Can you create an information context for the display?

Raymond Chen

Adrian McCarthy asks, “Can you create an information context for the display? … I can call CreateDC(“DISPLAY”), but perhaps that wouldn’t generalize for a multiple-monitor display with different settings on each screen. I’m trying to avoid constantly creating and destroying DCs when all I need to do is measure strings, check color depth, dpi, etc.” I admire the effort of trying to avoid creating a whole DC when all you want is to perform some inquiries. Some inquiries are monitor-independent, like getting the DPI or measuring strings, so you can just use GetDC(NULL) to get a temporary DC. This is cheaper than a full-on CreateDC since GetDC goes through the DC cache, so you’re just grabbing a DC out of the cache temporarily, doing a little computation, and then returning it to the cache (with ReleaseDC). If you are doing something that is monitor-specific, like getting its color depth, you can call EnumDisplayMonitors on the desktop DC to look at each monitor. (And just for completeness, to get the name for a specific monitor if you really do want to create an IC for it, call GetMonitorInfo with a MONITORINFOEX and look at the szDevice member.)

Update: Original text said “DC” in the last sentence by mistake.

Raymond Chen

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