From 12e0564f3ebe961265a7b49edfa083111c862f48 Mon Sep 17 00:00:00 2001
From: Birunthan Mohanathas <birunthan@mohanathas.com>
Date: Mon, 12 Aug 2013 18:50:24 +0300
Subject: [PATCH] Gfx: Avoid clipping with D2D when not needed

---
 Common/Gfx/CanvasD2D.cpp     | 68 +++++++++++++++++++-----------------
 Common/Gfx/CanvasD2D.h       |  7 ++--
 Common/Gfx/TextFormatD2D.cpp |  4 ++-
 Common/Gfx/TextFormatD2D.h   |  3 ++
 4 files changed, 47 insertions(+), 35 deletions(-)

diff --git a/Common/Gfx/CanvasD2D.cpp b/Common/Gfx/CanvasD2D.cpp
index 306e5746..7366d94a 100644
--- a/Common/Gfx/CanvasD2D.cpp
+++ b/Common/Gfx/CanvasD2D.cpp
@@ -52,7 +52,8 @@ Microsoft::WRL::ComPtr<IWICImagingFactory> CanvasD2D::c_WICFactory;
 
 CanvasD2D::CanvasD2D() : Canvas(),
 	m_Bitmap(),
-	m_TextAntiAliasing(false)
+	m_TextAntiAliasing(false),
+	m_CanUseAxisAlignClip(false)
 {
 }
 
@@ -169,8 +170,8 @@ bool CanvasD2D::BeginTargetDraw()
 
 		m_Target->BeginDraw();
 
-		// Apply any transforms that occurred before creation of m_Target
-		m_Target->SetTransform(GetCurrentTransform());
+		// Apply any transforms that occurred before creation of |m_Target|.
+		UpdateTargetTransform();
 
 		return true;
 	}
@@ -227,13 +228,18 @@ bool CanvasD2D::IsTransparentPixel(int x, int y)
 	return transparent;
 }
 
-D2D1_MATRIX_3X2_F CanvasD2D::GetCurrentTransform()
+void CanvasD2D::UpdateTargetTransform()
 {
-	D2D1_MATRIX_3X2_F d2dMatrix;
 	Gdiplus::Matrix gdipMatrix;
 	m_GdipGraphics->GetTransform(&gdipMatrix);
+
+	D2D1_MATRIX_3X2_F d2dMatrix;
 	gdipMatrix.GetElements((Gdiplus::REAL*)&d2dMatrix);
-	return d2dMatrix;
+
+	m_Target->SetTransform(d2dMatrix);
+	m_CanUseAxisAlignClip =
+		d2dMatrix._12 == 0.0f && d2dMatrix._21 == 0.0f &&
+		d2dMatrix._31 == 0.0f && d2dMatrix._32 == 0.0f;
 }
 
 void CanvasD2D::SetTransform(const Gdiplus::Matrix& matrix)
@@ -242,7 +248,7 @@ void CanvasD2D::SetTransform(const Gdiplus::Matrix& matrix)
 
 	if (m_Target)
 	{
-		m_Target->SetTransform(GetCurrentTransform());
+		UpdateTargetTransform();
 	}
 }
 
@@ -264,7 +270,7 @@ void CanvasD2D::RotateTransform(float angle, float x, float y, float dx, float d
 
 	if (m_Target)
 	{
-		m_Target->SetTransform(GetCurrentTransform());
+		UpdateTargetTransform();
 	}
 }
 
@@ -344,36 +350,34 @@ void CanvasD2D::DrawTextW(const WCHAR* str, UINT strLen, const TextFormat& forma
 			return yPos;
 		} ();
 
