Am 30.06.2022 um 17:03 schrieb Ondrej Pokorny via lazarus:
On 30.06.2022 16:54, Werner Pamler via lazarus wrote:
Am 30.06.2022 um 15:11 schrieb Mattias Gaertner via lazarus:
Maybe instead of the GraphicClass.ClassName the first extension can be
written.
That means, that an old IDE cannot read the graphic.
This will break Delphi compatibility, i.e. forms with an image in
which the Picture has been loaded by Delphi will not be readable by
Lazarus any more, and vice versa. Just checked again the signature
that Delphi writes to the begin of the Picture.Data: it's the class
name, not the extension.
And what about writing the extension to the data end?
Picture.Data = {
0B 54 49 6D 61 67 69 6E 67 50 4E 47 89 50 4E 47 0D 0A 1A 0A 00
00 00 0D 49 48 44 52 00 00 01 C6
11 T I m a g i n g P N G // 11 is the
length byte
03 p n g
That should be both Delphi and legacy Lazarus compatible if the reader
reads only the defined count of bytes for the classname?
But isn't this the same problem? When Vampyre is not installed, and the
streamer sees the TImageingPNG classname there is no way how to find the
end of the Picture.Data block.
Newer Lazarus versions would first search the extension and if not
found they search for the classname.
Where's that? AFAICS, TPicture only looks for the classname. From Laz/main:
procedure TPicture.ReadData(Stream: TStream);
var
GraphicClassName: Shortstring;
NewGraphic: TGraphic;
GraphicClass: TGraphicClass;
ok: boolean;
begin
* Stream.Read(GraphicClassName[0], 1);**
** Stream.Read(GraphicClassName[1], length(GraphicClassName));*
GraphicClass := GetPicFileFormats.FindClassName(GraphicClassName);
NewGraphic := nil;
if GraphicClass <> nil then begin
NewGraphic := GraphicClass.Create;
ok:=false;
try
NewGraphic.ReadData(Stream);
ok:=true;
finally
if not ok then NewGraphic.Free;
end;
end;
FGraphic.Free;
FGraphic := NewGraphic;
if NewGraphic <> nil then begin
NewGraphic.OnChange := @Changed;
NewGraphic.OnProgress := @Progress;
end;
Changed(Self);
end;
procedure TPicture.WriteData(Stream: TStream);
var
GraphicClassName: ShortString;
begin
with Stream do
begin
if Graphic <> nil then
GraphicClassName := Graphic.ClassName
else
GraphicClassName := '';
* Write(GraphicClassName, Length(GraphicClassName) + 1);*
if Graphic <> nil then
Graphic.WriteData(Stream);
end;
end;
--
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