This keeps the same rectangle packing behaviour, so to behave exactly as
before for what concerns batching the updates, but should be lighter
when looping to find the first good rectangle to use.
In rtree_insert(), some conditions in the if tests are implied by
previous conditions. And therefore the 2 successive for loops are
actually identical.
In rtree_node_insert(), it is wrong/harmful to insert zero sized
rectangles in the tree because they can never be selected and just make
the list longer. So rtree_node_create() should just return NULL when w
or h are 0.
See bug 694917, comments 51 to 61.
which is just a #define to g_assert for now, but can now easily be
turned into something that does some nicer debugging using our new
stack trace infrastructure. This commit also reverts all constructed()
functions to use assert again.
After commit 8029508fbe, we always
render the image in chunks that are at most
GIMP_DISPLAY_RENDER_BUF_WIDTH x GIMP_DISPLAY_RENDER_BUF_HEIGHT,
even when the window's scale factor is > 1.
