iOS Support

[cart]

It should be possible to run Bevy Apps on iOS

[MichaelHills]

Hi, what’s involved in setting up Bevy on iOS? My understanding is that it uses winit which should already support iOS?

[MichaelHills]

I followed this guide to just get a Rust lib working from an ios project. Then I tried to substitute a bevy example app in. During cargo lipo --release it fails to build bevy-glsl-to-spirv.

It looks like there's no prebuilt binary in that repo so it tries to build glslang and then cmake fails

  -- Check for working C compiler: /usr/bin/cc -- broken
...
Building C object CMakeFiles/cmTC_97014.dir/testCCompiler.c.o
      /usr/bin/cc   -fPIC -m64 -m64 -mios-simulator-version-min=7.0 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator13.2.sdk -fembed-bitcode  -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk   -o CMakeFiles/cmTC_97014.dir/testCCompiler.c.o   -c /Users/mikeh/rust-ios-example/rust/target/x86_64-apple-ios/release/build/bevy-glsl-to-spirv-51cc402e67486116/out/build/CMakeFiles/CMakeTmp/testCCompiler.c
      clang: warning: using sysroot for 'MacOSX' but targeting 'iPhone' [-Wincompatible-sysroot]

Apparently that last line is a key sign something is off. I take it the build for glslang doesn't work properly to target aarch64-apple-ios or x86_64-apple-ios.

[MichaelHills]

I tried a couple of things, but I'm new to rust and new to cross-compiling to iOS, though slowly figuring things out. The approach of spawning the glslValidator process probably isn't going to fly on iOS. MoltenVK apparently can build the iOS static lib libglslang.a so I considered trying to interface with that. The bevy-glsl-to-spirv repo says TODO to switch to shaderc-rs so I figured I'd have a crack at that but had trouble cross-compiling for iOS.

I ended up stubbing out the code in crates/bevy_render/src/shader/shader.rs just to see how far I could get. I also had to disable the optional bevy audio as it didn't compile either (forgot why).

I managed to finally get something to build, on the simulator gfx-rs / gfx-backend-metal failed with Target OS is incompatible: library was not compiled for the simulator so I ran it on my phone instead to which I got

EventLoop cannot be run after a call to UIApplicationMain on iOS.

Stopping for tonight. Here's my diff so far to get where i got to...

diff --git a/Cargo.toml b/Cargo.toml
index 90b2368d..3254fd6c 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -13,7 +13,8 @@ readme = "README.md"
 exclude = ["assets/**/*", "tools/**/*", ".github/**/*", "crates/**/*"]
 
 [features]
-default = ["bevy_audio", "bevy_gltf", "bevy_wgpu", "bevy_winit", "png", "hdr", "mp3"]
+#default = ["bevy_audio", "bevy_gltf", "bevy_wgpu", "bevy_winit", "png", "hdr", "mp3"]
+default = ["bevy_gltf", "bevy_wgpu", "bevy_winit", "png", "hdr"]
 profiler = ["bevy_ecs/profiler", "bevy_diagnostic/profiler"]
 wgpu_trace = ["bevy_wgpu/trace"]
 
@@ -22,10 +23,10 @@ png = ["bevy_render/png"]
 hdr = ["bevy_render/hdr"]
 
 # Audio format support (MP3 is enabled by default)
-mp3 = ["bevy_audio/mp3"]
-flac = ["bevy_audio/flac"]
-wav = ["bevy_audio/wav"]
-vorbis = ["bevy_audio/vorbis"]
+#mp3 = ["bevy_audio/mp3"]
+#flac = ["bevy_audio/flac"]
+#wav = ["bevy_audio/wav"]
+#vorbis = ["bevy_audio/vorbis"]
 
 serialize = ["bevy_input/serialize"]
 
@@ -56,7 +57,7 @@ bevy_ui = { path = "crates/bevy_ui", version = "0.1" }
 bevy_window = { path = "crates/bevy_window", version = "0.1" }
 
