Loadcursor and Mixed Dpi Multiple Monitors
When the Loadcursor Function Is Used to Load a Cursor from a Resource, the Resulting Hcursor Can Be Used Across Different Monitors and Always Appears at the...
When the LoadCursor function is used to load a cursor from a resource, the resulting HCURSOR can be used across different monitors and always appears at the correct size.
ie: typically:
- on a 96 dpi monitor the 32x32 resource is used,
- on a 192 dpi monitor the 64x64 resource is used.
However, when a cursor is programmatically created from memory (say using LookupIconIdFromDirectoryEx and CreateIconFromResourceEx) the resulting cursor has a fixed resolution. This means it appears at the wrong size on at least one monitor in a mixed DPI multi-monitor setup.
I also checked out the LoadCursorFromFile and it too provides this dynamic resolution behaviour like LoadCursor.
Is there a way to programmatically create a cursor that dynamically switches depending which monitor it's shown on? What magic is going on behind the scenes for cursors loaded with LoadCursor to work differently?
1 Answer
After much experimentation I finally discovered that WPF can load cursors from resource and memory streams and get the correct DPI behaviour if the scaleWithDpi option is used:
public Cursor(Stream cursorStream, bool scaleWithDpi)
Looking at the reference source it ends up in the function LoadFromStream which loads the stream by writing it to a temporary file and the loading from the file. See source
To sum up:
- It seems the only way to get a dynamic DPI cursor like this is with the Win32 native resource loading functions and by loading from a file. It doesn't seem like you can load a cursor directly from memory with this behavior.
- The "dynamic dpi" part of this behavior seems to be related to the
LR_DEFAULTSIZEflag passed to theLoadImagefunction.
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