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In my opinion, Twips is a measurement factor comparable to mm or cm or inch. I thought, it is possible to get with this measurement an output on the screen, which can be measured by a lineal.

In this example, my windows system tells me, the DPI of the monitor is 96. The monitor has a resolution of 3840px x 1600px, which is the native resolution. The scaling factor for output is 100%.

Now I put a button with the width of 1890 Twips on screen. I measured the displayed pixel on screen, which is in fact 126 px. It can be reproduced with 1890 = 1440/96 * 126px

When I calculate 1890 Twips to centimeters, I get roundabout 3.33 cm. I hoped to find this measure on the screen, but I failed. When I measure the button width on the screen, I get 2.85 cm.

So anything is wrong here. The system is lying about the true dpi of my monitor, which is in fact 3,33cm / 2,85cm * 96 dpi = 112,16 dpi

Can anybody explain the results? To make WYSIWYG I thought, I can measure directly from screen.

Symundo
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  • DPI is approximate measurement, not actual hardware one. See: [DPI and DIPs](https://microsoft.github.io/Win2D/WinUI3/html/DPI.htm) – Dalija Prasnikar Oct 16 '21 at 07:25
  • By the way: with this result it is indeed stupid, to use Twips in general. I can as well use pixel, because I never get an output in true measures. Does the system provide any information about the correction factor, when the 96dpi is a pure virtual unit? – Symundo Oct 16 '21 at 07:47
  • Maybe there is some information accessible through WMI, but I am not sure as I never needed to get actual DPI of a monitor. – Dalija Prasnikar Oct 16 '21 at 08:17
  • I think, it is somehow necessary. Think about a CAD, which is showing 100% of given measures in your drawings. 100% means in my opinion, I can measure directly on screen. How will a system provide the "100%", when the true DPI of the monitor is unknown? – Symundo Oct 16 '21 at 08:22
  • Thanks, because of that the scaling information 100% is lying. I think, with HDMI and newer technology it is indeed possible to get the true physical dpi. I will try to calculate the correction factor between LOGDPI and PHYSDPI, when measures of physical screen size are available. – Symundo Oct 16 '21 at 08:57

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