Sync SDL3 wiki -> header

docs/README-winrt.md

@@ -0,0 +1,483 @@
+WinRT
+=====
+
+This port allows SDL applications to run on Microsoft's platforms that require
+use of "Windows Runtime", aka. "WinRT", APIs.  Microsoft may, in some cases,
+refer to them as either "Windows Store", or for Windows 10, "UWP" apps.
+
+In the past, SDL has supported Windows RT 8.x, Windows Phone, etc, but in
+modern times this port is focused on UWP apps, which run on Windows 10,
+and modern Xbox consoles.
+
+
+Requirements
+------------
+
+* Microsoft Visual C++ (aka Visual Studio) 2019.
+  - Free, "Community" or "Express" editions may be used, so long as they
+    include support for either "Windows Store" or "Windows Phone" apps.
+    "Express" versions marked as supporting "Windows Desktop" development
+    typically do not include support for creating WinRT apps, to note.
+    (The "Community" editions of Visual C++ do, however, support both
+    desktop/Win32 and WinRT development).
+* A valid Microsoft account - This requirement is not imposed by SDL, but
+  rather by Microsoft's Visual C++ toolchain.  This is required to launch or
+  debug apps.
+
+
+Status
+------
+
+Here is a rough list of what works, and what doesn't:
+
+* What works:
+  * compilation via Visual C++ 2019.
+  * compile-time platform detection for SDL programs.  The C/C++ #define,
+    `SDL_PLATFORM_WINRT`, will be set to 1 (by SDL) when compiling for WinRT.
+  * GPU-accelerated 2D rendering, via SDL_Renderer.
+  * OpenGL ES 2, via the ANGLE library (included separately from SDL)
+  * software rendering, via either SDL_Surface (optionally in conjunction with
+    SDL_GetWindowSurface() and SDL_UpdateWindowSurface()) or via the
+    SDL_Renderer APIs
+  * threads
+  * timers (via SDL_GetTicks(), SDL_AddTimer(), SDL_GetPerformanceCounter(),
+    SDL_GetPerformanceFrequency(), etc.)
+  * file I/O via SDL_IOStream
+  * mouse input  (unsupported on Windows Phone)
+  * audio, via SDL's WASAPI backend (if you want to record, your app must
+    have "Microphone" capabilities enabled in its manifest, and the user must
+    not have blocked access. Otherwise, recording devices will fail to work,
+    presenting as a device disconnect shortly after opening it.)
+  * .DLL file loading.  Libraries *MUST* be packaged inside applications.  Loading
+    anything outside of the app is not supported.
+  * system path retrieval via SDL's filesystem APIs
+  * game controllers.  Support is provided via the SDL_Joystick and
+    SDL_Gamepad APIs, and is backed by Microsoft's XInput API.  Please
+    note, however, that Windows limits game-controller support in UWP apps to,
+    "Xbox compatible controllers" (many controllers that work in Win32 apps,
+    do not work in UWP, due to restrictions in UWP itself.)
+  * multi-touch input
+  * app events.  SDL_APP_WILLENTER* and SDL_APP_DIDENTER* events get sent out as
+    appropriate.
+  * window events
+  * using Direct3D 11.x APIs outside of SDL.  Non-XAML / Direct3D-only apps can
+    choose to render content directly via Direct3D, using SDL to manage the
+    internal WinRT window, as well as input and audio.  (Use
+    the window properties to get the WinRT 'CoreWindow', and pass it into
+    IDXGIFactory2::CreateSwapChainForCoreWindow() as appropriate.)
+
+* What partially works:
+  * keyboard input.  Most of WinRT's documented virtual keys are supported, as
+    well as many keys with documented hardware scancodes.  Converting
+    SDL_Scancodes to or from SDL_Keycodes may not work, due to missing APIs
+    (MapVirtualKey()) in Microsoft's Windows Store / UWP APIs.
+  * SDL_main.  WinRT uses a different signature for each app's main() function
+    and requires it to be implemented in C++, so SDL_main.h must be #include'd
+    in a C++ source file, that also must be compiled with /ZW.
+
+* What doesn't work:
+  * compilation with anything other than Visual C++
+  * programmatically-created custom cursors.  These don't appear to be supported
+    by WinRT.  Different OS-provided cursors can, however, be created via
+    SDL_CreateSystemCursor() (unsupported on Windows Phone)
+  * SDL_WarpMouseInWindow() or SDL_WarpMouseGlobal().  This are not currently
+    supported by WinRT itself.
