How to Convert this DPI Matrix transform code into C++?

Question

How to Convert this DPI Matrix transform code into C++?

MERUN KUMAR MAITY 636

Here is the code -

public class DpiDecorator : Decorator
     {
         public DpiDecorator()
         {
             this.Loaded += (s, e) =>
             {
                 System.Windows.Media.Matrix m = PresentationSource.FromVisual(this).CompositionTarget.TransformToDevice;
                 ScaleTransform dpiTransform = new ScaleTransform(1 / m.M11, 1 / m.M22);
                 if (dpiTransform.CanFreeze)
                     dpiTransform.Freeze();
                 this.LayoutTransform = dpiTransform;
             };
         }
     }

Viorel 122.6K Reputation points

2021-09-26T01:52:50.41+00:00

What kind of C++ project are you developing?
MERUN KUMAR MAITY 636 Reputation points

2021-09-26T14:59:46.59+00:00

Thank you sir, for your reply. Actually, I am developing a Win32 base C++ application to handle the DPI changes of any monitor and scale the user interfaces according to my choice. Another important question is my main project is WPF base so I have nothing to do with C++ because WPF is rely on C# and XAML. But I am unable to handle the DPI changes of my WPF application I tried a lot that means I use the Microsoft Per Monitor DPI and declare it in my WPF application application manifest but still my WPF application UI is not resizing as I want.

So, someone told me that I should use Win32 API for this purpose because they have some kind of WM_DPICHNAGE functionality which can handle this things flawlessly. But I don't know how to call that Win32 C++ DLL from my WPF application, I tried a lot but don't know how to do that.

That's why I think I should write my own C++ code to handle this DPI transformation.

If you know how to achieve this then please tell me.
Xiaopo Yang - MSFT 12,731 Reputation points Microsoft External Staff

2021-09-28T02:06:36.893+00:00

It seems m.M11 = LOGPIXELSX / 96 and m.M22 = LOGPIXELSY / 96 and Perhaps the GDI+ can also get the Matrix.

1 answer

Your answer

Viorel 122.6K Reputation points

2021-09-26T01:52:50.41+00:00

What kind of C++ project are you developing?
MERUN KUMAR MAITY 636 Reputation points

2021-09-26T14:59:46.59+00:00

Thank you sir, for your reply. Actually, I am developing a Win32 base C++ application to handle the DPI changes of any monitor and scale the user interfaces according to my choice. Another important question is my main project is WPF base so I have nothing to do with C++ because WPF is rely on C# and XAML. But I am unable to handle the DPI changes of my WPF application I tried a lot that means I use the Microsoft Per Monitor DPI and declare it in my WPF application application manifest but still my WPF application UI is not resizing as I want.

So, someone told me that I should use Win32 API for this purpose because they have some kind of WM_DPICHNAGE functionality which can handle this things flawlessly. But I don't know how to call that Win32 C++ DLL from my WPF application, I tried a lot but don't know how to do that.

That's why I think I should write my own C++ code to handle this DPI transformation.

If you know how to achieve this then please tell me.
Xiaopo Yang - MSFT 12,731 Reputation points Microsoft External Staff

2021-09-28T02:06:36.893+00:00

It seems m.M11 = LOGPIXELSX / 96 and m.M22 = LOGPIXELSY / 96 and Perhaps the GDI+ can also get the Matrix.

Answer 1

Castorix31 90,686

This code is for WPF
You can find the same code (less compacted, in different functions) in MS C++ sample : PerMonitorDPIWindow.cpp

MERUN KUMAR MAITY 636 Reputation points

2021-09-26T15:09:14.227+00:00

Thank your sir, for your reply. Actually, my main project is WPF base so I have nothing to do with C++ because WPF is rely on C# and XAML. But I am unable to handle the DPI changes of my WPF application I tried a lot that means I use the Microsoft Per Monitor DPI and declare it in my WPF application application manifest but still my WPF application UI is not resizing as I want.

So, someone told me that I should use Win32 API for this purpose because they have some kind of WM_DPICHNAGE functionality which can handle this things flawlessly. But I don't know how to call that Win32 C++ DLL from my WPF application, I tried a lot but don't know how to do that.

That's why I think I should write my own C++ code to handle this DPI transformation.

If you know how to achieve this then please tell me.
Castorix31 90,686 Reputation points

2021-09-26T15:25:59.337+00:00

The link I posted does exactly that...
(WPF c# project with a C++ DLL wich handles Per-monitor DPI )
MERUN KUMAR MAITY 636 Reputation points

2021-09-26T18:26:02.28+00:00

Thank you sir for your reply. But this is not the answer which I want to get.

By the way, can you help me to understand the answer of this stack overflow question. And this is the answer I want to get. But I am unable to understand that.

This is the link : https://stackoverflow.com/questions/55538032/is-there-a-way-to-disable-scaling-for-all-the-wpf-application-even-if-windows-ha

Please help sir.
Castorix31 90,686 Reputation points

2021-09-26T18:55:05.513+00:00

Have you tested the MS project ?
Because it does what you asked and works fine =>
MERUN KUMAR MAITY 636 Reputation points

2021-09-26T19:10:10.563+00:00

OMG! sir. You working very hard for me. I understand what you want to say. In this GIF which you shown, is perfectly fine that means when you changing the scaling to 100% to 125% the WPF application window will also get scaled automatically and it's UI get bigger.

But I want this functionality on resolution changing. That means when I change the resolution from 1920*1080 to any lower resolution suppose 1366*768 then this UI scaling that means UI get bigger should happen instead of changing the scaling from 100% to 125%. That the thing I want.

which part of code should I change ? so, that I add this UI scalable functionality to the resolution changing.
Castorix31 90,686 Reputation points

2021-09-26T19:31:18.007+00:00

But you wrote
"I am unable to handle the DPI changes of my WPF application "
which is done in the MS application in WM_DPICHANGED message, in PerMonitorDPIWindow::HandleMessages

Changing the resolution does not change DPI, it sends the WM_DISPLAYCHANGE message, that you can handle in the same handler if you want to resize windows/controls
MERUN KUMAR MAITY 636 Reputation points

2021-09-26T19:41:56.067+00:00

Yes, whatever that is. Please tell me with a code example that how I do that with the resolution change or DPI change.
If you have some demo project then please give me. Please sir, help me last time. Do that coding for me. Because Win32 is over my head. I am unable to understand C++ it is too much complex.

Give some WPF example of this resolution change. I know it's can be done by the same handler but I request you to modify the code. Please last help sir.

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How to Convert this DPI Matrix transform code into C++?

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