Is it possible for a Delphi application to receive a dfm file with objects, its properties and event assignments, and load up all those information just like when how they do with internal dfm compiled with it?
How could we do that? Is there a direct way?
Note: the application will already have the code with the correct classes and methods, events included.We could also remotely receive some kind of script that could be read by my application which would create the objects necessary to match the dfm file specifications. Just like Web browsers interpret the HTML, css and JS files...
It is indeed possible to load a .dfm file at runtime and create the form represented by that dfm file.
I have written some code to do exactly that:
However: please note: You will need to add more RegisterClass(TSomeComponent) lines in the RegisterNecessaryClasses procedure. As written, if you, for example, try to load a .dfm file that includes a TSpeedbutton, you will get an exception: just add the RegisterClass(TSpeedbutton) to the RegisterNecessaryClasses procedure.
unit DynaFormF; // This is a normal Delphi form - just an empty one (No components dropped on the form) interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs; type TfrmDynaForm = class(TForm) private { Private declarations } public { Public declarations } end; var frmDynaForm: TfrmDynaForm; implementation {$R *.dfm} end.
// :
unit DynaLoadDfmU; {$O-} interface uses Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls, ExtCtrls, ComCtrls, utils08, DynaFormF; var DebugSL : TStrings; procedure ShowDynaFormModal(Filename:String); implementation procedure RegisterNecessaryClasses; begin RegisterClass(TfrmDynaForm); RegisterClass(TPanel); RegisterClass(TMemo); RegisterClass(TTimer); RegisterClass(TListBox); RegisterClass(TSplitter); RegisterClass(TEdit); RegisterClass(TCheckBox); RegisterClass(TButton); RegisterClass(TLabel); RegisterClass(TRadioGroup); end; type TCrackedTComponent = class(TComponent) protected procedure UpdateState_Designing; end; var ClassRegistered : Boolean; procedure RemoveEventHandlers(SL:TStrings); const Key1 = ' On'; Key2 = ' = '; var i, k1,k2 : Integer; S : String; begin for i := SL.Count-1 downto 0 do begin S := SL[i]; k1 := pos(Key1, S); k2 := pos(Key2, S); if (k1 <> 0) AND (k2 > k1) then begin // remove it: SL.Delete(i); end; end; end; procedure ReportBoolean(S:String; B:Boolean); const Txts : Array[Boolean] of String = ( 'Cleared', 'Set' ); begin if Assigned(DebugSL) then begin S := S + ' : ' + Txts[B]; DebugSL.Add(S); end; end; procedure SetComponentStyles(AForm:TForm); var AComponent : TComponent; i : Integer; B1, B2 : Boolean; begin for i := 0 to AForm.ComponentCount-1 do begin AComponent := AForm.Components[i]; if AComponent is TTimer then begin // TTIMER: B1 := csDesigning in AComponent.ComponentState; // Does not work: an attempt to make the TTimer visible like it is in Delphi IDE's form designer. TCrackedTComponent(AComponent).UpdateState_Designing; B2 := csDesigning in AComponent.ComponentState; ReportBoolean('Before setting it: ', B1); ReportBoolean('After setting it: ', B2); end; end; end; procedure ShowDynaFormModalPrim(Filename:String); var FormDyna : TfrmDynaForm; S1 : TFileStream; S1m : TMemoryStream; S2 : TMemoryStream; S : String; k1, k2 : Integer; Reader : TReader; SLHelper : TStringlist; OK : Boolean; MissingClassName, FormName, FormTypeName : String; begin FormName := 'frmDynaForm'; FormTypeName := 'TfrmDynaForm'; FormDyna := NIL; OK := False; S1 := TFileStream.Create(Filename, fmOpenRead or fmShareDenyWrite); try S1m := TMemoryStream.Create; try SLHelper := TStringlist.Create; try SLHelper.LoadFromStream(S1); S := SLHelper[0]; k1 := pos(' ', S); k2 := pos(': ', S); if (k1 <> 0) AND (k2 > k1) then begin // match: SetLength(S, k2+1); S := 'object ' + FormName + ': ' + FormTypeName; SLHelper[0] := S; end; RemoveEventHandlers(SLHelper); SLHelper.SaveToStream(S1m); finally SLHelper.Free; end; S1m.Position := 0; S2 := TMemoryStream.Create; try ObjectTextToBinary(S1m, S2); S2.Position := 0; Reader := TReader.Create(S2, 4096); try try FormDyna := TfrmDynaForm.Create(NIL); Reader.ReadRootComponent(FormDyna); OK := True; SetComponentStyles(FormDyna); except on E:Exception do begin S := E.ClassName + ' ' + E.Message; if Assigned(DebugSL) then begin DebugSL.add(S); if (E.ClassName = 'EClassNotFound') then begin // the class is missing - we need one more "RegisterClass" line in the RegisterNecessaryClasses procedure. MissingClassName := CopyBetween(E.Message, 'Class ', ' not found'); S := ' RegisterClass(' + MissingClassName + ');'; DebugSL.Add(S); end; end; end; end; finally Reader.Free; end; finally S2.Free; end; finally S1m.Free; end; finally S1.Free; end; if OK then begin try FormDyna.Caption := 'Dynamically created form: ' + ' -- ' + FormDyna.Caption; FormDyna.ShowModal; finally FormDyna.Free; end; end else begin // failure: S := 'Dynamic loading of form file failed.'; if Assigned(DebugSL) then DebugSL.Add(S) end; end; procedure ShowDynaFormModal(Filename:String); begin if NOT ClassRegistered then begin ClassRegistered := True; RegisterNecessaryClasses; end; ShowDynaFormModalPrim(Filename); end; { TCrackedTComponent } procedure TCrackedTComponent.UpdateState_Designing; begin SetDesigning(TRUE, FALSE); end; end.
You are presented a DFM form design file, and you want to instantiate it?
Without the accompanying PAS source file, this is not possible. You need the implementation of how the class acts and interacts. (If there is no implementation, i.e. the DFM does not refer to event handlers, then you could create a class at runtime if you have or parse the classname from the DFM. But you would have to know or parse all published members of the form class, thus making this solution kind of academical).
Even if you have the source file, you would need it at compile time in order to be able to create the class.
If you have both design and source files at compile time, then add them to the project and you would not need to load the form from file since it is included in the executable's resources. Just use the default constructor Create at runtime to create the form.
When you have a secondary DFM form file for a single PAS source file, then use this kind of trick to create with the CreateNew constructor an alternative form object (e.g. with some controls hidden or styled) based on the same code.
If your DFM file is at runtime created from a specific state of the form, then create the form as normal but restore that particular state with one of the answers to this question.
