Discourage disabling shaders (luanti-org#15210)

Author: sfan5

builtin/settingtypes.txt

@@ -262,7 +262,7 @@ viewing_range (Viewing range) int 190 20 4000
 #    Higher values result in a less detailed image.
 undersampling (Undersampling) int 1 1 8
 
-[**Graphics Effects]
+[**Graphical Effects]
 
 #    Allows liquids to be translucent.
 translucent_liquids (Translucent liquids) bool true
@@ -468,12 +468,6 @@ enable_raytraced_culling (Enable Raytraced Culling) bool true
 
 [*Shaders]
 
-#    Shaders allow advanced visual effects and may increase performance on some video
-#    cards.
-#
-#    Requires: shaders_support
-enable_shaders (Shaders) bool true
-
 [**Waving Nodes]
 
 #    Set to true to enable waving leaves.
@@ -1866,6 +1860,11 @@ ignore_world_load_errors (Ignore world errors) bool false
 
 [**Graphics]
 
+#    Shaders are a fundamental part of rendering and enable advanced visual effects.
+#
+#    Requires: shaders_support
+enable_shaders (Shaders) bool true
+
 #    Path to shader directory. If no path is defined, default location will be used.
 #
 #    Requires: shaders
@@ -1889,6 +1888,7 @@ cloud_radius (Cloud radius) int 12 1 62
 desynchronize_mapblock_texture_animation (Desynchronize block animation) bool false
 
 #    Enables caching of facedir rotated meshes.
+#    This is only effective with shaders disabled.
 enable_mesh_cache (Mesh cache) bool false
 
 #    Delay between mesh updates on the client in ms. Increasing this will slow

src/client/shader.cpp

@@ -322,6 +322,9 @@ class ShaderSource : public IWritableShaderSource
 
 private:
 
+	// Are shaders even enabled?
+	bool m_enabled;
+
 	// The id of the thread that is allowed to use irrlicht directly
 	std::thread::id m_main_thread;
 
@@ -360,6 +363,12 @@ ShaderSource::ShaderSource()
 	// Add a dummy ShaderInfo as the first index, named ""
 	m_shaderinfo_cache.emplace_back();
 
+	m_enabled = g_settings->getBool("enable_shaders");
+	if (!m_enabled) {
+		warningstream << "You are running " PROJECT_NAME_C " with shaders disabled, "
+			"this is not a recommended configuration." << std::endl;
+	}
+
 	// Add main global constant setter
 	addShaderConstantSetterFactory(new MainShaderConstantSetterFactory());
 }
@@ -368,9 +377,11 @@ ShaderSource::~ShaderSource()
 {
 	MutexAutoLock lock(m_shaderinfo_cache_mutex);
 
+	if (!m_enabled)
+		return;
+
 	// Delete materials
-	video::IGPUProgrammingServices *gpu = RenderingEngine::get_video_driver()->
-		getGPUProgrammingServices();
+	auto *gpu = RenderingEngine::get_video_driver()->getGPUProgrammingServices();
 	for (ShaderInfo &i : m_shaderinfo_cache) {
 		if (!i.name.empty())
 			gpu->deleteShaderMaterial(i.material);
@@ -499,9 +510,11 @@ void ShaderSource::rebuildShaders()
 {
 	MutexAutoLock lock(m_shaderinfo_cache_mutex);
 
+	if (!m_enabled)
+		return;
+
 	// Delete materials
-	video::IGPUProgrammingServices *gpu = RenderingEngine::get_video_driver()->
-		getGPUProgrammingServices();
+	auto *gpu = RenderingEngine::get_video_driver()->getGPUProgrammingServices();
 	for (ShaderInfo &i : m_shaderinfo_cache) {
 		if (!i.name.empty()) {
 			gpu->deleteShaderMaterial(i.material);
@@ -548,12 +561,11 @@ ShaderInfo ShaderSource::generateShader(const std::string &name,
 	}
 	shaderinfo.material = shaderinfo.base_material;
 
-	bool enable_shaders = g_settings->getBool("enable_shaders");
-	if (!enable_shaders)
+	if (!m_enabled)
 		return shaderinfo;
 
 	video::IVideoDriver *driver = RenderingEngine::get_video_driver();
-	video::IGPUProgrammingServices *gpu = driver->getGPUProgrammingServices();
+	auto *gpu = driver->getGPUProgrammingServices();
 	if (!driver->queryFeature(video::EVDF_ARB_GLSL) || !gpu) {
 		throw ShaderException(gettext("Shaders are enabled but GLSL is not "
 			"supported by the driver."));