--- a/Makefile	Sat Dec 02 21:25:02 2023 +0100
+++ b/Makefile	Sat Dec 02 23:11:56 2023 +0100
@@ -20,8 +20,8 @@
 clean:
 	rm -rf build
 
-run: build/shader-shark build/jazz.png
-	$(<) --texture build/jazz.png
+run: build/shader-shark
+	SHADER_SHARK_DATA_DIR=. $(<)
 
 build:
 	mkdir -p $(@)
@@ -37,11 +37,3 @@
 build/shader-shark: $(SRC) build *.h
 	$(CXX) -std=c++20 -g -o $(@) $(SRC) $$(pkg-config --cflags --libs \
 	    epoxy x11 glu glm Magick++)
-
-build/jazz.png: textures/jazz.png
-	mkdir -p build
-	cp --reflink=auto $(<) $(@)
-	
-build/jazz.rgba: textures/jazz.png
-	mkdir -p build
-	convert -format rgba $(<) $(@)

--- a/Shark.cpp	Sat Dec 02 21:25:02 2023 +0100
+++ b/Shark.cpp	Sat Dec 02 23:11:56 2023 +0100
@@ -198,6 +198,7 @@
 	std::shared_ptr<Program> loadShaders();
 	bool reloadShader(const std::string& fileName);
 	void setTitle(const std::string& suffix = "");
+	static const std::string getDefaultFile(const std::string& relativePath);
 
 };
 
@@ -536,6 +537,19 @@
 	}
 }
 
+const std::string
+Shark::Shark::Impl::getDefaultFile(const std::string& relativePath) {
+	const char* envName = "SHADER_SHARK_DATA_DIR";
+	const char* envValue = ::getenv(envName);
+	if (envValue) {
+		return std::string(envValue) + "/" + relativePath;
+	} else {
+		throw std::invalid_argument(std::string("Configure $") + envName
+				+ " in order to use defaults"
+				" or specify textures and shaders as parameters");
+	}
+}
+
 Shark::Impl::Texture Shark::Impl::loadTexture(const std::string& fileName) {
 	Texture tex;
 	tex.fileName = fileName;
@@ -565,6 +579,10 @@
 }
 
 void Shark::Impl::loadTextures() {
+	// Load default texture if there is no configured:
+	if (cfg.textures.empty())
+		cfg.textures.push_back({getDefaultFile("textures/default.png")});
+
 	for (const Configuration::Texture& tex : cfg.textures) {
 		textures.push_back(loadTexture(tex.fileName));
 		watchedFiles.push_back(fileMonitor.watch(tex.fileName));
@@ -601,10 +619,16 @@
 		glGenBuffers(1, &vbo);
 		glBindBuffer(GL_ARRAY_BUFFER, vbo);
 
-		if (cfg.shaders.empty()) {
-			// TODO: configurable absolute path or embedded defaults
-			cfg.shaders.push_back({"shaders/first.vert", "vertex"});
-			cfg.shaders.push_back({"shaders/first.frag", "fragment"});
+		{
+			// Load default shaders if there are no configured:
+			int vc = 0;
+			int fc = 0;
+			auto& ss = cfg.shaders;
+			for (const auto& s : ss) if (s.type == "vertex") vc++;
+			for (const auto& s : ss) if (s.type == "fragment") fc++;
+			auto& d = getDefaultFile;
+			if (vc == 0) ss.push_back({d("shaders/default.vert"), "vertex"});
+			if (fc == 0) ss.push_back({d("shaders/default.frag"), "fragment"});
 		}
 
 		std::shared_ptr<Program> program = std::make_shared<Program>();

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/shaders/default.frag	Sat Dec 02 23:11:56 2023 +0100
@@ -0,0 +1,17 @@
+#version 330 core
+
+uniform  sampler2D  uTexture;
+in       vec2       vTextureXY;
+out      vec3       fColor;
+
+vec3 grayscale(vec3 original) {
+	const vec3 luminanceWeighting = vec3(0.2125, 0.7154, 0.0721);
+	float luminance = dot(original, luminanceWeighting);
+	return vec3(luminance);
+}
+
+void main(){
+	fColor = texture(uTexture, vTextureXY).rgb;
+	// fColor = grayscale(fColor);
+	// fColor *= vec3(0.8, 1., 0.2);
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/shaders/default.vert	Sat Dec 02 23:11:56 2023 +0100
@@ -0,0 +1,13 @@
+#version 330 core
+
+uniform  mat4  uModel;
+uniform  mat4  uView;
+uniform  mat4  uProjection;
+in       vec3  aVertexXYZ;
+in       vec2  aTextureXY;
+out      vec2  vTextureXY;
+
+void main() {
+	gl_Position = uProjection * uView * uModel * vec4(aVertexXYZ, 1.0f);
+	vTextureXY = aTextureXY;
+}

--- a/shaders/first.frag	Sat Dec 02 21:25:02 2023 +0100
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,17 +0,0 @@
-#version 330 core
-
-uniform  sampler2D  uTexture;
-in       vec2       vTextureXY;
-out      vec3       fColor;
-
-vec3 grayscale(vec3 original) {
-	const vec3 luminanceWeighting = vec3(0.2125, 0.7154, 0.0721);
-	float luminance = dot(original, luminanceWeighting);
-	return vec3(luminance);
-}
-
-void main(){
-	fColor = texture(uTexture, vTextureXY).rgb;
-	// fColor = grayscale(fColor);
-	// fColor *= vec3(0.8, 1., 0.2);
-}

--- a/shaders/first.vert	Sat Dec 02 21:25:02 2023 +0100
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,13 +0,0 @@
-#version 330 core
-
-uniform  mat4  uModel;
-uniform  mat4  uView;
-uniform  mat4  uProjection;
-in       vec3  aVertexXYZ;
-in       vec2  aTextureXY;
-out      vec2  vTextureXY;
-
-void main() {
-	gl_Position = uProjection * uView * uModel * vec4(aVertexXYZ, 1.0f);
-	vTextureXY = aTextureXY;
-}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/textures/default.png	Sat Dec 02 23:11:56 2023 +0100
@@ -0,0 +1,1 @@
+jazz.png
\ No newline at end of file