Layout#getOffsetForHorizontal was running in O(n^2) time, where n is the
length of the current line. The method is used when a touch event
happens on a text line, to compute the cursor offset (and the character)
where it happened. Although this is not an issue in common usecases,
where the number of characters on a line is relatively small, this can
be very inefficient as a consequence of Unicode containing 0-width
(invisible) characters. Specifically, there are characters defining the
text direction (LTR or RTL), which cause our algorithm to touch the
worst case quadratic runtime. For example, a person is able to send a
message containing a few visible characters, and also a lot of these
direction changing invisible ones. When the receiver touches the message
(causing the Layout#getOffsetForHorizontal method to be called), the
receiver's application would become not responsive.
This CL optimizes the method to run in O(n) worst case. This is achieved
by computing the measurements of all line prefixes at first, which can
be done in a single pass. Then, all the prefix measurement queries will
be answered in O(1), rather than O(n) as it was happening before.
Bug: 79215201
Test: manual testing
Change-Id: Ib66ef392c19c937718e7101f6d48fac3abe51ad0
Merged-In: Ib66ef392c19c937718e7101f6d48fac3abe51ad0
* limit the absolute maximum size of the label to 50000 characters
[which is probably far more than necessary, but, can be dialed down]
* use a string buffer while processing the string [instead of creating
multiple string objects]
Bug: 62537081
Test: Manual. Install APK in bug and see that it can be uninstalled
Change-Id: Ibf63c2691ad7438a123e92110d95b1f50050f8b1
Merged-In: Ibf63c2691ad7438a123e92110d95b1f50050f8b1
* changes:
[automerger] Update internal ViewPager's SavedState to match Support Library version am: 187964aca1 am: 4c24e4d831 am: fece305de0
[automerger] Update internal ViewPager's SavedState to match Support Library version am: 187964aca1 am: 4c24e4d831
[automerger] Update internal ViewPager's SavedState to match Support Library version am: 187964aca1
Update internal ViewPager's SavedState to match Support Library version
* changes:
[automerger] Update internal ViewPager's SavedState to match Support Library version am: 187964aca1 am: 4c24e4d831
[automerger] Update internal ViewPager's SavedState to match Support Library version am: 187964aca1
Update internal ViewPager's SavedState to match Support Library version
* changes:
[automerger] Update internal ViewPager's SavedState to match Support Library version am: 187964aca1
Update internal ViewPager's SavedState to match Support Library version
* changes:
[automerger] Update internal ViewPager's SavedState to match Support Library version am: 187964aca1 am: 4c24e4d831 am: fece305de0 am: cb362192e8 am: bc42f76941
[automerger] Update internal ViewPager's SavedState to match Support Library version am: 187964aca1 am: 4c24e4d831 am: fece305de0 am: cb362192e8
[automerger] Update internal ViewPager's SavedState to match Support Library version am: 187964aca1 am: 4c24e4d831 am: fece305de0
[automerger] Update internal ViewPager's SavedState to match Support Library version am: 187964aca1 am: 4c24e4d831
[automerger] Update internal ViewPager's SavedState to match Support Library version am: 187964aca1
Update internal ViewPager's SavedState to match Support Library version
* changes:
[automerger] Update internal ViewPager's SavedState to match Support Library version am: 187964aca1 am: 4c24e4d831 am: fece305de0 am: cb362192e8
[automerger] Update internal ViewPager's SavedState to match Support Library version am: 187964aca1 am: 4c24e4d831 am: fece305de0
[automerger] Update internal ViewPager's SavedState to match Support Library version am: 187964aca1 am: 4c24e4d831
[automerger] Update internal ViewPager's SavedState to match Support Library version am: 187964aca1
Update internal ViewPager's SavedState to match Support Library version
Length of the last array in readFromParcel should be the same as
value of mNextIndex.
Test: PoC app in the bug
Bug: 73252178
Change-Id: I69f935949e945c3a036b19b4f88684d906079ea5
