renderdiff: Use single lib for osmesa (#8255)

Previously, we linked against libOSMesa through the linker and
then used dlopen to link against libGL. This is not how libOSMesa
is intended to be used.  Instead, we use dlopen on libOSMesa
(via bluegl), which then will map the correct GL methods for us,
and for the OSMesa functions, we also map those functions
from libOSMesa (instead of relying on compile-time linker).

filament/backend/CMakeLists.txt

@@ -378,10 +378,6 @@ set(LINUX_LINKER_OPTIMIZATION_FLAGS
 if (LINUX AND FILAMENT_SUPPORTS_OSMESA)
     set(OSMESA_COMPILE_FLAGS
         -I${FILAMENT_OSMESA_PATH}/include/GL)
-    set(OSMESA_LINKER_FLAGS
-        -Wl,-L${FILAMENT_OSMESA_PATH}/lib/x86_64-linux-gnu/
-        -lOSMesa
-    )
 endif()
 
 if (MSVC)

filament/backend/include/backend/platforms/PlatformOSMesa.h

@@ -21,7 +21,7 @@
 
 #include "bluegl/BlueGL.h"
 
-#include "osmesa.h"
+#include <osmesa.h>
 
 #include <backend/platforms/OpenGLPlatform.h>
 #include <backend/DriverEnums.h>
@@ -56,6 +56,7 @@ class PlatformOSMesa : public OpenGLPlatform {
 
 private:
     OSMesaContext mContext;
+    void* mOsMesaApi = nullptr;
 };
 
 } // namespace filament::backend

filament/backend/src/opengl/platforms/PlatformOSMesa.cpp

@@ -19,6 +19,7 @@
 #include <utils/Log.h>
 #include <utils/Panic.h>
 
+#include <dlfcn.h>
 #include <memory>
 
 namespace filament::backend {
@@ -41,13 +42,56 @@ struct OSMesaSwapchain {
     std::unique_ptr<uint8_t[]> buffer;
 };
 
-} // anonymous namespace
+struct OSMesaAPI {
+private:
+    using CreateContextFunc = OSMesaContext (*)(GLenum format, OSMesaContext);
+    using DestroyContextFunc = GLboolean (*)(OSMesaContext);
+    using MakeCurrentFunc = GLboolean (*)(OSMesaContext ctx, void* buffer, GLenum type,
+            GLsizei width, GLsizei height);
+    using GetProcAddressFunc = OSMESAproc (*)(const char* funcName);
+
+public:
+    CreateContextFunc OSMesaCreateContext;
+    DestroyContextFunc OSMesaDestroyContext;
+    MakeCurrentFunc OSMesaMakeCurrent;
+    GetProcAddressFunc OSMesaGetProcAddress;
+
+    OSMesaAPI() {
+        constexpr char const* libraryNames[] = {"libOSMesa.so", "libosmesa.so"};
+        for (char const* libName: libraryNames) {
+            mLib = dlopen(libName, RTLD_GLOBAL | RTLD_NOW);
+            if (mLib) {
+                break;
+            }
+        }
+        FILAMENT_CHECK_PRECONDITION(mLib)
+                << "Unable to dlopen libOSMesa to create a software GL context";
+
+        OSMesaGetProcAddress = (GetProcAddressFunc) dlsym(mLib, "OSMesaGetProcAddress");
+
+        OSMesaCreateContext = (CreateContextFunc) OSMesaGetProcAddress("OSMesaCreateContext");
+        OSMesaDestroyContext =
+                (DestroyContextFunc) OSMesaGetProcAddress("OSMesaDestroyContext");
+        OSMesaMakeCurrent = (MakeCurrentFunc) OSMesaGetProcAddress("OSMesaMakeCurrent");
+    }
+
+    ~OSMesaAPI() {
+        dlclose(mLib);
+    }
+private:
+    void* mLib = nullptr;
+};
+
+}// anonymous namespace
 
