[OpenJDK 2D-Dev] RFR: 8221305: java/awt/FontMetrics/MaxAdvanceIsMax.java fails on MacOS + Solaris

[Sergey Bylokhov]

On 4/29/20 2:33 pm, Philip Race wrote:
> Now that is another topic and unrelated to max advance
> I think a spec update and CSR would be required for getWidths()
> and I'd still say this test is not worth it.

Probably yes, because it is currently states that "Gets the advance
widths of the first 256 characters " and it is bizarre that the
getMaxAdvance() may return smaller size even for the  simple char's.

Currently ina few places we have code like this:
     columnWidth = metrics.charWidth('m');

Which is far than optimal, and getMaxAdvance() should fit better than
the size of the "m"(or 'w'), but seems this method and its current
implementation is completely useless.

> 
> -phil
> 
> On 4/29/20, 2:21 PM, Sergey Bylokhov wrote:
>> On 4/28/20 4:28 pm, Philip Race wrote:
>>>>> And max advance is NOT only about the advance of the first 256 characters anyway
>>>> Yes but it makes it a little bit more useful, it least it will always return correct max
>>>> advance for the first characters.
>>>
>>> Actually I'll argue it can be the opposite.
>>> Doing this you ask it to go check in fallback fonts and in the failure I
>>> analysed on macos we got a fallback from a CJK font for an unprintable character.
>>> Now whilst that may make it "more likely" if we include that in the maxadvance
>>> and care only about chars 0-255 it will pass, you've now got a very different max
>>> advance returned than is the design centre for the primary font and REAL uses
>>> of chars 0-255 which would never try to display char 132 etc.
>>
>> Then probably we could skip any unprintable characters?
>>


-- 
Best regards, Sergey.