+  * joysticks and game controllers that either are not supported by
+    Microsoft's XInput API, or are not supported within UWP apps (many
+    controllers that work in Win32, do not work in UWP, due to restrictions in
+    UWP itself).
+  * turning off VSync when rendering on Windows Phone.  Attempts to turn VSync
+    off on Windows Phone result either in Direct3D not drawing anything, or it
+    forcing VSync back on.  As such, vsync will always get turned-on on Windows
+    Phone.  This limitation is not present in non-Phone WinRT (such as Windows 8.x),
+    where turning off VSync appears to work.
+  * probably anything else that's not listed as supported
+
+
+
+Setup, High-Level Steps
+-----------------------
+
+The steps for setting up a project for an SDL/WinRT app looks like the
+following, at a high-level:
+
+1. create a new Visual C++ project using Microsoft's template for a,
+   "Direct3D App".
+2. remove most of the files from the project.
+3. make your app's project directly reference SDL/WinRT's own Visual C++
+   project file, via use of Visual C++'s "References" dialog.  This will setup
+   the linker, and will copy SDL's .dll files to your app's final output.
+4. adjust your app's build settings, at minimum, telling it where to find SDL's
+   header files.
+5. add files that contains a WinRT-appropriate main function, along with some
+   data to make sure mouse-cursor-hiding (via SDL_ShowCursor(SDL_DISABLE) calls)
+   work properly.
+6. add SDL-specific app code.
+7. build and run your app.
+
+
+Setup, Detailed Steps
+---------------------
+
+### 1. Create a new project ###
+
+Create a new project using one of Visual C++'s templates for a plain, non-XAML,
+"Direct3D App" (XAML support for SDL/WinRT is not yet ready for use).  If you
+don't see one of these templates, in Visual C++'s 'New Project' dialog, try
+using the textbox titled, 'Search Installed Templates' to look for one.
+
+
+### 2. Remove unneeded files from the project ###
+
+In the new project, delete any file that has one of the following extensions:
+
+- .cpp
+- .h
+- .hlsl
+
+When you are done, you should be left with a few files, each of which will be a
+necessary part of your app's project.  These files will consist of:
+
+- an .appxmanifest file, which contains metadata on your WinRT app.  This is
+  similar to an Info.plist file on iOS, or an AndroidManifest.xml on Android.
+- a few .png files, one of which is a splash screen (displayed when your app
+  launches), others are app icons.
+- a .pfx file, used for code signing purposes.
+
+
+### 3. Add references to SDL's project files ###
+
+SDL/WinRT can be built in multiple variations, spanning across three different
+CPU architectures (x86, x64, and ARM) and two different configurations
+(Debug and Release).  WinRT and Visual C++ do not currently provide a means
+for combining multiple variations of one library into a single file.
+Furthermore, it does not provide an easy means for copying pre-built .dll files
+into your app's final output (via Post-Build steps, for example).  It does,
+however, provide a system whereby an app can reference the MSVC projects of
+libraries such that, when the app is built:
+
+1. each library gets built for the appropriate CPU architecture(s) and WinRT
+   platform(s).
+2. each library's output, such as .dll files, get copied to the app's build
+   output.
+
+To set this up for SDL/WinRT, you'll need to run through the following steps:
+
+1. open up the Solution Explorer inside Visual C++ (under the "View" menu, then
+   "Solution Explorer")
+2. right click on your app's solution.
+3. navigate to "Add", then to "Existing Project..."
+4. find SDL/WinRT's Visual C++ project file and open it, in the `VisualC-WinRT`
+   directory.
+5. once the project has been added, right-click on your app's project and
+   select, "References..."
+6. click on the button titled, "Add New Reference..."
+7. check the box next to SDL
+8. click OK to close the dialog
+9. SDL will now show up in the list of references.  Click OK to close that
+   dialog.
+
+Your project is now linked to SDL's project, insofar that when the app is
+built, SDL will be built as well, with its build output getting included with
+your app.
+
+
+### 4. Adjust Your App's Build Settings ###
+
+Some build settings need to be changed in your app's project.  This guide will
+outline the following:
+
+- making sure that the compiler knows where to find SDL's header files
+- **Optional for C++, but NECESSARY for compiling C code:** telling the
+  compiler not to use Microsoft's C++ extensions for WinRT development.
+- **Optional:** telling the compiler not generate errors due to missing
+  precompiled header files.
