On 10/27/2016 7:38 PM, Sergey Bylokhov wrote:
On 27.10.16 19:21, Semyon Sadetsky wrote:
Probably you've confused that root is not an instance of the
JRootPane.
It is a HW container that is parent of the root pane.
But there is an another color discrepancy here. Since the HW container
is not opaque the background color should not be painted. But we fill
background to clear the updated area. Probably the fill color
should be
Color(0,0,0,0) in this case but currently the getBackground() color is
used if painting is executed without back buffer (see
java.awt.Window#paint()).
When the backbuffer is disabled: The code in the Window#paint() should
be executed when the Window(top level is painted). After that the
child components should be painted on top of that(srcOver will be
used). Note that we should not fill background of the parent when we
paint a child.
It is always painted in case of non-opaque window in
java.awt.Window#paint(). Are you proposing to change that?
It should not be changed. It is painted by the Window@paint() method,
which is located in the window class, which paints its own backgound.
When the backbuffer is enabled for one components or for all
components, we should draw hierarchy of components one by one to the
backbuffer(in one step), and then src-blit the backbuffer to the
window. Or we can paint only some of components via buffer, but in
this case we should clear the buffer to (0,0,0,0), draw the component,
then srcover-blit to the parent. It is unclear why we should clear
buffer to the parent's color when we draw a child, because the parent
itself should draw this background to the backbuffer, or to the window.
Because the back buffer is used for swing components (JRootPane is back
buffered) while HW container paint is not back buffered but it should
contribute to the painting to get the same result as without
back-buffering.
Please be more specific on your suggestions.
As you mention above background of the window will be always cleared
by the window itself, and we can get double alpha in the background
when we blit the backbuffer to the window. What composite is used when
we draw backbuffer to the window?
It is src-over.
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().
