Add VariantResource editor previews

Only `Color` is supported for now.

Made sure to initialize via `EditorNode::add_init_callback`, else would crash.

core/SCsub

@@ -10,3 +10,6 @@ if env["goost_math_enabled"]:
 
 env_goost.add_source_files(env.modules_sources, "*.cpp")
 env_goost.add_source_files(env.modules_sources, "types/*.cpp")
+
+if env["tools"]:
+    env_goost.add_source_files(env.modules_sources, "types/editor/*.cpp")

core/register_core_types.cpp

@@ -1,17 +1,37 @@
 #include "register_core_types.h"
 
+#include "core/engine.h"
+
 #include "image/register_image_types.h"
 #include "math/register_math_types.h"
 #include "types/list.h"
 #include "types/variant_resource.h"
 
+#ifdef TOOLS_ENABLED
+#include "editor/editor_node.h"
+#include "editor/editor_resource_preview.h"
+#include "types/editor/variant_resource_preview.h"
+#endif
+
 namespace goost {
 
+#ifdef TOOLS_ENABLED
+static void _variant_resource_preview_init() {
+	Ref<VariantResourcePreviewGenerator> variant_resource_preview;
+	variant_resource_preview.instance();
+	EditorResourcePreview::get_singleton()->add_preview_generator(variant_resource_preview);
+}
+#endif
+
 void register_core_types() {
 	ClassDB::register_class<ListNode>();
 	ClassDB::register_class<LinkedList>();
 
 	ClassDB::register_class<VariantResource>();
+#ifdef TOOLS_ENABLED
+	EditorNode::add_init_callback(_variant_resource_preview_init);
+#endif
+
 #ifdef GOOST_IMAGE_ENABLED
 	register_image_types();
 #endif

core/types/editor/variant_resource_preview.cpp

@@ -0,0 +1,34 @@
+#include "variant_resource_preview.h"
+
+bool VariantResourcePreviewGenerator::handles(const String &p_type) const {
+	return p_type == "VariantResource";
+}
+
+Ref<Texture> VariantResourcePreviewGenerator::generate(const Ref<Resource> &p_from, const Size2 &p_size) const {
+	Ref<VariantResource> var = p_from;
+	ERR_FAIL_COND_V_MSG(var.is_null(), Ref<VariantResource>(), "Invalid reference to a VariantResource object.");
+
+    const Variant &value = var->get(var->get_property_name());
+
+    if (value.get_type() == Variant::NIL) {
+        return Ref<Texture>();
+    }
+	Ref<Image> image;
+	image.instance();
+	image->create(p_size.x, p_size.y, false, Image::FORMAT_RGBA8);
+
+    switch (value.get_type()) {
+        case Variant::COLOR: {
+            Color color = value;
+            image->fill(color);
+        } break;
+        default: {
+            return Ref<Texture>();
+        };
+    }
+	Ref<ImageTexture> tex;
+    tex.instance();
+	tex->create_from_image(image, 0);
+
+	return tex;
+}

core/types/editor/variant_resource_preview.h

@@ -0,0 +1,18 @@
+#ifndef VARIANT_RESOURCE_PREVIEW_H
+#define VARIANT_RESOURCE_PREVIEW_H
+
+#include "editor/editor_resource_preview.h"
+#include "../variant_resource.h"
+
+class VariantResourcePreviewGenerator : public EditorResourcePreviewGenerator {
+	GDCLASS(VariantResourcePreviewGenerator, EditorResourcePreviewGenerator);
+
+public:
+	virtual bool handles(const String &p_type) const;
+	virtual Ref<Texture> generate(const RES &p_from, const Size2 &p_size) const;
+
+	virtual bool generate_small_preview_automatically() const { return true; };
+	virtual bool can_generate_small_preview() const { return true; };
+};
+
+#endif // VARIANT_RESOURCE_PREVIEW_H