 # bevy (optional)
-bevy_audio = { path = "crates/bevy_audio", optional = true, version = "0.1" }
+#bevy_audio = { path = "crates/bevy_audio", optional = true, version = "0.1" }
 bevy_gltf = { path = "crates/bevy_gltf", optional = true, version = "0.1" }
 bevy_wgpu = { path = "crates/bevy_wgpu", optional = true, version = "0.1" }
 bevy_winit = { path = "crates/bevy_winit", optional = true, version = "0.1" }
diff --git a/crates/bevy_render/Cargo.toml b/crates/bevy_render/Cargo.toml
index ea29b856..53fe2af4 100644
--- a/crates/bevy_render/Cargo.toml
+++ b/crates/bevy_render/Cargo.toml
@@ -24,7 +24,7 @@ bevy_window = { path = "../bevy_window", version = "0.1" }
 
 # rendering
 spirv-reflect = "0.2.3"
-bevy-glsl-to-spirv = "0.1.7"
+#bevy-glsl-to-spirv = { path = "/Users/mikeh/repos/glsl-to-spirv" } #"0.1.7"
 image = { version = "0.23", default-features = false }
 
 # misc
diff --git a/crates/bevy_render/src/shader/shader.rs b/crates/bevy_render/src/shader/shader.rs
index f963c0c9..dd448e74 100644
--- a/crates/bevy_render/src/shader/shader.rs
+++ b/crates/bevy_render/src/shader/shader.rs
@@ -1,6 +1,6 @@
 use super::ShaderLayout;
 use bevy_asset::Handle;
-use bevy_glsl_to_spirv::compile;
+//use bevy_glsl_to_spirv::compile;
 use std::{io::Read, marker::Copy};
 
 /// The stage of a shader
@@ -11,25 +11,26 @@ pub enum ShaderStage {
     Compute,
 }
 
-impl Into<bevy_glsl_to_spirv::ShaderType> for ShaderStage {
-    fn into(self) -> bevy_glsl_to_spirv::ShaderType {
-        match self {
-            ShaderStage::Vertex => bevy_glsl_to_spirv::ShaderType::Vertex,
-            ShaderStage::Fragment => bevy_glsl_to_spirv::ShaderType::Fragment,
-            ShaderStage::Compute => bevy_glsl_to_spirv::ShaderType::Compute,
-        }
-    }
-}
+//impl Into<bevy_glsl_to_spirv::ShaderType> for ShaderStage {
+//    fn into(self) -> bevy_glsl_to_spirv::ShaderType {
+//        match self {
+//            ShaderStage::Vertex => bevy_glsl_to_spirv::ShaderType::Vertex,
+//            ShaderStage::Fragment => bevy_glsl_to_spirv::ShaderType::Fragment,
+//            ShaderStage::Compute => bevy_glsl_to_spirv::ShaderType::Compute,
+//        }
+//    }
+//}
 
 fn glsl_to_spirv(
     glsl_source: &str,
     stage: ShaderStage,
     shader_defs: Option<&[String]>,
 ) -> Vec<u32> {
-    let mut output = compile(glsl_source, stage.into(), shader_defs).unwrap();
+    //let mut output = compile(glsl_source, stage.into(), shader_defs).unwrap();
     let mut spv_bytes = Vec::new();
-    output.read_to_end(&mut spv_bytes).unwrap();
-    bytes_to_words(&spv_bytes)
+    //output.read_to_end(&mut spv_bytes).unwrap();
+    //bytes_to_words(&spv_bytes)
+    spv_bytes
 }
 
 fn bytes_to_words(bytes: &[u8]) -> Vec<u32> {

[MichaelHills]

Looks like cross-compiling iOS stuff with cmake-rs is currently broken rust-lang/cmake-rs#96 so that's probably the source of some of my woes

[MichaelHills]

Success! I managed to get the 3d_scene demo loading in portrait mode (albeit a bit warped) on my phone.

