I tried to build the python bindings under emen. Here's how it

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Python Bindings under Emscripten? about magnum-bindings HOT 3 OPEN

mosra commented on May 18, 2024

Python Bindings under Emscripten?

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pmp-p commented on May 18, 2024

@gabriel-v would you mind give try with https://github.com/pygame-web/python-wasm-sdk ?

use . /opt/python-wasm-sdk/wasm32-mvp-emscripten-shell.sh to enter C/C++ build env
and/or /opt/python-wasm-sdk/python3-wasm to run setup.py bdist_wheel or -m build

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mosra commented on May 18, 2024

Hi, wow, you're adventurous :) I never even thought the python bindings would be useful under Emscripten, so the code doesn't contain any Emscripten-/WebGL-specific handling at the moment.

For the LONG_BIT part I'm afraid I can't help. For the emconfigure options I think we're fine:

--host=wasm32-unknown-emscripten is compiling for 32-bit WASM, which is the default in the toolchain. The other option is wasm64-unknown-emscripten and AFAIK it's still in very early stages, with no browser support yet.
--enable-wasm-dynamic-linking=no is also the default in my toolchain
--with-emscripten-target=browser isn't that important I think, the default is both a browser and a console. In case of Magnum, the ability to run JS in a console (via node) is useful for unit tests and other command-line tools.

For the build errors, the bindings codebase doesn't handle a case of plugin managers without dynamic library support (i.e., *.so and *.dll plugins, it's also related to the emconfigure option above, and while it could technically be possible now, I didn't bother with adding support because the overhead would be so big that it wouldn't make sense). The solution is to #ifndef the related parts accordingly:

diff --git a/src/python/corrade/pluginmanager.cpp b/src/python/corrade/pluginmanager.cpp
index 487bf06..1d5c436 100644
--- a/src/python/corrade/pluginmanager.cpp
+++ b/src/python/corrade/pluginmanager.cpp
@@ -42,16 +42,21 @@ void pluginmanager(py::module_& m) {
     py::enum_<PluginManager::LoadState> loadState{m, "LoadState", "Plugin load state"};
     loadState
         .value("NOT_FOUND", PluginManager::LoadState::NotFound)
+        #ifndef CORRADE_PLUGINMANAGER_NO_DYNAMIC_PLUGIN_SUPPORT
         .value("WRONG_PLUGIN_VERSION", PluginManager::LoadState::WrongPluginVersion)
         .value("WRONG_INTERFACE_VERSION", PluginManager::LoadState::WrongInterfaceVersion)
         .value("WRONG_METADATA_FILE", PluginManager::LoadState::WrongMetadataFile)
         .value("UNRESOLVED_DEPENDENCY", PluginManager::LoadState::UnresolvedDependency)
+        #endif
         .value("STATIC", PluginManager::LoadState::Static)
         .value("LOADED", PluginManager::LoadState::Loaded)
+        #ifndef CORRADE_PLUGINMANAGER_NO_DYNAMIC_PLUGIN_SUPPORT
         .value("NOT_LOADED", PluginManager::LoadState::NotLoaded)
         .value("UNLOAD_FAILED", PluginManager::LoadState::UnloadFailed)
         .value("REQUIRED", PluginManager::LoadState::Required)
-        .value("USED", PluginManager::LoadState::Used);
+        .value("USED", PluginManager::LoadState::Used)
+        #endif
+        ;
     corrade::enumOperators(loadState);
 
     PyNonDestructibleClass<PluginManager::AbstractManager> manager{m, "AbstractManager", "Base for plugin managers"};
@@ -61,6 +66,7 @@ void pluginmanager(py::module_& m) {
             /** @todo drop std::string in favor of our own string caster */
             return std::string{self.pluginInterface()};
         }, "Plugin interface")
+        #ifndef CORRADE_PLUGINMANAGER_NO_DYNAMIC_PLUGIN_SUPPORT
         .def_property("plugin_directory",
             /** @todo drop std::string in favor of our own string caster */
             [](PluginManager::AbstractManager& self) {
@@ -69,6 +75,7 @@ void pluginmanager(py::module_& m) {
                 self.setPluginDirectory(directory);
             }, "Plugin directory")
         .def("reload_plugin_directory", &PluginManager::AbstractManager::reloadPluginDirectory, "Reload plugin directory")
+        #endif
         /** @todo setPreferredPlugins (takes an init list) */
         .def_property_readonly("plugin_list", [](PluginManager::AbstractManager& self) {
             /** @todo make a generic caster for arbitrary arrays and strings */

