docs/README-winrt.md
author Sam Lantinga <slouken@libsdl.org>
Tue, 23 Apr 2019 07:59:31 -0700
changeset 12714 9b7633bd0aa0
parent 11726 27d08f1aab80
child 12810 77707a081153
permissions -rw-r--r--
Use _Exit() when available
     1 WinRT
     2 =====
     3 
     4 This port allows SDL applications to run on Microsoft's platforms that require
     5 use of "Windows Runtime", aka. "WinRT", APIs.  Microsoft may, in some cases,
     6 refer to them as either "Windows Store", or for Windows 10, "UWP" apps.
     7 
     8 Some of the operating systems that include WinRT, are:
     9 
    10 * Windows 10, via its Universal Windows Platform (UWP) APIs
    11 * Windows 8.x
    12 * Windows RT 8.x (aka. Windows 8.x for ARM processors)
    13 * Windows Phone 8.x
    14 
    15 
    16 Requirements
    17 ------------
    18 
    19 * Microsoft Visual C++ (aka Visual Studio), either 2017, 2015, 2013, or 2012
    20   - Free, "Community" or "Express" editions may be used, so long as they
    21     include  support for either "Windows Store" or "Windows Phone" apps.
    22     "Express" versions marked as supporting "Windows Desktop" development
    23     typically do not include support for creating WinRT apps, to note.
    24     (The "Community" editions of Visual C++ do, however, support both
    25     desktop/Win32 and WinRT development).
    26   - Visual Studio 2017 can be used, however it is recommended that you install
    27     the Visual C++ 2015 build tools.  These build tools can be installed
    28     using VS 2017's installer.  Be sure to also install the workload for
    29     "Universal Windows Platform development", its optional component, the
    30     "C++ Universal Windows Platform tools", and for UWP / Windows 10
    31     development, the "Windows 10 SDK (10.0.10240.0)".  Please note that
    32     targeting UWP / Windows 10 apps from development machine(s) running
    33     earlier versions of Windows, such as Windows 7, is not always supported
    34     by Visual Studio, and you may get error(s) when attempting to do so.
    35   - Visual C++ 2012 can only build apps that target versions 8.0 of Windows,
    36     or  Windows Phone.  8.0-targeted apps will run on devices running 8.1
    37     editions of Windows, however they will not be able to take advantage of
    38     8.1-specific features.
    39   - Visual C++ 2013 cannot create app projects that target Windows 8.0.
    40     Visual C++ 2013 Update 4, can create app projects for Windows Phone 8.0,
    41     Windows Phone 8.1, and Windows 8.1, but not Windows 8.0.  An optional
    42     Visual Studio add-in, "Tools for Maintaining Store apps for Windows 8",
    43     allows Visual C++ 2013 to load and build Windows 8.0 projects that were
    44     created with Visual C++ 2012, so long as Visual C++ 2012 is installed
    45     on the same machine.  More details on targeting different versions of
    46     Windows can found at the following web pages:
    47       - [Develop apps by using Visual Studio 2013](http://msdn.microsoft.com/en-us/library/windows/apps/br211384.aspx)
    48       - [To add the Tools for Maintaining Store apps for Windows 8](http://msdn.microsoft.com/en-us/library/windows/apps/dn263114.aspx#AddMaintenanceTools)
    49 * A valid Microsoft account - This requirement is not imposed by SDL, but
    50   rather by Microsoft's Visual C++ toolchain.  This is required to launch or 
    51   debug apps.
    52 
    53 
    54 Status
    55 ------
    56 
    57 Here is a rough list of what works, and what doesn't:
    58 
    59 * What works:
    60   * compilation via Visual C++ 2012 through 2015
    61   * compile-time platform detection for SDL programs.  The C/C++ #define,
    62     `__WINRT__`, will be set to 1 (by SDL) when compiling for WinRT.
    63   * GPU-accelerated 2D rendering, via SDL_Renderer.
