[perl-win32-gui-users] Font size - problems and workaround

[Marjolein K. <win...@ja...>]

I'vew been running into problems getting and setting correct font sizes. 
Since I'm new to this list, I searched the archives, but could find no reference. What I did find was a problem with GetTextExtentPoint32( STRING, [FONT] ) reported to always deliver values that were too large. I didn't investigate, but it might be related to what I'm seeing.
I don't know if it's platform dependent (I'm working on Win2000 SP1) but I hope not: if so, my workaround would not work on other platfoms (Win95/98/ME?).

The first thing I noticed was then when I create a Textfield and set the font size for it, the fiont size ended up actually smaller than what I specified. Other weird things happened too.
So, making a variation on the example program found with the package, I started to experiment and found a number of interlocking problems. Here's a summary:

- To ceate a font, there are both size and height attributes. Both should set the font size in points (I think).
- When using a font size for a control, it turns out too small
- When using the Font dialog, both size and height are returned as output; but both are incorrect: size is size as specified in the dialog - only 10 times larger; height is repirted as a negative number, but even the absolute value is too large.

It took a bit of trial and error to figure out what "too small" and "too large" actually meant but looking at the numbers I got a sudden hunch: screens are often assumed to be 72 pixels per inch - but for PCs that is actually (supposed to be) 96 pixels per inch. Guess what: the proportion 96/72 fit exactly the too large/too small values I was experiencing.

My workarounds:

- To specify a font size for a control, multiply by 96/72 and round up to the nearest integer
- If output from a Font dialog is to be used to change the font size for a control, *delete* the size attribute (it's 10 x too large) and take the absolute value of the reported height attribute (still too large inreal terms, but that has the 96/72 "correction" already built in).

Examples using the workarounds:

#create a Font to use in a  control:
$fontsize = 8;                              # intended size
$fontsize = int($fontsize*(96/72)+0.5);     # workaround for specifying size
$fontname = "Lucida console";
#print "fudged font size: $fontsize \n";
$dispFont = new Win32::GUI::Font(
    -name   => $fontname,
    -size   => $fontsize,
);
#now use it:
$W->AddTextfield(
    -name       => "dispDtdFile",
    -multiline  => 1,
    -vscroll    => 1,
    -hscroll    => 1,
    -top        => $titleheight+2*$pad,
    -left       => $lblleft,
    -width      => $w-2*$pad,
    -height     => $th-2*$btnvspace,
    -font       => $dispFont,
    -background => $txtback,
    -foreground => $txtfore,                # try if we can color it
);

#Change font size for the control (a button "Font..." calls up the Font dialog):
sub btnFont_Click {
    my $key = ();
    $W->Disable();                          # disable window before showing font dialog
    # --- current font ----------------------
    my $hcurFont = $W->dispDtdFile->GetFont();
    my %fontdetails = Win32::GUI::Font::Info($hcurFont);
    # --- choose font -----------------------
    my @newFont = Win32::GUI::ChooseFont(%fontdetails);
    %fontdetails = @newFont;
    # --- create new font -----------------------
    # make -height positive and delete -size to create "corrected" input for creating new font
    $fontdetails{"-height"} = abs($fontdetails{"-height"});
    delete $fontdetails{"-size"};
    # --- apply font -----------------------
    # create new font object with these parameters
    my $newFontObj = new Win32::GUI::Font(%fontdetails);
    $dispFont = $newFontObj;                # redefine global font object; $newFontObj gets destroyed
    $W->dispDtdFile->SetFont($dispFont);    # undocumented method!!!
    $W->dispDtdFile->Hide();                # force repaint
    $W->Enable();
    $W->SetForegroundWindow();
    show_controls();
}



Cheers,

Marjolein Katsma
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