mORMot Open Source

I made an experiment with this.

We observed that the dashed lines are "simulated" by drawing many ellipses.
I think the problem is that the clipping doesn't work correctly. The stroke should be clipped to the boundaries of the ellipses, so that the resulting line is the correct width. As the clipping doesn't work the result is a fatter line.

So, here is my experiment: I draw a simple triangle with a texture inside, and it is not clipped on PDF via mormot.ui.pdf.
Again, the same code works correctly on canvas and on printer (the texture is clipped to the shape).

What do you think?

I still have one question though.

You confirmed that in the "print as pdf" file that I posted, the dashed line is still created as many segments (ellipses) and not as a real dashed line.
How does it display correctly then? What does it do differently?

I really appreciate your efforts, did you look at the PDF I linked in the previous post? https://file.io/jwK2sU2v0k2J  (3Kb)

This was done with the same code just by printing on the Microsoft PDF printer.

In your previous post you were able to look into the PDF file internal commands, maybe you can look into this and see how it is done properly to achieve the correct result.

Since the printer canvas and the PDF file can handle the result well, the problem must be somewhere between the GDI and the way the mormot.ui.pdf library reads it.

Thank you for taking your time to look into this

In my small example program, you can use the print button to print on PDF using a PDF printer (eg. change 'My Printer' with 'Microsoft Print on PDF', included in Windows).
The resulting PDF of the print will be perfect (both lines with width=1), so it is not a limitation of the PDF format, it must be something in the mormot pdf library.

Hello,

I prepared a stand-alone sample code, as requested.
Please note that the code is minimalist (no "try finally", error checking etc) for the sake of the example.

Here is the main function that does the drawing.
It does not use any external library, except mormot.ui.pdf.
It draws two lines, one solid line for reference, one dashed line. Both lines are drawn with a width=1 but the dashed line is wider on PDF.

uses mormot.ui.pdf, Winapi.GDIPAPI, Winapi.GDIPOBJ;

procedure Draw(Handle:HDC);
const Dashed: array [0..1] of Single = (5,4);
var Graphics: TGPGraphics;
    Pen: TGPPen;
    path: TGPGraphicsPath;
begin
    Graphics:= TGPGraphics.Create(Handle);
    Pen:= TGPPen.Create(MakeColor(255,0,0,255),1);
    Pen.SetLineCap(LineCapRound,LineCapRound,DashCapRound);

    //normal line
    path:= TGPGraphicsPath.Create();
    path.AddLine(30,500,40,40);
    path.AddLine(40,40,300,50);
    Graphics.DrawPath(Pen,path);
    FreeAndNil(path);

    //dashed line
    Pen.SetColor(MakeColor(255,0,255,0));
    Pen.SetDashPattern(@Dashed,2);
    path:= TGPGraphicsPath.Create();
    path.AddLine(50,500,60,60);
    path.AddLine(60,60,300,70);
    Graphics.DrawPath(Pen,path);
    FreeAndNil(path);

    FreeAndNil(Pen);
    FreeAndNil(Graphics);
end;

You can then call the drawing function like this, to save on PDF:

procedure DrawOnPdf;
var pdf: TPdfDocumentGDI;
begin
    pdf:= TPdfDocumentGDI.Create;
    pdf.AddPage;
    Draw(pdf.VclCanvas.Handle);
    pdf.SaveToFile('C:\test.pdf');
end;

If you want to check, you can also draw on a form canvas, or even print the drawing (add Vcl.Printers in the uses) like this.
Both on the form and on printer, the drawing is correct (both lines have same width).

procedure DrawOnForm;
begin
    Draw(Form1.Canvas.Handle);
end;

procedure DrawOnPrinter;
begin
    Printer.PrinterIndex:= Printer.Printers.IndexOf('My Printer');
    Printer.BeginDoc;
    Draw(Printer.Canvas.Handle);
    Printer.EndDoc;
end;

I also created a small self-contained project demonstrating the above, with a form and three buttons to perform the three types of drawing (form, pdf, print).
You can download it here: https://file.io/pTvvnrYbisxY  (54Kb).

Thank you.

There is no error there.
The solid line in the screenshot is an example for reference (correct), the problem is with the dashed line which, despite using width=1 the same as the solid line, it is drawn much bigger.

Hello again ab,

Regarding the latest commit above, I spotted a bug that doesn't mark the end of the optional content.

The GdiComment for pgcEndMarkContent has a size of 1 (just the identifier) while in the EnumEMFFunc for the EMR_GDICOMMENT checks the data size to be >1, thus failing in case of the pgcEndMarkContent. (mortmot.ui.pdf.pas ~line 10939)

I hope my explanation is clear, if you need further info let me know.

Looks great *thumbs up*.

About mormot.ui.pdf.pas, can it be used standalone? Otherwise I will port the modifications to SynPDF.

Hello ab, I gave a look, interesting solution.
Am I wrong or it creates a new group at each call? I would much prefer to pass the TPdfOptionalContentGroup object that references the group, maybe saving in the comment the pdf group object id instead of the title.