<Swing Dev> [13] RFR JDK-8214702:Wrong text position for whitespaced string in printing Swing text
Phil Race
philip.race at oracle.com
Wed Apr 17 19:01:42 UTC 2019
On 4/16/19 3:38 AM, Prasanta Sadhukhan wrote:
>
> Hi Phil,
>
> It seems screenWidth or "advance of the string at screen-resolution"
> is 533 whereas string advance calculated using printer fontmetrics is 503
>
> Now, TextLine#getJustifiedLine() [called from
> TextLayout.getJustifiedLayout] again calculates "justifyAdvance" for
> TextLineComponent which comes out to be 503,then it calculates
> the actual justification "delta" by subtracting justifyAdvance from
> screenWidth which is 533-503=30 and it then does
> TextJustifier.justify(delta)
> which calculates the amount by which each side of each glyph should
> grow or shrink.
>
> Then TextLine.getJustifiedLine() applies this value by calling
> TextLineComponent.applyJustificationDeltas() where it
> handle whitespace by modifying advance but handle everything else by
> modifying position before and after,
> so "spaces" seem to grow in size resulting in shifting of text with
> whitespaces.
The spaces being used to add needed or absorb surplus space is what I
understood the current code to be doing,
However I am not sure what you mean by this :-
"but handle everything else by modifying position before and after,"
Code run through text layout will always have glyph positions assigned,
so I would suppose modifying the position
is how the spaces were handled too .. and of course this means running
through all preceding glyphs to make
it consistent .. and I thought it was only adjusting the spaces, so what
is "everything else"
>
> Since it was mentioned in TextLayout.getJustifiedLayout() that " For
> best results, justificationWidth should not be too different from the
> current advance of the line"
So for "best" results don't try to adjust a string that's 3 words and 80
pixels to a 500 pixel width.
> I am proposing a fix to conditionally call
> TextLayout.getJustifiedLayout() only if the difference between
> justificationWidth and advance with for printer is more than 10.
>
I had proposed investigating what happens if you simply don't use
justification when the text will fit.
Maybe you are refining that but I am not sure about the details.
10 is one arbitrary number and is not proportional to the length - which
is what I would be
thinking about first in succh an approach
And I am not even sure you mean what you say.
You say "more" than 10, yet your code implements "less" than 10.
And moreover its an absolute value you are using, which re-introduces
the clipping problem, doesn't it ?
ie you are purely looking at the difference and it isn't what I has
proposed and I thought you were trying.
-phil
> webrev: http://cr.openjdk.java.net/~psadhukhan/8214702/webrev.3/
>
> Regards
> Prasanta
> On 26-Feb-19 12:30 PM, Philip Race wrote:
>>
>>
>> On 2/25/19, 10:21 PM, Prasanta Sadhukhan wrote:
>>>
>>> Thanks Phil for review. So, you are doubting it will regress swing
>>> printing tests. As you told earlier, I have ran the following
>>> regression test with this fix
>>>
>>
>> It may not regress a test if the test is not being tested under the
>> same conditions for which it is created but I am telling you for a
>> fact that the fix is wrong. screenWidth should be "width on the screen"
>>>
>>> (https://bugs.openjdk.java.net/browse/JDK-6488219 The bug above is
>>> covered by java/awt/print/PrinterJob/SwingUIText.java)
>>> and I did not notice any regression. Any other test we have for
>>> swing printing that we can run?
>>>
>>
>> No idea which tests will show this today but I know it is an issue.
>> No way we can push this and then just wait for the complaints.
>>
>>> >>Previously we were using DEFAULT_FRC to make it a screen width
>>> which except for maybe needing to be updated for hi-dpi screens is
>>> what we want.
>>> This issue was there from jdk1.6. If it is for hidpi screen, we
>>> would have seen it from jdk9 onwards where we supported hidpi, no?
>>
>> What I am saying here is that DEFAULT_FRC means "screen frc" and
>> I think that should have been updated in 1.9 but was missed because
>> it (hidpi for windows) was not a small or contained task.
>> This is an ancilliary observation of something that should be looked
>> at entirely independent of this bug.
>>
>> -phil.
>>
>>>
>>> Regards
>>> Prasanta
>>> On 26-Feb-19 3:25 AM, Phil Race wrote:
>>>> The current fix confused me for a while as I could not see how it was
>>>> at all different than the existing code, since I can't imagine when
>>>> we'd
>>>> ever take the "else" branch here :
>>>> 533 TextLayout layout;
>>>> 534 if (!isFontRenderContextPrintCompatible(frc, deviceFRC)) {
>>>> 535 layout = createTextLayout(c, text, g2d.getFont(), deviceFRC);
>>>> 536 } else {
>>>> 537 layout = createTextLayout(c, text, g2d.getFont(), frc);
>>>> 538 } Eventually when walking through it I noticed this 531
>>>> FontMetrics fm = g2d.getFontMetrics();
>>>> 532 float screenWidth = SwingUtilities2.stringWidth(c, fm
>>>> ,trimmedText);
>>>>
>>>> "fm" from line 532 is getting a FontMetrics from the PRINTER - ie
>>>> the scaled FontRenderContext.
>>>> It then uses this to calculate the advance width for such a case -
>>>> ie the printer
>>>> but then *assigns it to a variable called screenWidth*.
>>>>
>>>> Previously we were using DEFAULT_FRC to make it a screen width
>>>> which except
>>>> for maybe needing to be updated for hi-dpi screens is what we want.
>>>>
>>>> So in the updated proposed fix the wrong width is passed to
>>>> getJustifiedLayout().
