Add rendering implementation for LWJGL

buildSrc/build.gradle

@@ -0,0 +1,19 @@
+plugins {
+    id 'groovy'
+}
+
+repositories {
+    jcenter()
+    mavenCentral()
+}
+
+ext {
+    jnigenVersion = '1.9.10'
+}
+
+dependencies {
+    implementation gradleApi()
+    implementation localGroovy()
+
+    implementation "com.badlogicgames.gdx:gdx-jnigen:$jnigenVersion"
+}

buildSrc/src/main/groovy/imgui/generate/GenerateLibs.groovy

@@ -0,0 +1,43 @@
+package imgui.generate
+
+import com.badlogic.gdx.jnigen.*
+import groovy.transform.CompileStatic
+import org.gradle.api.DefaultTask
+import org.gradle.api.file.CopySpec
+import org.gradle.api.tasks.TaskAction
+
+@CompileStatic
+class GenerateLibs extends DefaultTask {
+    String description = 'Generates native libraries using classes under ":imgui-binding" and Dear-ImGui itself from "imgui" submodule.'
+
+    private final String sourceDir = project.file('src/main/java')
+    private final String classpath = project.file('build/classes/java/main')
+    private final String jniDir = project.buildDir.path + '/jni'
+    private final String tmpFolder = project.buildDir.path + '/tmp'
+    private final String libsFolder = 'libsNative'
+
+    @TaskAction
+    void generate() {
+        // Generate h/cpp files for JNI
+        new NativeCodeGenerator().generate(sourceDir, classpath, jniDir)
+
+        // Copy ImGui h/cpp files
+        project.copy { CopySpec spec ->
+            spec.from(project.rootProject.file('imgui')) { CopySpec it -> it.include('*.h', '*.cpp') }
+            spec.from(project.file('src/main/native'))
+            spec.into(jniDir)
+        }
+
+        // Generate platform dependant ant configs and header files
+        def buildConfig = new BuildConfig('imgui-java', tmpFolder, libsFolder, jniDir)
+        def win64 = BuildTarget.newDefaultTarget(BuildTarget.TargetOs.Windows, true)
+        new AntScriptGenerator().generate(buildConfig, win64)
+
+        // Generate native libraries
+        BuildExecutor.executeAnt(jniDir + '/build-windows64.xml', '-v', '-Dhas-compiler=true', '-Drelease=true', 'clean', 'postcompile')
+        BuildExecutor.executeAnt(jniDir + '/build.xml', '-v', 'pack-natives')
+
+        // Ant creates this folder in the root of the project. Since it will be empty we delete it
+        project.rootProject.file(libsFolder).deleteDir()
+    }
+}