[PD] Pd internal font size inconsistency on Raspbian

[katja]

Hi Jonathan,

Considering the fact that IEM guis display with correct font size on
Raspbian, there must be a way to do it right. The difference between
IEM guis and object/message/comment is that in the first case you
specify font type and size explicitly, and a choice of available types
is presented according to platform. It is up to the patch developer to
select a font that is available on each platform if reproducible
appearance is important for the patch. For object/message/comment
instead, you can just select font size at patch creation time, not
font type.

Until a few days ago I knew little about font size, but I learned that
it is a pretty well-defined entity in DTP: the total number of pixels
from highest ascender till lowest descender in the character set for a
given font. For DejaVu Sans Mono, 'd' has the highest ascender and 'p'
has the lowest descender, therefore it is possible to check actual
font size by counting total pixel height in 'pd'. So it is only about
height, not width. Width of a word or line at a particular font size
can vary substantially according to font type. Also note that fonts in
some programs may be scaled through DPI settings, where 72 DPI  is the
reference (while 96 DPI is default on Windows and Linux).

In a code editor for text-based computer languages you simply set a
monospace font to get an orderly appearance. Pd is more like a wysiwyg
markup language and code editor at the same time. Quite ambitious,
isn't it? It's remarkable how well it works most of the time across
platforms, particularly in Pd-extended. Pixel-precise cross-platform
appearance can only be achieved if monospace fonts with equivalent
height-width ratio are used, and font size is implemented literally
like it is probably done for the IEM guis.

Considering Pd as a markup language: a fundamental difference between
Pd and HTML is the way how elements are positioned (pixel coordinates
vs relative position of concatenated blocks). In HTML a block can grow
or shrink according to content, font size or font type, and push away
neighbor blocks. Pd elements can't do that, and scalable pixel
coordinates don't magically enable such behavior.