>>>>
>>>> This may not matter here because there is plenty of space, but in
>>>> other cases
>>>> Swing printing will be clipped as a result. And there were many,
>>>> many, bug reports about
>>>> that. Which is why the code is laying out to the screenwidth
>>>> because that is where the
>>>> UI component size available came from. Buttons & Label text are the
>>>> typical cases where
>>>> this showed up.
>>>>
>>>> There maybe other things to change, as well but the incorrect
>>>> screenWidth is the
>>>> main problem I see here.
>>>>
>>>> -phil.
>>>>
>>>> On 2/25/19 12:05 AM, Prasanta Sadhukhan wrote:
>>>>>
>>>>>
>>>>> On 21-Feb-19 4:50 AM, Sergey Bylokhov wrote:
>>>>>> On 13/02/2019 22:53, Prasanta Sadhukhan wrote:
>>>>>>> Hi Sergey,
>>>>>>>
>>>>>>> I believe drawChars() also has same printing issue [and should
>>>>>>> be changed like modified drawString()] but I am not able to test
>>>>>>> it as reproducer testcase uses JLabel whose constructor can only
>>>>>>> accept "String" and not char[] so I can only test drawString().
>>>>>>> Using drawChars() implementation in drawString() still
>>>>>>> reproduces the issue.
>>>>>>
>>>>>> Is it possible temporary replace the call to drawString() by the
>>>>>> drawChars(), to check how drawChars() will work?
>>>>> As I told, it behaves similarly to unmodified drawString and the
>>>>> issue can still be seen. I think we should commit this
>>>>> drawString() change in this fix and I can open another bug to
>>>>> investigate drawChars() impl and reproducer. Will that be fine?
>>>>>
>>>>> Regards
>>>>> Prasanta
>>>>>> or probably we can implement drawChars() on top of drawString()?
>>>>>>
>>>>>>>
>>>>>>> Regards
>>>>>>> Prasanta
>>>>>>> On 14-Feb-19 4:12 AM, Sergey Bylokhov wrote:
>>>>>>>> Hi, Prasanta.
>>>>>>>>
>>>>>>>>> I modified the fix to use deviceFRC if not compatible and in
>>>>>>>>> sync with the comment which says "obtain a TextLayout with
>>>>>>>>> advances for the printer graphics FRC"
>>>>>>>>> I used SwingUtilies2.getStringWidth() which calculates the
>>>>>>>>> advances of the string if text layouting is used.
>>>>>>>>>
>>>>>>>>> http://cr.openjdk.java.net/~psadhukhan/8214702/webrev.2/
>>>>>>>>
>>>>>>>> Can you please take a look to the existed drawChars() method,
>>>>>>>> which is implemented in the similar way as drawStringImpl() and
>>>>>>>> new version of drawString(), but they have some small
>>>>>>>> difference. Why we cannot use the same logic?
>>>>>>>>
>>>>>>>> For example in the drawChars:
>>>>>>>> =========
>>>>>>>> FontRenderContext deviceFontRenderContext = g2d.
>>>>>>>> getFontRenderContext();
>>>>>>>> FontRenderContext frc = getFontRenderContext(c);
>>>>>>>> if (frc != null &&
>>>>>>>> !isFontRenderContextPrintCompatible
>>>>>>>> (deviceFontRenderContext, frc)) {
>>>>>>>> String text = new String(data, offset, length);
>>>>>>>> TextLayout layout = new TextLayout(text,
>>>>>>>> g2d.getFont(),
>>>>>>>> deviceFontRenderContext);
>>>>>>>> String trimmedText = trimTrailingSpaces(text);
>>>>>>>> if (!trimmedText.isEmpty()) {
>>>>>>>> float screenWidth = (float)g2d.getFont().
>>>>>>>> getStringBounds(trimmedText, frc).getWidth();
>>>>>>>> layout =
>>>>>>>> layout.getJustifiedLayout(screenWidth);
>>>>>>>>
>>>>>>>> ==========
>>>>>>>> Similar but not the same logic in the fix:
>>>>>>>>
>>>>>>>> 524 FontRenderContext frc =
>>>>>>>> getFontRenderContext(c);
>>>>>>>> 525 if (frc.isAntiAliased() ||
>>>>>>>> frc.usesFractionalMetrics()) {
>>>>>>>> 526 frc = new
>>>>>>>> FontRenderContext(frc.getTransform(), false, false);
>>>>>>>> 527 }
>>>>>>>> 528 FontRenderContext deviceFRC =
>>>>>>>> g2d.getFontRenderContext();
>>>>>>>> 529 String trimmedText =
>>>>>>>> trimTrailingSpaces(text);
>>>>>>>> 530 if (!trimmedText.isEmpty()) {
>>>>>>>> 531 FontMetrics fm = g2d.getFontMetrics();
>>>>>>>> 532 float screenWidth =
>>>>>>>> SwingUtilities2.stringWidth(c, fm ,trimmedText);
>>>>>>>> 533 TextLayout layout;
>>>>>>>> 534 if
>>>>>>>> (!isFontRenderContextPrintCompatible(frc, deviceFRC)) {
>>>>>>>> 535 layout = createTextLayout(c, text,
>>>>>>>> g2d.getFont(), deviceFRC);
>>>>>>>> 536 } else {
>>>>>>>> 537 layout = createTextLayout(c, text,
>>>>>>>> g2d.getFont(), frc);
>>>>>>>> 538 }
>>>>>>>> 540 layout =
>>>>>>>> layout.getJustifiedLayout(screenWidth);
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mail.openjdk.java.net/pipermail/swing-dev/attachments/20190417/93ff2db9/attachment-0001.html>
More information about the swing-dev
mailing list