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Lajos Juhász

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Posts posted by Lajos Juhász


  1. 3 hours ago, Serge_G said:

    But I don't understand where I miss something because I have some memoryleaks

    ---------------------------

    It's very simple take a look at TImage.SetBitmap. The TImage object will assign the bitmap to the internal bitmap and will not take the ownership over of the parameter. You've to write:
     

    var 
      lbm: TBitmap;
    begin
      if OpenDialog1.Execute then
      begin
        Image1.Bitmap.LoadFromFile(OpenDialog1.FileName);
        lbm:=ConvertToGrayscale(image1.Bitmap);
        try
          Image2.Bitmap:=lbm;
        finally
          lbm.Free;
        end;
      end;  
    end;



     

    • Thanks 1

  2. Changing a DPI can also cause the following error message:

    ---------------------------
    Debugger Exception Notification
    ---------------------------
    Project XXXXX.exe raised exception class EReadError with message 'Stream read error'.
    ---------------------------
    Break   Continue   Help   Copy   
    ---------------------------
     

    With call stack: 

     

    :7538b522 KERNELBASE.RaiseException + 0x62
    :030f850a HookedRaiseException + $66
    :50162931 rtl280.@System@Classes@TReader@ReadBuffer$qqrio + 0x55

     

    After that the following exception is:

     

    First chance exception at $7538B522. Exception class EArgumentOutOfRangeException with message 'Argument out of range'. Process XXXXX.exe (17800)

    :7538b522 KERNELBASE.RaiseException + 0x62
    :030f850a HookedRaiseException + $66
    :50159093 rtl280.@System@Classes@TCollection@GetItem$qqri + 0x13
    :50159093 rtl280.@System@Classes@TCollection@GetItem$qqri + 0x13
    :50cc5327 vcl280.@Vcl@Controls@TControl@Resize$qqrv + 0x1b
    :50ccac1a ; C:\Program Files (x86)\Embarcadero\Studio\22.0\bin\vcl280.bpl
    :50ccacec vcl280.@Vcl@Controls@TWinControl@AlignControl$qqrp21Vcl@Controls@TControl + 0x68
    :50ccad47 vcl280.@Vcl@Controls@TWinControl@Realign$qqrv + 0x7
    :50ccf78c vcl280.@Vcl@Controls@TWinControl@ScaleForPPI$qqri + 0xc8
    :50ccf78c vcl280.@Vcl@Controls@TWinControl@ScaleForPPI$qqri + 0xc8
    :50ccf78c vcl280.@Vcl@Controls@TWinControl@ScaleForPPI$qqri + 0xc8
    :50ccf78c vcl280.@Vcl@Controls@TWinControl@ScaleForPPI$qqri + 0xc8
    :50ccf78c vcl280.@Vcl@Controls@TWinControl@ScaleForPPI$qqri + 0xc8
    :50ccf78c vcl280.@Vcl@Controls@TWinControl@ScaleForPPI$qqri + 0xc8
    :50ccf78c vcl280.@Vcl@Controls@TWinControl@ScaleForPPI$qqri + 0xc8
    :50e021a3 vcl280.@Vcl@Forms@TCustomForm@ScaleForPPIRect$qqrip18System@Types@TRect + 0x9b
    :fffffff8

     

    I don't have a test case for this as I put it on delay and re-testing with D12. Since Embarcadero thinks that it is not relevant to give a valid roadmap I promised to management at the company I work for that this should be fixed in Delphi 12. It's bad that Embarcadero follows the pattern from the past and now entered into the period when they hide every possible information.

     


  3. 16 minutes ago, David Heffernan said:

    No. The try finally here protects the lifetime management of the instantiated object, after the constructor has completed. An exception in the constructor will bubble up from here and never enter the try. This is a very very common misunderstanding. 

    Exactly what I was saying.