Katja


On Fri, Oct 9, 2015 at 4:39 AM, Jonathan Wilkes <jancsika at yahoo.com> wrote:
> Hi katja,
> What you say is completely reasonable.  And according to Pd's source code,
> it also happens to be wrong.
>
> Here's the definition of a size "10" font, from sys_fontlist of s_main.c:
> fi_fontsize = 10 (we don't know what the units are but I'm guessing it's
> supposed to be points)
> fi_maxwidth = 7 (pixels)
> fi_maxheight = 13 (pixels)
>
> So according to Pd, a size "10" font is the largest font size
> listed that has a width no greater than 7 pixels and a height
> no greater than 13.  (Unless _no_ font will fit in that spec in
> which case the smallest font size is used.)  Pd doesn't care if the font is
> "Crazy Cursive Condensed" at size
> "33.3333pts".  As long as that font fits the closest to the max
> height/width, it can be used for size "10".
>
> Regardless of how the font metrics proc is picking that
> 11px font, it still fits the metrics Pd gives for a size "10" font.
> Even if we "fixed" this bug, any other user on any other OS
> can have a size "10" font with characters that measure 7x13
> pixels.  And because it's ultimately up to the font engine
> exactly how the characters get rendered, such a user could
> even be using "DejaVu Sans Mono" and hit this
> discrepancy.  They wouldn't know they hit it until they
> compared their screenshot to yours.
>
> The only solution is to always render the box for the max
> width/height characters.  That would almost be guaranteed
> to look ugly on everyone's system, but at least you'd be
> guaranteed never to accidentally create a patch where
> boxes overlap on someone else's machine.
>
> I'll admit that in the GUI port I haven't addressed this
> problem.
>
> -Jonathan
>
>
>
>
> On Thursday, October 8, 2015 8:20 PM, katja <katjavetter at gmail.com> wrote:
>
>
> On Thu, Oct 8, 2015 at 3:41 PM, Jonathan Wilkes <jancsika at yahoo.com> wrote:
>> Four things:
>> 1) The font dialog shouldn't use numbers.  It should say "tiny", "small",
>> "medium", etc. because those numbers just mislead the user.
>
> Numbers only mislead the user when the wrong font size is displayed,
> like on Raspbian (size 11 where 10 is requested, as revealed by your
> bugfinder code). Since objects are positioned at fixed coordinates in
> a Pd patch, and coordinates are given in pixels, it is required to
> define and register everything else in exact pixels too, in order to
> display patches undistorted across platforms and independent from DPI
> settings.
>
> Attached are two zoomed screenshots where font pixels can be counted:
> 10 pix total height on Xubuntu and 11 on Raspbian, exactly the size as
> reported by Tk. Why Tk gives size 11 when Pd wants 10 I don't know but
> it is a bug and apart from the bug everything is totally accurate.
>
>
>
>> 2)  Font dialog number "10" in Vanilla may correspond to any font size
>> that
>> has
>> a width less than or equal to 7 pixels (and height <= 13).  That includes
>> DejaVu Sans Mono at pixel size 11 on Raspbian.  Since the text fits in the
>> box in your screenshot we can tell Tk is measuring the actual font
>> correctly.  (Well, more or
>> less-- what happens with a message box that has, say 50 lines?).
>>
>> 3) I can't figure out how pd_font_10 ends up with pixel size "11".
>>
>> 4) There are only two ways I can think of to fix this problem.  One is to
>> always
>> size boxes according to fi_maxwidth and fi_maxheight.  The other is to
>> forgo
>> the automated metrics and brute-force it so that DejaVu Sans Mono fits
>> exactly
>> into the hardcoded metrics of s_main.c.  I chose the 2nd solution in the
>> GUI
>> port, but only because I have decimal pixel sizes to choose from.  Tcl/tk
>> doesn't
>> let you do that.
>>
>> I'll check again but I think my method looks fine on Raspbian as well as
>> Ubuntu.
>>
>> I also played around with Droid Sans Mono Dotted because it has CJK
>> characters.  But DejaVu Sans Mono evidently has them, too-- or at least
>> when
>> I copy/paste them they show up correctly.  (Perhaps there's some kind of
>> fallback mechanism that I'm not seeing.)  Those characters open up a
>> wellspring of new problems.  They are referred to as "full width", but
>> take
>> up something like 1.5x width of ascii characters.  If you use them in
>> any flavor of Pd they overflow the object/message box borders.
>>
>> -Jonathan
>>
>>
>>
>> On Thursday, October 8, 2015 2:53 AM, katja <katjavetter at gmail.com> wrote:
>>
>>
>> On Thu, Oct 8, 2015 at 12:23 AM, Jonathan Wilkes <jancsika at yahoo.com>
>> wrote:
