On 26/04/16 22:31, Phil Race wrote:
On 04/26/2016 11:26 AM, Alexandr Scherbatiy wrote:
On 4/26/2016 8:38 PM, Phil Race wrote:
On 04/19/2016 01:08 AM, Alexandr Scherbatiy wrote:
On 4/11/2016 4:29 PM, Philip Race wrote:
On 4/6/16, 1:23 PM, Alexander Scherbatiy wrote:
Hello,
Could you review the updated fix:
http://cr.openjdk.java.net/~alexsch/8132119/webrev.09
- TextUIDrawing interface and its default implementaion
BasicTextUIDrawing class are added
- font metrics argument description is updated
On 31/03/16 23:23, Phil Race wrote:
Another webrev where you have to slip past 40_ files to get to
the two that really matter :-)
I would have put SwingUtilities2.java and TextUIDrawing.java as
the first files.
Updated.
Some of what I have to say here is more along the lines of
things to think
about rather than things that are wrong .. but there are also
maybe some things
that need to be fixed.
Is javax.swing.plaf really the right package for the new class ?
I suppose it is for the use by the UI classes so maybe its right.
Should the methods be taking "double" instead of "int" for
location ?
This means the measurement APIs too.
None of the JDK 1.2 text APIs use ints. That is all 1.0 legacy.
So if Swing internally wants to use ints that is OK but maybe
the API
should be floating point (double).
The provided methods use Graphics as argument which only has
drawString(String, int, int) method.
If it is possible it is better to add the methods with float
arguments and Graphics2D later.
Would that help hi-dpi at all ?
The hi-dpi support mostly does not require changes in Swing.
What it does just scales graphics using default transform from
graphics configuration.
Yes, but in another bug you are dealing with a problem positioning
the caret because of (somewhat) similar issues where coordinates
have been
rounded to an integral. A floating point value allows you to say that
this is 25.5 in user-space, even it if is 51.0 in device space.
It needs some more investigation.
What I have now is Swing uses font metrics to calculate a string
width (FontMetrics.charsWidth(...)) which sums up float char values.
The difference between font metrics used by Swing and font
metrics from graphics passed to paint method is that the fist has
null frc.tx matrix and the second one has a matrix with scales 2 on
HiDPI display.
The returned char width by the font metrics with null transform
has value 7 for char 'a' (linear advance is 6.67 and xAdvance is 7).
The char width for the font metrics with scaled transform is 6.5
for the same font and char. FileFontStrike requests glyph metrics
and gets linear advance 13.35 (dev transform is taken into
account) xAdvance 13 - and apply the reverse transform. The
result is 13 / 2 = 6.5.
And this bothers me because a result for applying the tx
transform and inverting it is different than just use the identity
transform. There are definitely problems with advance rounding but
it seems they are placed out of the Swing area.
I am not sure if you are implying a bug in the font code, but there
is none that I see
from the above.
There are several distinct issues here
1) You must specify the device transform, unless you are requesting
and using linear advances.
2) Linear advance is not generally used by Swing since it implies
unhinted text
3) Rounding of advances back to user space is OK in the case of
hinted advances and
identity transform - ie the traditional Swing case - but in the
case like that you describe
where the device pixel advance is 13 for a (2.0,2.0) device
scale then the translation
back to user space can't express that accurately if it only has
int to work with,
If Swing is not using the same device transform in calculating the
advance as it is when
drawing then that is a bug . That was the point of the comment we
added below about
obtaining the correct FontMetrics .. our L&Fs should be doing that
as well as admonishing
others to do so.
It is true that Swing uses FontRenderingContext which does not
take the graphics configuration transform into account.
However, there are use case which should be considered:
Using graphics configuration transform in Swing
FontRenderingContext leads that text component size will depend on
the graphics device.
Let's take an a frame which has some text components placed in
one row. Moving a frame from a non-HiDPI display to HiDPI display can
lead that the size of text components can be changed and they will be
rearranged in two rows.
The same can be applicable for printing. Printing a text
component from HiDPI display can lead that text will be shorter or
longer than component bounds on a page.
Indeed .. and there have been bugs on this where Swing text is clipped
when printed.
Sadly I don't believe the bug tail from that has been completely
squashed.
There is one more case. A text component before it is added to a
frame does not know about device where it will be shown.
So the following is possible:
-----------------
JTextField textField = new JTextField("ABC");
int width1 = textField.getWidth(); // no graphics
configuration is provided, frc Tx is identity
frame.add(textField);
int width2 = textField.getWidth(); // frc Tx is 2 on HiDPI
display
-----------------
Now it is possible that width1 is not equal to width2.
Absolutely true. And it is something Swing needs to handle.
Even more, it is not will be possible to rely on the fact that width
of number of chars is just sum of each char width.
For example, on graphics configuration with transform 2 the glyph
xAdvance can be 13 and the char width in user space will be calculated
as 13 / 2 = 6.5.
FontMetrics. charWidth('a') will return 7 and charsWidth(array of 10
'a' ) will be 65 wich is not 7 * 10.
Thanks,
Alexandr.
-phil.
Thanks,
Alexandr.
I suppose it would add over-head since all the existing code
uses int
and we are no worse off and can add double methods later if we
want to.
Regarding FontMetrics we need to add a caution that is must be a
FontMetrics
*obtained from the correct font and graphics*.
Updated.
i.e what about attributes on the font such as "tracking" ?
or on the graphics such as FRACTIONALMETRICS
It looks like Swing might already fail if that were used.
Look at this code :-
public static int stringWidth(JComponent c, FontMetrics fm,
String string){
if (string == null || string.equals("")) {
return 0;
}
boolean needsTextLayout = ((c != null) &&
(c.getClientProperty(TextAttribute.NUMERIC_SHAPING) != null));
if (needsTextLayout) {
synchronized(charsBufferLock) {
int length = syncCharsBuffer(string);
needsTextLayout = isComplexLayout(charsBuffer,
0, length);
}
}
if (needsTextLayout) {
TextLayout layout = createTextLayout(c, string,
fm.getFont(),
fm.getFontRenderContext());
return (int) layout.getAdvance();
} else {
return fm.stringWidth(string);
}
}
The only thing Swing is looking at is one TextAttribute and
whether we have complex text.
That is not enough. This is an existing implementation issue but
one we should fix here.
You need to examine all the methods for similar issues.
I created an enhancement for this:
JDK-8153662
SwingUtilities2.drawString()/getStringWidth()/clipString() should
use more text attributes
https://bugs.openjdk.java.net/browse/JDK-8153662
you mean bug ? I upgraded it to P3 because it matters a lot more now
with this public API
I do not think that it is a bug because the main request was to
have methods which draw strings in the same way as it is done by
Swing L&Fs.
It seems like a bug to me
This will allow to have custom UI component which mimic to the
standard L&Fs.
It is also can be considered from the following point of view: is
the proposed request to use more text attributes more important for
standard Swing L&F or for custom L&F.
It seems is not the first case because Swing lives with the
current implementation for the long time.
For the second case we provide the public TextUIDrawing interface
which a developer can override and use any text attributes that are
necessary.
We aren't talking about a separate API to provide text attributes,
we are talking about the
ones that are part of the font and the implementation is not
respecting.
-phil.
