Gfx: Implement GDI+ fallback

Common/Gfx/Canvas.cpp

@@ -17,6 +17,9 @@
 */
 
 #include "Canvas.h"
+#include "CanvasD2D.h"
+#include "CanvasGDIP.h"
+#include "../Platform.h"
 
 namespace Gfx {
 
@@ -31,6 +34,34 @@ Canvas::~Canvas()
 {
 }
 
+Canvas* Canvas::Create(Renderer renderer)
+{
+	if (renderer == Renderer::GDIP)
+	{
+		return new CanvasGDIP();
+	}
+	else if (renderer == Renderer::D2D && Platform::IsAtLeastWin7())
+	{
+		if (CanvasD2D::Initialize())
+		{
+			return new CanvasD2D();
+		}
+
+		CanvasD2D::Finalize();
+	}
+	else if (renderer == Renderer::PreferD2D)
+	{
+		if (Canvas* canvas = Create(Renderer::D2D))
+		{
+			return canvas;
+		}
+
+		return Create(Renderer::GDIP);
+	}
+
+	return nullptr;
+};
+
 void Canvas::Resize(int w, int h)
 {
 	m_W = w;

Common/Gfx/Canvas.h

@@ -26,12 +26,24 @@
 
 namespace Gfx {
 
+enum class Renderer
+{
+	GDIP,
+	D2D,
+
+	// Attempts to use D2D. If D2D is not available, fallbacks to use GDI+.
+	PreferD2D
+};
+
 // Provides methods for drawing text, bitmaps, etc.
 class __declspec(novtable) Canvas
 {
 public:
 	virtual ~Canvas();
 
+	// Creates the canvas using the specified rendering engine. May return nullptr.
+	static Canvas* Create(Renderer renderer);
+
 	int GetW() const { return m_W; }
 	int GetH() const { return m_H; }
 

Common/Gfx/CanvasD2D.cpp

@@ -53,7 +53,6 @@ CanvasD2D::CanvasD2D() : Canvas(),
 	m_Bitmap(),
 	m_TextAntiAliasing(false)
 {
-	Initialize();
 }
 
 CanvasD2D::~CanvasD2D()

Common/Gfx/CanvasD2D.h

@@ -38,9 +38,6 @@ namespace Gfx {
 class CanvasD2D : public Canvas
 {
 public:
-	CanvasD2D();
-	~CanvasD2D();
-
 	virtual void Resize(int w, int h);
 
 	virtual bool BeginDraw();
@@ -75,9 +72,12 @@ public:
 	virtual void FillRectangle(Gdiplus::Rect& rect, const Gdiplus::SolidBrush& brush) override;
 
 private:
+	friend class Canvas;
 	friend class FontCollectionD2D;
 	friend class TextFormatD2D;
 
+	CanvasD2D();
+	~CanvasD2D();
 	CanvasD2D(const CanvasD2D& other) {}
 
 	static bool Initialize();

Common/Gfx/CanvasGDIP.h

@@ -32,9 +32,6 @@ namespace Gfx {
 class CanvasGDIP : public Canvas
 {
 public:
-	CanvasGDIP();
-	~CanvasGDIP();
-
 	virtual void Resize(int w, int h);
 
 	virtual bool BeginDraw();
@@ -69,6 +66,10 @@ public:
 	virtual void FillRectangle(Gdiplus::Rect& rect, const Gdiplus::SolidBrush& brush) override;
 
 private:
+	friend class Canvas;
+
+	CanvasGDIP();
+	~CanvasGDIP();
 	CanvasGDIP(const CanvasGDIP& other) {}
 
 	void Dispose();

Library/MeterWindow.cpp

@@ -37,8 +37,7 @@
 #include "MeasureScript.h"
 #include "../Version.h"
 #include "../Common/PathUtil.h"
-#include "../Common/Gfx/CanvasD2D.h"
+#include "../Common/Gfx/Canvas.h"
-#include "../Common/Gfx/CanvasGDIP.h"
 
 using namespace Gdiplus;
 
@@ -2078,8 +2077,7 @@ bool MeterWindow::ReadSkin()
 		useD2D = 0!=m_Parser.ReadInt(L"Rainmeter", L"__UseD2D", useD2D ? 1 : 0);
 	}
 
-	m_Canvas = (Platform::IsAtLeastWinVista() && useD2D) ?
+	m_Canvas = Gfx::Canvas::Create(useD2D ? Gfx::Renderer::PreferD2D : Gfx::Renderer::GDIP);
-		(Gfx::Canvas*)new Gfx::CanvasD2D() : (Gfx::Canvas*)new Gfx::CanvasGDIP();
 
 	// Gotta have some kind of buffer during initialization
 	CreateDoubleBuffer(1, 1);