From 37fd10565080352d9e03a1dcdd5a88e02537d6f8 Mon Sep 17 00:00:00 2001
From: Birunthan Mohanathas <birunthan@mohanathas.com>
Date: Wed, 31 Jul 2013 13:09:48 +0300
Subject: [PATCH] Gfx: Add Util::GetAdjustedDWriteTextLayoutMetrics to reduce
 code duplication

---
 Common/Gfx/CanvasD2D.cpp          | 45 +++++++------------------------
 Common/Gfx/Util/DWriteHelpers.cpp | 24 +++++++++++++++++
 Common/Gfx/Util/DWriteHelpers.h   |  5 ++++
 3 files changed, 39 insertions(+), 35 deletions(-)

diff --git a/Common/Gfx/CanvasD2D.cpp b/Common/Gfx/CanvasD2D.cpp
index 52429d6f..4db268cb 100644
--- a/Common/Gfx/CanvasD2D.cpp
+++ b/Common/Gfx/CanvasD2D.cpp
@@ -19,6 +19,7 @@
 #include "CanvasD2D.h"
 #include "TextFormatD2D.h"
 #include "Util/DWriteFontCollectionLoader.h"
+#include "Util/DWriteHelpers.h"
 #include "Util/WICBitmapLockGDIP.h"
 #include "../../Library/Litestep.h"
 
@@ -321,7 +322,7 @@ void CanvasD2D::DrawTextW(const WCHAR* str, UINT strLen, const TextFormat& forma
 
 		if (!m_AccurateText && m_TextAntiAliasing)
 		{
-			float emOffset = xOffset / 25.0f;
+			const float emOffset = xOffset / 25.0f;
 
 			DWRITE_TEXT_RANGE range = {0, strLen};
 			Microsoft::WRL::ComPtr<IDWriteTextLayout1> textLayout;
@@ -349,23 +350,10 @@ bool CanvasD2D::MeasureTextW(const WCHAR* str, UINT strLen, const TextFormat& fo
 		textLayout.GetAddressOf());
 	if (SUCCEEDED(hr))
 	{
-		DWRITE_TEXT_METRICS metrics;
-		textLayout->GetMetrics(&metrics);
-
-		if (!m_AccurateText)
-		{
-			float size = 0.0f;
-			textLayout->GetFontSize(0, &size);
-
-			rect.Width = floor(metrics.width + (size / 2.05f) + (metrics.width / 55.0f) - 0.5f);
-			rect.Height = floor(metrics.height + (size / 9.25f) + 0.3f);
-		}
-		else
-		{
-			rect.Width = metrics.width;
-			rect.Height = metrics.height;
-		}
-
+		const DWRITE_TEXT_METRICS metrics =
+			Util::GetAdjustedDWriteTextLayoutMetrics(textLayout.Get(), !m_AccurateText);
+		rect.Width = metrics.width;
+		rect.Height = metrics.height;
 		return true;
 	}
 
@@ -386,23 +374,10 @@ bool CanvasD2D::MeasureTextLinesW(const WCHAR* str, UINT strLen, const TextForma
 		textLayout.GetAddressOf());
 	if (SUCCEEDED(hr))
 	{
-		DWRITE_TEXT_METRICS metrics;
-		textLayout->GetMetrics(&metrics);
-
-		if (!m_AccurateText)
-		{
-			float size = 0.0f;
-			textLayout->GetFontSize(0, &size);
-
-			rect.Width = floor(metrics.width + (size / 2.05f) + (metrics.width / 55.0f) - 0.5f);
-			rect.Height = floor(metrics.height + (size / 9.25f) + 0.3f);
-		}
-		else
-		{
-			rect.Width = metrics.width;
-			rect.Height = metrics.height + 1.0f;
-		}
-
+		const DWRITE_TEXT_METRICS metrics =
+			Util::GetAdjustedDWriteTextLayoutMetrics(textLayout.Get(), !m_AccurateText);
+		rect.Width = metrics.width;
+		rect.Height = metrics.height;
 		lines = metrics.lineCount;
 		return true;
 	}
diff --git a/Common/Gfx/Util/DWriteHelpers.cpp b/Common/Gfx/Util/DWriteHelpers.cpp
index a93d6377..1f564acd 100644
--- a/Common/Gfx/Util/DWriteHelpers.cpp
+++ b/Common/Gfx/Util/DWriteHelpers.cpp
@@ -18,10 +18,34 @@
 
 #include "DWriteHelpers.h"
 #include <wrl/client.h>
+#include <cmath>
 
 namespace Gfx {
 namespace Util {
 
+DWRITE_TEXT_METRICS GetAdjustedDWriteTextLayoutMetrics(
+	IDWriteTextLayout* textLayout, bool gdiEmulation)
+{
+	DWRITE_TEXT_METRICS metrics;
+	textLayout->GetMetrics(&metrics);
+
+	if (gdiEmulation)
+	{
+		float size = 0.0f;
+		textLayout->GetFontSize(0, &size);
+		metrics.width = floor(metrics.width + (size / 2.05f) + (metrics.width / 55.0f) - 0.5f);
+		metrics.height = floor(metrics.height + (size / 9.25f) + 0.3f);
+	}
+	else
+	{
+		// GDI+ draws multi-line text even though the last line may be clipped slightly at the bottom.
+		// This is a workaround to emulate that behaviour.
+		metrics.height += 1.0f;
+	}
+
+	return metrics;
+}
+
 HRESULT GetDWritePropertiesFromGDIProperties(
 	IDWriteFactory* factory, const WCHAR* gdiFamilyName, const bool gdiBold, const bool gdiItalic,
 	DWRITE_FONT_WEIGHT& dwriteFontWeight, DWRITE_FONT_STYLE& dwriteFontStyle,
diff --git a/Common/Gfx/Util/DWriteHelpers.h b/Common/Gfx/Util/DWriteHelpers.h
index 1140e2a5..278f0b36 100644
--- a/Common/Gfx/Util/DWriteHelpers.h
+++ b/Common/Gfx/Util/DWriteHelpers.h
@@ -24,6 +24,11 @@
 namespace Gfx {
 namespace Util {
 
+// If |gdiEmulation| is true, the returns metrics have similar characteristics to those provided
+// by GDI+.
+DWRITE_TEXT_METRICS GetAdjustedDWriteTextLayoutMetrics(
+	IDWriteTextLayout* textLayout, bool gdiEmulation);
+
 // Maps the GDI family name and italic/bold flags to the DirectWrite family name, weight, style,
 // and stretch.
 HRESULT GetDWritePropertiesFromGDIProperties(