    64   * OpenGL ES 2, via the ANGLE library (included separately from SDL)
    65   * software rendering, via either SDL_Surface (optionally in conjunction with
    66     SDL_GetWindowSurface() and SDL_UpdateWindowSurface()) or via the
    67     SDL_Renderer APIs
    68   * threads
    69   * timers (via SDL_GetTicks(), SDL_AddTimer(), SDL_GetPerformanceCounter(),
    70     SDL_GetPerformanceFrequency(), etc.)
    71   * file I/O via SDL_RWops
    72   * mouse input  (unsupported on Windows Phone)
    73   * audio, via SDL's WASAPI backend (if you want to record, your app must 
    74     have "Microphone" capabilities enabled in its manifest, and the user must 
    75     not have blocked access. Otherwise, capture devices will fail to work,
    76     presenting as a device disconnect shortly after opening it.)
    77   * .DLL file loading.  Libraries *MUST* be packaged inside applications.  Loading
    78     anything outside of the app is not supported.
    79   * system path retrieval via SDL's filesystem APIs
    80   * game controllers.  Support is provided via the SDL_Joystick and
    81     SDL_GameController APIs, and is backed by Microsoft's XInput API.  Please
    82     note, however, that Windows limits game-controller support in UWP apps to,
    83     "Xbox compatible controllers" (many controllers that work in Win32 apps,
    84     do not work in UWP, due to restrictions in UWP itself.) 
    85   * multi-touch input
    86   * app events.  SDL_APP_WILLENTER* and SDL_APP_DIDENTER* events get sent out as
    87     appropriate.
    88   * window events
    89   * using Direct3D 11.x APIs outside of SDL.  Non-XAML / Direct3D-only apps can
    90     choose to render content directly via Direct3D, using SDL to manage the
    91     internal WinRT window, as well as input and audio.  (Use
    92     SDL_GetWindowWMInfo() to get the WinRT 'CoreWindow', and pass it into
    93     IDXGIFactory2::CreateSwapChainForCoreWindow() as appropriate.)
    94 
    95 * What partially works:
    96   * keyboard input.  Most of WinRT's documented virtual keys are supported, as
    97     well as many keys with documented hardware scancodes.  Converting
    98     SDL_Scancodes to or from SDL_Keycodes may not work, due to missing APIs
    99     (MapVirtualKey()) in Microsoft's Windows Store / UWP APIs.
   100   * SDLmain.  WinRT uses a different signature for each app's main() function.
   101     SDL-based apps that use this port must compile in SDL_winrt_main_NonXAML.cpp
   102     (in `SDL\src\main\winrt\`) directly in order for their C-style main()
   103     functions to be called.
   104 
   105 * What doesn't work:
   106   * compilation with anything other than Visual C++
   107   * programmatically-created custom cursors.  These don't appear to be supported
   108     by WinRT.  Different OS-provided cursors can, however, be created via
   109     SDL_CreateSystemCursor() (unsupported on Windows Phone)
   110   * SDL_WarpMouseInWindow() or SDL_WarpMouseGlobal().  This are not currently
   111     supported by WinRT itself.
   112   * joysticks and game controllers that either are not supported by
   113     Microsoft's XInput API, or are not supported within UWP apps (many
   114     controllers that work in Win32, do not work in UWP, due to restrictions in
   115     UWP itself).
   116   * turning off VSync when rendering on Windows Phone.  Attempts to turn VSync
   117     off on Windows Phone result either in Direct3D not drawing anything, or it
   118     forcing VSync back on.  As such, SDL_RENDERER_PRESENTVSYNC will always get
   119     turned-on on Windows Phone.  This limitation is not present in non-Phone
   120     WinRT (such as Windows 8.x), where turning off VSync appears to work.
   121   * probably anything else that's not listed as supported
   122 
   123 
   124 
   125 Upgrade Notes
   126 -------------
   127 
   128 #### SDL_GetPrefPath() usage when upgrading WinRT apps from SDL 2.0.3
   129 
   130 SDL 2.0.4 fixes two bugs found in the WinRT version of SDL_GetPrefPath().
   131 The fixes may affect older, SDL 2.0.3-based apps' save data.  Please note
   132 that these changes only apply to SDL-based WinRT apps, and not to apps for
   133 any other platform.