    In case you'write:

     

    try

      lObj:=TMyClass.create;

    finally

      lObj.Free;

    end;

    If the constructor raises the exception the RTL will clear that for you. However in case lObj as the name suggest is a local variable and you didn't assigned nil to it the value will be undefined and calling free on that reference can cause AV (in case you're not lucky that the value was nil).


  4. 13 minutes ago, David Heffernan said:

    Again, can somebody explain what problem is caused by raising in a constructor

    The only problem with it is that you've to write your code in form:

     

    lObj:=TMyClass.Create(....);
    try
    .....
    finally
      lObj.Free;
    end;

    Anyway you would write it in this form. So there is no problem. I believe it's just another phobia. People can be afraid from correct coding style but will happily use FreeAndNil everywhere in the code.


  5. It's a missing property for TIDMessage class and it's not related to win10. Search in dfm files for DeleteTempFiles and remove the property. In Indy10 TIdMessage doesn't have that property. I don't know whenever it ever had that property (I've never worked with that old version of Indy).

     

    Edit: The only case when the application is compiled to use runtime packages. In that case if you provide the wrong bpls for Indy could result this error.


  6. I cannot reproduce this in a simple test program. What I did is placed a TFDMemTable into a form:

     

      object FDMemTable1: TFDMemTable
        FetchOptions.AssignedValues = [evMode]
        FetchOptions.Mode = fmAll
        ResourceOptions.AssignedValues = [rvSilentMode]
        ResourceOptions.SilentMode = True
        UpdateOptions.AssignedValues = [uvCheckRequired, uvAutoCommitUpdates]
        UpdateOptions.CheckRequired = False
        UpdateOptions.AutoCommitUpdates = True
        Left = 304
        Top = 224
        object FDMemTable1a: TIntegerField
          FieldName = 'a'
        end
        object FDMemTable1b: TStringField
          FieldName = 'b'
          Size = 150
        end
      end
     

    and a button with the following onclick event:

     

    procedure TForm1.Button1Click(Sender: TObject);
    begin
      if not FDMemTable1.Active then
        FDMemTable1.CreateDataSet
      else
      begin
    //    FDMemTable1.Open; <- There is no need to do this Active is true
        FDMemTable1.EmptyDataSet;
      end;
    
      FDMemTable1.Append;
      FDMemTable1['a']:=1;
      FDMemTable1['b']:='1';
      FDMemTable1.Append;
      FDMemTable1['a']:=2;
      FDMemTable1['b']:='2';
      FDMemTable1.Append;
      FDMemTable1['a']:=3;
      FDMemTable1['b']:='3';
      FDMemTable1.Append;
      FDMemTable1['a']:=4;
      FDMemTable1['b']:='4';
      FDMemTable1.Post;
    end;

    It's working with multiple clicks.


  7. In case you're connecting to remote servers you have to buy Enterprise or Architect version. Professional supports only local databases and doesn't include the source code for FD.

     

    Before you open the project you have to migrate your project using the included refind utility using the included FireDAC_Migrate_BDE.txt.


  8. 9 minutes ago, audi30tdi said:

    Is it easy to convert from Delphi7 with BDE to the nevest Delphi/Embarcadero version with FireDAC, or must I rewrite all my code??

    FireDAC was written to be replacement for the BDE and there is a script that converts the properties. It really depends the database and methods from BDE you are using in your code.

     

    Unfortunately if you're using persistent fields you will have to recreate them as most probably FD will require another class.

     

    (You can try to map the data types in the TFDConnection object to the old classes, however I like to keep mapping to minimum.)


  9. BDE is deprecated for 20 years. You can upgrade Delphi but that will change nothing how BDE interacts with Windows. The only solution is to migrate the application to anothe DAC.


  10. Maybe you should try the old way. Append the memtable and set the value for the fields. Depending if you have only couple of fields you can write an the assign statements otherwise use a for loop.

