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• How do you keep application logic separate from UI when UI components have built-in functionality?

  - by Al C

  I know it's important to keep user interface code separated from domain code--the application is easier to understand, maintain, change, and (sometimes) isolate bugs. But here's my mental block ... Delphi comes with components with methods that do what I want, e.g., a RichText Memo component lets me work with rich text. Other components, like TMS's string grid not only do what I want, but I paid extra for the functionality. These features put the R in RAD. It seems illogical to write my own classes to do things somebody else has already done for me. It's reinventing the wheel [ever tried working directly with rich text? :-) ] But if I use the functionality built into components like these, then I will end up with lots of intermingled UI and domain code--I'll have a form with most of my code built into its event handlers. How do you deal with this issue? ... Or, if I want to continue using the code others have already written for me, how would you suggest I deal with the issue?

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• Why can't I start the Windows Update control panel with WinExec?

  - by Bill

  In Executing Control Panel Items, MSDN says this: Windows Vista Canonical Names In Windows Vista and later, the preferred method of launching a Control Panel item from a command line is to use the Control Panel item's canonical name. According to the Microsoft website this should work: The following example shows how an application can start the Control Panel item Windows Update with WinExec. WinExec("%systemroot%\system32\control.exe /name Microsoft.WindowsUpdate", SW_NORMAL); For Delphi 2010 I tried: var CaptionString: string; Applet: string; Result: integer; ParamString: string; CaptionString := ListviewApplets1.Items.Item[ ListviewApplets1.ItemIndex ].Caption; if CaptionString = 'Folder Options' then { 6DFD7C5C-2451-11d3-A299-00C04F8EF6AF } Applet := 'Microsoft.FolderOptions' else if CaptionString = 'Fonts' then {93412589-74D4-4E4E-AD0E-E0CB621440FD} Applet := 'Microsoft.Fonts' else if CaptionString = 'Windows Update' then { 93412589-74D4-4E4E-AD0E-E0CB621440FD } Applet := 'Microsoft.WindowsUpdate' else if CaptionString = 'Game Controllers' then { 259EF4B1-E6C9-4176-B574-481532C9BCE8 } Applet := 'Microsoft.GameControllers' else if CaptionString = 'Get Programs' then { 15eae92e-f17a-4431-9f28-805e482dafd4 } Applet := 'Microsoft.GetPrograms' //... ParamString := ( SystemFolder + '\control.exe /name ' ) + Applet; WinExec( ParamString, SW_NORMAL); <= This does not execute and when I trapped the error it returned ERROR_FILE_NOT_FOUND. I tried a ExecAndWait( ParamString ) method and it works perfectly with the same ParamString used with WinExec: ParamString := ( SystemFolder + '\control.exe /name ' ) + Applet; ExecAndWait( ParamString ); <= This executes and Runs perfectly The ExecAndWait method I used calls Windows.CreateProcess: if Windows.CreateProcess( nil, PChar( CommandLine ), nil, nil, False, 0, nil, nil, StartupInfo, ProcessInfo ) then begin try Does WinExec require a different ParamString, or am I doing this wrong with WinExec? I did not post the full ExecAndWait method but I can if someone wants to see it.

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• Why doesn't access database update?

  - by Ryan

  Recently I met a strange problem, see code snips as below: var sqlCommand: string; connection: TADOConnection; qry: TADOQuery; begin connection := TADOConnection.Create(nil); try connection.ConnectionString := 'Provider=Microsoft.Jet.OLEDB.4.0;Data Source=Test.MDB;Persist Security Info=False'; connection.Open(); qry := TADOQuery.Create(nil); try qry.Connection := connection; qry.SQL.Text := 'Select * from aaa'; qry.Open; qry.Append; qry.FieldByName('TestField1').AsString := 'test'; qry.Post; beep; finally qry.Free; end; finally connection.Free; end; end; First, Create a new access database named test.mdb and put it under the directory of this test project, we can create a new table named aaa in it which has only one text type field named TestField1. We set a breakpoint at line of "beep", then lunch the test application under ide debug mode, when ide stops at the breakpoint line (qry.post has been executed), at this time we use microsoft access to open test.mdb and open table aaa you will find there are no any changes in table aaa, if you let the ide continue running after pressing f9 you can find a new record is inserted in to table aaa, but if you press ctrl+f2 to terminate the application at the breakpoint, you will find the table aaa has no record been inserted, but in normal circumstance, a new record should be inserted in to the table aaa after qry.post executed. who can explain this problem , it troubles me so long time. thanks !!! BTW, the ide is delphi 2010, and the access mdb file is created by microsoft access 2007 under windows 7

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• Real time location tracking - windows program or browser based?

  - by mawg

  I want to track a few hundred, maybe a few thousand people in real time. Let's say that the hardware aspects are sorted out and I can get the data into a database. Now, I want to get it out and show it, in real-time. Weeeell ... "real-enough" time. Let's say that I want to draw a floorplan of a building and plot everyone every 1 to 5 seconds. (I might want to show only certain "kinds" of people at the click of a button; I will need datamining, etc, but let's stick with the worse case scenario). I am comfortable enough with PHP, though not this sort of thing. I personally would be happier with a windows app coded in Delphi, but the trend seems to be to make everything browser based. So, the question, I guess is whether a browser can handle this and whether there are compelling arguments for a windows-based or browser-based solution. If browser-based can handle this (displaying a few thousand data-points a second), and there are no overwhelming arguments for windows then I guess I will go for browser-based and learn a few new tricks. The obvious advantage being that I could also re-use a large part of my code for (vehicle) tracking on Google maps.

