docs/README-nacl.md
author Philipp Wiesemann <philipp.wiesemann@arcor.de>
Wed, 06 Jan 2016 22:39:29 +0100
changeset 10037 e2343ac4788e
parent 9066 c2af3ff967cc
child 10486 5bf595c48fd4
permissions -rw-r--r--
Fixed compile warnings about uninitialized variables in test library.

Found by buildbot.
     1 Native Client
     2 ================================================================================
     3 
     4 Requirements: 
     5 
     6 * Native Client SDK (https://developer.chrome.com/native-client), 
     7   (tested with Pepper version 33 or higher).
     8 
     9 The SDL backend for Chrome's Native Client has been tested only with the PNaCl
    10 toolchain, which generates binaries designed to run on ARM and x86_32/64 
    11 platforms. This does not mean it won't work with the other toolchains!
    12 
    13 ================================================================================
    14 Building SDL for NaCl
    15 ================================================================================
    16 
    17 Set up the right environment variables (see naclbuild.sh), then configure SDL with:
    18 
    19     configure --host=pnacl --prefix some/install/destination
    20     
    21 Then "make". 
    22 
    23 As an example of how to create a deployable app a Makefile project is provided 
    24 in test/nacl/Makefile, which includes some monkey patching of the common.mk file 
    25 provided by NaCl, without which linking properly to SDL won't work (the search 
    26 path can't be modified externally, so the linker won't find SDL's binaries unless 
    27 you dump them into the SDK path, which is inconvenient).
    28 Also provided in test/nacl is the required support file, such as index.html, 
    29 manifest.json, etc.
    30 SDL apps for NaCl run on a worker thread using the ppapi_simple infrastructure.
    31 This allows for blocking calls on all the relevant systems (OpenGL ES, filesystem),
    32 hiding the asynchronous nature of the browser behind the scenes...which is not the
    33 same as making it disappear!
    34 
    35 
    36 ================================================================================
    37 Running tests
    38 ================================================================================
    39 
    40 Due to the nature of NaCl programs, building and running SDL tests is not as
    41 straightforward as one would hope. The script naclbuild.sh in build-scripts 
    42 automates the process and should serve as a guide for users of SDL trying to build 
    43 their own applications.
    44 
    45 Basic usage:
    46     
    47     ./naclbuild.sh path/to/pepper/toolchain (i.e. ~/naclsdk/pepper_35)
    48     
    49 This will build testgles2.c by default.
    50 
    51 If you want to build a different test, for example testrendercopyex.c:
    52     
    53     SOURCES=~/sdl/SDL/test/testrendercopyex.c ./naclbuild.sh ~/naclsdk/pepper_35
    54     
    55 Once the build finishes, you have to serve the contents with a web server (the
    56 script will give you instructions on how to do that with Python).
    57 
    58 ================================================================================
    59 RWops and nacl_io
    60 ================================================================================
    61 
    62 SDL_RWops work transparently with nacl_io. Two functions control the mount points:
    63     
    64     int mount(const char* source, const char* target, 
    65                       const char* filesystemtype, 
    66                       unsigned long mountflags, const void *data);
    67     int umount(const char *target);
    68     
    69     For convenience, SDL will by default mount an httpfs tree at / before calling 
    70 the app's main function. Such setting can be overridden by calling:
    71     
    72     umount("/");
    73 
    74 And then mounting a different filesystem at /
    75 
    76 It's important to consider that the asynchronous nature of file operations on a
    77 browser is hidden from the application, effectively providing the developer with
    78 a set of blocking file operations just like you get in a regular desktop 
    79 environment, which eases the job of porting to Native Client, but also introduces 
    80 a set of challenges of its own, in particular when big file sizes and slow 
    81 connections are involved.
    82 
    83 For more information on how nacl_io and mount points work, see:
    84     
    85     https://developer.chrome.com/native-client/devguide/coding/nacl_io
    86     https://src.chromium.org/chrome/trunk/src/native_client_sdk/src/libraries/nacl_io/nacl_io.h
    87 
    88 To be able to save into the directory "/save/" (like backup of game) :
    89 
    90     mount("", "/save", "html5fs", 0, "type=PERSISTENT");
    91 
    92 And add to manifest.json :
    93 
    94     "permissions": [
    95         "unlimitedStorage"
    96     ]
    97 
    98 ================================================================================
    99 TODO - Known Issues
   100 ================================================================================
   101 * Testing of all systems with a real application (something other than SDL's tests)
   102 * Key events don't seem to work properly
   103