   134 
   135 1. SDL_GetPrefPath() would return an invalid path, one in which the path's
   136    directory had not been created.  Attempts to create files there
   137    (via fopen(), for example), would fail, unless that directory was
   138    explicitly created beforehand.
   139 
   140 2. SDL_GetPrefPath(), for non-WinPhone-based apps, would return a path inside
   141    a WinRT 'Roaming' folder, the contents of which get automatically
   142    synchronized across multiple devices.  This process can occur while an
   143    application runs, and can cause existing save-data to be overwritten
   144    at unexpected times, with data from other devices.  (Windows Phone apps
   145    written with SDL 2.0.3 did not utilize a Roaming folder, due to API
   146    restrictions in Windows Phone 8.0).
   147 
   148 
   149 SDL_GetPrefPath(), starting with SDL 2.0.4, addresses these by:
   150 
   151 1. making sure that SDL_GetPrefPath() returns a directory in which data
   152    can be written to immediately, without first needing to create directories.
   153 
   154 2. basing SDL_GetPrefPath() off of a different, non-Roaming folder, the
   155    contents of which do not automatically get synchronized across devices
   156    (and which require less work to use safely, in terms of data integrity).
   157 
   158 Apps that wish to get their Roaming folder's path can do so either by using
   159 SDL_WinRTGetFSPathUTF8(), SDL_WinRTGetFSPathUNICODE() (which returns a
   160 UCS-2/wide-char string), or directly through the WinRT class,
   161 Windows.Storage.ApplicationData.
   162 
   163 
   164 
   165 Setup, High-Level Steps
   166 -----------------------
   167 
   168 The steps for setting up a project for an SDL/WinRT app looks like the
   169 following, at a high-level:
   170 
   171 1. create a new Visual C++ project using Microsoft's template for a,
   172    "Direct3D App".
   173 2. remove most of the files from the project.
   174 3. make your app's project directly reference SDL/WinRT's own Visual C++
   175    project file, via use of Visual C++'s "References" dialog.  This will setup
   176    the linker, and will copy SDL's .dll files to your app's final output.
   177 4. adjust your app's build settings, at minimum, telling it where to find SDL's
   178    header files.
   179 5. add files that contains a WinRT-appropriate main function, along with some
   180    data to make sure mouse-cursor-hiding (via SDL_ShowCursor(SDL_DISABLE) calls)
   181    work properly.
   182 6. add SDL-specific app code.
   183 7. build and run your app.
   184 
   185 
   186 Setup, Detailed Steps
   187 ---------------------
   188 
   189 ### 1. Create a new project ###
   190 
   191 Create a new project using one of Visual C++'s templates for a plain, non-XAML,
   192 "Direct3D App" (XAML support for SDL/WinRT is not yet ready for use).  If you
   193 don't see one of these templates, in Visual C++'s 'New Project' dialog, try
   194 using the textbox titled, 'Search Installed Templates' to look for one.
   195 
   196 
   197 ### 2. Remove unneeded files from the project ###
   198 
   199 In the new project, delete any file that has one of the following extensions:
   200 
   201 - .cpp
   202 - .h
   203 - .hlsl
   204 
   205 When you are done, you should be left with a few files, each of which will be a
   206 necessary part of your app's project.  These files will consist of:
   207 
   208 - an .appxmanifest file, which contains metadata on your WinRT app.  This is
   209   similar to an Info.plist file on iOS, or an AndroidManifest.xml on Android.
   210 - a few .png files, one of which is a splash screen (displayed when your app
   211   launches), others are app icons.
   212 - a .pfx file, used for code signing purposes.
   213 
   214 
   215 ### 3. Add references to SDL's project files ###
   216 
   217 SDL/WinRT can be built in multiple variations, spanning across three different
   218 CPU architectures (x86, x64, and ARM) and two different configurations
   219 (Debug and Release).  WinRT and Visual C++ do not currently provide a means
   220 for combining multiple variations of one library into a single file.