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• Start the Control Panel item Windows Update with WinExec.

  - by Bill

  Windows Vista Canonical Names The Microsoft website says "In Windows Vista and later, the preferred method of launching a Control Panel item from a command line is to use the Control Panel item's canonical name." According to the Microsoft website this should work: The following example shows how an application can start the Control Panel item Windows Update with WinExec. WinExec("%systemroot%\system32\control.exe /name Microsoft.WindowsUpdate", SW_NORMAL); For Delphi 2010 I tried: var CaptionString: string; Applet: string; Result: integer; ParamString: string; CaptionString := ListviewApplets1.Items.Item[ ListviewApplets1.ItemIndex ].Caption; if CaptionString = 'Folder Options' then { 6DFD7C5C-2451-11d3-A299-00C04F8EF6AF } Applet := 'Microsoft.FolderOptions' else if CaptionString = 'Fonts' then {93412589-74D4-4E4E-AD0E-E0CB621440FD} Applet := 'Microsoft.Fonts' else if CaptionString = 'Windows Update' then { 93412589-74D4-4E4E-AD0E-E0CB621440FD } Applet := 'Microsoft.WindowsUpdate' else if CaptionString = 'Game Controllers' then { 259EF4B1-E6C9-4176-B574-481532C9BCE8 } Applet := 'Microsoft.GameControllers' else if CaptionString = 'Get Programs' then { 15eae92e-f17a-4431-9f28-805e482dafd4 } Applet := 'Microsoft.GetPrograms' //... ParamString := ( SystemFolder + '\control.exe /name ' ) + Applet; WinExec( ParamString, SW_NORMAL); <= This does not execute and when I trapped the error it returned ERROR_FILE_NOT_FOUND. I tried a ExecAndWait( ParamString ) method and it works perfectly with the same ParamString used with WinExec: ParamString := ( SystemFolder + '\control.exe /name ' ) + Applet; ExecAndWait( ParamString ); <= This executes and Runs perfectly The ExecAndWait method I used creates a Windows.CreateProcess... if Windows.CreateProcess( nil, PChar( CommandLine ), nil, nil, False, 0, nil, nil, StartupInfo, ProcessInfo ) then begin try My Question Does WinExec require a different ParamString or am I doing this wrong with WinExec? I did not post the full ExecAndWait method but I can if someone wants to see it...

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• How to use a TFileStream to read 2D matrices into dynamic array?

  - by Robert Frank

  I need to read a large (2000x2000) matrix of binary data from a file into a dynamic array with Delphi 2010. I don't know the dimensions until run-time. I've never read raw data like this, and don't know IEEE so I'm posting this to see if I'm on track. I plan to use a TFileStream to read one row at a time. I need to be able to read as many of these formats as possible: 16-bit two's complement binary integer 32-bit two's complement binary integer 64-bit two's complement binary integer IEEE single precision floating-point For 32-bit two's complement, I'm thinking something like the code below. Changing to Int64 and Int16 should be straight forward. How can I read the IEEE? Am I on the right track? Any suggestions on this code, or how to elegantly extend it for all 4 data types above? Since my post-processing will be the same after reading this data, I guess I'll have to copy the matrix into a common format when done. I have no problem just having four procedures (one for each data type) like the one below, but perhaps there's an elegant way to use RTTI or buffers and then move()'s so that the same code works for all 4 datatypes? Thanks! type TRowData = array of Int32; procedure ReadMatrix; var Matrix: array of TRowData; NumberOfRows: Cardinal; NumberOfCols: Cardinal; CurRow: Integer; begin NumberOfRows := 20; // not known until run time NumberOfCols := 100; // not known until run time SetLength(Matrix, NumberOfRows); for CurRow := 0 to NumberOfRows do begin SetLength(Matrix[CurRow], NumberOfCols); FileStream.ReadBuffer(Matrix[CurRow], NumberOfCols * SizeOf(Int32)) ); end; end;

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• Why is DivMod Limited to Words (<=65535)?

  - by Andreas Rejbrand

  In Delphi, the declaration of the DivMod function is procedure DivMod(Dividend: Cardinal; Divisor: Word; var Result, Remainder: Word); Thus, the divisor, result, and remainder cannot be grater than 65535, a rather severe limitation. Why is this? Why couldn't the delcaration be procedure DivMod(Dividend: Cardinal; Divisor: Cardinal; var Result, Remainder: Cardinal); The procedure is implemented using assembly, and is therefore probably extremely fast. Would it not be possible for the code PUSH EBX MOV EBX,EDX MOV EDX,EAX SHR EDX,16 DIV BX MOV EBX,Remainder MOV [ECX],AX MOV [EBX],DX POP EBX to be adapted to cardinals? How much slower is the naïve attempt procedure DivModInt(const Dividend: integer; const Divisor: integer; out result: integer; out remainder: integer); begin result := Dividend div Divisor; remainder := Dividend mod Divisor; end; that is not (?) limited to 16-bit integers?