+
+To change these settings:
+
+1. right-click on the project
+2. choose "Properties"
+3. in the drop-down box next to "Configuration", choose, "All Configurations"
+4. in the drop-down box next to "Platform", choose, "All Platforms"
+5. in the left-hand list, expand the "C/C++" section
+   **Note:** If you don't see this section, you may have to add a .c or .cpp
+   Source file to the Project first.
+6. select "General"
+7. edit the "Additional Include Directories" setting, and add a path to SDL's
+   "include" directory
+8. **Optional: to enable compilation of C code:** change the setting for
+   "Consume Windows Runtime Extension" from "Yes (/ZW)" to "No".  If you're
+   working with a completely C++ based project, this step can usually be
+   omitted.
+9. **Optional: to disable precompiled headers (which can produce
+   'stdafx.h'-related build errors, if setup incorrectly:** in the left-hand
+   list, select "Precompiled Headers", then change the setting for "Precompiled
+   Header" from "Use (/Yu)" to "Not Using Precompiled Headers".
+10. close the dialog, saving settings, by clicking the "OK" button
+
+
+### 5. Add a WinRT-appropriate main function, and a blank-cursor image, to the app. ###
+
+A few files should be included directly in your app's MSVC project, specifically:
+1. a WinRT-appropriate main function (which is different than main() functions on
+   other platforms)
+2. a Win32-style cursor resource, used by SDL_ShowCursor() to hide the mouse cursor
+   (if and when the app needs to do so).  *If this cursor resource is not
+   included, mouse-position reporting may fail if and when the cursor is
+   hidden, due to possible bugs/design-oddities in Windows itself.*
+
+To include these files for C/C++ projects:
+
+1. right-click on your project (again, in Visual C++'s Solution Explorer),
+   navigate to "Add", then choose "Existing Item...".
+2. navigate to the directory containing SDL's source code, then into its
+   subdirectory, 'src/main/winrt/'.  Select, then add, the following files:
+   - `SDL3-WinRTResources.rc`
+   - `SDL3-WinRTResource_BlankCursor.cur`
+3. For the next step you need a C++ source file.
+   - If your standard main() function is implemented in a **C++** source file,
+     use that file.
+   - If your standard main() function is implemented in a **plain C** source file,
+     create an empty .cpp source file (e.g. `main.cpp`) that only contains the line
+     `#include <SDL3/SDL_main.h>` and use that file instead.
+4. Right click on the C++ source file from step 3 (as listed in your project),
+   then click on "Properties...".
+5. in the drop-down box next to "Configuration", choose, "All Configurations"
+6. in the drop-down box next to "Platform", choose, "All Platforms"
+7. in the left-hand list, click on "C/C++"
+8. change the setting for "Consume Windows Runtime Extension" to "Yes (/ZW)".
+9. click the OK button.  This will close the dialog.
+
+**NOTE: C++/CX compilation is currently required in at least one file of your
+app's project.  This is to make sure that Visual C++'s linker builds a 'Windows
+Metadata' file (.winmd) for your app.  Not doing so can lead to build errors.**
+
+For non-C++ projects, you will need to call SDL_RunApp from your language's
+main function, and generate SDL3-WinRTResources.res manually by using `rc` via
+the Developer Command Prompt and including it as a <Win32Resource> within the
+first <PropertyGroup> block in your Visual Studio project file.
+
+### 6. Add app code and assets ###
+
+At this point, you can add in SDL-specific source code.  Be sure to include a
+C-style main function (ie: `int main(int argc, char *argv[])`).  From there you
+should be able to create a single `SDL_Window` (WinRT apps can only have one
+window, at present), as well as an `SDL_Renderer`.  Direct3D will be used to
+draw content.  Events are received via SDL's usual event functions
+(`SDL_PollEvent`, etc.)  If you have a set of existing source files and assets,
+you can start adding them to the project now.  If not, or if you would like to
+make sure that you're setup correctly, some short and simple sample code is
+provided below.
+
+
+#### 6.A. ... when creating a new app ####
+
+If you are creating a new app (rather than porting an existing SDL-based app),
+or if you would just like a simple app to test SDL/WinRT with before trying to
+get existing code working, some working SDL/WinRT code is provided below.  To
+set this up:
+
+1. right click on your app's project
+2. select Add, then New Item.  An "Add New Item" dialog will show up.
+3. from the left-hand list, choose "Visual C++"
+4. from the middle/main list, choose "C++ File (.cpp)"
+5. near the bottom of the dialog, next to "Name:", type in a name for your
+source file, such as, "main.cpp".
