We need to use the built-in WinForms tooltip control to display a very long tooltip (about 4000 characters) for one of our controls. But if we do so, the form freezes for a minute or two when we place the mouse pointer into the target control to see the tip. And nothing happens after that.
We experimented and detected that the standard tooltip starts to work very slow when it has about 2000 chars, and the situation becomes much worse when we increase the number of chars. Is it a known issue, and is there any workaround for it? Please, don't suggest to trim the tip text - we need to display the string as is.
When you assign a string of text to a ToolTip, part of the process of drawing it involves calls to USP10.dll which handles Unicode layout of characters on screen. I was able to see this by looking at the stack trace while the program was freezing. The performance of this layout is terrible for long strings.
Disabling Visual Styles for the application (commenting out EnableVisualStyles()) fixed the problem - the tooltip displays immediately, though this is not an optimal solution.
I kept looking and found this page which indicates the problem may be linked to layout of long strings where word-wrap is necessary. By inserting line breaks into the tooltip text, I found that the string displayed immediately. So, if you can determine where to insert the line breaks manually, the ToolTip should display quickly.