this should implement feature request of zoom mode for multi-columns
page in #501
This PR depends on koreader/koreader-base#435
How to use?
1. Tap the top left corner of a PDF/Djvu page to get into the flipping
mode
2. Double-tap on text block will zoom in to that column
3. Double-tap on any area will zoom out to an overview of the page
4. repeat step 2 to focus to another page block
How does it work?
1. We first find the mask of text blocks in the page. (Pic 1)
2. Then we intersect page boxes with user tap to form a page block. (Pic 2)
3. Finally we zoom the page to the page block and center current view to
that block. (Pic 3)
A new feature 'read from right to left' is added, which is more fit for
Traditional Chinese and Japanese books. Once the feature is enabled:
1. The gesture region of TapForward and area will be flipped
horizonally;
2. The action for swiping to west and to east will be exchanged.
Since the doShowReader will run in nextTick, it will get picked up by
checkTask, which is in the beginning of next UI loop and blocks
UIManager from redrawing the screen for the info popup.
bring back the old behavior: when width and height are set and all the
zooming options are false, zoom the image to that size. The last commit
to Imagewidget.lua caused it ignores the set width and height and use
the image's original size instead when no zoom option is set. This
caused #1979. Although #1979 can be fixed by setting autostretch=true,
but I think it's good to fix here.
to make koreader on Android more stable
and with these opt params:
```
require("jit.opt").start("sizemcode=64","maxmcode=64", "hotloop=10000")
```
The strategy here is that we only use precious mcode memory (jitting)
on deep loops like the several blitting methods in blitbuffer.lua and
the pixel-copying methods in mupdf.lua. So that a small amount of mcode
memory (64KB) allocated when koreader is launched in the android.lua
is enough for the program and it won't need to jit other parts of lua
code and thus won't allocate mcode memory any more which by our
observation will be harder and harder as we run koreader.
