starred/terminal
1
0
Fork 0
mirror of https://github.com/microsoft/terminal.git synced 2026-02-04 05:35:20 +00:00
Code Issues 19.0k Packages Projects Releases 20 Wiki Activity

Translate all Dispatcher().RunAsync([](){}) lambdas into coroutines #5517

New Issue
Closed
opened 2026-01-31 00:15:15 +00:00 by claunia · 6 comments
claunia commented 2026-01-31 00:15:15 +00:00
Owner
Copy Link

Originally created by @DHowett-MSFT on GitHub (Dec 11, 2019).

I believe there is a trivial mechanical translation that'll get us better code clarity and perhaps a better understanding of the flow of ownership through our code.

from

void TerminalPage::_SetFocusedTabIndex(int tabIndex)
{
    auto tab = _tabs.at(tabIndex);
    auto weakThis{ get_weak() };
    _tabView.Dispatcher().RunAsync(CoreDispatcherPriority::Normal, [tab, weakThis]() {
        if (auto page{ weakThis.get() })
        {
            page->_tabView.SelectedItem(tab->GetTabViewItem());
        }
    });
}

to

winrt::fire_and_forget TerminalPage::_SetFocusedTabIndex(int tabIndex)
{
    // GH#1117: This is a workaround because _tabView.SelectedIndex(tabIndex)
    //          sometimes set focus to an incorrect tab after removing some tabs
    auto tab = _tabs.at(tabIndex);
    auto weakThis{ get_weak() };

    co_await winrt::resume_foreground(_tabView.Dispatcher()); // transition to the dispatcher thread

    if (auto page{ weakThis.get() })
    {
        page->_tabView.SelectedItem(tab->GetTabViewItem());
    }
}

There's a bunch more information about concurrency and coroutines in C++/WinRT here.

Originally created by @DHowett-MSFT on GitHub (Dec 11, 2019). I believe there is a trivial mechanical translation that'll get us better code clarity and perhaps a better understanding of the flow of ownership through our code. ### from ```c++ void TerminalPage::_SetFocusedTabIndex(int tabIndex) { auto tab = _tabs.at(tabIndex); auto weakThis{ get_weak() }; _tabView.Dispatcher().RunAsync(CoreDispatcherPriority::Normal, [tab, weakThis]() { if (auto page{ weakThis.get() }) { page->_tabView.SelectedItem(tab->GetTabViewItem()); } }); } ``` ### to ```c++ winrt::fire_and_forget TerminalPage::_SetFocusedTabIndex(int tabIndex) { // GH#1117: This is a workaround because _tabView.SelectedIndex(tabIndex) // sometimes set focus to an incorrect tab after removing some tabs auto tab = _tabs.at(tabIndex); auto weakThis{ get_weak() }; co_await winrt::resume_foreground(_tabView.Dispatcher()); // transition to the dispatcher thread if (auto page{ weakThis.get() }) { page->_tabView.SelectedItem(tab->GetTabViewItem()); } } ``` There's a bunch more information about concurrency and coroutines in C++/WinRT [here](https://docs.microsoft.com/en-us/windows/uwp/cpp-and-winrt-apis/concurrency-2).
claunia commented 2026-01-31 00:15:16 +00:00
Author
Owner
Copy Link

@DHowett-MSFT commented on GitHub (Dec 11, 2019):

Not to be in the business of nominating community members out of the blue to do labor on our behalf, but I really think @mkitzan might be great here: he's looked at a lot of ownership issues and dispatch queues lately, and this could be right up his alley.

@DHowett-MSFT commented on GitHub (Dec 11, 2019): Not to be in the business of nominating community members out of the blue to do labor on our behalf, but I really think @mkitzan might be great here: he's looked at a lot of ownership issues and dispatch queues lately, and this could be right up his alley.
claunia commented 2026-01-31 00:15:16 +00:00
Author
Owner
Copy Link

@zadjii-msft commented on GitHub (Dec 11, 2019):

Overall this does look better, though I'd want to be careful with this - the first pattern is a little more obvious when we're accidentally using this within the body of the dispatched lambda, while the second will make it easier for us to forget that we shouldn't be using this there.

Unless there's also another way for us to resume_foreground_unless_this_goes_away or something

@zadjii-msft commented on GitHub (Dec 11, 2019): Overall this does look better, though I'd want to be careful with this - the first pattern is a little more obvious when we're accidentally using `this` within the body of the dispatched lambda, while the second will make it easier for us to forget that we shouldn't be using `this` there. Unless there's also another way for us to `resume_foreground_unless_this_goes_away` or something
claunia commented 2026-01-31 00:15:16 +00:00
Author
Owner
Copy Link

@DHowett-MSFT commented on GitHub (Dec 11, 2019):

To be fair, using this is totally valid after the weak ref is locked. It may even be preferred as it lets us avoid having to access member variables on someOtherObject->

@DHowett-MSFT commented on GitHub (Dec 11, 2019): To be fair, using `this` is totally valid after the weak ref is locked. It may even be preferred as it lets us avoid having to access member variables on `someOtherObject->`
claunia commented 2026-01-31 00:15:17 +00:00
Author
Owner
Copy Link

@DHowett-MSFT commented on GitHub (Dec 11, 2019):

There's some suggestions here, actually: instead of making these weak, we can make them strong and perform the capture before the co_await.

