Debugging Uno.UI
Debugging Uno.UI samples
To debug the SamplesApp in the Uno.UI solution, which includes an extensive set of samples and test cases for the controls supported by Uno.UI, as well as non-UI features:
- Clone the repo, and ensure using a short target path, e.g. D:\uno etc.
Note
This is required to avoid path length limitations in the .NET framework being used by Visual Studio.
- Open the solution filter in Visual Studio for the target platform you wish to run on, as detailed here.
- Set
SamplesApp.[TargetPlatform]
as the selected Startup Project. - Launch the samples app from Visual Studio.
See this article for more information on working with the SamplesApp and authoring new samples.
Debugging Uno in another application
It is also possible to debug Uno.UI code in an application outside the Uno.UI solution. The Uno.UI build process has an opt-in mechanism to overwrite the contents of the NuGet cache, causing the application to use your local build of Uno.
This is useful when debugging a problem that can't easily be reproduced outside the context of the app where it was discovered.
It can even speed up your development loop when working on a new feature or fixing a bug with a standalone repro, because a small 'Hello World' app builds considerably faster than the full SamplesApp.
First, you'll need to install, in the app you want to debug with, a published Uno.WinUI package version which is close to your branch's code, preferably a -dev.xxx
version. When using an Uno.SDK app, this version can be found in the readme file of the Uno.Sdk package, or in the solution explorer packages node for the project.
Then, here are the steps to use a local build of Uno.UI in another application:
- Configure the Uno.UI solution to build for the target platform you wish to debug, as detailed here.
- Close any instances of Visual Studio with the Uno.UI solution opened.
- Open the solution containing the application you wish to debug to ensure the package is restored and cached.
- Prepare the application
- Replace the Uno.Sdk references to
Uno.Sdk.Private
everywhere in the app (e.g.global.json
,props
,csproj
, andtargets
files). Make sure to wait for the NuGet packages to be restored entirely. - Note the NuGet version of Uno.WinUI (or Uno.WinUI.WebAssembly/Uno.WinUI.Skia) or Uno.Sdk being used by the application (eg
5.1.0-dev.432
).
- Replace the Uno.Sdk references to
- Make a copy of
src/crosstargeting_override.props.sample
and name it assrc/crosstargeting_override.props
. - In
src/crosstargeting_override.props
, uncomment the line<!--<UnoNugetOverrideVersion>xx.xx.xx-dev.xxx</UnoNugetOverrideVersion>-->
as well as theUnoTargetFrameworkOverride
to match your app's debugging target. - Replace the version number with the version being used by the application you wish to debug.
- Open the appropriate Uno.UI solution filter and build the following:
- For iOS/Android native, you can right-click on the
Uno.UI
project - For WebAssembly/native, you can right-click on the
Uno.UI.Runtime.WebAssembly
project - For Skia, you can right-click on the corresponding
Uno.UI.Runtime.Skia.[Win32|X11|macOS|iOS|Android|Wpf]
project.
- For iOS/Android native, you can right-click on the
To debug Uno.UI code in the application, follow these steps (using FrameworkElement.MeasureOverride()
as an example):
- Open
FrameworkElement.cs
in the Uno.UI solution. - Right-click on the
FrameworkElement.cs
tab header in Visual Studio and choose 'Copy Full Path'. - Switch to the Visual Studio instance where your application is open.
- In your application solution, choose File->Open->File... or simply
Ctrl+O
, paste the path toFrameworkElement.cs
into the file open dialog, and openFrameworkElement.cs
in the application solution. - Put a breakpoint in the
MeasureOverride()
method. - Launch the application.
- You should hit the breakpoint, opening the
FrameworkElement.cs
file, and be able to see local variable values, etc. - To revert to the original Uno.UI version from NuGet, simply navigate to the NuGet cache folder (
%USERPROFILE%\.nuget\packages
) and delete theUno.UI
folder within it. You may need to close Visual Studio first. The original version will be automatically restored the next time the application builds.
Tips about the NuGet version override process
Be aware that setting
UnoNugetOverrideVersion
will overwrite your local NuGet cache for the nominated Uno.UI version. Any applications that you build locally will use your local build if they depend on that Uno.UI version.Building for Android requires the API level to match the version you specified in
UnoTargetFrameworkOverride
. A common issue is that the app being debugged uses Android 10.0, andUno.UI
is built using Android 11.0. You can change the API level in the debugged project's build properties.The NuGet override process only works on already installed versions. The best way to ensure that the override is successful is to build the debugged application once before overriding the Uno.UI version the app uses.
Make sure to close the application that uses the overridden nuget package, to avoid locked files issues on Windows.
Troubleshooting
It may happen that the package cache for the version you're debugging is corrupted, and the override is not working as intended.
If this is the case:
- In your debugged app, install another package version you've never debugged with
- Make sure to build the app once to populate the NuGet cache
- Rebuild the Uno.UI project (or Uno.UI.WebAssembly/Uno.UI.Runtime.Skia.*) to replace the binaries with your debug versions
- Rebuild your app and debug it again
Microsoft Source Link support
Uno.UI supports SourceLink and it now possible to step into Uno.UI without downloading the repository.
Make sure Enable source link support check box is checked in Tools / Options / Debugging / General properties page.