GDI text in large point sizes is slow to render since Creators update

[Terence Kelly]

I am posting here in the hope that someone at Microsoft will realize that they created a problem with the rendering of GDI text in large point sizes in the Creators update to Windows 10. While smaller point sizes render at "normal" speed, anything 36 point or larger renders v e r y s l o w l y. As the author of music notation software that runs just fine under the first two versions of Windows 10, I was surprised to see a radical slowdown under the Creators update when using a high dpi monitor. I upgraded my program to work in a high dpi environment when Windows 8.1 was released, but high dpi requires that the standard size of the Musical Symbols font be at least 36 points to be legible. The Creators update takes over twice as long to render the font, and since music notation requires a separate call to TextOut() for every note or notehead, my program slows to a crawl. In standard resolution it runs normally unless I scale the output larger, whereupon it slows immediately. I have observed the behavior consistently on three different Windows 10 systems, and found references on the internet to a number of other GDI programs with the same issue. It definitely is something that affects GDI text across the board. The only workaround I've found so far is to turn off clear type, but that should not be necessary. I'm guessing that the alterations added to the Creators update to intercept and scale older WIN32 programs to high dpi somehow messed up GDI text that is properly coded for high dpi. I tried changing all the compatibility settings for scaling, but they have no effect. I have made a pdf showing the difference in rendering times between version 1607 and 1709, but apparently it is too large to post here. If someone could possibly forward this post to the team that worked on high dpi scaling that would be great. Even an e-mail address for a contact to the high dpi team would be helpful. Then I could make sure my data gets to someone who knows what I'm talking about.

Terry Kelly

 

[Regedit32]

Hi Terrence,

This is a Windows 10 Forum, but no one here works for Microsoft.

If you are wanting to inform Microsoft of an issue you should:

• Click Start
• Scroll down and select Feedback Hub and create a post there on this issue