Safely accessing the this pointer in a class-member coroutine

@DHowett-MSFT commented on GitHub (Dec 11, 2019): There's some suggestions here, actually: instead of making these _weak_, we can make them _strong_ and perform the capture before the `co_await`. [Safely accessing the _this_ pointer in a class-member coroutine](https://docs.microsoft.com/en-us/windows/uwp/cpp-and-winrt-apis/weak-references#safely-accessing-the-this-pointer-in-a-class-member-coroutine)
claunia commented 2026-01-31 00:15:17 +00:00
Author
Owner
Copy Link

@DHowett-MSFT commented on GitHub (Dec 11, 2019):

Oh my gosh, it gets even better. Check this out!

For a weak reference, call get_weak. C++/WinRT ensures that the resulting delegate holds a weak reference. At the last minute, and behind the scenes, the delegate attempts to resolve the weak reference to a strong one, and only calls the member function if it's successful.

event_source.Event({ get_weak(), &EventRecipient::OnEvent });
@DHowett-MSFT commented on GitHub (Dec 11, 2019): Oh my gosh, it gets even better. Check this out! > For a weak reference, call get_weak. C++/WinRT ensures that the resulting delegate holds a weak reference. At the last minute, and behind the scenes, the delegate attempts to resolve the weak reference to a strong one, and only calls the member function if it's successful. ``` event_source.Event({ get_weak(), &EventRecipient::OnEvent }); ```
claunia commented 2026-01-31 00:15:17 +00:00
Author
Owner
Copy Link

@mkitzan commented on GitHub (Dec 11, 2019):

Woah WinRT has it all! I'd be up to rework the Dispatcher().RunAsync calls to whatever pattern is decided on. I think the co routine pattern + get_strong() would be the most readable/understandable.
Also, I've been trying to turn one of the TermControl instances to the { get_weak(), &EventRecipient::OnEvent } form. However, the pointer to member form doesn't capture information about the arguments to provide the function and probably has to have specific parameters.

@mkitzan commented on GitHub (Dec 11, 2019): Woah WinRT has it all! I'd be up to rework the `Dispatcher().RunAsync` calls to whatever pattern is decided on. I think the co routine pattern + get_strong() would be the most readable/understandable. ~Also, I've been trying to turn one of the `TermControl` instances to the `{ get_weak(), &EventRecipient::OnEvent }` form. However, the pointer to member form doesn't capture information about the arguments to provide the function and probably has to have specific parameters.~
Sign in to join this conversation.
No Branch/Tag Specified
Branches Tags
Labels
Clear labels
⛺ Reserved
A11yCO
A11yMAS
A11ySev1
A11ySev2
A11ySev3
A11yTTValidated
A11yUsable
A11yVoiceAccess
A11yWCAG
Area-Accessibility
Area-AtlasEngine
Area-AzureShell
Area-Build
Area-Build
Area-Chat
Area-CmdPal
Area-CodeHealth
Area-Commandline
Area-CookedRead
Area-DefApp
Area-Extensibility
Area-Fonts
Area-GroupPolicy
Area-i18n
Area-Input
Area-Interaction
Area-Interop
Area-Localization
Area-Output
Area-Performance
Area-Portable
Area-Quality
Area-Remoting
Area-Rendering
Area-Schema
Area-Server
Area-Settings
Area-SettingsUI
Area-ShellExtension
Area-ShellExtension
Area-ShellExtension
Area-Suggestions
Area-Suggestions
Area-TerminalConnection
Area-TerminalControl
Area-Theming
Area-UserInterface
Area-VT
Area-Windowing
Area-WPFControl
AutoMerge
Blocking-Ingestion
Culprit-Centennial
Culprit-WinUI
Disability-All
Disability-Blind
Disability-LowVision
Disability-Mobility
External-Blocked-WinUI3
Fixed
Gathering-Data
good first issue
HCL-E+D
HCL-WindowsTerminal
Help Wanted
Impact-Compatibility
Impact-Compliance
Impact-Correctness
Impact-Visual
In-PR
InclusionBacklog
InclusionBacklog-Windows TerminalWin32
InclusionCommitted-202206
Issue-Bug
Issue-Docs
Issue-Feature
Issue-Feature
Issue-Question
Issue-Samples
Issue-Scenario
Issue-Task
Needs-Attention
Needs-Author-Feedback
Needs-Bisect
Needs-Discussion
Needs-Repro
Needs-Tag-Fix
Needs-Tag-Fix
Needs-Triage
No-Recent-Activity
Priority-0
Priority-1
Priority-2
Priority-3
Product-Cmd.exe
Product-Colortool
Product-Colortool
Product-Colortool
Product-Conhost
Product-Conpty
Product-Meta
Product-Powershell
Product-Terminal
Product-WSL
pull-request
Mirrored from GitHub Pull Request
 Resolution-Answered
Resolution-By-Design
Resolution-Duplicate
Resolution-External
Resolution-Fix-Available
Resolution-Fix-Committed
Resolution-No-Repro
Resolution-Won't-Fix
Severity-Blocking
Severity-Crash
Severity-DataLoss
spam
this-will-be-a-breaking-change
Tracking-External
WindowsTerminal_Win32
Work-Item
zAskModeBug
zInbox-Bug
No Label Area-CodeHealth Help Wanted Issue-Task Product-Terminal Resolution-Fix-Committed
Milestone
No items
No Milestone
Projects
Clear projects
No project
Assignees
Clear assignees
claunia
No Assignees
1 Participants
Notifications
Due Date
No due date set.
Dependencies

No dependencies set.

Reference: starred/terminal#5517
Delete Branch "%!s()"

Deleting a branch is permanent. Although the deleted branch may continue to exist for a short time before it actually gets removed, it CANNOT be undone in most cases. Continue?