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• Invalid Pointer Operation, advice requested with debugging

  - by Xanyx

  I appear to have created code that is trashing memory. Having never had such problems before, i am now settign an Invalid Pointer Operation. In the following the value of the const string sFilename gets trashed after my call to PromptForXYZPropertiesSettings. // Allow the user to quickly display the properties of XYZ without needing to display the full Editor function PromptForXYZProperties(const sFilename:string; var AXYZProperties: TXYZProperties): boolean; var PropEditor: TdlgEditor; begin PropEditor:= TdlgEditor.create(nil); try PropEditor.LoadFromFile(sFilename); Other Details: Delphi 2007, Windows 7 64 bit, but can reproduce when testing EXE on XP REMOVING CONST STOPS PROBLEM FROM EXHIBITING (but presumably the problem is thus just lurking) PropEditor.PromptForXYZPropertiesSettings creates and shows a form. If I disable the ShowModal call then the memory is not trashed. Even though i have REMOVED ALL CONTROLS AND CODE from the form So I would like some advice on how to debug the issue. I was thinking perhaps watching the memory pointer where the sFilename var exists to see where it gets trashed, but not sure how i would do that (obviously needs to be done within the app so is owned memory). Thanks

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• Filling a region draws it off canvas

  - by Xanyx

  Hi Using the following code in Delphi 2007: procedure TfrmTest.PaintBox1Paint(Sender: TObject); const Rect_Size = 10; begin PaintBox1.Canvas.Brush.Color := clYellow; PaintBox1.Canvas.FillRect(Rect(0, 0, PaintBox1.width, PaintBox1.height)); PaintBox1.Canvas.Brush.Color := clRed; DrawARect(PaintBox1.Canvas, 0, 0, Rect_Size, Rect_Size); end; procedure TfrmTest.DrawARect(ACanvas: TCanvas; iLeft, iTop, iWidth, iHeight: Integer); var rgnMain: HRGN; begin rgnMain := CreateRectRgn(iLeft, iTop, iLeft + iWidth, iTop + iHeight); try SelectClipRgn(ACanvas.handle, rgnMain); ACanvas.FillRect(ACanvas.ClipRect); SelectClipRgn(ACanvas.handle, 0); finally DeleteObject(rgnMain); end; end; I get this: (Yellow area shows boundaries of PaintBox1). HMMM, NOT ALLOWED TO POST IMAGE Please go to: http://www.freeimagehosting.net/uploads/62cf687d29.jpg (Linked image shows a form with a yellow box [PaintBox1] in the center. However my red rectange [rgnMain] has been drawn at pos 0,0 on the form) My expectation was that the red rectangle would be at the top left of the PaintBox1 canvas, not the form's canvas. Why is it not? Can regions only be used with controls that have a Windows handle? Thanks

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• Indy client receive string

  - by Eszee

  Im writing an Indy chat app, and am wondering if there is a way for the server component to tell the client that there is a string waiting, or even a way for the client to have an "OnExecute" like event. This is what i have now: server: procedure TServer.ServerExecute(AContext: TIdContext); var sResponse: string; I: Integer; list: Tlist; begin List := Server.Contexts.LockList; sResponse:= AContext.Connection.Socket.ReadLn; try for I := 0 to List.Count-1 do begin try TIdContext(List[I]).Connection.IOHandler.WriteLn(sResponse); except end; end; finally Server.Contexts.UnlockList; end; end; Client: procedure TForm1.Button1Click(Sender: TObject); var sMsg : string; begin Client.Socket.WriteLn(edit1.Text); sMsg := Client.Socket.ReadLn; Memo1.Lines.Add(sMsg); end; The problem is when i have 2 or more clients running the messages keep stacking because the button only processes 1 message a time. I'd like a way for the client to wait for messages and when it is triggered it processes those messages, like it does now under the button procedure. I've tried to put the "readln" part under a timer, but that causes some major problems. Im Using Delphi 2010 and Indy 10

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• Browse for folder can't see camera device

  - by Robert Frank

  In Delphi 2010, I want to allow users to browse and select a folder. The folder is on a device (?) created by a DSLR: The folder is visible in the Windows Explorer as shown above. And, the folder is visible in a TOpenDialog, allowing them to browse into the folder and choose a file. Unfortunately, I have been unable to get either SHBrowseForFolder (code I found on the web but don't understand) or SelectDirectory to see the camera device or folder beneath it. (Side note: IMO, SelectDirectory is a far nicer UI, since the user can see the files in the folders while browsing.) I assume this has to do with the fact that the folder is in a device (?) created by the camera software. I've seen some tricks where you call TOpenDialog to browse for folders with '*.' and then ExtractFileDir on the result, but that's not robust or, IMO, a good UI. What I'm looking for is a "Browse for folder" that can see the same devices (including the camera device) the TOpenDialog & Windows Explorer can see. (Ideally, it would have the nice appearance like the one below!) Any suggestions? Image of a MS-Word's folder browsing in Win7. (I wonder if it looks this pretty in XP.)

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• Best way to create a collection of a class

  - by smartins

  I'm trying to create some classes that allow me to retrieve and manipulate a set of backups my application will create and manage. I've come up with the following code (not tested yet), but I'm not sure if it's the best way of accomplishing this or if there's any easier/better way. I'm using Delphi 2010. I have a class that holds the backup details (TBackupItem), then I need to have a class that will hold a collection of TBackupItem and finally I'll have a class that manages the reading and writing of backups and also exposes a property that accesses the collection of TBackupItem. type TBackupItem = class private FBackupProgram: string; FBackupProgramVersion: string; // There are more variables and properties but for the sake of simplicity I've listed only two public property BackupProgram: string read FBackupProgram write FBackupProgram; property BackupProgramVersion: string read FBackupProgramVersion write FBackupProgramVersion; end; TBackupsList = class(???) private // This class will hold a list of TBackupItem. What should I use to accomplish this? end; TBackupsManager = class(TObject) private FBackups: TBackupsList; public property Backups: TBackupsList read FBackups write FBackups; end; Do you guys have any comments and/or examples on the best way of accomplishing this? Thanks!