-		DWRITE_OVERHANG_METRICS overhangMetrics;
-		formatD2D.m_TextLayout->GetOverhangMetrics(&overhangMetrics);
-
-		D2D1::Matrix3x2F transformMatrix;
-		m_Target->GetTransform(&transformMatrix);
-		const bool identityTransform = transformMatrix.IsIdentity();
-
-		// TODO: Determine if we can avoid clipping.
-		D2D1_RECT_F clipRect = ToRectF(rect);
-		clipRect.bottom += ceil(overhangMetrics.bottom);
-		if (identityTransform)
+		if (formatD2D.m_Trimming)
 		{
-			m_Target->PushAxisAlignedClip(clipRect, D2D1_ANTIALIAS_MODE_ALIASED);
-		}
-		else
-		{
-			const D2D1_LAYER_PARAMETERS layerParams =
-				D2D1::LayerParameters(clipRect, nullptr, D2D1_ANTIALIAS_MODE_ALIASED);
-			m_Target->PushLayer(layerParams, nullptr);
+			D2D1_RECT_F clipRect = ToRectF(rect);
+
+			if (m_CanUseAxisAlignClip)
+			{
+				m_Target->PushAxisAlignedClip(clipRect, D2D1_ANTIALIAS_MODE_ALIASED);
+			}
+			else
+			{
+				const D2D1_LAYER_PARAMETERS layerParams =
+					D2D1::LayerParameters(clipRect, nullptr, D2D1_ANTIALIAS_MODE_ALIASED);
+				m_Target->PushLayer(layerParams, nullptr);
+			}
 		}
 
 		m_Target->DrawTextLayout(drawPosition, formatD2D.m_TextLayout.Get(), solidBrush.Get());
 
-		if (identityTransform)
+		if (formatD2D.m_Trimming)
 		{
-			m_Target->PopAxisAlignedClip();
-		}
-		else
-		{
-			m_Target->PopLayer();
+			if (m_CanUseAxisAlignClip)
+			{
+				m_Target->PopAxisAlignedClip();
+			}
+			else
+			{
+				m_Target->PopLayer();
+			}
 		}
 	}
 }
diff --git a/Common/Gfx/CanvasD2D.h b/Common/Gfx/CanvasD2D.h
index bb15b4eb..94179b8b 100644
--- a/Common/Gfx/CanvasD2D.h
+++ b/Common/Gfx/CanvasD2D.h
@@ -86,8 +86,8 @@ private:
 	bool BeginTargetDraw();
 	void EndTargetDraw();
 
-	// Retrieves current GDI+ transform (if any) and converts to a D2D Matrix
-	D2D1_MATRIX_3X2_F GetCurrentTransform();
+	// Sets the |m_Target| transformation to be equal to that of |m_GdipGraphics|.
+	void UpdateTargetTransform();
 
 	Microsoft::WRL::ComPtr<ID2D1RenderTarget> m_Target;
 	Util::WICBitmapDIB m_Bitmap;
@@ -98,6 +98,9 @@ private:
 
 	bool m_TextAntiAliasing;
 
+	// |true| if PushAxisAlignedClip()/PopAxisAlignedClip() can be used.
+	bool m_CanUseAxisAlignClip;
+
 	static UINT c_Instances;
 	static Microsoft::WRL::ComPtr<ID2D1Factory1> c_D2DFactory;
 	static Microsoft::WRL::ComPtr<IDWriteFactory1> c_DWFactory;
diff --git a/Common/Gfx/TextFormatD2D.cpp b/Common/Gfx/TextFormatD2D.cpp
index 7314322d..5a395bfa 100644
--- a/Common/Gfx/TextFormatD2D.cpp
+++ b/Common/Gfx/TextFormatD2D.cpp
@@ -24,7 +24,8 @@ namespace Gfx {
 
 TextFormatD2D::TextFormatD2D() :
 	m_ExtraHeight(),
-	m_LineGap()
+	m_LineGap(),
+	m_Trimming()
 {
 }
 
@@ -297,6 +298,7 @@ DWRITE_TEXT_METRICS TextFormatD2D::GetMetrics(
 
 void TextFormatD2D::SetTrimming(bool trim)
 {
+	m_Trimming = trim;
 	IDWriteInlineObject* inlineObject = nullptr;
 	DWRITE_TRIMMING trimming = {};
 	DWRITE_WORD_WRAPPING wordWrapping = DWRITE_WORD_WRAPPING_NO_WRAP;
diff --git a/Common/Gfx/TextFormatD2D.h b/Common/Gfx/TextFormatD2D.h
index 543c71d4..777c2d8f 100644
--- a/Common/Gfx/TextFormatD2D.h
+++ b/Common/Gfx/TextFormatD2D.h
@@ -70,6 +70,9 @@ private:
 	// Used to emulate GDI+ behaviour.
 	float m_ExtraHeight;
 	float m_LineGap;
+
+	// Contains the value passed to the last call of of SetTrimming().
+	bool m_Trimming;
 };
 
 }  // namespace Gfx