     

    Something like this should work (you're copying the structure thus the order of the fields should be the same):

     

    var

      i: integer;

     

    begin
      kbmMemTable.Append;

      for i:=0 to kbmMemTable.fieldCount-1 do

         kbmMemTable.fields.value:=myTEDBTable.fields.value;

    end;

     

     

     


  11. 7 hours ago, Qasim Shahzad said:

    Now Please guide why this is a bad idea. It reduces a lot of code duplication and we can add Form Creation procedure in a common library.

    When you're displaying the forms this way they are useless there are no input values to the form and the form doesn't produce any result. You're destroying the instance before the calling code could read the results back.

     

    I am aware that you can initialize the form in the formcreate and write the results back in formdestroy but that is a bad design.

    • Like 1

  12. I think this is a bad idea, however here is a code for VCL:

     

    procedure ShowForm ( ThisForm: TFormClass ) ;
    var
      lForm: TForm;
    begin
      lForm := ThisForm.Create(nil);
      try
        lForm.ShowModal;
      finally
        lForm.Free;
      end;
    end;
    
    {Example to use}
    procedure TForm1.Button1Click(Sender: TObject);
    begin
      ShowForm(Tform1);
    end;
    
    procedure TForm1.Button2Click(Sender: TObject);
    begin
      ShowForm(Tform2);
    end;

    The difference between VCL and Fmx is that in Fmx you've to define TFormClass:

    type
      TFormClass = class of TForm;

     

    • Thanks 1

  13. Here is the content (I assume by Gary Darby):

    HexView will display the contents of any file using hexadecimal (base 16) digits.   There are 16 hexadecimal digits with values 0 through 15 but labeled "0" through "9" and "A" though "F" for convenience.  Each hex digit could also be written with 4 binary bits (0000 to 1111).   

     

     Hexadecimal numbers are convenient for use in displaying computer memory or files  because two of those 4 bit hex digits can represent the basic unit of memory storage, the 8-bit "byte"

     

    I've had a version of this one floating around for my own use for years, but just recently realized that i had never posted it. 

     

    Use of the program is self explanatory; , select a file to browse and use PgUp, PgDn keys to page through it.  Ctrl+PgUp will jump to page 1, Ctrl+PgDn will jump to the last page.  The "Esc"  escape key will close the file.  Characters which represent valid characters will be displayed on each line beside the hexadecimal data. 

     

    Programmer's Notes

     

    A TFileStream control is used to access the file to be displayed.   In order to avoid memory problems with large files, the amount of data (BufLen) to fill a page is calculated for each display operation based on the current size of the TMemo control.  For each page, procedure ShowPage seeks to the start of the next page to be displayed (CurPage*BufLen) and reads BufLen bytes of data.   Hexchars is the array containing the 16 hexadecimal character labels.  The Delphi code  uses a loop on N and J to convert each byte for each line into two display characters and add it to the string, Hex.  N reflects the position of the current line start within the buffer and J points tpo the current character being converted.  The conversion line of code looks like this:


    hex:=hex+hexchars[(buffer[n+j] and $F0) shr 4] + hexchars[(buffer[n+j] and $0F)];

     

    The left hand "nibble" (4 bits of a byte) is converted by "and"ing it with hex F0 (11110000 binary) to clear out the right side nibble and then shifted right (= divided by 16) to get it back in the range 0-15 which is then used as an index into the Hexchars array.  The right half of the bite is then converted similarly except that there's no need to divide by 16.HexViewSource.zip

     

    The displayed lines are added to a TStringlist (List) whose strings are assigned  to the Memo1.Lines property after the page has been built.  This eliminated a flicker problem that occurred when lines were built directly into Memo1.

     

    One more interesting problem that I ran into and which might save some time for you in the future.  When a control is aligned to the bottom of the form (like the TStatictext control in this case), and the form is resized to a smaller height, the control is placed below any existing controls.  Adjusting the sizes in the OnResize exit is too late to prevent this problem.   The solution is to use the OnCanResize exit to predict where the bottom aligned control will be and readjust the size and tops of the other controls in advance of the actual resize operation.. 

    • Thanks 1
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