Re: towards 4.4

[Ethan M. <merritt@u.washington.edu>]

On Monday 01 February 2010 13:37:04 Benjamin Lindner wrote:
> Hans-Bernhard Bröker wrote:
> > Benjamin Lindner wrote:
> > 
> > [about wgnuplot 4.4 candidate:]
> >> There is still one issue open I believe:
> >> - Copying to clipboard as metafile is broken.
> > 
> > Broken how, exactly?
> > 
> 
> in the way that the command
> 
>   plot sin(x) with linespoints, cos(x) with linespoints
> 
> produces the attached term window, but when doing Options->Copy to Clipboard
> and then pasting as Metafile in openoffice the result looks like the 
> second attachment.
> 
> benjamin

I am totally unfamiliar with the mechanisms for loading or dumping the
MSWin clipboard. But that doesn't stop me from looking at the code :-)

Two thoughts:

In wgraph.c (CopyClip) line 1434:
	 hdc = CreateMetaFile((LPSTR)NULL);

According to the on-line docs at msdn.microsoft.com, since 2000 it is better
to use CreateEnhMetaFile(), and if necessary convert this afterwards to a
backwards compatible [unenhanced] metafile.  Can the clipboard not handle 
an enhanced metafile?


I also notice the following in the current code, and I wonder if it explains
the lack of text output in your clipboard screenshots:

wgraph.c line 849:
    /* HBB 20010218: the GDI status query functions don't work on Metafile
     * handles, so can't know whether the screen is actually showing
     * color or not, if drawgraph() is being called from CopyClip().
     * Solve by defaulting isColor to 1 if hdc is a metafile. */
    isColor = (((GetDeviceCaps(hdc, PLANES) * GetDeviceCaps(hdc,BITSPIXEL))>2)
               || (GetDeviceCaps(hdc, TECHNOLOGY) == DT_METAFILE));


The comment indicates that GetDeviceCaps() can fail if the context is creation
of a metafile, as it is when loading the clipboard.  But then elsewhere in the
code....


wgraph.c (MakeFonts) 
line 661:
	lpgw->lf.lfHeight = -MulDiv(lpgw->fontsize, GetDeviceCaps(hdc, LOGPIXELSY), 72);
line 689:
       /* CMW: Base tick size on character size */
        lpgw->htic = lpgw->hchar / 2;
        cy = MulDiv(cx/20, GetDeviceCaps(hdc, LOGPIXELSY), GetDeviceCaps(hdc, LOGPIXELSX));
        lpgw->vtic = MulDiv(cy,lpgw->ymax,lprect->bottom - lprect->top);
        /* find out if we can rotate text 90deg */
        SelectObject(hdc, lpgw->hfontv);
        result = GetDeviceCaps(hdc, TEXTCAPS);

If the comment is correct, then maybe other places where there is a call to
GetDeviceCaps() must be modified to do something else during metafile creation. 
I.e., maybe the font size is being set to 0 because GetDeviceCaps() returns
something other than a useful screen resolution.


Finally, if the clipboard wants an enhanced metafile, is it possible that an
alternative approach is to replace CopyClip() with an equivalent to
      tmpgc = CreateEnhMetaFile(...)
      set term push
      set term emf [some new option to attach the output to tmpgc]
      replot
      set term pop


-- 
Ethan A Merritt
Biomolecular Structure Center
University of Washington, Seattle 98195-7742