Native Tooltips in WPF (Part 1)

View source on GitHub.

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One of my hobbies is getting WPF controls to look more like their native counterparts. I’ve been shoehorning the UxTheme APIs (and older equivalents when theming is unavailable) into something that can be used by WPF over the past year or more, and I’ll write about this process at some point in the future (I’ve implemented native-looking push buttons, radio buttons, checkboxes, scrollbars, list views/list view items, text boxes, group boxes and read-only combo boxes). These efforts pay off the most in Windows 8, since WPF’s theme for that OS leaves much to be desired (just look at the push buttons!). This isn’t entirely surprising given that the theme wasn’t finalised until post-RC, leaving the WPF team without much time to do a good job.

</preamble>

In this post I’ll compare WPF tooltips with Win32 tooltips, and in part 2 I’ll demonstrate how to use Win32 tooltips in a WPF application and post some sample code.

Tooltips in WPF look more or less like traditional Windows tooltip controls. Here are some advantages and disadvantages of each:

WPF Tooltips

Advantages:

• Can host any content, not just text.
• Style them like any WPF control.
• Drop shadow fades in and out.

Disadvantages:

• Colours aren’t quite the same as native tooltips.
• Weird bottom margin/padding with Aero theme.
• Drop shadows don’t look exactly like Win32 tooltip shadows.
• Drop shadows are missing in the Windows 8 theme, regardless of system settings (can be fixed by modifying the control template, which is missing SystemDropShadowChrome, meaning the ‘HasDropShadow’ property does nothing).
• No ClearType without RenderOptions.ClearTypeHint.

Win32 Tooltips

Advantages:

• Consistent with tooltips in native applications.

Disadvantages:

• Can only display text (displaying other things is non-trivial).
• Can’t be styled.
• Drop shadows don’t fade in or out.
• Animations sometimes don’t fire (particularly the fade-in animation).
• Updating the text of an open tooltip can cause redraw flicker.
• Custom positioning can involve a lot of work.

There are some other very minor differences:

• The algorithm for finding the position under the mouse is different in WPF, even though it’s based on the ‘_GetHcursorPdy3’ function from tooltips.cpp, according to the reference source.
• When the content of a native tooltip changes, the tooltip will be repositioned beneath the cursor. WPF tooltips remain fixed in place.