<Swing Dev> [9] Review request for 8027639: JComboBox's popup leaves tracks after closing

[Semyon Sadetsky]

On 23.11.2016 20:46, Sergey Bylokhov wrote:
> On 14.11.16 12:03, Semyon Sadetsky wrote:
>> Please review the updated webrev:
>> http://cr.openjdk.java.net/~ssadetsky/8027639/webrev.01/
>> - buffer fill color is changed to 0,0,0,0
>> - graphics context background color and composition is restored
>> - scenario when the buffered JComponent has transparent background and
>> opaque=true is taken into account
>
> I am not sure that the change in JComponent is necessary, because it 
> is responsibility of the component to return false from isOpaque() if 
> it has transparent background. Did you find what 
> components(lookAndFeels) breaks this contract?
Imagine you set a transparent background for the JRootPane but make it 
opaque. Having this allowed for JComponents (unlike HW components) the 
underling Window becomes visible but its surface is never cleared 
without fixing the JComponent logic that stops repaint propagation at 
the first opaque component without checking its background transparency. 
So, to avoid artifacts one need either fix JComponent paint logic, 
either disable for an opaque JComponent to have transparent background.
>
>> On 11/7/2016 7:01 PM, Sergey Bylokhov wrote:
>>> On 07.11.16 18:31, Semyon Sadetsky wrote:
>>>>> If it is src-over mean that in the window you will get a composite of
>>>>> colors, which was drawn to the backbuffer and the colors which was
>>>>> drawn in the window(which was drawn by the window itself). And in 
>>>>> this
>>>>> case you will get a different results when you paint via 
>>>>> backbuffer or
>>>>> when you skip it.
>>>> I did not get this. You've state if JRootPane has own different
>>>> transparent color than it may be painted twice.
>>>
>>> I am talking about the color of the window, you said that it is always
>>> painted.
>>> http://mail.openjdk.java.net/pipermail/swing-dev/2016-October/006854.html 
>>>
>>> So if it always painted in case of non-opaque windows and you paint it
>>> to the backbuffer means that you paint it twice, no?
>>>
>>>> At first, I'm not sure that JRootPane may have such color. Because we
>>>> only support window translucency if window is non-opaque and having
>>>> non-opaque window with opaque JRootPane seems incorrect usage.
>>>
>>> The components can be opaque/non-opaque even if the window is
>>> opaque/non-opaque. They have a different meaning. For window this
>>> means that it has a transparent background, for components it means
>>> that before the component is painted all its containers should be
>>> painted first.
>>>
>>>> But anyway I don't see the way how the JRootPane transparent color may
>>>> be pained twice. For non-opaque JRootPane it's background color is not
>>>> painted, regardless of transparency. With opaque JRootPane the parent
>>>> window paint() method will not be called and  window background 
>>>> will not
>>>> be painted.
>>>>>
>>>>>>>>>>>   Should the previous composite be restored after the rect
>>>>>>>>>>> filling?
>>>>>>>>>> SRC should be the default composite type.
>>>>>>>>>
>>>>>>>>> default composite type should be srcOver, and it should be 
>>>>>>>>> restored
>>>>>>>>> before call paintToOffscreen().
>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>
>>>
>>>
>>
>
>