   221 Furthermore, it does not provide an easy means for copying pre-built .dll files
   222 into your app's final output (via Post-Build steps, for example).  It does,
   223 however, provide a system whereby an app can reference the MSVC projects of
   224 libraries such that, when the app is built:
   225 
   226 1. each library gets built for the appropriate CPU architecture(s) and WinRT
   227    platform(s).
   228 2. each library's output, such as .dll files, get copied to the app's build 
   229    output.
   230 
   231 To set this up for SDL/WinRT, you'll need to run through the following steps:
   232 
   233 1. open up the Solution Explorer inside Visual C++ (under the "View" menu, then
   234    "Solution Explorer")
   235 2. right click on your app's solution.
   236 3. navigate to "Add", then to "Existing Project..."
   237 4. find SDL/WinRT's Visual C++ project file and open it.  Different project
   238    files exist for different WinRT platforms.  All of them are in SDL's
   239    source distribution, in the following directories:
   240     * `VisualC-WinRT/UWP_VS2015/`        - for Windows 10 / UWP apps
   241     * `VisualC-WinRT/WinPhone81_VS2013/` - for Windows Phone 8.1 apps
   242     * `VisualC-WinRT/WinRT80_VS2012/`    - for Windows 8.0 apps
   243     * `VisualC-WinRT/WinRT81_VS2013/`    - for Windows 8.1 apps
   244 5. once the project has been added, right-click on your app's project and
   245    select, "References..."
   246 6. click on the button titled, "Add New Reference..."
   247 7. check the box next to SDL
   248 8. click OK to close the dialog
   249 9. SDL will now show up in the list of references.  Click OK to close that
   250    dialog.
   251 
   252 Your project is now linked to SDL's project, insofar that when the app is
   253 built, SDL will be built as well, with its build output getting included with
   254 your app.
   255 
   256 
   257 ### 4. Adjust Your App's Build Settings ###
   258 
   259 Some build settings need to be changed in your app's project.  This guide will
   260 outline the following:
   261 
   262 - making sure that the compiler knows where to find SDL's header files
   263 - **Optional for C++, but NECESSARY for compiling C code:** telling the
   264   compiler not to use Microsoft's C++ extensions for WinRT development.
   265 - **Optional:** telling the compiler not generate errors due to missing
   266   precompiled header files.
   267 
   268 To change these settings:
   269 
   270 1. right-click on the project
   271 2. choose "Properties"
   272 3. in the drop-down box next to "Configuration", choose, "All Configurations"
   273 4. in the drop-down box next to "Platform", choose, "All Platforms"
   274 5. in the left-hand list, expand the "C/C++" section
   275 6. select "General"
   276 7. edit the "Additional Include Directories" setting, and add a path to SDL's
   277    "include" directory
   278 8. **Optional: to enable compilation of C code:** change the setting for
   279    "Consume Windows Runtime Extension" from "Yes (/ZW)" to "No".  If you're 
   280    working with a completely C++ based project, this step can usually be 
   281    omitted.
   282 9. **Optional: to disable precompiled headers (which can produce 
   283    'stdafx.h'-related build errors, if setup incorrectly:** in the left-hand 
   284    list, select "Precompiled Headers", then change the setting for "Precompiled 
   285    Header" from "Use (/Yu)" to "Not Using Precompiled Headers".
   286 10. close the dialog, saving settings, by clicking the "OK" button
   287 
   288 
   289 ### 5. Add a WinRT-appropriate main function, and a blank-cursor image, to the app. ###
   290 
   291 A few files should be included directly in your app's MSVC project, specifically:
   292 1. a WinRT-appropriate main function (which is different than main() functions on
   293    other platforms)
   294 2. a Win32-style cursor resource, used by SDL_ShowCursor() to hide the mouse cursor
   295    (if and when the app needs to do so).  *If this cursor resource is not
   296    included, mouse-position reporting may fail if and when the cursor is
   297    hidden, due to possible bugs/design-oddities in Windows itself.*
   298 
   299 To include these files:
   300 
   301 1. right-click on your project (again, in Visual C++'s Solution Explorer), 
   302    navigate to "Add", then choose "Existing Item...".
