Go back to using implementation types in TermControl by DHowett · Pull Request #20721 · microsoft/terminal

Dustin L. Howett (DHowett) · 2026-09-25T19:33:01Z

This reverts a large part of #10051 and moves us back to using the native implementation-namespace types from TermControl to talk to ControlInteractivity and ControlCore.

I started down this rabbit hole because I was trying to get rid of InteractivityAutomationPeer, and I learned that we introduced it as a go-between for the process-split TermControl/Interactivity.

InteractviityAutomationPeer is not required, and removing it lets us get rid of some other mild annoyances:

We don't need to push the bounds of the control down into Interactivity any longer
Likewise for padding

Bounds and padding can simply be read directly from the control.

I also undid the move from HANDLE to uint64_t which was only required for projecting HANDLEs.

The only thing we risked losing out on was automatic event revokers, but this pull request adds winrt::auto_revoke support directly to til::event. It is suitably terrifying.

Dustin L. Howett (DHowett) · 2026-09-25T19:37:02Z

            _lastSwapChainHandle = std::move(duplicatedHandle);
            // Now bubble the event up to the control.
-            SwapChainChanged.raise(*this, winrt::box_value<uint64_t>(reinterpret_cast<uint64_t>(_lastSwapChainHandle.get())));
+            SwapChainChanged.raise(*this, nullptr);


change: the recipient will just call .SwapChainHandle on us...

Prevents us from having to use projected types just to see autorevokers.

Leonard Hecker (lhecker)

The middle comment may be worth addressing.

Leonard Hecker (lhecker) · 2026-10-07T21:44:30Z

-                _automationPeer = winrt::make<implementation::TermControlAutomationPeer>(get_strong(), padding, interactivityAutoPeer);
-                return _automationPeer;
-            }
+            _automationPeer = winrt::make_self<implementation::TermControlAutomationPeer>(get_strong());


This reference cycle was intentional right?

yes, TCAP stores it as a weak_ref actually but it needs the full realized pointer to hand to the parent class (inside xaml)

Leonard Hecker (lhecker) · 2026-10-07T21:46:29Z

+        {
+            return { til::math::rounding, control->_core->FontSize() };
+        }
+        return {};


Should probably """return""" UIA_E_ELEMENTNOTAVAILABLE, because other parts of the peer call GetFontSize() and would otherwise div-by-zero.

This pull request replaces all of HwndTerminal, which used to be a thin layer on top of TerminalCore.lib, with a new implementation that relies on the Interactivity and Core layers in TerminalControl.lib. We used to spend a lot of time reimplementing interactivity components for HwndTerminal or--if I'm being honest--letting it rot and never giving it the improvements the rest of the application got. Among those improvements: - Automatic scrolling finally works (as of #20710) - Selection works the same way as it does in Terminal proper (starts on the half-cell, uses an exclusive range) - Consistent double- and triple-click behavior without having to reimplement word- and line-wise expansion - Scroll wheel behavior - Shift+Click to suppress VT mouse mode - Scrolling and focus handling move down into the Win32 message loop from WPF This pull request seeks to get HwndTerminal back to where it was (plus the things we naturally get from switching over). In the future, we can more easily add: - title reporting (surprised we didn't have this) - clickable URLs - automatic copy-to-clipboard - right-click menu support - DTTERM window manipulation - shaders - Ctrl+Scroll zoom Implementation Details ---------------------- The WPF control is backed by a flat "C" API, which takes in a `void*` and does some stuff to it. We call that a `PTERM`. References to "Flat C" in this commit body describe the body of work below WPF. X-macros are used to fill out the definintions of every C API and bridge it to a properly typed C++ member function. Ugh. No more crap where we split the implementation into half C export and half C++ member. ControlCore and ControlInteractivity require something that looks like TerminalSettings. The WPF control only supports the most basic settings, in `struct TerminalTheme`, and so I've added a bridge WinRT type to adapt TerminalTheme to IXxxSettings. Most of the values it returns are our "defaults", and some of them are overridden. Core requires an `ITerminalConnection`, but the WPF API uses a pair of "write output" and "send input" callbacks. Flat C provides an ITerminalConnection that bridges those callbacks. It does not communicate connection state or anything else. Resizing is probably going to be a problem. Core requires a dispatcher queue to ensure that some operations happen on the UI thread. I have stubbed out an implementation of `IDispatcherQueue` that calls a couple function pointers with a context pointer; the WPF code hooks up to that and bridges it into the WPF dispatcher. Yes, the Core's dispatcher queue _is_ the WPF main UI thread. It has to be, otherwise we'll explode the first time we try to update the scroll bar. Prep work was done in #20713. To make the above easier, I removed all use of DispatcherTimer (see #20711). Attempts to use it will almost certainly cause the WPF control to implode. Core needed to be taught a couple tricks to start up targeting an HWND instead of a composition handle. See #20722 for more. Refs #20710 Refs #20711 Refs #20713 Refs #20722 Required #20721 Refs #20745 Related to #6999

Dustin L. Howett (DHowett) commented Sep 25, 2026

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Dustin L. Howett (DHowett) changed the title ~~Go back to using internal types in TermControl~~ Go back to using implementation types in TermControl Sep 28, 2026

github-advanced-security Bot found potential problems Sep 28, 2026

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Comment thread src/inc/til/winrt.h Fixed

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Dustin L. Howett (DHowett) force-pushed the dev/duhowett/stop-using-projection-for-control-innards branch from a752604 to 8067dca Compare September 29, 2026 22:22

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Dustin L. Howett (DHowett) force-pushed the dev/duhowett/stop-using-projection-for-control-innards branch from 2ba16ab to dd04072 Compare September 29, 2026 23:29

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Dustin L. Howett (DHowett) force-pushed the dev/duhowett/stop-using-projection-for-control-innards branch from dd04072 to 307abbb Compare September 29, 2026 23:33

Dustin L. Howett (DHowett) mentioned this pull request Sep 29, 2026

Remove ControlInteractivity and ControlCore from TermControl API #20745

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Dustin L. Howett (DHowett) added this pull request to stack #20746 September 29, 2026 23:43

Dustin L. Howett (DHowett) added 9 commits September 29, 2026 18:45

Undo most of 7f3bc3c

5c8399b

Undo the HANDLE<->uint64 stuff from 7f3bc3c

25efa9f

Fixes, plus remove TermControlAutoPeer from idl

e86fd74

everything but the event handlers

7ac2c15

remove all get_self on com_ptr types

cd74dc8

begone padding

a218e02

for now, hook event callbacks up to the projected side

8c04979

why

f03d23c

add til::event_revoker for auto-revoking til::events

b8ea704

Prevents us from having to use projected types just to see autorevokers.

Dustin L. Howett (DHowett) force-pushed the dev/duhowett/stop-using-projection-for-control-innards branch from 307abbb to b8ea704 Compare September 29, 2026 23:45

Leonard Hecker (lhecker) approved these changes Oct 7, 2026

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Dustin L. Howett (DHowett) merged commit d2fac6e into main Oct 7, 2026
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Dustin L. Howett (DHowett) deleted the dev/duhowett/stop-using-projection-for-control-innards branch October 7, 2026 22:32

Dustin L. Howett (DHowett) mentioned this pull request Oct 19, 2026

Rewrite HwndTerminal to build on ControlInteractivity and -Core #20812

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Go back to using implementation types in TermControl - #20721

Go back to using implementation types in TermControl#20721
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Dustin L. Howett (DHowett) commented Sep 25, 2026 •

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