Add offscreen text rendering.

test/test_utils/CMakeLists.txt

@@ -6,6 +6,7 @@ add_library(test_utils STATIC
     TestCaseRunner.cpp
 	TestUiApplication.h
 	TestUiApplication.cpp
+	TestRenderUtils.h
     )
 
 target_include_directories(test_utils PUBLIC ${CMAKE_CURRENT_SOURCE_DIR} ${CMAKE_CURRENT_BINARY_DIR})

test/test_utils/TestRenderUtils.h

@@ -0,0 +1,40 @@
+#pragma once
+
+#include "DrawingSurface.h"
+#include "DrawingContext.h"
+#include "AbstractPainter.h"
+#include "Image.h"
+#include "PngWriter.h"
+#include "Scene.h"
+
+class TestRenderer
+{
+public:
+	TestRenderer(unsigned width = 1000, unsigned height = 1000)
+	{
+		mSurface = std::make_unique<DrawingSurface>();
+		mSurface->setSize(width, height);
+
+		mDrawingContext = std::make_unique<DrawingContext>(mSurface.get());
+	}
+
+	Scene* getScene() const
+	{
+		return mSurface->getScene();
+	}
+
+	void write(const Path& path)
+	{
+		mDrawingContext->paint();
+
+		auto image = mSurface->getImage();
+
+		PngWriter writer;
+		writer.setPath(path);
+		writer.write(image);
+	}
+
+private:
+	std::unique_ptr<DrawingSurface> mSurface;
+	std::unique_ptr<DrawingContext> mDrawingContext;
+};