   303 2. navigate to the directory containing SDL's source code, then into its
   304    subdirectory, 'src/main/winrt/'.  Select, then add, the following files:
   305    - `SDL_winrt_main_NonXAML.cpp`
   306    - `SDL2-WinRTResources.rc`
   307    - `SDL2-WinRTResource_BlankCursor.cur`
   308 3. right-click on the file `SDL_winrt_main_NonXAML.cpp` (as listed in your
   309    project), then click on "Properties...".
   310 4. in the drop-down box next to "Configuration", choose, "All Configurations"
   311 5. in the drop-down box next to "Platform", choose, "All Platforms"
   312 6. in the left-hand list, click on "C/C++"
   313 7. change the setting for "Consume Windows Runtime Extension" to "Yes (/ZW)".
   314 8. click the OK button.  This will close the dialog.
   315 
   316 
   317 **NOTE: C++/CX compilation is currently required in at least one file of your 
   318 app's project.  This is to make sure that Visual C++'s linker builds a 'Windows 
   319 Metadata' file (.winmd) for your app.  Not doing so can lead to build errors.**
   320 
   321 
   322 ### 6. Add app code and assets ###
   323 
   324 At this point, you can add in SDL-specific source code.  Be sure to include a 
   325 C-style main function (ie: `int main(int argc, char *argv[])`).  From there you 
   326 should be able to create a single `SDL_Window` (WinRT apps can only have one 
   327 window, at present), as well as an `SDL_Renderer`.  Direct3D will be used to 
   328 draw content.  Events are received via SDL's usual event functions 
   329 (`SDL_PollEvent`, etc.)  If you have a set of existing source files and assets, 
   330 you can start adding them to the project now.  If not, or if you would like to 
   331 make sure that you're setup correctly, some short and simple sample code is 
   332 provided below.
   333 
   334 
   335 #### 6.A. ... when creating a new app ####
   336 
   337 If you are creating a new app (rather than porting an existing SDL-based app), 
   338 or if you would just like a simple app to test SDL/WinRT with before trying to 
   339 get existing code working, some working SDL/WinRT code is provided below.  To 
   340 set this up:
   341 
   342 1. right click on your app's project
   343 2. select Add, then New Item.  An "Add New Item" dialog will show up.
   344 3. from the left-hand list, choose "Visual C++"
   345 4. from the middle/main list, choose "C++ File (.cpp)"
   346 5. near the bottom of the dialog, next to "Name:", type in a name for your 
   347 source file, such as, "main.cpp".
   348 6. click on the Add button.  This will close the dialog, add the new file to 
   349 your project, and open the file in Visual C++'s text editor.
   350 7. Copy and paste the following code into the new file, then save it.
   351 
   352 
   353     #include <SDL.h>
   354     
   355     int main(int argc, char **argv)
   356     {
   357         SDL_DisplayMode mode;
   358         SDL_Window * window = NULL;
   359         SDL_Renderer * renderer = NULL;
   360         SDL_Event evt;
   361     
   362         if (SDL_Init(SDL_INIT_VIDEO) != 0) {
   363             return 1;
   364         }
   365     
   366         if (SDL_GetCurrentDisplayMode(0, &mode) != 0) {
   367             return 1;
   368         }
   369     
   370         if (SDL_CreateWindowAndRenderer(mode.w, mode.h, SDL_WINDOW_FULLSCREEN, &window, &renderer) != 0) {
   371             return 1;
   372         }
   373     
   374         while (1) {
   375             while (SDL_PollEvent(&evt)) {
   376             }
   377     
   378             SDL_SetRenderDrawColor(renderer, 0, 255, 0, 255);
   379             SDL_RenderClear(renderer);
   380             SDL_RenderPresent(renderer);
   381         }
   382     }
   383 
   384 
   385 #### 6.B. Adding code and assets ####
   386 
   387 If you have existing code and assets that you'd like to add, you should be able 
   388 to add them now.  The process for adding a set of files is as such.
