Graphics.DrawString vs TextRenderer.DrawText?Which can Deliver Better Quality

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i’m going to cross-post my answer from over here, just so that the information gets around.

There are two ways of drawing text in .NET:

  • GDI+: graphics.MeasureString and graphics.DrawString
  • GDI: TextRenderer.MeasureText and TextRenderer.DrawText

In .NET 1.1 everything used GDI+ for text rendering. But there were some problems:

  • There are some performance issues caused by the somewhat stateless nature of GDI+, where device contexts would be set and then the original restored after each call.
  • The shaping engines for international text have been updated many times for Windows/Uniscribe and for Avalon (Windows Presentation Foundation), but have not been updated for GDI+, which causes international rendering support for new languages to not have the same level of quality.

So they knew they wanted to change the .NET framework to stop using GDI+‘s text rendering system, and use GDI. At first they hoped they could simply change:

graphics.DrawString

to call the old DrawText API, instead of GDI+. But they couldn’t make the text-wrapping and spacing match exactly as what GDI+ did.

In Windows Forms 2.0, we added support for drawing GDI text. At first we had grandiose plans of poking and prodding at the DrawText API such that we could make it match up exactly how GDI+’s DrawString API works. I actually think we got pretty close, but there are fundamental differences in word wrapping and character spacing that as mere consumers of the both APIs, Windows Forms could not solve.

So now we’re presented with a problem: we want to switch everyone over to the new TextRenderer APIs so text will look better, localize better, draw more consistently with other dialogs in the operating system… …but we dont want to break folks counting on GDI+ measure string for calculations of where their text should line up.

So they were forced to keep graphics.DrawString to call GDI+ (compatiblity reasons; people who were calling graphics.DrawString would suddenly find that their text didn’t wrap the way it used to). From MSDN:

The GDI based TextRenderer class was introduced in the .NET Framework 2.0 to improve performance, make text look better, and improve support for international fonts. In earlier versions of the .NET Framework, the GDI+ based Graphics class was used to perform all text rendering. GDI calculates character spacing and word wrapping differently from GDI+. In a Windows Forms application that uses the Graphics class to render text, this could cause the text for controls that use TextRenderer to appear different from the other text in the application. To resolve this incompatibility, you can set the UseCompatibleTextRendering property to true for a specific control. To set UseCompatibleTextRendering to true for all supported controls in the application, call the Application.SetCompatibleTextRenderingDefault method with a parameter of true.

A new static TextRenderer class was created to wrap GDI text rendering. It has two methods:

TextRenderer.MeasureText
TextRenderer.DrawText

Note: TextRenderer is a wrapper around GDI, while graphics.DrawString is still a wrapper around GDI+.

Then there was the issue of what to do with all the existing .NET controls, e.g.:

  • Label
  • Button
  • TextBox

They wanted to switch them over to use TextRenderer (i.e. GDI), but they had to be careful. There might be people who depended on their controls drawing like they did in .NET 1.1. And so was born “compatible text rendering“.

By default controls in application behave like they did in .NET 1.1 (they are “compatible“).

You turn off compatibility mode by calling:

Application.SetCompatibleTextRenderingDefault(false);

This makes your application better, faster, with better international support. To sum up:

SetCompatibleTextRenderingDefault(true)  SetCompatibleTextRenderingDefault(false)
=======================================  ========================================
 default                                  opt-in
 bad                                      good
 the one we don't want to use             the one we want to use
 uses GDI+ for text rendering             uses GDI for text rendering
 graphics.MeasureString                   TextRenderer.MeasureText
 graphics.DrawString                      TextRenderer.DrawText
 Behaves same as 1.1                      Behaves *similar* to 1.1
                                          Looks better
                                          Localizes better
                                          Faster

It’s also useful to note the mapping between GDI+ TextRenderingHint and the corresponding LOGFONT Quality used for GDI font drawing:

TextRenderingHint           mapped by TextRenderer to LOGFONT quality
========================    =========================================================
ClearTypeGridFit            CLEARTYPE_QUALITY (5) (Windows XP: CLEARTYPE_NATURAL (6))
AntiAliasGridFit            ANTIALIASED_QUALITY (4)
AntiAlias                   ANTIALIASED_QUALITY (4)
SingleBitPerPixelGridFit    PROOF_QUALITY (2)
SingleBitPerPixel           DRAFT_QUALITY (1)
else (e.g.SystemDefault)    DEFAULT_QUALITY (0)

Samples

Here’s some comparisons of GDI+ (graphics.DrawString) verses GDI (TextRenderer.DrawText) text rendering:

GDI+: TextRenderingHintClearTypeGridFit, GDI: CLEARTYPE_QUALITY:

enter image description here

GDI+: TextRenderingHintAntiAlias, GDI: ANTIALIASED_QUALITY:

enter image description here

GDI+: TextRenderingHintAntiAliasGridFit, GDI: not supported, uses ANTIALIASED_QUALITY:

enter image description here

GDI+: TextRenderingHintSingleBitPerPixelGridFit, GDI: PROOF_QUALITY:

enter image description here

GDI+: TextRenderingHintSingleBitPerPixel, GDI: DRAFT_QUALITY:

enter image description here

i find it odd that DRAFT_QUALITY is identical to PROOF_QUALITY, which is identical to CLEARTYPE_QUALITY.

See also

  • UseCompatibleTextRendering – Compatible with whaaaaaat?
  • Sorting it all out: A quick look at Whidbey’s TextRenderer
  • MSDN: LOGFONT Structure
  • AppCompat Guy: GDI vs. GDI+ Text Rendering Performance
  • GDI+ Text, Resolution Independence, and Rendering Methods.
    Or – Why does my text look different in GDI+ and in GDI?

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