• I pinned cmake-rs to 0.1.43 because that's the version which had the working iOS support
• Dropped bevy-glsl-to-spirv in favour of using shaderc-rs directly from crates/bevy_render/src/shader/shader.rs
• Created a main.swift to call out to my bevy_main() function directly which was the 3d_sprite main function renamed like this

#[no_mangle]
pub extern fn bevy_main() {

In xcode I had to add the static lib / header and search paths as per this site and I also had to link against lc++. Basically atm I build my "game" as a static lib and then call out to it manually from in an ios xcode project.

Trying to figure out how to get it into landscape mode now.

[cart]

Whoa that's huge! Thanks for the hard work here. People are going to love this!

[MichaelHills]

No worries. :) When I saw the post on Bevy on HN I thought it looked pretty awesome. I previously had started making a PC game in UE4 but life got busy. Decided I wanted to prototype it out as a mobile game instead and learn some Rust/ECS while I'm at it.

How should I go about getting stuff landed? I think the switch to shaderc-rs in general can be done now (tested a couple of examples still work). Did you want that to be done inside of bevy-glsl-to-spirv? I've currently just implemented it directly in crates/bevy_render/src/shader/shader.rs while hacking this all up.

In order to get iOS integration to "just work" the following issues need to be solved properly:

• Land using shaderc-rs in bevy
• Get that iOS support commit in cmake-rs fixed up and re-landed there
• In shaderc-rs I had to edit CMakeLists.txt in the glsl and shaderc submodules (see below), so maybe... get those landed there?
• Figure out why coreaudio-sys v0.2.5 panics during compile (that was why I had to disable audio)

shaderc

diff --git a/glslc/CMakeLists.txt b/glslc/CMakeLists.txt
index acf6fb0..4ec0067 100644
--- a/glslc/CMakeLists.txt
+++ b/glslc/CMakeLists.txt
@@ -40,6 +40,7 @@ shaderc_add_asciidoc(glslc_doc_README README)

 if(SHADERC_ENABLE_INSTALL)
   install(TARGETS glslc_exe
+    BUNDLE DESTINATION ${CMAKE_INSTALL_BINDIR}
     RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
 endif(SHADERC_ENABLE_INSTALL)

glslang

diff --git a/StandAlone/CMakeLists.txt b/StandAlone/CMakeLists.txt
index 2cf2899c..f84fdd2b 100644
--- a/StandAlone/CMakeLists.txt
+++ b/StandAlone/CMakeLists.txt
@@ -50,11 +50,13 @@ endif(WIN32)

 if(ENABLE_GLSLANG_INSTALL)
     install(TARGETS glslangValidator EXPORT glslangValidatorTargets
+            BUNDLE DESTINATION ${CMAKE_INSTALL_BINDIR}
             RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
     install(EXPORT glslangValidatorTargets DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake)

     if(ENABLE_SPVREMAPPER)
         install(TARGETS spirv-remap EXPORT spirv-remapTargets
+            BUNDLE DESTINATION ${CMAKE_INSTALL_BINDIR}
             RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
         install(EXPORT spirv-remapTargets DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake)
     endif()

Also here's the change to shader.rs

diff --git a/crates/bevy_render/src/shader/shader.rs b/crates/bevy_render/src/shader/shader.rs
index f963c0c9..2e710cd0 100644
--- a/crates/bevy_render/src/shader/shader.rs
+++ b/crates/bevy_render/src/shader/shader.rs
@@ -1,7 +1,6 @@
 use super::ShaderLayout;
 use bevy_asset::Handle;
-use bevy_glsl_to_spirv::compile;
-use std::{io::Read, marker::Copy};
+use std::{marker::Copy};
 