   389 
   390 1. right click on the app's project
   391 2. select Add, then click on "New Item..."
   392 3. open any source, header, or asset files as appropriate.  Support for C and 
   393 C++ is available.
   394 
   395 Do note that WinRT only supports a subset of the APIs that are available to 
   396 Win32-based apps.  Many portions of the Win32 API and the C runtime are not 
   397 available.
   398 
   399 A list of unsupported C APIs can be found at 
   400 <http://msdn.microsoft.com/en-us/library/windows/apps/jj606124.aspx>
   401 
   402 General information on using the C runtime in WinRT can be found at 
   403 <https://msdn.microsoft.com/en-us/library/hh972425.aspx>
   404 
   405 A list of supported Win32 APIs for WinRT apps can be found at 
   406 <http://msdn.microsoft.com/en-us/library/windows/apps/br205757.aspx>.  To note, 
   407 the list of supported Win32 APIs for Windows Phone 8.0 is different.  
   408 That list can be found at 
   409 <http://msdn.microsoft.com/en-us/library/windowsphone/develop/jj662956(v=vs.105).aspx>
   410 
   411 
   412 ### 7. Build and run your app ###
   413 
   414 Your app project should now be setup, and you should be ready to build your app.  
   415 To run it on the local machine, open the Debug menu and choose "Start 
   416 Debugging".  This will build your app, then run your app full-screen.  To switch 
   417 out of your app, press the Windows key.  Alternatively, you can choose to run 
   418 your app in a window.  To do this, before building and running your app, find 
   419 the drop-down menu in Visual C++'s toolbar that says, "Local Machine".  Expand 
   420 this by clicking on the arrow on the right side of the list, then click on 
   421 Simulator.  Once you do that, any time you build and run the app, the app will 
   422 launch in window, rather than full-screen.
   423 
   424 
   425 #### 7.A. Running apps on older, ARM-based, "Windows RT" devices ####
   426 
   427 **These instructions do not include Windows Phone, despite Windows Phone
   428 typically running on ARM processors.**  They are specifically for devices
   429 that use the "Windows RT" operating system, which was a modified version of
   430 Windows 8.x that ran primarily on ARM-based tablet computers.
   431 
   432 To build and run the app on ARM-based, "Windows RT" devices, you'll need to:
   433 
   434 - install Microsoft's "Remote Debugger" on the device.  Visual C++ installs and 
   435   debugs ARM-based apps via IP networks.
   436 - change a few options on the development machine, both to make sure it builds 
   437   for ARM (rather than x86 or x64), and to make sure it knows how to find the 
   438   Windows RT device (on the network).
   439 
   440 Microsoft's Remote Debugger can be found at 
   441 <https://msdn.microsoft.com/en-us/library/hh441469.aspx>.  Please note 
   442 that separate versions of this debugger exist for different versions of Visual 
   443 C++, one each for MSVC 2015, 2013, and 2012.
   444 
   445 To setup Visual C++ to launch your app on an ARM device:
   446 
   447 1. make sure the Remote Debugger is running on your ARM device, and that it's on 
   448    the same IP network as your development machine.
   449 2. from Visual C++'s toolbar, find a drop-down menu that says, "Win32".  Click 
   450    it, then change the value to "ARM".
   451 3. make sure Visual C++ knows the hostname or IP address of the ARM device.  To 
   452    do this:
   453     1. open the app project's properties
   454     2. select "Debugging"
   455     3. next to "Machine Name", enter the hostname or IP address of the ARM 
   456        device
   457     4. if, and only if, you've turned off authentication in the Remote Debugger,
   458        then change the setting for "Require Authentication" to No
   459     5. click "OK"
   460 4. build and run the app (from Visual C++).  The first time you do this, a 
   461    prompt will show up on the ARM device, asking for a Microsoft Account.  You 
   462    do, unfortunately, need to log in here, and will need to follow the 
   463    subsequent registration steps in order to launch the app.  After you do so, 
   464    if the app didn't already launch, try relaunching it again from within Visual 
   465    C++.
   466 
   467 
   468 Troubleshooting
   469 ---------------
   470 
   471 #### Build fails with message, "error LNK2038: mismatch detected for 'vccorlib_lib_should_be_specified_before_msvcrt_lib_to_linker'"
   472 
   473 Try adding the following to your linker flags.  In MSVC, this can be done by
   474 right-clicking on the app project, navigating to Configuration Properties ->
   475 Linker -> Command Line, then adding them to the Additional Options
   476 section.