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• Calling member functions dynamically

  - by user652511

  I'm pretty sure it's possible to call a class and its member function dynamically in Delphi, but I can't quite seem to make it work. What am I missing? // Here's a list of classes (some code removed for clarity) moClassList : TList; moClassList.Add( TClassA ); moClassList.Add( TClassB ); // Here is where I want to call an object's member function if the // object's class is in the list: for i := 0 to moClassList.Count - 1 do if oObject is TClass(moClassList[i]) then with oObject as TClass(moClassList[i]) do Foo(); I get an undeclared identifier for Foo() at compile. Clarification/Additional Information: What I'm trying to accomplish is to create a Change Notification system between business classes. Class A registers to be notified of changes in Class B, and the system stores a mapping of Class A - Class B. Then, when a Class B object changes, the system will call a A.Foo() to process the change. I'd like the notification system to not require any hard-coded classes if possible. There will always be a Foo() for any class that registers for notification. Maybe this can't be done or there's a completely different and better approach to my problem. By the way, this is not exactly an "Observer" design pattern because it's not dealing with objects in memory. Managing changes between related persistent data seems like a standard problem to be solved, but I've not found very much discussion about it. Again, any assistance would be greatly appreciated. Jeff

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• Why could "insert (...) values (...)" not insert a new row?

  - by nang

  Hi, I have a simple SQL insert statement of the form: insert into MyTable (...) values (...) It is used repeatedly to insert rows and usually works as expected. It inserts exactly 1 row to MyTable, which is also the value returned by the Delphi statement AffectedRows:= myInsertADOQuery.ExecSQL. After some time there was a temporary network connectivity problem. As a result, other threads of the same application perceived EOleExceptions (Connection failure, -2147467259 = unspecified error). Later, the network connection was reestablished, these threads reconnected and were fine. The thread responsible for executing the insert statement described above, however, did not perceive the connectivity problems (No exceptions) - probably it was simply not executed while the network was down. But after the network connectivity problems myInsertADOQuery.ExecSQL always returned 0 and no rows were inserted to MyTable anymore. After a restart of the application the insert statement worked again as expected. For SQL Server, is there any defined case where an insert statment like the one above would not insert a row and return 0 as the number of affected rows? Primary key is an autogenerated GUID. There are no unique or check constraints (which should result in an exception anyway rather than not inserting a row). Are there any known ADO bugs (Provider=SQLOLEDB.1)? Any other explanations for this behaviour? Thanks, Nang.

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• Authentication system - Return information that have to change every time

  - by paulohr

  I have a application (made in Delphi) that contains a Authentication system (login & password). This system is in PHP, and the application get results from PHP using HTTP GET method. The system returns 'OK' if login and password are correct, and 'NO' if not correct. Like this... procedure Check; var x: string; begin x:=Get('www.mywebsite.com/auth.php?user=xxxxxx&pass=zzzzzz'); if x='OK' then UnlockFeatures else MessageBox(0,'You're not VIP','Error',0); end; Well, it works fine, but it is very easy to circumvent this system with sniffers, packet editor or proxy. So, I want to get some information (in PHP) that changes every time, and that could be possible get the same information by my application. What can I do? I don't need codes. Just tips, suggestions, please... Thanks...

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• The application called an interface that was marshalled for a different thread

  - by X-Ray

  i'm writing a delphi app that communicates with excel. one thing i noticed is that if i call the Save method on the Excel workbook object, it can appear to hang because excel has a dialog box open for the user. i'm using the late binding. i'd like for my app to be able to notice when Save takes several seconds and then take some kind of action like show a dialog box telling this is what's happening. i figured this'd be fairly easy. all i'd need to do is create a thread that calls Save and have that thread call Excel's Save routine. if it takes too long, i can take some action. procedure TOfficeConnect.Save; var Thread:TOfficeHangThread; begin // spin off as thread so we can control timeout Thread:=TOfficeSaveThread.Create(m_vExcelWorkbook); if WaitForSingleObject(Thread.Handle, 5 {s} * 1000 {ms/s})=WAIT_TIMEOUT then begin Thread.FreeOnTerminate:=true; raise Exception.Create(_('The Office spreadsheet program seems to be busy.')); end; Thread.Free; end; TOfficeSaveThread = class(TThread) private { Private declarations } m_vExcelWorkbook:variant; protected procedure Execute; override; procedure DoSave; public constructor Create(vExcelWorkbook:variant); end; { TOfficeSaveThread } constructor TOfficeSaveThread.Create(vExcelWorkbook:variant); begin inherited Create(true); m_vExcelWorkbook:=vExcelWorkbook; Resume; end; procedure TOfficeSaveThread.Execute; begin m_vExcelWorkbook.Save; end; i understand this problem happens because the OLE object was created from another thread (absolutely). how can i get around this problem? most likely i'll need to "re-marshall" for this call somehow... any ideas? thank you!

