core: emdawnwebgpu build support (#4370)

CMakeLists.txt

@@ -1211,7 +1211,7 @@ endif()
 # The Xcode generator with Dawn component targets (no monolithic library) breaks export()
 # because dawn_native/dawn_proc aren't in an export set. Skip export in that case.
 set(_can_export TRUE)
-if(TARGET mbgl-vendor-dawn AND NOT TARGET dawn::webgpu_dawn)
+if(TARGET mbgl-vendor-dawn AND NOT TARGET dawn::webgpu_dawn AND NOT MLN_WEBGPU_EMDAWN)
     set(_can_export FALSE)
 endif()
 if(_can_export)

cmake/webgpu.cmake

@@ -20,7 +20,6 @@ list(APPEND
         ${PROJECT_SOURCE_DIR}/src/mbgl/webgpu/buffer_resource.cpp
         ${PROJECT_SOURCE_DIR}/src/mbgl/webgpu/context.cpp
         ${PROJECT_SOURCE_DIR}/src/mbgl/webgpu/command_encoder.cpp
-        ${PROJECT_SOURCE_DIR}/src/mbgl/webgpu/headless_backend.cpp
         ${PROJECT_SOURCE_DIR}/src/mbgl/webgpu/renderer_backend.cpp
         ${PROJECT_SOURCE_DIR}/src/mbgl/webgpu/drawable.cpp
         ${PROJECT_SOURCE_DIR}/src/mbgl/webgpu/drawable_builder.cpp
@@ -119,8 +118,14 @@ include(${PROJECT_SOURCE_DIR}/vendor/webgpu.cmake)
 if(MLN_WEBGPU_IMPL_DAWN)
     include(${PROJECT_SOURCE_DIR}/vendor/dawn.cmake)
     if(TARGET mbgl-vendor-dawn)
+        if(MLN_WEBGPU_EMDAWN)
+            # Emdawn is a compiler/linker port rather than a conventional
+            # library. Consumers must inherit its final-link options.
+            target_link_libraries(mbgl-core PUBLIC mbgl-vendor-dawn)
+        else()
             target_link_libraries(mbgl-core PRIVATE mbgl-vendor-dawn)
         endif()
+    endif()
 elseif(MLN_WEBGPU_IMPL_WGPU OR MLN_WEBGPU_IMPL_FFI)
     # Include wgpu-native integration
     include(${PROJECT_SOURCE_DIR}/vendor/wgpu.cmake)
@@ -130,3 +135,8 @@ elseif(MLN_WEBGPU_IMPL_WGPU OR MLN_WEBGPU_IMPL_FFI)
         list(APPEND SRC_FILES ${PROJECT_SOURCE_DIR}/src/mbgl/webgpu/webgpu_cpp_impl.cpp)
     endif()
 endif()
+
+# Headless backend uses Dawn native / wgpu-native bootstrap; skip for emdawnwebgpu.
+if(NOT MLN_WEBGPU_EMDAWN)
+    list(APPEND SRC_FILES ${PROJECT_SOURCE_DIR}/src/mbgl/webgpu/headless_backend.cpp)
+endif()

include/mbgl/webgpu/renderer_backend.hpp

@@ -37,6 +37,8 @@ public:
     void setSurface(void* nativeWindow);
 
     // WebGPU-specific methods
+    // Emdawn hosts that use synchronous readback must create the instance with
+    // WGPUInstanceFeatureName_TimedWaitAny enabled.
     void setInstance(void* instance);
     void setDevice(WGPUDevice device);
     void setQueue(WGPUQueue queue);

platform/default/include/mbgl/gfx/headless_backend.hpp

@@ -16,11 +16,18 @@ namespace gfx {
 class HeadlessBackend : public gfx::Renderable {
 public:
     // Factory.
+#if MLN_WEBGPU_EMDAWN
+    static std::unique_ptr<HeadlessBackend> Create(const Size size = {256, 256},
+                                                   SwapBehaviour swapBehavior = SwapBehaviour::NoFlush,
+                                                   const gfx::ContextMode contextMode = gfx::ContextMode::Unique) =
+        delete;
+#else
     static std::unique_ptr<HeadlessBackend> Create(const Size size = {256, 256},
                                                    SwapBehaviour swapBehavior = SwapBehaviour::NoFlush,
                                                    const gfx::ContextMode contextMode = gfx::ContextMode::Unique) {
         return Backend::Create<HeadlessBackend, Size, SwapBehaviour, gfx::ContextMode>(size, swapBehavior, contextMode);
     }
+#endif
 
     virtual PremultipliedImage readStillImage() = 0;
     virtual RendererBackend* getRendererBackend() = 0;

src/mbgl/webgpu/offscreen_texture.cpp

@@ -140,7 +140,7 @@ public:
         }
 
         // Process all pending device operations to ensure rendering is complete
-#if MLN_WEBGPU_IMPL_DAWN
+#if MLN_WEBGPU_IMPL_DAWN && !MLN_WEBGPU_EMDAWN
         wgpuDeviceTick(device);
 #endif
 

vendor/dawn.cmake

@@ -8,6 +8,38 @@ if(NOT MLN_WITH_WEBGPU)
     return()
 endif()
 
