<Swing Dev> [10] RFR JDK-8187957:Tab Size does not work correctly in JTextArea

[Prasanta Sadhukhan]

Hi Semyon,

Please find the modified webrev for automated test.
http://cr.openjdk.java.net/~psadhukhan/8187957/webrev.01/

Regards
Prasanta
On 11/9/2017 11:36 PM, Semyon Sadetsky wrote:
> Hi Prasanta,
>
>
> On 11/09/2017 01:56 AM, Prasanta Sadhukhan wrote:
>> I guess by "manual implementation", Sergey was mentioning about 
>> programmer doing the calculation rather than using system api to do 
>> the job for us.
>>
>> Anyway, I saw using Math.ceil and no "nTabs+1", alignment does not work
>>
>> This is because
>> For ex, if x = 66.0, tabSize = 48.0, tabBase = 0, then nTabs = 
>> ceil(66/48) = 2 and tabStop=tabBase + ntabs * tabSize=96
>> Now, nextTabStop is called from Utilities.getTabbedTextWidth() in a 
>> loop passing the same value which it gets as return value from 
>> nextTabStop, for "x"
>> so x = 96.0, tabSize=48.0,ntabs = ceil(96/48)=2 and tabStop=96 again 
>> and it go on getting same tabStop.
>>
>> With
>> int ntabs = (int) ((x - tabBase) / tabSize);
>>         return tabBase + ((ntabs + 1) * tabSize);
>>
>> we get proper alignment
>> x 66.0 tabSize 48.0 ntabs 1 tabstop 96.0
>> x 96.0 tabSize 48.0 ntabs 2 tabstop 144.0
>> x 144.0 tabSize 48.0 ntabs 3 tabstop 192.0
>>
>> So, I guess, as Semyon suggested, making the "result of the sentence 
>> should be  truncated to int, not its members" should be the way to go.
>>
>> Lastly, could you please suggest as to how to automate this test?
> I think the easiest way is to set the caret in the corresponding 
> position and read its coordinates.
>
> --Semyon
>>
>> Regards
>> Prasanta
>> On 11/9/2017 8:36 AM, semyon.sadetsky at oracle.com wrote:
>>> On 11/8/17 12:24 PM, Sergey Bylokhov wrote:
>>>
>>>> On 08/11/2017 11:38, Semyon Sadetsky wrote:
>>>>>> Yes "(int)+1" is also can be used for positive values, but the 
>>>>>> "ceil()" is better since this purpose of this method, and in 
>>>>>> general it works for negative values as well.
>>>>> There may not be negative values here, so Math.ceil() is redundant.
>>>>
>>>> I do not see a reason why standard function can be redundant, and 
>>>> why manual implementation is better. Since even in the first 
>>>> version of the fix there is an issues in manual implementation.
>>> I don't see it standard, just redundant in the case. What did you 
>>> mean under "manual implementation"?
>>>
>>> --Semyon
>>>>
>>>>>
>>>>> --Semyon
>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On 11/08/2017 10:24 AM, Sergey Bylokhov wrote:
>>>>>>>> Hi, Prasanta.
>>>>>>>> Is it possible that dropping the float part of "tabSize" and 
>>>>>>>> "x" will cause Off-by-one error? For example:
>>>>>>>>     float tabSize=3.99f;
>>>>>>>>     float x=21.9f;
>>>>>>>>     int tabBase=0;
>>>>>>>>  649         int ntabs = ((int) x - tabBase) / (int)tabSize;
>>>>>>>>  650         return tabBase + ((ntabs + 1) * tabSize);
>>>>>>>>
>>>>>>>> The result is: ntabs=7 -> 31.92 which is not correct.
>>>>>>>>
>>>>>>>> I guess you will need something like this:
>>>>>>>>     int ntabs = (int) Math.ceil((x - tabBase) / tabSize);
>>>>>>>>     return tabBase + ntabs * tabSize;
>>>>>>>> The result is: ntabs=6 -> 23.94
>>>>>>>>
>>>>>>>>
>>>>>>>> On 08/11/2017 03:25, Prasanta Sadhukhan wrote:
>>>>>>>>> Hi All,
>>>>>>>>>
>>>>>>>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8187957
>>>>>>>>> webrev: http://cr.openjdk.java.net/~psadhukhan/8187957/webrev.00/
>>>>>>>>>
>>>>>>>>> Please review a fix for an issue where it is seen string with 
>>>>>>>>> "tab" in them are not aligned properly.
>>>>>>>>> This is because while calculating tab stop postion, it is 
>>>>>>>>> calculating number of tabs in float value (an aftereffect of 
>>>>>>>>> JDK-8156217 <https://bugs.openjdk.java.net/browse/JDK-8156217>)
>>>>>>>>> so next tab stop location is coming out wrong.
>>>>>>>>> Fix is to use "number of tabs" as an integer value in order to 
>>>>>>>>> calculate the tab position correctly.
>>>>>>>>>
>>>>>>>>> Regards
>>>>>>>>> Prasanta
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>
>>>>
>>>
>>
>