Trying to implment MacOS PMGetPageFormatPaper in FireMonkey

Trying to get (and eventually set) the paper selection at runtime using Delphi FireMonkey for MacOS. I've substituted what I think are the correct variables and functions into a routine that I have used successfully to get the paperrect and the pagerect, as well as the orientation. But this code gives me an access error when I release FPrintInfo. I'm sure it's something simple. Hoping a kind programmer can help.

function getPaperName: string;
var
  FPrintInfo: NSPrintInfo;
  paper: integer;
begin
  result:='';
  FPrintInfo := TNSPrintInfo.Wrap(TNSPrintInfo.OCClass.sharedPrintInfo);
  FPrintInfo.retain;
  PMGetPageFormatPaper(FPrintInfo.PMPageFormat, @paper);
  FPrintInfo.release;
  result:=IntToStr(paper);
end;

Possible hint... Here is the PMGetPageFormatPaper function in the Apple documentation:

func PMGetPageFormatPaper(
    _ format: PMPageFormat,
    _ paper: UnsafeMutablePointer<PMPaper?>
) -> OSStatus

I notice that the pointer variable <PMPaper?> includes a question mark, while the corresponding variables in the functions that I am using successfully do not. I imagine that is telling me something important, but I don't know what.

Thanks for any help.

Scott

Solution

The second parameter for the call to PMGetPageFormatPaper is of type PPMPaper, not an Integer. It is essentially a pointer to a handle that can be used to call the PMPaperXXX functions e.g. PMPaperGetName, PMPaperGetHeight, PMPaperGetWidth etc. The whole process is a bit more complicated, however this might do what you want:

uses
  Macapi.PrintCore, Macapi.AppKit, Macapi.CoreFoundation, Macapi.CocoaTypes, Macapi.Helpers, Macapi.Foundation;

function getPaperName: string;
var
  LPrintInfo: NSPrintInfo;
  LPaper: PMPaper;
  LName: CFStringRef;
  LPrinter: PMPrinter;
  LSession: PMPrintSession;
begin
  Result := '';
  if PMCreateSession(@LSession) = 0 then
  begin
    if PMSessionGetCurrentPrinter(LSession, @LPrinter) = 0 then
    begin
      LPrintInfo := TNSPrintInfo.Wrap(TNSPrintInfo.OCClass.sharedPrintInfo);
      if (PMGetPageFormatPaper(LPrintInfo.PMPageFormat, @LPaper) = 0) then
      begin
        if PMPaperCreateLocalizedName(LPaper, LPrinter, @LName) = 0 then
        try
          Result := NSStrToStr(TNSString.Wrap(LName));
        finally
          CFRelease(LName);
        end;
      end;
    end;
  end;
end;

Ultimately, the PMPaperCreateLocalizedName method needs to be called to get the paper name. PMPaperGetName appears to have been removed from later macOS SDKs without Apple updating their documentation, though they do recommend using PMPaperCreateLocalizedName anyway

This method requires a handle to the printer (of type PMPrinter), which is obtained using PMSessionGetCurrentPrinter, and this requires a PMPrintSession, so this is obtained using PMCreateSession.

The paperName parameter of PMPaperCreateLocalizedName is a pointer to a CFStringRef, which can just be wrapped as an NSString using TNSString.Wrapand converted into a string using NSStrToStr

Since the method has the word Create in it, the convention in Apple APIs is that if something is created, it needs to be released, hence the call to CFRelease