   477 
   478 * For Release builds / MSVC-Configurations, add:
   479 
   480     /nodefaultlib:vccorlib /nodefaultlib:msvcrt vccorlib.lib msvcrt.lib
   481 
   482 * For Debug builds / MSVC-Configurations, add:
   483 
   484     /nodefaultlib:vccorlibd /nodefaultlib:msvcrtd vccorlibd.lib msvcrtd.lib
   485 
   486 
   487 #### Mouse-motion events fail to get sent, or SDL_GetMouseState() fails to return updated values
   488 
   489 This may be caused by a bug in Windows itself, whereby hiding the mouse
   490 cursor can cause mouse-position reporting to fail.
   491 
   492 SDL provides a workaround for this, but it requires that an app links to a
   493 set of Win32-style cursor image-resource files.  A copy of suitable resource
   494 files can be found in `src/main/winrt/`.  Adding them to an app's Visual C++
   495 project file should be sufficient to get the app to use them.
   496 
   497 
   498 #### SDL's Visual Studio project file fails to open, with message, "The system can't find the file specified."
   499 
   500 This can be caused for any one of a few reasons, which Visual Studio can
   501 report, but won't always do so in an up-front manner.
   502 
   503 To help determine why this error comes up:
   504 
   505 1. open a copy of Visual Studio without opening a project file.  This can be
   506    accomplished via Windows' Start Menu, among other means.
   507 2. show Visual Studio's Output window.  This can be done by going to VS'
   508    menu bar, then to View, and then to Output.
   509 3. try opening the SDL project file directly by going to VS' menu bar, then
   510    to File, then to Open, then to Project/Solution.  When a File-Open dialog
   511    appears, open the SDL project (such as the one in SDL's source code, in its
   512    directory, VisualC-WinRT/UWP_VS2015/).
   513 4. after attempting to open SDL's Visual Studio project file, additional error
   514    information will be output to the Output window.
   515 
   516 If Visual Studio reports (via its Output window) that the project:
   517 
   518 "could not be loaded because it's missing install components. To fix this launch Visual Studio setup with the following selections:
   519 Microsoft.VisualStudio.ComponentGroup.UWP.VC"
   520 
   521 ... then you will need to re-launch Visual Studio's installer, and make sure that
   522 the workflow for "Universal Windows Platform development" is checked, and that its
   523 optional component, "C++ Universal Windows Platform tools" is also checked.  While
   524 you are there, if you are planning on targeting UWP / Windows 10, also make sure
   525 that you check the optional component, "Windows 10 SDK (10.0.10240.0)".  After
   526 making sure these items are checked as-appropriate, install them.
   527 
   528 Once you install these components, try re-launching Visual Studio, and re-opening
   529 the SDL project file.  If you still get the error dialog, try using the Output
   530 window, again, seeing what Visual Studio says about it.
   531 
   532 
   533 #### Game controllers / joysticks aren't working!
   534 
   535 Windows only permits certain game controllers and joysticks to work within
   536 WinRT / UWP apps.  Even if a game controller or joystick works in a Win32
   537 app, that device is not guaranteed to work inside a WinRT / UWP app.
   538 
   539 According to Microsoft, "Xbox compatible controllers" should work inside
   540 UWP apps, potentially with more working in the future.  This includes, but
   541 may not be limited to, Microsoft-made Xbox controllers and USB adapters.
   542 (Source: https://social.msdn.microsoft.com/Forums/en-US/9064838b-e8c3-4c18-8a83-19bf0dfe150d/xinput-fails-to-detect-game-controllers?forum=wpdevelop)
   543 
   544