Can someone explain in laymans terms what DPI resolution is, and whether it is a characteristic of a monitor or the operating system

I have a Winforms application that is working correctly on various versions of windows and various resolutions. When the application runs on a Motion CL900 tablet, however, the layouts are completely messed up; mainly caused by panel controls that are perfectly sized on other computers now being too small and causing scrollbars. The Motion devices are running Windows 7 Professional.

I have read on a few posts on stackoverflow that Windows machines have a s开发者_如何学Ctandard DPI of 96, but this device clearly isn't 96 DPI. Is the fact that this device is "non-standard" a result of it's screen or is it caused by a setting in it's OEM version of Windows 7? I have read that I must set AutoScalingDimensions for my form to reflect the DPI of the PC I am developing on. But how do I even know what DPI my machine/screen is that I am developing on?

I have the following in my designer file for the form that has the layout issues:

this.AutoScaleDimensions = new System.Drawing.SizeF(96F, 96F);
this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Dpi;

I would appreciate anyone who has had experience with working with Winforms at various DPI resolutions shedding some light on this question, and maybe give some guidelines for .Net developers how to successfully handle non-standard DPIs.

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There's indeed two different uses of the term here:

1. The display device's native resolution. This is actually how many pixels are within 2.54 cm. Larger values mean obviously a clearer, but smaller picture overall.

2. The OS' scaling of fonts and widgets. 96 dpi is the "native" size for Windows for example. That is, if you have a display that also has 96 dpi, then the controls are the size they should be when you look at them. Also point sizes for fonts are exactly the right size, then. If you have a display with, say, 120 dpi and set the OS to that measure too and then put both side by side you could measure with a ruler and find widgets and fonts in both cases to be the same size.

Nowadays the second measure mostly controls widget size if your eyes are not capable of working with too small controls. And plenty of applications have problems displaying correctly if you change it, although it's far better since Vista.

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Dot per inch are related to the monitor/video card/resolution and just means how many points (or pixels) are shown in the length unit (inch).

Clearly is not related to the OS because you can have same values in all OS (Windows, Linux, Mac)...

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DPI is dots per inch and it is a setting you can set in your OS. However, it is a characteristic of the monitor.

Since you are on Windows 7, to change DPI settings, you would want to do:

1. Control Panel
2. Appearance and Personalization
3. Display
4. Set Custom Text Size (DPI) - (on side bar)

Just change it till you get to 96 DPI (100% usually).

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Windows 7 has an option in the Display properties called "Set custom text size (DPI)" if this is set to more than 100% it can impact how elements appear in an application, and can cause layout problems. I'd recommend keeping this at 100%, which is 96 DPI in Windows terms.

Note: the actual DPI resolution is determined by your monitor.