>>> Ok, try this in place of the command that was giving the error:
>>> pdtk_post "rank tk speculation follows: [font actual [get_font_for_size
>>> $font_size] -displayof $tkcanvas]\n"
>>>
>>
>> There you got it, inspector Wilkes! For Xubuntu the output is:
>>
>> rank tk speculation follows: -family {DejaVu Sans Mono} -size -10
>> -weight normal -slant roman -underline 0 -overstrike 0
>>
>> For Raspbian:
>>
>> rank tk speculation follows: -family {DejaVu Sans Mono} -size -11
>> -weight normal -slant roman -underline 0 -overstrike 0
>>
>> In both cases the font size menu says "10".
>>
>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> On Wednesday, October 7, 2015 4:33 PM, Jonathan Wilkes via Pd-list
>>> <pd-list at lists.iem.at> wrote:
>>>
>>>
>>> Sorry, I thought that would work.  I'll sit down and wade through all the
>>> indirection later to get a working debug printout.
>>>
>>> -Jonathan
>>>
>>>
>>>
>>> On Wednesday, October 7, 2015 4:26 PM, katja <katjavetter at gmail.com>
>>> wrote:
>>>
>>>
>>> On Wed, Oct 7, 2015 at 9:40 PM, Jonathan Wilkes <jancsika at yahoo.com>
>>> wrote:
>>>> For the official record-- I'm holding my tongue, in the hopes that when
>>>> others look at the code
>>>> in my GUI port they'll practice similar restraint.
>>>>
>>>> Ok, add this:
>>>>
>>>> pdtk_post "for real this time-- the actual font we are sending to tk is:
>>>> [set [get_font_for_size $font_size]]\n"
>>>
>>> Pd list is now looking at a line that doesn't work. The error is:
>>>
>>> can't read "::pd_font_10": no such variable
>>>
>>>
>>>
>>>
>>>> -Jonathan
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> On Wednesday, October 7, 2015 3:19 PM, katja <katjavetter at gmail.com>
>>>> wrote:
>>>>
>>>>
>>>> On Wed, Oct 7, 2015 at 8:37 PM, Jonathan Wilkes <jancsika at yahoo.com>
>>>> wrote:
>>>>> Silly me, I forgot this is Pd so it has to be way more complex than
>>>>> that...
>>>>>
>>>>> Add this line to pdtk_text_new in pdtk_text.tcl:
>>>>>
>>>>> pdtk_post "the actual font we are sending to tk is: [get_font_for_size
>>>>> $font_size]\n"
>>>>>
>>>>> Now do the test I mentioned before.
>>>>
>>>> The answer is in both cases:
>>>>
>>>> "the actual font we are sending to tk is: ::pd_font_10"
>>>>
>>>>
>>>>
>>>>> -Jonathan
>>>>>
>>>>>
>>>>>
>>>>> On Wednesday, October 7, 2015 2:16 PM, Jonathan Wilkes via Pd-list
>>>>> <pd-list at lists.iem.at> wrote:
>>>>>
>>>>>
>>>>> Hi katja,
>>>>>
>>>>> Could you do a test?  Make a simple patch with a single object in it,
>>>>> and
>>>>> use the same canvas font size you did above.  Then run Pd with -d 3
>>>>> flag
>>>>> and
>>>>> see what font size is actually being sent from Pd to the GUI on each
>>>>> distro.
>>>>>
>>>>> -Jonathan
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> On Wednesday, October 7, 2015 12:28 PM, katja <katjavetter at gmail.com>
>>>>> wrote:
>>>>>
>>>>>
>>>>> Hello,
>>>>>
>>>>> A particular font size issue can be observed in vanilla Pd and package
>>>>> puredata on Raspbian Wheezy and Jessie: font size 10 is larger for
>>>>> object boxes, message boxes and comments than for IEM guis (bang,
>>>>> toggle, slider, radio button, canvas). Object/message/comment
>>>>> characters are too large in number of pixels. When Edit > Font > Font
>>>>> Size is set to 8, their size is identical to IEM gui font size 10.
>>>>> This inconsistency does not happen for me on Xubuntu. A test patch and
>>>>> two screenshots are attached for illustration.
>>>>>
>>>>> For IEM guis, font size 10 translates to 6 pixels per character on
>>>>> both systems, given the default font type DejaVu Sans Mono. For object
>>>>> boxes, message boxes and comments, font size 10 is 6 pixels on Xubuntu
>>>>> and almost 7 pixels on Raspbian.
>>>>>
>>>>> I don't know if this issue is related to font size effects on Windows
>>>>> as described by Roman in another thread. In any case, consequences are
>>>>> similar: patches created on Xubuntu tend to look messy on Raspbian,
>>>>> sometimes with overlapping texts. With XFCE (Xubuntu's default desktop
>>>>> environment) installed on Raspbian the issue still persists. Custom
>>>>> dpi setting has no effect on Pd. What else might cause the difference
>>>>> in behavior on those systems?
>>>>>
>>>>> Katja
>>>>>
>>>>> _______________________________________________
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>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Pd-list at lists.iem.at mailing list
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>>>>>
>>>>>
>>>>
>>>>
>>>
>>>
>>>
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>>
>>
>
>