<Swing Dev> [11] RFR: JDK-8199441: Wrong caret position in multiline text components on Windows with a screen resolution higher than 100%

[Prasanta Sadhukhan]

Hi Phil,

Any feedback as to why you find this is not the right fix? I could not 
find anything in JDK-8168992 to guess it is not.
As told, there was no regression with jck and jtreg tests with the fix.

Regards
Prasanta
On 5/9/2018 12:41 AM, Phil Race wrote:
> I am not sure this is the right fix.
> If the intention had been to change all calls to getTabbedTextOffset() 
> to use the FP
> API it would have just been changed .. rather than adding a new API 
> that provides
> the option to specify whether to use FP.
>
> So perhaps the problem is that internal code needs to be updated to 
> call the FP
> version directly ..
> I'd like to read https://bugs.openjdk.java.net/browse/JDK-8168992 to see
> what was said there but JBS just went down for 5 hours maintenance ..
>
> -phil.
>
> On 05/07/2018 11:54 PM, Prasanta Sadhukhan wrote:
>> Hi Sergey,
>>
>> I have run javax/swing/text jtreg and jck tests and did not observe 
>> any regressions.
>>
>> Regards
>> Prasanta
>> On 4/28/2018 5:38 AM, Sergey Bylokhov wrote:
>>> Hi, Prasanta.
>>> Please confirm that you run related jck/reg tests.
>>>
>>> On 26/04/2018 23:52, Prasanta Sadhukhan wrote:
>>>> Hi All,
>>>>
>>>> Please review a fix for an issue where it is seen that,
>>>>   with a screen resolution higher than 100% and then clicking in a 
>>>> JTextArea having setLineWrap(true) set, the caret (insertion point) 
>>>> is not aligned with the cursor.
>>>>
>>>> The issue seems to stem from the fact that caret position 
>>>> calculation in DefaultCaret class utilises API that uses integer 
>>>> calculation than floating point calculations.
>>>> The code flow as seen is
>>>> DefaultCaret#positionCaret=>BasicTextUI#viewToModel=>BoxView.viewToModel=>CompositeView#viewToModel=>WrappedPlainView#viewToModel=>Utilities.getTabbedOffset 
>>>>
>>>> Now, getTabbedOffset utilises FontMetrics.charsWidth() which uses 
>>>> integer arithmetic to get the caret position.
>>>> The same getTabbedOffset uses Font.getStringBounds() which uses 
>>>> floating point arithmetic via Rectangle2D.Float.
>>>>
>>>> Proposed fix is to make sure getTabbedOffset uses floating point 
>>>> calculations by using getStringBounds() instead of charsWidth() so 
>>>> that it calculates
>>>> the character width(s) of text present in JTextArea in floating 
>>>> point to align the caret.
>>>>
>>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8199441
>>>> webrev: http://cr.openjdk.java.net/~psadhukhan/8199441/webrev.00/
>>>>
>>>> Regards
>>>> Prasanta
>>>
>>>
>>
>