For the GL errors it's similar, the codebase is currently handling differences between GL and GLES (which is a subset of GL), but it doesn't handle WebGL differences (which itself is an even more restricted subset of GLES). A patch that attempts to fix at least some of these is below:

diff --git a/src/python/magnum/gl.cpp b/src/python/magnum/gl.cpp
index 533f481..4498492 100644
--- a/src/python/magnum/gl.cpp
+++ b/src/python/magnum/gl.cpp
@@ -307,6 +307,7 @@ void gl(py::module_& m) {
     {
         py::class_<GL::Context, ContextHolder<GL::Context>> context{m, "Context", "Magnum OpenGL context"};
 
+        #ifndef MAGNUM_TARGET_WEBGL
         py::enum_<GL::Context::Flag> contextFlag{context, "Flag", "Context flag"};
         contextFlag
             .value("DEBUG", GL::Context::Flag::Debug)
@@ -319,6 +320,7 @@ void gl(py::module_& m) {
             #endif
             .value("NONE", GL::Context::Flag{});
         corrade::enumOperators(contextFlag);
+        #endif
 
         py::enum_<GL::Context::State> contextState{context, "State", "State to reset"};
         contextState
@@ -844,6 +846,7 @@ void gl(py::module_& m) {
         .value("STENCIL", GL::FramebufferClear::Stencil);
     corrade::enumOperators(framebufferClear);
 
+    #if !(defined(MAGNUM_TARGET_WEBGL) && defined(MAGNUM_TARGET_GLES2))
     py::enum_<GL::FramebufferBlit> framebufferBlit{m, "FramebufferBlit", "Mask for framebuffer blitting"};
     framebufferBlit
         .value("COLOR", GL::FramebufferBlit::Color)
@@ -854,6 +857,7 @@ void gl(py::module_& m) {
     py::enum_<GL::FramebufferBlitFilter>{m, "FramebufferBlitFilter", "Framebuffer blit filtering"}
         .value("NEAREST", GL::FramebufferBlitFilter::Nearest)
         .value("LINEAR", GL::FramebufferBlitFilter::Linear);
+    #endif
 
     py::class_<GL::AbstractFramebuffer, NonDefaultFramebufferHolder<GL::AbstractFramebuffer>> abstractFramebuffer{m,
         "AbstractFramebuffer", "Base for default and named framebuffers"};
@@ -862,12 +866,14 @@ void gl(py::module_& m) {
         /** @todo limit queries */
 
         /* Using lambdas to supply an enum and not enum set */
+        #if !(defined(MAGNUM_TARGET_WEBGL) && defined(MAGNUM_TARGET_GLES2))
         .def_static("blit", [](GL::AbstractFramebuffer& source, GL::AbstractFramebuffer& destination, const Range2Di& sourceRectangle, const Range2Di& destinationRectangle, GL::FramebufferBlit mask, GL::FramebufferBlitFilter filter) {
             GL::AbstractFramebuffer::blit(source, destination, sourceRectangle, destinationRectangle, mask, filter);
         }, "Copy a block of pixels", py::arg("source"), py::arg("destination"), py::arg("source_rectangle"), py::arg("destination_rectangle"), py::arg("mask"), py::arg("filter"))
         .def_static("blit", [](GL::AbstractFramebuffer& source, GL::AbstractFramebuffer& destination, const Range2Di& rectangle, GL::FramebufferBlit mask) {
             GL::AbstractFramebuffer::blit(source, destination, rectangle, mask);
         }, "Copy a block of pixels", py::arg("source"), py::arg("destination"), py::arg("rectangle"), py::arg("mask"))
+        #endif
         .def("bind", &GL::AbstractFramebuffer::bind, "Bind framebuffer for drawing")
         .def_property("viewport", &GL::AbstractFramebuffer::viewport, &GL::AbstractFramebuffer::setViewport, "Viewport")
         /* Using lambdas to avoid method chaining getting into signatures */

I don't have an easy way to verify that the patches are complete, so it will likely need more #ifndefing. The workflow in that case would be that for every error you look at the corresponding definition in the Magnum header and copy the appropriate #ifndef over.

Hope this helps -- and of course I'll be very happy to integrate your patches once you get this to build :)

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mosra commented on May 18, 2024

Oh, and one other thing that might be a source of pain is the Sdl2Application library that the current Python examples rely on -- hopefully it will work as-is (enable it with MAGNUM_WITH_SDL2APPLICATION), maybe you'll need to add similar ifdefs there as well (#ifndef CORRADE_TARGET_EMSCRIPTEN most probably).

The go-to application to use on the web would be EmscriptenApplication though, which would need to be added as a new binding file into platform/.

The windowless / EGL applications could also work there, but are not essential for anything -- they're used just by unit tests.

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Python Bindings under Emscripten? about magnum-bindings HOT 3 OPEN

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