Polish rendering driver refactor further

Mainly:
- Make `max_descriptors_per_pool` project setting Vulkan-specific.
- Use a common, render driver agnostic magic FourCC for shader binary data.
- Downgrade spirv_reflect to Vulkan-only dependency.
- Add a `RENDER_DRIVER_*` macro to GLSL shader code for per-driver customizations.

2 files changed, 4 insertions, 2 deletions

diff --git a/servers/rendering/renderer_rd/shader_rd.cpp b/servers/rendering/renderer_rd/shader_rd.cpp
index 0f2dea6fe9..5e9eadadd9 100644
--- a/servers/rendering/renderer_rd/shader_rd.cpp
+++ b/servers/rendering/renderer_rd/shader_rd.cpp
@@ -180,6 +180,7 @@ void ShaderRD::_build_variant_code(StringBuilder &builder, uint32_t p_variant, c
 #if defined(MACOS_ENABLED) || defined(IOS_ENABLED)
 				builder.append("#define MOLTENVK_USED\n");
 #endif
+				builder.append(String("#define RENDER_DRIVER_") + OS::get_singleton()->get_current_rendering_driver_name().to_upper() + "\n");
 			} break;
 			case StageTemplate::Chunk::TYPE_MATERIAL_UNIFORMS: {
 				builder.append(p_version->uniforms.get_data()); //uniforms (same for vertex and fragment)
diff --git a/servers/rendering_server.cpp b/servers/rendering_server.cpp
index 750121719f..5bd4bae4cb 100644
--- a/servers/rendering_server.cpp
+++ b/servers/rendering_server.cpp
@@ -2868,12 +2868,13 @@ void RenderingServer::init() {
 
 	GLOBAL_DEF("rendering/2d/shadow_atlas/size", 2048);
 
-	// Already defined in RenderingDeviceVulkan::initialize which runs before this code.
+	// Already defined in some RenderingDevice*::initialize, which run before this code.
 	// We re-define them here just for doctool's sake. Make sure to keep default values in sync.
 	GLOBAL_DEF("rendering/rendering_device/staging_buffer/block_size_kb", 256);
 	GLOBAL_DEF("rendering/rendering_device/staging_buffer/max_size_mb", 128);
 	GLOBAL_DEF("rendering/rendering_device/staging_buffer/texture_upload_region_size_px", 64);
-	GLOBAL_DEF("rendering/rendering_device/descriptor_pools/max_descriptors_per_pool", 64);
+	// Vulkan-specific.
+	GLOBAL_DEF("rendering/rendering_device/vulkan/max_descriptors_per_pool", 64);
 
 	GLOBAL_DEF("rendering/shader_compiler/shader_cache/enabled", true);
 	GLOBAL_DEF("rendering/shader_compiler/shader_cache/compress", true);