Capture Irrlicht's shader error message and include it in our error m…

…essage

src/client/shader.cpp

@@ -322,6 +322,23 @@ class MainShaderConstantSetterFactory : public IShaderConstantSetterFactory
 };
 
 
+class ShaderEventReceiver : public IEventReceiver
+{
+public:
+	std::string output;
+
+	virtual bool OnEvent(const SEvent &event) {
+		if (event.EventType == EET_LOG_TEXT_EVENT &&
+				event.LogEvent.Level == ELL_ERROR) {
+			// Log messages from Irrlicht are *usually* not newline-terminated.
+			output.append(event.LogEvent.Text).append("\n");
+			return true;
+		}
+
+		return false;
+	}
+};
+
 /*
 	ShaderSource
 */
@@ -777,21 +794,30 @@ ShaderInfo ShaderSource::generateShader(const std::string &name,
 
 	irr_ptr<ShaderCallback> cb{new ShaderCallback(m_setter_factories)};
 	infostream<<"Compiling high level shaders for "<<name<<std::endl;
+
+	IrrlichtDevice *device = RenderingEngine::get_raw_device();
+	IEventReceiver *old_recv = device->getEventReceiver();
+	ShaderEventReceiver recv;
+	device->setEventReceiver(&recv);
+
 	s32 shadermat = gpu->addHighLevelShaderMaterial(
 		vertex_shader.c_str(), nullptr, video::EVST_VS_1_1,
 		fragment_shader.c_str(), nullptr, video::EPST_PS_1_1,
 		geometry_shader_ptr, nullptr, video::EGST_GS_4_0, scene::EPT_TRIANGLES, scene::EPT_TRIANGLES, 0,
 		cb.get(), shaderinfo.base_material,  1);
+
+	device->setEventReceiver(old_recv);
+
 	if (shadermat == -1) {
-		errorstream<<"generate_shader(): "
-				"failed to generate \""<<name<<"\", "
-				"addHighLevelShaderMaterial failed."
-				<<std::endl;
 		dumpShaderProgram(warningstream, "Vertex", vertex_shader);
 		dumpShaderProgram(warningstream, "Fragment", fragment_shader);
 		dumpShaderProgram(warningstream, "Geometry", geometry_shader);
-		throw ShaderException("Failed to compile the \"" + name + "\" shader. "
-			"Check debug.txt for details.");
+
+		throw ShaderException("Failed to compile the \"" + name + "\" shader.\n" +
+				recv.output + "Check debug.txt for details.");
+	} else if (!recv.output.empty()) {
+		// Don't suppress any error messages.
+		errorstream << recv.output;
 	}
 
 	// Apply the newly created material type