Blank page with scale other than 100%

[ovidiumchis]

Is there an existing issue for this?

• I have searched both open/closed issues, no issue already exists.

CefSharp Version

151.3.170

Operating System

Windows 11

Architecture

x64

.Net Version

.NET 4.8.1

Implementation

WinForms

Reproduction Steps

Right Click on Desktop -> Display Settings -> Set the scale to 200%.
Run the application, load a webpage.

public void InitializeCefSharp()
{
        var cefSettings = new CefSettings();
        cefSettings.CefCommandLineArgs.Add("disable-gpu", "1"); // Disable GPU acceleration
        cefSettings.CefCommandLineArgs.Add("disable-gpu-vsync", "1"); //Disable GPU vsync
        cefSettings.CefCommandLineArgs.Add("do-not-de-elevate", "1");
        cefSettings.CefCommandLineArgs.Add("no-proxy-server", "1");
        cefSettings.CefCommandLineArgs.Add("content-shell-hide-toolbar", "1");
        Cef.Initialize(cefSettings);
        Cef.GetGlobalCookieManager().DeleteCookies("", "");
}

Expected behavior

Elements should scale correctly.

Actual behavior

A blank (white) page is displayed. Elements are there, as I can see the mouse icon change when I hover over certain areas of the page, where buttons/text usually is.

Regression?

This worked perfectly on 138.0.340.
Any other version after that, it did not work.

Known Workarounds

Tried several possible workarounds, nothing worked.

Does this problem also occur in the CEF Sample Application

No

Other information

I tried setting the DPI Awarness programatically, but it still didn't work.

internal static class NativeMethods
{
    [DllImport("user32.dll", SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    public static extern bool SetProcessDpiAwarenessContext(IntPtr value);

    // DPI_AWARENESS_CONTEXT_UNAWARE = ((DPI_AWARENESS_CONTEXT)-1)
    public static readonly IntPtr DPI_AWARENESS_CONTEXT_UNAWARE = new(-1);
}

[amaitland]

You are using .Net 4.8.1 so you should follow the instructions at https://learn.microsoft.com/en-us/dotnet/desktop/winforms/high-dpi-support-in-windows-forms?view=netframeworkdesktop-4.8 to make your application DPI aware.

Remove all your command line args if that doesn't work.

It's very unlikely this is a bug in CefSharp, more likely your application isn't configured as Chromium expects it to be.

[ovidiumchis]

@amaitland thanks for the instructions.
I did all the steps suggested in the doc, also removed all the line args, but I'm still facing the same issue.

Just a note, I had to set the DpiAwareness to Unaware.
If I set it to anything other than Unaware, all my forms get messed up to a point you can barely use the app.
The elements on the Web Page do appear if it's not set to Unware, but like for the other forms, they get messed up that you cannot actually use it.

I'm not necessarily saying that it's a bug, but something did change after version 138.0.340 that I need to adjust on my side.
At the moment, my only solution is to downgrade and stay on that version.

[ovidiumchis]

I think I nailed down the problematic combination.
The following scenarios happen at 1920 x 1200 and 200% Scale.

If DPI Awarness is ON, the Web Page loads properly all elements are there.
However, check what it does to the textbox/button.

Now, if I set the DPI Awarness to OFF, the C# elements are displayed properly.
But check the webpage. It added some sort of white border on the left/top,
Weird thing is, I cannot even scroll to see what happens on the right/bottom of the page.