+if(MLN_WEBGPU_EMDAWN)
+    set(MLN_WEBGPU_EMDAWN_PORT "emdawnwebgpu"
+        CACHE STRING "Emscripten port name or path used for emdawnwebgpu")
+
+    message(STATUS "Configuring emdawnwebgpu port: ${MLN_WEBGPU_EMDAWN_PORT}")
+    add_library(mbgl-vendor-dawn INTERFACE)
+
+    # The port provides the WebGPU headers during compilation and its C++/JS
+    # implementation during linking. Asyncify lets synchronous APIs such as
+    # readStillImage() wait for browser WebGPU promises to resolve.
+    target_compile_options(
+        mbgl-vendor-dawn
+        INTERFACE "--use-port=${MLN_WEBGPU_EMDAWN_PORT}"
+    )
+    target_link_options(
+        mbgl-vendor-dawn
+        INTERFACE
+            "--use-port=${MLN_WEBGPU_EMDAWN_PORT}"
+            "-sASYNCIFY=1"
+    )
+
+    set_target_properties(
+        mbgl-vendor-dawn
+        PROPERTIES
+            INTERFACE_MAPLIBRE_NAME "emdawnwebgpu"
+            INTERFACE_MAPLIBRE_URL "https://dawn.googlesource.com/dawn"
+            INTERFACE_MAPLIBRE_AUTHOR "Chromium Dawn Team"
+            INTERFACE_MAPLIBRE_LICENSE "${PROJECT_SOURCE_DIR}/vendor/emdawnwebgpu.LICENSE"
+    )
+    return()
+endif()
+
 if(POLICY CMP0169)
     cmake_policy(SET CMP0169 OLD)
 endif()

vendor/emdawnwebgpu.LICENSE

@@ -0,0 +1,92 @@
+Emdawnwebgpu contains code under the BSD 3-Clause License and code derived
+from Emscripten under either the MIT License or the University of
+Illinois/NCSA Open Source License.
+
+==============================================================================
+
+BSD 3-Clause License
+
+Copyright 2017-2026 The Dawn & Tint Authors
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright notice,
+   this list of conditions and the following disclaimer.
+
+2. Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+3. Neither the name of the copyright holder nor the names of its contributors
+   may be used to endorse or promote products derived from this software
+   without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGE.
+
+==============================================================================
+
+MIT License
+
+Copyright (c) 2010-2014 Emscripten authors, see AUTHORS file.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+
+==============================================================================
+
+University of Illinois/NCSA Open Source License
+
+Copyright (c) 2010-2014 Emscripten authors, see AUTHORS file.
+All rights reserved.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+with the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+Redistributions of source code must retain the above copyright notice, this
+list of conditions and the following disclaimers.
+
+Redistributions in binary form must reproduce the above copyright notice,
+this list of conditions and the following disclaimers in the documentation
+and/or other materials provided with the distribution.
+
+Neither the names of Mozilla, nor the names of its contributors may be used
+to endorse or promote products derived from this Software without specific
+prior written permission.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+CONTRIBUTORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

vendor/webgpu.cmake

@@ -3,22 +3,36 @@
 
 set(MLN_WEBGPU_IMPL_DAWN OFF CACHE STRING "WebGPU with Dawn implementation")
 set(MLN_WEBGPU_IMPL_WGPU OFF CACHE STRING "WebGPU with wgpu implementation")
+set(MLN_WEBGPU_EMDAWN OFF
+    CACHE BOOL "Use Emscripten emdawnwebgpu with Dawn headers (requires MLN_WEBGPU_IMPL_DAWN)")
 set(MLN_WEBGPU_IMPL_FFI OFF CACHE STRING "WebGPU with ffi interface")
 set(MLN_WEBGPU_IMPL_WEBGPU_HEADER_DIR "" CACHE STRING "If not empty use this path to the webgpu.h file")
 
 if(MLN_WITH_WEBGPU)
+    if(MLN_WEBGPU_EMDAWN AND NOT EMSCRIPTEN)
+        message(FATAL_ERROR "MLN_WEBGPU_EMDAWN requires Emscripten")
+    endif()
+
+    if(MLN_WEBGPU_EMDAWN AND NOT MLN_WEBGPU_IMPL_DAWN)
+        message(FATAL_ERROR "MLN_WEBGPU_EMDAWN requires MLN_WEBGPU_IMPL_DAWN")
+    endif()
+
     if(MLN_WEBGPU_IMPL_DAWN)
         message(STATUS "Using Dawn as WebGPU backend")
-        add_compile_definitions(MLN_WEBGPU_IMPL_DAWN)
+        target_compile_definitions(mbgl-core PUBLIC MLN_WEBGPU_IMPL_DAWN)
+        if(MLN_WEBGPU_EMDAWN)
+            message(STATUS "Using emdawnwebgpu port for browser WebGPU")
+            target_compile_definitions(mbgl-core PUBLIC MLN_WEBGPU_EMDAWN)
+        endif()
 
     elseif(MLN_WEBGPU_IMPL_WGPU)
         message(STATUS "Using wgpu as WebGPU backend")
-        add_compile_definitions(MLN_WEBGPU_IMPL_WGPU)
+        target_compile_definitions(mbgl-core PUBLIC MLN_WEBGPU_IMPL_WGPU)
     else()
         message(FATAL_ERROR "MLN_WEBGPU_IMPL_DAWN or MLN_WEBGPU_IMPL_WGPU must be set")
     endif()
 
     if(MLN_WEBGPU_IMPL_FFI)
-        add_compile_definitions(MLN_WEBGPU_IMPL_FFI)
+        target_compile_definitions(mbgl-core PUBLIC MLN_WEBGPU_IMPL_FFI)
     endif()
 endif()