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

[Semyon Sadetsky]

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
>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>
>>>
>>>
>>
>