From e5100d9a9fa6b76dfab1dd767a8ec645d4678fce Mon Sep 17 00:00:00 2001
From: Birunthan Mohanathas <birunthan@mohanathas.com>
Date: Thu, 28 Mar 2013 15:51:12 +0200
Subject: [PATCH] Gfx: Make text rendering with D2D more efficient by reusing
 layout

---
 Common/Gfx/CanvasD2D.cpp     | 20 ++++++------------
 Common/Gfx/TextFormatD2D.cpp | 41 ++++++++++++++++++++++++++++++++++++
 Common/Gfx/TextFormatD2D.h   |  9 ++++++++
 3 files changed, 57 insertions(+), 13 deletions(-)

diff --git a/Common/Gfx/CanvasD2D.cpp b/Common/Gfx/CanvasD2D.cpp
index 80a3fbc9..20770035 100644
--- a/Common/Gfx/CanvasD2D.cpp
+++ b/Common/Gfx/CanvasD2D.cpp
@@ -278,21 +278,15 @@ void CanvasD2D::DrawTextW(const WCHAR* str, UINT strLen, const TextFormat& forma
 	HRESULT hr = m_Target->CreateSolidColorBrush(ToColorF(color), &solidBrush);
 	if (SUCCEEDED(hr))
 	{
-		const bool right = ((TextFormatD2D&)format).GetHorizontalAlignment() == Gfx::HorizontalAlignment::Right;
+		TextFormatD2D& formatD2D = (TextFormatD2D&)format;
+		const bool right = formatD2D.GetHorizontalAlignment() == Gfx::HorizontalAlignment::Right;
 
-		// TODO: Draw cached layout?
-		//m_Target->DrawTextLayout(
-		//	D2D1::Point2F(right ? rect.X - 2 : rect.X + 2.0f, rect.Y - 1.0f),
-		//	textLayout,
-		//	solidBrush);
+		formatD2D.CreateLayout(str, strLen, rect.Width, rect.Height);
 
-		auto dst = D2D1::RectF(
-			right ? rect.X - 2 : rect.X + 2.0f,
-			rect.Y - 1.0f,
-			(right ? rect.X - 2 : rect.X + 2.0f) + rect.Width,
-			rect.Y + rect.Height  - 1.0f);
-
-		m_Target->DrawTextW(str, strLen, ((TextFormatD2D&)format).m_TextFormat, dst, solidBrush);
+		m_Target->DrawTextLayout(
+			D2D1::Point2F(right ? rect.X - 2 : rect.X + 2.0f, rect.Y - 1.0f),
+			formatD2D.m_TextLayout,
+			solidBrush);
 
 		solidBrush->Release();
 	}
diff --git a/Common/Gfx/TextFormatD2D.cpp b/Common/Gfx/TextFormatD2D.cpp
index 04d4d40c..2dae6375 100644
--- a/Common/Gfx/TextFormatD2D.cpp
+++ b/Common/Gfx/TextFormatD2D.cpp
@@ -23,6 +23,7 @@ namespace Gfx {
 
 TextFormatD2D::TextFormatD2D() :
 	m_TextFormat(),
+	m_TextLayout(),
 	m_InlineEllipsis()
 {
 }
@@ -40,6 +41,12 @@ void TextFormatD2D::Dispose()
 		m_TextFormat = nullptr;
 	}
 
+	if (m_TextLayout)
+	{
+		m_TextLayout->Release();
+		m_TextLayout = nullptr;
+	}
+
 	if (m_InlineEllipsis)
 	{
 		m_InlineEllipsis->Release();
@@ -47,6 +54,40 @@ void TextFormatD2D::Dispose()
 	}
 }
 
+void TextFormatD2D::CreateLayout(const WCHAR* str, UINT strLen, float maxW, float maxH)
+{
+	bool strChanged = false;
+	if (strLen != m_LastString.length() ||
+		memcmp(str, m_LastString.c_str(), (strLen + 1) * sizeof(WCHAR)) != 0)
+	{
+		strChanged = true;
+		m_LastString.assign(str, strLen);
+	}
+
+	if (m_TextLayout && !strChanged)
+	{
+		if (maxW != m_TextLayout->GetMaxWidth())
+		{
+			m_TextLayout->SetMaxWidth(maxW);
+		}
+
+		if (maxH != m_TextLayout->GetMaxHeight())
+		{
+			m_TextLayout->SetMaxWidth(maxH);
+		}
+	}
+	else
+	{
+		if (m_TextLayout)
+		{
+			m_TextLayout->Release();
+			m_TextLayout = nullptr;
+		}
+
+		CanvasD2D::c_DW->CreateTextLayout(str, strLen, m_TextFormat, maxW, maxH, &m_TextLayout);
+	}
+}
+
 void TextFormatD2D::SetProperties(const WCHAR* fontFamily, int size, bool bold, bool italic, Gdiplus::PrivateFontCollection* fontCollection)
 {
 	Dispose();
diff --git a/Common/Gfx/TextFormatD2D.h b/Common/Gfx/TextFormatD2D.h
index 10a0d769..7e44bf39 100644
--- a/Common/Gfx/TextFormatD2D.h
+++ b/Common/Gfx/TextFormatD2D.h
@@ -20,6 +20,7 @@
 #define RM_GFX_TEXTFORMATD2D_H_
 
 #include "TextFormat.h"
+#include <string>
 #include <dwrite.h>
 
 namespace Gfx {
@@ -44,8 +45,16 @@ private:
 
 	void Dispose();
 
+	// Creates a new DirectWrite text layout if |str| has changed since last call. Since creating
+	// the layout is costly, it is more efficient to keep reusing the text layout until the text
+	// changes.
+	void CreateLayout(const WCHAR* str, UINT strLen, float maxW, float maxH);
+
 	IDWriteTextFormat* m_TextFormat;
+	IDWriteTextLayout* m_TextLayout;
 	IDWriteInlineObject* m_InlineEllipsis;
+
+	std::wstring m_LastString;
 };
 
 }  // namespace Gfx