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)
Currently only tested on Ubuntu-touch emulator with framework
ubuntu-sdk-14.10 for armhf.
The ubuntu-touch port is binary compatible with the Kobo port
major changes in this PR are:
1. rename the emulator device to sdl device since both the emulator
and the ubuntu-touch target use libsdl to handle input/output.
2. ubuntu-touch app has no write access to the installation dir so
all write-outs should be in a seperate dir definded in `datastorage`.
On kindle, kobo and pocketbook the data directory is the current
running directory but on Android the app is installed in system
defined location and users may have no access to that location.
The same circumstances should be true for the upcoming Koreader for
Ubuntu touch, so the data directory (in which tessdata, dictionaries,
global settings, persistant defaults and probably history data are
stored) could be stored in another place.
to support custom font directory for EPUB documents
Now Koreader could find fonts in the "fonts" directory in the USB root
directory of kindle, Kobo and PocketBook devices, thus no need to copy
fonts to "koreader/fonts" directory.
This is a major overhaul of the hardware abstraction layer.
A few notes:
General platform distinction happens in
frontend/device.lua
which will delegate everything else to
frontend/device/<platform_name>/device.lua
which should extend
frontend/device/generic/device.lua
Screen handling is implemented in
frontend/device/screen.lua
which includes the *functionality* to support device specifics.
Actually setting up the device specific functionality, however,
is done in the device specific setup code in the relevant
device.lua file.
The same goes for input handling.
so that when document is modified the persistent cache will
be invalidated automatically because the cache key will not
be matched. There is no perfermance overhead here at all. We
even don't need to check the modification time of the cache item
on disk, because the name of the on disk cache is a md5sum of the
cacheitem key, now the filename of the cache files contains the
modification time information.
If the document is modified since one rendered page is cached to disk,
the cache key won't match the cache file. And the cache file will
be discarded without the need to open the cache file or to check
the modification time of the cache file itself.