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• LsaAddAccountRights not working for me

  - by SteveL

  Using: Delphi 2010 and the JEDI Windows API and JWSCL I am trying to assign the Logon As A Service privilege to a user using LsaAddAccountRights function but it does not work ie. after the function returns, checking in Group Policy Editor shows that the user still does not have the above mentioned privilege. I'm running the application on Windows XP. Would be glad if someone could point out what is wrong in my code: unit Unit1; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls, JwaWindows, JwsclSid; type TForm1 = class(TForm) Button1: TButton; procedure Button1Click(Sender: TObject); private { Private declarations } public { Public declarations } end; var Form1: TForm1; implementation {$R *.dfm} function AddPrivilegeToAccount(AAccountName, APrivilege: String): DWORD; var lStatus: TNTStatus; lObjectAttributes: TLsaObjectAttributes; lPolicyHandle: TLsaHandle; lPrivilege: TLsaUnicodeString; lSid: PSID; lSidLen: DWORD; lTmpDomain: String; lTmpDomainLen: DWORD; lTmpSidNameUse: TSidNameUse; lPrivilegeWStr: String; begin ZeroMemory(@lObjectAttributes, SizeOf(lObjectAttributes)); lStatus := LsaOpenPolicy(nil, lObjectAttributes, POLICY_LOOKUP_NAMES, lPolicyHandle); if lStatus <> STATUS_SUCCESS then begin Result := LsaNtStatusToWinError(lStatus); Exit; end; try lTmpDomainLen := DNLEN; // In 'clear code' this should be get by LookupAccountName SetLength(lTmpDomain, lTmpDomainLen); lSidLen := SECURITY_MAX_SID_SIZE; GetMem(lSid, lSidLen); try if LookupAccountName(nil, PChar(AAccountName), lSid, lSidLen, PChar(lTmpDomain), lTmpDomainLen, lTmpSidNameUse) then begin lPrivilegeWStr := APrivilege; lPrivilege.Buffer := PChar(lPrivilegeWStr); lPrivilege.Length := Length(lPrivilegeWStr) * SizeOf(Char); lPrivilege.MaximumLength := lPrivilege.Length; lStatus := LsaAddAccountRights(lPolicyHandle, lSid, @lPrivilege, 1); Result := LsaNtStatusToWinError(lStatus); end else Result := GetLastError; finally FreeMem(lSid); end; finally LsaClose(lPolicyHandle); end; end; procedure TForm1.Button1Click(Sender: TObject); begin AddPrivilegeToAccount('Sam', 'SeServiceLogonRight'); end; end. Thanks in advance.

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• How do I debug a difficult-to-reproduce crash with no useful call stack?

  - by David M

  I am encountering an odd crash in our software and I'm having a lot of trouble debugging it, and so I am seeking SO's advice on how to tackle it. The crash is an access violation reading a NULL pointer: First chance exception at $00CF0041. Exception class $C0000005 with message 'access violation at 0x00cf0041: read of address 0x00000000'. It only happens 'sometimes' - I haven't managed to figure out any rhyme or reason, yet, for when - and only in the main thread. When it occurs, the call stack contains one incorrect entry: For the main thread, which this is, it should show a large stack full of other items. At this point, all other threads are inactive (mostly sitting in WaitForSingleObject or a similar function.) I have only seen this crash occur in the main thread. It always has the same call stack of one entry, in the same method at the same address. This method may or may not be related - we do use the VCL in our application. My bet, though, is that something (possibly quite a while ago) is corrupting the stack, and the address where it's crashing is effectively random. Note it has been the same address across several builds, though - it's probably not truly random. Here is what I've tried: Trying to reproduce it reliably at a certain point. I have found nothing that reproduces it every time, and a couple of things that occasionally do, or do not, for no apparent reason. These are not 'narrow' enough actions to narrow it down to a particular section of code. It may be timing related, but at the point the IDE breaks in, other threads are usually doing nothing. I can't rule out a threading problem, but think it's unlikely. Building with extra debugging statements (extra debug info, extra asserts, etc.) After doing so, the crash never occurs. Building with Codeguard enabled. After doing so, the crash never occurs and Codeguard shows no errors. My questions: 1. How do I find what code caused the crash? How do I do the equivalent of walking back up the stack? 2. What general advice do you have for how to trace the cause of this crash? I am using Embarcadero RAD Studio 2010 (the project mostly contains C++ Builder code and small amounts of Delphi.)

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• Memory corruption in System.Move due to changed 8087CW mode (png + stretchblt)

  - by André Mussche

  I have strange a memory corruption problem. After many hours debugging and trying I think I found something. For example: I do a simple string assignment: sTest := 'SET LOCK_TIMEOUT '; However, the result sometimes becomes: sTest = 'SET LOCK'#0'TIMEOUT ' So, the _ gets replaced by an 0 byte. I have seen this happening once (reproducing is tricky, dependent on timing) in the System.Move function, when it uses the FPU stack (fild, fistp) for fast memory copy (in case of 9 till 32 bytes to move): ... @@SmallMove: {9..32 Byte Move} fild qword ptr [eax+ecx] {Load Last 8} fild qword ptr [eax] {Load First 8} cmp ecx, 8 jle @@Small16 fild qword ptr [eax+8] {Load Second 8} cmp ecx, 16 jle @@Small24 fild qword ptr [eax+16] {Load Third 8} fistp qword ptr [edx+16] {Save Third 8} ... Using the FPU view and 2 memory debug views (Delphi - View - Debug - CPU - Memory) I saw it going wrong... once... could not reproduce however... This morning I read something about the 8087CW mode, and yes, if this is changed into $27F I get memory corruption! Normally it is $133F: The difference between $133F and $027F is that $027F sets up the FPU for doing less precise calculations (limiting to Double in stead of Extended) and different infiniti handling (which was used for older FPU’s, but is not used any more). Okay, now I found why but not when! I changed the working of my AsmProfiler with a simple check (so all functions are checked at enter and leave): if Get8087CW = $27F then //normally $1372? if MainThreadID = GetCurrentThreadId then //only check mainthread DebugBreak; I "profiled" some units and dll's and bingo (see stack): Windows.StretchBlt(3372289943,0,0,514,345,4211154027,0,0,514,345,13369376) pngimage.TPNGObject.DrawPartialTrans(4211154027,(0, 0, 514, 345, (0, 0), (514, 345))) pngimage.TPNGObject.Draw($7FF62450,(0, 0, 514, 345, (0, 0), (514, 345))) Graphics.TCanvas.StretchDraw((0, 0, 514, 345, (0, 0), (514, 345)),$7FECF3D0) ExtCtrls.TImage.Paint Controls.TGraphicControl.WMPaint((15, 4211154027, 0, 0)) So it is happening in StretchBlt... What to do now? Is it a fault of Windows, or a bug in PNG (included in D2007)? Or is the System.Move function not failsafe?

