Prioritize system libraries on linux SDL backend (fix build-related issues on linux)

backends/backend-sdl/build.gradle

@@ -6,6 +6,10 @@ dependencies {
     testImplementation aproj(":arc-core")
 }
 
+ext {
+    windowsVersion = [sdl: "2.0.20", glew: "2.2.0"]
+}
+
 apply plugin: "com.badlogicgames.gdx.gdx-jnigen"
 
 file("jni").mkdir()
@@ -14,14 +18,14 @@ task preJni{
     //this absolutely needs to run during configuration so jnigen can run downloaded sdl-config scripts for configuration of library flags
     try{
         if(!file("jni/glew.zip").exists()){
-            println "Fetching GLEW source..."
-            "curl -o $rootDir/backends/backend-sdl/jni/glew.zip -L https://github.com/nigels-com/glew/releases/download/glew-2.2.0/glew-2.2.0.zip".execute().waitFor()
+            println "Fetching GLEW $windowsVersion.glew source..."
+            "curl -o $rootDir/backends/backend-sdl/jni/glew.zip -L https://github.com/nigels-com/glew/releases/download/glew-$windowsVersion.glew/glew-${windowsVersion.glew}.zip".execute().waitFor()
             "unzip -qq -d $rootDir/backends/backend-sdl/jni $rootDir/backends/backend-sdl/jni/glew.zip".execute().waitFor()
         }
 
         if(!file("jni/sdlmingw.tar.gz").exists()){
-            println "Fetching SDL-mingw builds..."
-            "curl -o $rootDir/backends/backend-sdl/jni/sdlmingw.tar.gz -L https://www.libsdl.org/release/SDL2-devel-2.0.20-mingw.tar.gz".execute().waitFor()
+            println "Fetching SDL-$windowsVersion.sdl-mingw builds..."
+            "curl -o $rootDir/backends/backend-sdl/jni/sdlmingw.tar.gz -L https://www.libsdl.org/release/SDL2-devel-$windowsVersion.sdl-mingw.tar.gz".execute().waitFor()
             "tar -xvzf $rootDir/backends/backend-sdl/jni/sdlmingw.tar.gz -C $rootDir/backends/backend-sdl/jni".execute().waitFor()
         }
     }catch(Exception youAreProbablyOnWindowsOrDontHaveUnzip){}
@@ -72,35 +76,34 @@ jnigen{
     temporaryDir = file("build/target/native").absolutePath
     libsDir = file("libs").absolutePath
 
-    def sdlVersion = "2.0.20"
 
     all{
         cppIncludes = ["*.cpp"]
-        cIncludes = ["*.c", "glew-2.2.0/src/glew.c"]
-        headerDirs += ["glew-2.2.0/include"]
+        cIncludes = ["*.c"]
     }
     add(Linux, x64){
-        cppFlags += " " + execCmd("sdl2-config --cflags")
+        cppFlags += " " + execCmd("pkg-config --cflags glew sdl2")
         cFlags = cppFlags
-        //NOTE: for this to statically link properly, you need to add -L/path/to/folder/with/custom/libSDL2.a
-        //where this folder contains a custom build of SDL2 with the -fPIC flag (added to the makefile in the cflags section after configure)
-        //--static-libs and ?.replace("-lSDL2", "-l:libSDL2.a")
-        libraries = execCmd("sdl2-config --libs") + " -Wl,-Bdynamic -lGL "
+        libraries = execCmd("pkg-config --libs glew sdl2") + " -Wl,-Bdynamic"
         linkerFlags = "-shared -m64"
     }
     add(Windows, x64){
-        def path = "SDL2-$sdlVersion/x86_64-w64-mingw32"
+        def sdlPath = "SDL2-$windowsVersion.sdl/x86_64-w64-mingw32"
+        def glewPath = "glew-$windowsVersion.glew"
         def root = "$rootDir/backends/backend-sdl/jni"
-        headerDirs += ["$path/include/SDL2"]
-        cppFlags += " " + execCmd("sh $root/$path/bin/sdl2-config --cflags")
+        headerDirs += ["$sdlPath/include/SDL2", "$glewPath/include"]
+        cIncludes += ["$glewPath/src/glew.c"]
+        cppFlags += " " + execCmd("sh $root/$sdlPath/bin/sdl2-config --cflags")
         cFlags = cppFlags
-        libraries = execCmd("sh $root/$path/bin/sdl2-config --static-libs") + " -lopengl32"
-        linkerFlags += " -L $root/$path/lib"
+        libraries = execCmd("sh $root/$sdlPath/bin/sdl2-config --static-libs") + " -lopengl32"
+        linkerFlags += " -L $root/$sdlPath/lib"
     }
     add(Windows, x32){
-        def path = "SDL2-$sdlVersion/i686-w64-mingw32"
+        def sdlPath = "SDL2-$windowsVersion.sdl/i686-w64-mingw32"
+        def glewPath = "glew-$windowsVersion.glew"
         def root = "$rootDir/backends/backend-sdl/jni"
-        headerDirs += ["$path/include/SDL2"]
+        headerDirs += ["$sdlPath/include/SDL2", "$glewPath/include"]
+        cIncludes += ["$glewPath/src/glew.c"]
         cppFlags += " " + execCmd("sh $root/$path/bin/sdl2-config --cflags")
         cFlags = cppFlags
         libraries = execCmd("sh $root/$path/bin/sdl2-config --static-libs") + " -lopengl32"
@@ -130,4 +133,4 @@ getTasksByName("jnigen", true).each{
     it.dependsOn preJni
     it.dependsOn classes
     it.dependsOn aproj(":arc-core").getTasksByName("compileJava", true)
-}
+}

backends/backend-sdl/src/arc/backend/sdl/jni/SDL.java

@@ -121,17 +121,27 @@ public class SDL{
         new SharedLibraryLoader(){
             @Override
             protected Throwable loadFile(String sourcePath, String sourceCrc, File extractedFile){
-                //skip dynamic load for me because it crashes otherwise
-                if(OS.isLinux && !OS.hasProp("SDL2_STATIC") && !OS.username.equals("anuke")){
-                    //on linux, the SDL shared library isn't statically linked, try to load it first
-                    try{
-                        String name = "libSDL2.so";
-                        File result = new File(extractedFile.getParentFile() == null ? name : (extractedFile.getParentFile() + "/" + name));
-                        extractFile(name, crc(readFile(name)), result);
-                        System.load(result.getAbsolutePath());
-                    }catch(Throwable ignored){
+                //Return early if we're not on linux
+                if(!OS.isLinux)
+                    return super.loadFile(sourcePath, sourceCrc, extractedFile);
+
+                //We need to load SDL2, GLEW, and their dependencies
+                final String[] libs = {"SDL2", "GLEW", "EGL", "GL", "GLU", "OpenGL"};
+                for(String lib : libs) {
+                    //Try loading system version of each library first
+                    try {
+                        System.loadLibrary(lib);
+                    } catch (Throwable ignored){
+                        //If that fails, load the bundled one as a fallback
+                        try{
+                            final String name = System.mapLibraryName(lib);
+                            File result = new File(extractedFile.getParentFile() == null ? name : (extractedFile.getParentFile() + "/" + name));
+                            extractFile(name, crc(readFile(name)), result);
+                            System.load(result.getAbsolutePath());
+                        } catch (Throwable noLib){}
                     }
                 }
+
                 return super.loadFile(sourcePath, sourceCrc, extractedFile);
             }
         }.load("sdl-arc");