcomp.lang.pascal.delphi.components.misccomp.lang.pascal.delphi.components.usagecomp.lang.pascal.delphi.components.writingcomp.lang.pascal.delphi.databasescomp.lang.pascal.delphi.misccomp.sources.delphi JBuilder Newsgroups----------------JBuilderJBuilder AnnouncementsJBuilder Applet IssuesJBuilder As400JBuilder CompilerJBuilder CORBA/RMIJBuilder DatabasesJBuilder DB SwingJBuilder DebuggerJBuilder DeploymentJBuilder DocumentationJBuilder EnterpriseJBuilder HandheldJBuilder IDEJBuilder JavaJBuilder JavaAPIJBuilder Java LanguageJBuilder Java SwingJBuilder Java BeansJBuilder Java Beans UsageJBuilder Java Beans DevelopmentJBuilder JBCLJBuilder JDataStoreJBuilder JobsJBuilder LinuxJBuilder MacintoshJBuilder & MobileSetJBuilder MultiLingual AppsJBuilder Non-TechnicalJBuilder OpenToolsJBuilder Servlets (JSP)JBuilder StudentsJBuilder Team DevelopmentJBuilder Thirdparty ToolsJBuilder UpgradeJBuilder Installation InterBase Newsgroups----------------InterBaseInterBase Bug DiscussionInterBase GeneralInterBase IBConsoleInterBase OpenSourceInterBase ReplicationInterBase SQLInterBase ThirdpartyInterBase Installation Miscellaneous Borland Newsgroups----------------AppCenterAppServerEnteraVisiBroker  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.