Search code examples
delphidelphi-7

Error compiling HtmlViewer component for Delphi 7

I am trying the compile the HtmlViewer component for Delphi 7 (https://github.com/BerndGabriel/HtmlViewer). Opened the project Frameviewer7.dpk under package subdir

However I am getting the following compilation errors: HtmlBuffer.pas(1611): Array Type required.

Which corresponds to the following code:

 if FStart.BytePtr[0] = 0

And FStart is defined as FStart: TBuffPointer;

TBuffPointer = record
    case Integer of
      0: (BytePtr: PByte;);
      1: (WordPtr: PWord;);
      2: (AnsiChr: PAnsiChar;);
      3: (WideChr: PWideChar;);
    end;

Not sure what is wrong here. My compiler is Delphi7

Solution

  • FStart.BytePtr[0] indicates that FStart.BytePtr is an array, and the value of this expression is the first (0th) element in this array.

    However, FStart.BytePtr is actually a pointer. But often you can use arrays and pointers to achieve the same task -- either you use an array of TSomeType, or you use a pointer to the first element in an in-memory list of TSomeType items.

    I assume this is what is going on here. Hence, you want to get the first item of a list of byte values, the first occurring at address FStart.BytePtr. To obtain the byte at this location, you dereference the pointer using ^: FStart.BytePtr^.

    The code you have found tries to access data using array notation on a pointer. This syntactic sugar might work in some newer version or Delphi, or using some compiler option. (I don't recall.)