Fastest API for rendering text in Windows Forms?

Question

We need to optimize the text rendering for a C# Windows Forms application displaying a large number of small strings in an irregular grid. At any time there can be well ove

Answer 1

On my Windows 7 64 Bit system TextOut is even a bit slower than DrawString! TextRenderer.DrawText is much slower than DrawString.

Answer 2

GDI is faster at drawing in general that GDI+. I worked on a project that had to draw thousands of lines and text strings and switching from GDI+ to GDI made a significant performance improvement. That was using Windows XP so I cannot comment on Vista. I would also recommend using double buffering for your drawing to also improve performance. Create a compatible off screen bitmap and reuse that each time you need to draw.

Answer 3

5000+ text rendering is slow even with GDI, especially if you need scrolling. Create a separate rendering thread and notify the UI thread every 200 ms and bitblt the current results. It gives a smooth user experience.

Answer 4

From recent experience, fastest text output is achieved via ExtTextOut with ETO_GLYPH_INDEX flag. This comes at a price, and it’s that you aren’t printing characters anymore, but font glyphs directly. This means that you need to translate your regular character strings to glyph indexes strings prior calling ExtTextOut, either by calling GetCharacterPlacement everytime, or calling this function just once to build your own translation table, that will be valid until a new font is selected in the DC. Remember that glyph indexes are 16bit, so you can store them in a Unicode string and call ExtTextOutW version regardless of original string character size.

Answer 5

A Microsoft developer has posted a GDI vs. GDI+ Text Rendering Performance article on his blog which answers the raw speed question: on his system, GDI DrawText was about 6 times faster than GDI+ DrawString.

If you need to be a real speed demon, TextOut is faster than DrawText, but you'll have to take care of clipping and word-wrapping yourself. ExtTextOut supports clipping.

GDI rendering (TextRenderer) will be more consistent with other parts of Windows using GDI; GDI+ tries to be device-independent and so some spacing and emboldening are inconsistent. See the SQL Server 2005 Surface Area Configuration tool for an example of inconsistent rendering.

Answer 6

Creating a C++/CLI interop class to do the drawing in native code will result in crazy-fast drawing. We've witnesses this and measured it.

If you're not up to doing that, we've found graphics.DrawString is just slightly faster than than TextRenderer.DrawText.