+6. click on the Add button.  This will close the dialog, add the new file to
+your project, and open the file in Visual C++'s text editor.
+7. Copy and paste the following code into the new file, then save it.
+
+```c
+#include <SDL3/SDL.h>
+#include <SDL3/SDL_main.h>
+
+int main(int argc, char **argv)
+{
+    SDL_Window *window = NULL;
+    SDL_Renderer *renderer = NULL;
+    SDL_Event evt;
+    SDL_bool keep_going = SDL_TRUE;
+
+    if (!SDL_Init(SDL_INIT_VIDEO)) {
+        return 1;
+    } else if (!SDL_CreateWindowAndRenderer("Hello SDL", 0, 0, SDL_WINDOW_FULLSCREEN, &window, &renderer)) {
+        return 1;
+    }
+
+    while (keep_going) {
+        while (SDL_PollEvent(&evt)) {
+            if ((evt.type == SDL_EVENT_KEY_DOWN) && (evt.key.keysym.sym == SDLK_ESCAPE)) {
+                keep_going = SDL_FALSE;
+            }
+        }
+
+        SDL_SetRenderDrawColor(renderer, 0, 255, 0, 255);
+        SDL_RenderClear(renderer);
+        SDL_RenderPresent(renderer);
+    }
+
+    SDL_Quit();
+    return 0;
+}
+```
+
+#### 6.B. Adding code and assets ####
+
+If you have existing code and assets that you'd like to add, you should be able
+to add them now.  The process for adding a set of files is as such.
+
+1. right click on the app's project
+2. select Add, then click on "New Item..."
+3. open any source, header, or asset files as appropriate.  Support for C and
+C++ is available.
+
+Do note that WinRT only supports a subset of the APIs that are available to
+Win32-based apps.  Many portions of the Win32 API and the C runtime are not
+available.
+
+A list of unsupported C APIs can be found at
+<http://msdn.microsoft.com/en-us/library/windows/apps/jj606124.aspx>
+
+General information on using the C runtime in WinRT can be found at
+<https://msdn.microsoft.com/en-us/library/hh972425.aspx>
+
+A list of supported Win32 APIs for WinRT apps can be found at
+<http://msdn.microsoft.com/en-us/library/windows/apps/br205757.aspx>.  To note,
+the list of supported Win32 APIs for Windows Phone 8.0 is different.
+That list can be found at
+<http://msdn.microsoft.com/en-us/library/windowsphone/develop/jj662956(v=vs.105).aspx>
+
+
+### 7. Build and run your app ###
+
+Your app project should now be setup, and you should be ready to build your app.
+To run it on the local machine, open the Debug menu and choose "Start
+Debugging".  This will build your app, then run your app full-screen.  To switch
+out of your app, press the Windows key.  Alternatively, you can choose to run
+your app in a window.  To do this, before building and running your app, find
+the drop-down menu in Visual C++'s toolbar that says, "Local Machine".  Expand
+this by clicking on the arrow on the right side of the list, then click on
+Simulator.  Once you do that, any time you build and run the app, the app will
+launch in window, rather than full-screen.
+
+
+#### 7.A. Running apps on older, ARM-based, "Windows RT" devices ####
+
+**These instructions do not include Windows Phone, despite Windows Phone
+typically running on ARM processors.**  They are specifically for devices
+that use the "Windows RT" operating system, which was a modified version of
+Windows 8.x that ran primarily on ARM-based tablet computers.
+
+To build and run the app on ARM-based, "Windows RT" devices, you'll need to:
+
+- install Microsoft's "Remote Debugger" on the device.  Visual C++ installs and
+  debugs ARM-based apps via IP networks.
+- change a few options on the development machine, both to make sure it builds
+  for ARM (rather than x86 or x64), and to make sure it knows how to find the
+  Windows RT device (on the network).
+
+Microsoft's Remote Debugger can be found at
+<https://msdn.microsoft.com/en-us/library/hh441469.aspx>.  Please note
+that separate versions of this debugger exist for different versions of Visual
+C++, one each for MSVC 2015, 2013, and 2012.
+
+To setup Visual C++ to launch your app on an ARM device:
+
+1. make sure the Remote Debugger is running on your ARM device, and that it's on
+   the same IP network as your development machine.
+2. from Visual C++'s toolbar, find a drop-down menu that says, "Win32".  Click
+   it, then change the value to "ARM".
