On Thu, 9 Aug 2018, Jesus Reyes A. via Lazarus wrote:
En Sat, 28 Jul 2018 08:05:31 -0500, Michael Van Canneyt via Lazarus
<lazarus@lists.lazarus-ide.org> escribió:
Hi,
The selectprinter demo prints a kind of test page.
However, on linux the rectangle it draws on the page seems to be off. The
left margin seems to be about right, but the bottom and top margins fall
off
the page.
If I try to code something myself, I would code it like this:
procedure TMainForm.GetPageRect(Out PageRect : TRect);
Function ToPixels(aUnit,ares : Integer) : Integer;
begin
if PSDemo.Units in [pmDefault,pmMillimeters] then
// 1/1000 of a mm
Result:=Round(((aUnit div 1000) / 25.4) * Ares)
else
Result:=aUnit * Ares
end;
Var
LM,RM,TM,BM,H,W : Integer;
begin
H:=Printer.PaperSize.Height;
W:=Printer.PaperSize.Width;
LM:=ToPixels(PSDemo.MarginLeft,Printer.XDPI);
RM:=ToPixels(PSDemo.MarginRight,Printer.XDPI);
TM:=ToPixels(PSDemo.MarginLeft,Printer.YDPI);
BM:=ToPixels(PSDemo.MarginBottom,Printer.YDPI);
PageRect:=Rect(LM,TM,W-RM,H-BM);
end;
PSDemo is a TPageSetupDialog. The values displayed by the lazarus test
program match more or less what my code gets. Similarly, if I draw a
rectangle with the rectangle defined as above, the bottom-right falls
off the page.
So the question is: what is the origin of the printer canvas ? Top-left
corner of the paper (What it should be IMO ?)
Or is it the Top-left corner of the printable area of the page ?
The top-left of the paper canvas is 0,0 and coincide with the area of the
whole paper. Any drawing outside of this area would be clipped. Some
printers also do not allow drawing outside of the working area.
This does not correspond to my findings.
I did many tests (using a lot of paper in the process) and found
that (0,0) is the origin of the printable area, NOT the paper area.
How to obtain the origin of the printable area ?
Is the PageWidth/Pageheight relative to this origin ?
The printable area should be Printer.PaperSize.PaperRect.WorkRect
Yes.
I printed a rectangle with 2 cm sides, at (0,0), and it is printed exactly
where workrect top,left says it should be, so my conclusion is that (0,0)
is the origin of the printable area.
(which, in my opinion, also makes more sense)
Or is there something else wrong in the printer class or the demo code ?
(using GTK2, 64-bit)
Should not matter in this case but it seems TM is using the left margin
instead of the top margin.
I know, I already corrected that before carrying out tests.
As the TPageSetupDialog works with the current printer just need to check
that selected printer is not changed after TPageSetupDialog execution.
Little chance of that.
There is only 1 printer, and 1 paper type on my system.
About why the selectprinter demo is wrong have to check, last time I did
it worked fine in windows, linux at least, IIRC.
Well, definitely not today on a HP laserjet P2015n, linux mint, 64bit, GTK2.
I can send a picture of the produced output if you want :-)
Michael.
--
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