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• Which network protocol to use for lightweight notification of remote apps?

  - by Chris Thornton

  I have this situation.... Client-initiated SOAP 1.1 communication between one server and let's say, tens of thousands of clients. Clients are external, coming in through our firewall, authenticated by certificate, https, etc.. They can be anywhere, and usually have their own firewalls, NAT routers, etc... They're truely external, not just remote corporate offices. They could be in a corporate/campus network, DSL/Cable, even Dialup. Client uses Delphi (2005 + SOAP fixes from 2007), and the server is C#, but from an architecture/design standpoint, that shouldn't matter. Currently, clients push new data to the server and pull new data from the server on 15-minute polling loop. The server currently does not push data - the client hits the "messagecount" method, to see if there is new data to pull. If 0, it sleeps for another 15 min and checks again. We're trying to get that down to 7 seconds. If this were an internal app, with one or just a few dozen clients, we'd write a cilent "listener" soap service, and would push data to it. But since they're external, sit behind their own firewalls, and sometimes private networks behind NAT routers, this is not practical. So we're left with polling on a much quicker loop. 10K clients, each checking their messagecount every 10 seconds, is going to be 1000/sec messages that will mostly just waste bandwidth, server, firewall, and authenticator resources. So I'm trying to design something better than what would amount to a self-inflicted DoS attack. I don't think it's practical to have the server send soap messages to the client (push) as this would require too much configuration at the client end. But I think there are alternatives that I don't know about. Such as: 1) Is there a way for the client to make a request for GetMessageCount() via Soap 1.1, and get the response, and then perhaps, "stay on the line" for perhaps 5-10 minutes to get additional responses in case new data arrives? i.e the server says "0", then a minute later in response to some SQL trigger (the server is C# on Sql Server, btw), knows that this client is still "on the line" and sends the updated message count of "5"? 2) Is there some other protocol that we could use to "ping" the client, using information gathered from their last GetMessageCount() request? 3) I don't even know. I guess I'm looking for some magic protocol where the client can send a GetMessageCount() request, which would include info for "oh by the way, in case the answer changes in the next hour, ping me at this address...". Also, I'm assuming that any of these "keep the line open" schemes would seriously impact the server sizing, as it would need to keep many thousands of connections open, simultaneously. That would likely impact the firewalls too, I think. Is there anything out there like that? Or am I pretty much stuck with polling? TIA, Chris

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• How to override loading a TImage from the object inspector (at run-time)?

  - by Mawg

  Further to my previous question, which did not get a useful answer despite a bounty, I will try rephrasing the question. Basically, when the user clicks the ellipsis in the object inspector, Delphi opens a file/open dialog. I want to replace this handling with my own, so that I can save the image's path. I would have expected that all I need to do is to derive a class from TImage and override the Assign() function, as in the following code. However, when I do the assign function is never called. So, it looks like I need to override something else, but what? unit my_Image; interface uses Classes, ExtCtrls, Jpeg, Graphics; type Tmy_Image = class(Timage) private FPicture : TPicture; protected procedure OnChange(Sender: TObject); public { Public declarations } Constructor Create(AOwner: TComponent); override; procedure SetPicture(picture : TPicture); procedure Assign(Source: TPersistent); override; published { Published declarations - available in the Object Inspector at design-time } property Picture : TPicture read FPicture write SetPicture; end; // of class Tmy_Image() procedure Register; implementation uses Controls, Dialogs; procedure Register; begin RegisterComponents('Standard', [Tmy_Image]); end; Constructor Tmy_Image.Create(AOwner: TComponent); begin inherited; // Call the parent Create method Hint := 'Add an image from a file|Add an image from a file'; // Tooltip | status bar text AutoSize := True; // Control resizes when contents change (new image is loaded) Height := 104; Width := 104; FPicture := TPicture.Create(); self.Picture.Bitmap.LoadFromResourceName(hInstance, 'picture_poperty_bmp'); end; procedure Tmy_Image.OnChange(Sender: TObject); begin Constraints.MaxHeight := Picture.Height; Constraints.MaxWidth := Picture.Width; Self.Height := Picture.Height; Self.Width := Picture.Width; end; procedure Tmy_Image.SetPicture(picture : TPicture); begin MessageDlg('Tmy_Image.SetPicture', mtWarning, [mbOK], 0); // never called end; procedure Tmy_Image.Assign(Source: TPersistent); begin MessageDlg('Tmy_Image.Assign', mtWarning, [mbOK], 0); // never called end; end.

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• What can cause System.Move to occasionaly give wrong results?