+3. make sure Visual C++ knows the hostname or IP address of the ARM device.  To
+   do this:
+    1. open the app project's properties
+    2. select "Debugging"
+    3. next to "Machine Name", enter the hostname or IP address of the ARM
+       device
+    4. if, and only if, you've turned off authentication in the Remote Debugger,
+       then change the setting for "Require Authentication" to No
+    5. click "OK"
+4. build and run the app (from Visual C++).  The first time you do this, a
+   prompt will show up on the ARM device, asking for a Microsoft Account.  You
+   do, unfortunately, need to log in here, and will need to follow the
+   subsequent registration steps in order to launch the app.  After you do so,
+   if the app didn't already launch, try relaunching it again from within Visual
+   C++.
+
+
+Troubleshooting
+---------------
+
+#### Build fails with message, "error LNK2038: mismatch detected for 'vccorlib_lib_should_be_specified_before_msvcrt_lib_to_linker'"
+
+Try adding the following to your linker flags.  In MSVC, this can be done by
+right-clicking on the app project, navigating to Configuration Properties ->
+Linker -> Command Line, then adding them to the Additional Options
+section.
+
+* For Release builds / MSVC-Configurations, add:
+
+    /nodefaultlib:vccorlib /nodefaultlib:msvcrt vccorlib.lib msvcrt.lib
+
+* For Debug builds / MSVC-Configurations, add:
+
+    /nodefaultlib:vccorlibd /nodefaultlib:msvcrtd vccorlibd.lib msvcrtd.lib
+
+
+#### Mouse-motion events fail to get sent, or SDL_GetMouseState() fails to return updated values
+
+This may be caused by a bug in Windows itself, whereby hiding the mouse
+cursor can cause mouse-position reporting to fail.
+
+SDL provides a workaround for this, but it requires that an app links to a
+set of Win32-style cursor image-resource files.  A copy of suitable resource
+files can be found in `src/main/winrt/`.  Adding them to an app's Visual C++
+project file should be sufficient to get the app to use them.
+
+
+#### SDL's Visual Studio project file fails to open, with message, "The system can't find the file specified."
+
+This can be caused for any one of a few reasons, which Visual Studio can
+report, but won't always do so in an up-front manner.
+
+To help determine why this error comes up:
+
+1. open a copy of Visual Studio without opening a project file.  This can be
+   accomplished via Windows' Start Menu, among other means.
+2. show Visual Studio's Output window.  This can be done by going to VS'
+   menu bar, then to View, and then to Output.
+3. try opening the SDL project file directly by going to VS' menu bar, then
+   to File, then to Open, then to Project/Solution.  When a File-Open dialog
+   appears, open the SDL project (such as the one in SDL's source code, in its
+   directory, VisualC-WinRT/UWP_VS2015/).
+4. after attempting to open SDL's Visual Studio project file, additional error
+   information will be output to the Output window.
+
+If Visual Studio reports (via its Output window) that the project:
+
+"could not be loaded because it's missing install components. To fix this launch Visual Studio setup with the following selections:
+Microsoft.VisualStudio.ComponentGroup.UWP.VC"
+
+... then you will need to re-launch Visual Studio's installer, and make sure that
+the workflow for "Universal Windows Platform development" is checked, and that its
+optional component, "C++ Universal Windows Platform tools" is also checked.  While
+you are there, if you are planning on targeting UWP / Windows 10, also make sure
+that you check the optional component, "Windows 10 SDK (10.0.10240.0)".  After
+making sure these items are checked as-appropriate, install them.
+
+Once you install these components, try re-launching Visual Studio, and re-opening
+the SDL project file.  If you still get the error dialog, try using the Output
+window, again, seeing what Visual Studio says about it.
+
+
+#### Game controllers / joysticks aren't working!
+
+Windows only permits certain game controllers and joysticks to work within
+WinRT / UWP apps.  Even if a game controller or joystick works in a Win32
+app, that device is not guaranteed to work inside a WinRT / UWP app.
+
+According to Microsoft, "Xbox compatible controllers" should work inside
+UWP apps, potentially with more working in the future.  This includes, but
+may not be limited to, Microsoft-made Xbox controllers and USB adapters.
+(Source: https://social.msdn.microsoft.com/Forums/en-US/9064838b-e8c3-4c18-8a83-19bf0dfe150d/xinput-fails-to-detect-game-controllers?forum=wpdevelop)
+
+