 Driver* PlatformOSMesa::createDriver(void* const sharedGLContext,
         const DriverConfig& driverConfig) noexcept {
+    OSMesaAPI* api = new OSMesaAPI();
+    mOsMesaApi = api;
+
     FILAMENT_CHECK_PRECONDITION(sharedGLContext == nullptr)
             << "shared GL context is not supported with PlatformOSMesa";
-    mContext = OSMesaCreateContext(GL_RGBA, NULL);
+    mContext = api->OSMesaCreateContext(GL_RGBA, NULL);
 
     // We need to do a no-op makecurrent here so that the context will be in a correct state before
     // any GL calls.
@@ -62,7 +106,11 @@ Driver* PlatformOSMesa::createDriver(void* const sharedGLContext,
 }
 
 void PlatformOSMesa::terminate() noexcept {
-    OSMesaDestroyContext(mContext);
+    OSMesaAPI* api = (OSMesaAPI*) mOsMesaApi;
+    api->OSMesaDestroyContext(mContext);
+    delete api;
+    mOsMesaApi = nullptr;
+
     bluegl::unbind();
 }
 
@@ -84,11 +132,12 @@ void PlatformOSMesa::destroySwapChain(Platform::SwapChain* swapChain) noexcept {
 
 bool PlatformOSMesa::makeCurrent(ContextType type, SwapChain* drawSwapChain,
         SwapChain* readSwapChain) noexcept {
+    OSMesaAPI* api = (OSMesaAPI*) mOsMesaApi;
     OSMesaSwapchain* impl = (OSMesaSwapchain*) drawSwapChain;
 
-    auto result = OSMesaMakeCurrent(mContext, (BackingType*) impl->buffer.get(), BACKING_GL_TYPE,
-            impl->width, impl->height);
-    FILAMENT_CHECK_POSTCONDITION(result) << "OSMesaMakeCurrent failed!";
+    auto result = api->OSMesaMakeCurrent(mContext, (BackingType*) impl->buffer.get(),
+            BACKING_GL_TYPE, impl->width, impl->height);
+    FILAMENT_CHECK_POSTCONDITION(result == GL_TRUE) << "OSMesaMakeCurrent failed!";
 
     return true;
 }

libs/bluegl/CMakeLists.txt

@@ -36,6 +36,8 @@ elseif (APPLE AND NOT IOS)
 elseif(LINUX)
     if(FILAMENT_SUPPORTS_EGL_ON_LINUX)
         set(SRCS ${SRCS} src/BlueGLLinuxEGL.cpp)
+    elseif(FILAMENT_SUPPORTS_OSMESA)
+        set(SRCS ${SRCS} src/BlueGLLinuxOSMesa.cpp)
     else()
         set(SRCS ${SRCS} src/BlueGLLinux.cpp)
     endif()

libs/bluegl/src/BlueGLLinuxOSMesa.cpp

@@ -0,0 +1,59 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <GL/gl.h>
+#include <dlfcn.h>
+#include <string.h>
+
+namespace bluegl {
+
+namespace {
+using ProcAddressFunc = void*(*)(char const* funcName);
+}
+
+struct Driver {
+    ProcAddressFunc OSMesaGetProcAddress;
+    void* library;
+} g_driver = {nullptr, nullptr};
+
+bool initBinder() {
+    constexpr char const* libraryNames[] = {"libOSMesa.so", "libosmesa.so"};
+    for (char const* name : libraryNames) {
+        g_driver.library = dlopen(name, RTLD_GLOBAL | RTLD_NOW);
+        if (g_driver.library) {
+            break;
+        }
+    }
+    if (!g_driver.library) {
+        return false;
+    }
+
+    g_driver.OSMesaGetProcAddress = (ProcAddressFunc)
+            dlsym(g_driver.library, "OSMesaGetProcAddress");
+
+    return g_driver.OSMesaGetProcAddress;
+}
+
+void* loadFunction(const char* name) {
+    return (void*) g_driver.OSMesaGetProcAddress(name);
+}
+
+void shutdownBinder() {
+    dlclose(g_driver.library);
+    memset(&g_driver, 0, sizeof(g_driver));
+}
+
+} // namespace bluegl