  - by Fredrik Loftheim

  The last few days we have had some strange problems with our database components developed by a third party. There has been no changes to these components for months. The code that HAS changed the last few days is our own code and we have also updated our gui-components developed by another third party. After debugging I have found that a call to System.Move in one of the database component procedures occationaly gives wrong results! Please take a look at the code below from the database components and read my comments. How can this inconsistent behaviour happen? Can anyone give me an idea of how to procede to find the cause of this inconsistent behaviour? NB! I dont think there is anything wrong with THIS code, it is only shown to explain the problem "symptoms". My guess is that there is some sort of memory corruption or something, caused by our code or the updated gui-component-code. Edit: Take a look at the blogpost linked below. It seems that it could be related to my problem. At least as I read it it confirms that System.Move can give wrong results: http://blog.excastle.com/2007/08/28/delphi-bug-of-the-day-fpu-stack-leak/ Procedure InternalDescribe; var cbufl: sb4; //sb4=LongInt cbuf: array[0..30] of char; cbufp: PChar; //.... begin //..Some code repeat //...Some code to initialize cbufp and cbufl //On the 15. iteration the values immediately Before Move are always these: //cbufp = 'STDPRODUCTSTOREDELEMENTSCOUNT' //cbuf = ('S', 'T', 'A', 'T', 'U', 'S', #0, 'E', 'V', 'A', 'R', 'R', 'E', 'C', 'I', 'D', #0, 'D', 'U', 'C', 'T', 'I', 'D', #0, #0, #0, #0, #0, #0, #0, #0) //cbufl = 29 Move(cbufp^, cbuf, cbufl); //Values immediately After Move should then be: //cbuf = ('S', 'T', 'D', 'P', 'R', 'O', 'D', 'U', 'C', 'T', 'S', 'T', 'O', 'R', 'E', 'D', 'E', 'L', 'E', 'M', 'E', 'N', 'T', 'S', 'C', 'O', 'U', 'N', 'T', #0, #0) //But sometimes this Move results in this value( 1 in 5..15 times): //cbuf = ('S', 'T', 'D', 'P', 'R', 'O', 'D', 'U', 'C', 'T', 'S', 'T', 'O', 'R', 'E', 'D', #0, #0, #0, #0, #0, 'N', 'T', 'S', 'C', 'O', 'U', 'N', 'T', #0, #0) } until SomeCondition; //...Some more code end;

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• Programmatically swap colors from a loaded bitmap to Red, Green, Blue or Gray, pixel by pixel.

  - by eyeClaxton

  Download source code here: http://www.eyeClaxton.com/download/delphi/ColorSwap.zip I would like to take a original bitmap (light blue) and change the colors (Pixel by Pixel) to the red, green, blue and gray equivalence relation. To get an idea of what I mean, I have include the source code and a screen shot. Any help would be greatly appreciated. If more information is needed, please feel free to ask. If you could take a look at the code below, I have three functions that I'm looking for help on. The functions "RGBToRed, RGBToGreen and RGBToRed" I can't seem to come up with the right formulas. unit MainUnit; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, ExtCtrls, StdCtrls; type TMainFrm = class(TForm) Panel1: TPanel; Label1: TLabel; Panel2: TPanel; Label2: TLabel; Button1: TButton; BeforeImage1: TImage; AfterImage1: TImage; RadioGroup1: TRadioGroup; procedure FormCreate(Sender: TObject); procedure Button1Click(Sender: TObject); private { Private declarations } public { Public declarations } end; var MainFrm: TMainFrm; implementation {$R *.DFM} function RGBToGray(RGBColor: TColor): TColor; var Gray: Byte; begin Gray := Round( (0.90 * GetRValue(RGBColor)) + (0.88 * GetGValue(RGBColor)) + (0.33 * GetBValue(RGBColor))); Result := RGB(Gray, Gray, Gray); end; function RGBToRed(RGBColor: TColor): TColor; var Red: Byte; begin // Not sure of the algorithm for this color Result := RGB(Red, Red, Red); end; function RGBToGreen(RGBColor: TColor): TColor; var Green: Byte; begin // Not sure of the algorithm for this color Result := RGB(Green, Green, Green); end; function RGBToBlue(RGBColor: TColor): TColor; var Blue: Byte; begin // Not sure of the algorithm for this color Result := RGB(Blue, Blue, Blue); end; procedure TMainFrm.FormCreate(Sender: TObject); begin BeforeImage1.Picture.LoadFromFile('Images\RightCenter.bmp'); end; procedure TMainFrm.Button1Click(Sender: TObject); var Bitmap: TBitmap; I, X: Integer; Color: Integer; begin Bitmap := TBitmap.Create; try Bitmap.LoadFromFile('Images\RightCenter.bmp'); for X := 0 to Bitmap.Height do begin for I := 0 to Bitmap.Width do begin Color := ColorToRGB(Bitmap.Canvas.Pixels[I, X]); case Color of $00000000: ; // Skip any Color Here! else case RadioGroup1.ItemIndex of 0: Bitmap.Canvas.Pixels[I, X] := RGBToBlue(Color); 1: Bitmap.Canvas.Pixels[I, X] := RGBToRed(Color); 2: Bitmap.Canvas.Pixels[I, X] := RGBToGreen(Color); 3: Bitmap.Canvas.Pixels[I, X] := RGBToGray(Color); end; end; end; end; AfterImage1.Picture.Graphic := Bitmap; finally Bitmap.Free; end; end; end. Okay, I apologize for not making it clearer. I'm trying to take a bitmap (blue in color) and swap the blue pixels with another color. Like the shots below.