 /// The stage of a shader
 #[derive(Hash, Eq, PartialEq, Copy, Clone, Debug)]
@@ -11,14 +10,14 @@ pub enum ShaderStage {
     Compute,
 }
 
-impl Into<bevy_glsl_to_spirv::ShaderType> for ShaderStage {
-    fn into(self) -> bevy_glsl_to_spirv::ShaderType {
-        match self {
-            ShaderStage::Vertex => bevy_glsl_to_spirv::ShaderType::Vertex,
-            ShaderStage::Fragment => bevy_glsl_to_spirv::ShaderType::Fragment,
-            ShaderStage::Compute => bevy_glsl_to_spirv::ShaderType::Compute,
-        }
-    }
+impl Into<shaderc::ShaderKind> for ShaderStage {
+   fn into(self) -> shaderc::ShaderKind {
+       match self {
+           ShaderStage::Vertex => shaderc::ShaderKind::Vertex,
+           ShaderStage::Fragment => shaderc::ShaderKind::Fragment,
+           ShaderStage::Compute => shaderc::ShaderKind::Compute,
+       }
+   }
 }
 
 fn glsl_to_spirv(
@@ -26,10 +25,19 @@ fn glsl_to_spirv(
     stage: ShaderStage,
     shader_defs: Option<&[String]>,
 ) -> Vec<u32> {
-    let mut output = compile(glsl_source, stage.into(), shader_defs).unwrap();
-    let mut spv_bytes = Vec::new();
-    output.read_to_end(&mut spv_bytes).unwrap();
-    bytes_to_words(&spv_bytes)
+    let mut compiler = shaderc::Compiler::new().unwrap();
+    let mut options = shaderc::CompileOptions::new().unwrap();
+    if let Some(shader_defs) = shader_defs {
+        for def in shader_defs.iter() {
+            options.add_macro_definition(def, None);
+        }
+    }
+
+    let binary_result = compiler.compile_into_spirv(
+        glsl_source, stage.into(),
+        "shader.glsl", "main", Some(&options)).unwrap();
+
+    binary_result.as_binary().to_vec()
 }
 
 fn bytes_to_words(bytes: &[u8]) -> Vec<u32> {

[MichaelHills]

Stumbled across this issue in CMake https://gitlab.kitware.com/cmake/cmake/-/issues/20956 which suggests that the whole BUNDLE DESTINATION thing might be due to some CMake default that doesn't make sense when building libs, and I don't need to try and get BUNDLE DESINATION added to shaderc and glsl.

[naithar]

Basically atm I build my "game" as a static lib and then call out to it manually from in an ios xcode project.

Godot works in same way, though it implements it's own main which gets used by iOS application.

Obj-C can be used too, but this would require only main.mm file like this:

@import UIKit;

extern "C" void bevy_main(void);

int main(int argc, char * argv[]) {
    bevy_main();
}

And additional values in Other C Flags in Build Settings: -fmodules -fcxx-modules.

I've tested with 2d -> sprite.rs example, but got empty window.
I guess asset loading would require some work for iOS, but correct (?) texture handle was returned Handle<Texture>(82f42690-2c58-4843-a88a-aa066583f97d), so I'm not sure.

• Figure out why coreaudio-sys v0.2.5 panics during compile (that was why I had to disable audio)

This PR (RustAudio/coreaudio-sys#33) seems to be addressing this issue, but I wasn't able to make it work even with this changes. But maybe it's just me as I don't really have much experience with rust.

[MichaelHills]

@naithar oh cool glad to see someone else getting it working too. Yeah I didn’t get the sprite example working, I also assumed it was related to asset loading but I haven’t looked into that yet.

Interesting I’ll try pulling that audio PR later to see if it works.

[MichaelHills]

By the way were you able to get the simulator working? I’m still getting the issue with Target OS is incompatible: library was not compiled for the simulator but supposedly there should be simulator metal support gfx-rs/gfx#2873 so not sure yet what the problem with that is.