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• Large number of soft page faults when assigning a TJpegImage to a TBitmap

  - by Robert Oschler

  I have a Delphi 6 Pro application that processes incoming jpeg frames from a streaming video server. The code works but I recently noticed that it generates a huge number of soft page faults over time. After doing some investigation, the page faults appear to be coming from one particular graphics operation. Note, the uncompressed bitmaps in question are 320 x 240 or about 300 KB in size so it's not due to the handling of large images. The number of page faults being generated isn't tolerable. Over an hour it can easily top 1000000 page faults. I created a stripped down test case that executes the code I have included below on a timer, 10 times a second. The page faults appear to happen when I try to assign the TJpegImage to a TBitmap in the GetBitmap() method. I know this because I commented out that line and the page faults do not occur. The assign() triggers a decompression operation on the part of TJpegImage as it pushes the decompressed bits into a newly created bitmap that GetBitmap() returns. When I run Microsoft's pfmon utility (page fault monitor), I get a huge number of soft page fault error lines concerning RtlFillMemoryUlong, so it appears to happen during a memory buffer fill operation. One puzzling note. The summary part of pfmon's report where it shows which DLL caused what page fault does not show any DLL names in the far left column. I tried this on another system and it happens there too. Can anyone suggest a fix or a workaround? Here's the code. Note, IReceiveBufferForClientSocket is a simple class object that holds bytes in an accumulating buffer. function GetBitmap(theJpegImage: TJpegImage): Graphics.TBitmap; begin Result := TBitmap.Create; Result.Assign(theJpegImage); end; // --------------------------------------------------------------- procedure processJpegFrame(intfReceiveBuffer: IReceiveBufferForClientSocket); var theBitmap: TBitmap; theJpegStream, theBitmapStream: TMemoryStream; theJpegImage: TJpegImage; begin theBitmap := nil; theJpegImage := TJPEGImage.Create; theJpegStream:= TMemoryStream.Create; theBitmapStream := TMemoryStream.Create; try // 2 // ************************ BEGIN JPEG FRAME PROCESSING // Load the JPEG image from the receive buffer. theJpegStream.Size := intfReceiveBuffer.numBytesInBuffer; Move(intfReceiveBuffer.bufPtr^, theJpegStream.Memory^, intfReceiveBuffer.numBytesInBuffer); theJpegImage.LoadFromStream(theJpegStream); // Convert to bitmap. theBitmap := GetBitmap(theJpegImage); finally // Free memory objects. if Assigned(theBitmap) then theBitmap.Free; if Assigned(theJpegImage) then theJpegImage.Free; if Assigned(theBitmapStream) then theBitmapStream.Free; if Assigned(theJpegStream) then theJpegStream.Free; end; // try() end; // --------------------------------------------------------------- procedure TForm1.Timer1Timer(Sender: TObject); begin processJpegFrame(FIntfReceiveBufferForClientSocket); end; // --------------------------------------------------------------- procedure TForm1.FormCreate(Sender: TObject); var S: string; begin FIntfReceiveBufferForClientSocket := TReceiveBufferForClientSocket.Create(1000000); S := loadStringFromFile('c:\test.jpg'); FIntfReceiveBufferForClientSocket.assign(S); end; // --------------------------------------------------------------- Thanks, Robert

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• How do I solve "Two different CRTLDLLs are loaded" when using packages in C++ Builder 2010?

  - by David M

  Hi, We are trying to split up our monolithic EXE into a combination of an EXE and several packages. So far, we have one package that we're trying to use, and when running the EXE Codeguard shows the following error on startup: CG Error Two different CRTLDLLs are loaded. CG might report false errors (C:\Windows\system32\CC32100MT.DLL) (D:\Projects\Foo\Bar.bpl) OK I read this as two different runtime libraries being loaded - one, the correct one (CC32100MT.dll), one incorrect, which is the package we're trying to use. Continuing to run the program shows odd errors, especially casting between classes or passing a pointer to a class as a parameter in a method that crosses the EXE/DLL boundary. Codeguard itself doesn't show any other errors at all though. How do we solve this? Some more details We've looked at as many things as we (the developer working on this and I) can collectively think of: Each project is built using runtime packages. The EXE host lists Bar in its package list. Each project is set to compile with dynamic RTL. However, changing this does not solve the problem. The package is linked to the EXE via its BPI file, but linking via a LIB makes no difference either. The EXE and BPL are compiled with the same project settings, where the same options exist for both types of project. We think, anyway :) There is only one copy of the BPL and BPI on the system: it's definitely linking to the right one. Examining the EXE and BPL with Depends and TDump show they are both using C:\Windows\system32\CC32100MT.DLL. They should both be using the one RTL. Creating a new project (a plain VCL forms application) and linking to the BPL (via its BPI) works fine. Something in the process of adding all the files and LIBs that make our EXE contain the code it needs to changes this, but we haven't been able to figure out what. The LIBs all either correspond to DLLs we use (flat C interface, usually look as though they were built with MSVC) or are simple projects with lots of related files, compiled to a lib for the purpose of linking into the EXE - these correspond roughly to the areas of the program we want to split to BPLs, by the way. There don't seem to be project options for the LIB projects that would affect RTL linking, unless we've missed them. I have exhaustively hunted through Depends and looked at all RTL and CC32*.dll files the EXE and every single DLL references. All are identical: rtl140.bpl and CC32100MT.DLL. Fully qualified paths show they are the same files, too. Everything should be using the one same run-time library. We're stumped. Absolutely stumped. We've had other problems using BPLs (they seem to be surprisingly tricky things, especially using C++) but have managed to solve them all. This one we've had no luck at all and we'd really appreciate any insights :) We're using C++Builder 2010 (as part of RAD Studio actually, but with little Delphi code apart from components.)

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