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[0.84] fix: correct CompositionHwndHost initialization order for DPI-aware second windows #16148

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[0.84] fix: correct CompositionHwndHost initialization order for DPI-aware second windows #16148

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fix: correct CompositionHwndHost initialization order for DPI-aware s…
gmacmaster May 18, 2026
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gmacmaster May 18, 2026
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7 changes: 7 additions & 0 deletions change/react-native-windows-c628c673-e01f-4887-9fcf-b1e5c468d311.json
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Original file line number Diff line number Diff line change
@@ -0,0 +1,7 @@
{
"type": "prerelease",
"comment": "Fix CompositionHwndHost initialization order: ResizePolicy is now set before Connect and ScaleFactor before the island is connected, matching the ReactNativeWindow reference pattern, so that secondary windows render with correct DPI-aware touch coordinates.",
"packageName": "react-native-windows",
"email": "gordomacmaster@gmail.com",
"dependentChangeType": "patch"
}
15 changes: 9 additions & 6 deletions vnext/Microsoft.ReactNative/Fabric/Composition/CompositionHwndHost.cpp
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Expand Up @@ -34,16 +34,19 @@ void CompositionHwndHost::Initialize(uint64_t hwnd) noexcept {
ReactViewHost().ReactNativeHost().InstanceSettings().Properties());
m_compRootView = winrt::Microsoft::ReactNative::ReactNativeIsland(compositor);

auto bridge = winrt::Microsoft::UI::Content::DesktopChildSiteBridge::Create(
m_bridge = winrt::Microsoft::UI::Content::DesktopChildSiteBridge::Create(
compositor, winrt::Microsoft::UI::GetWindowIdFromWindow(m_hwnd));

auto island = m_compRootView.Island();

bridge.Connect(island);
bridge.Show();
// ResizePolicy must be set before Connect so the bridge configures the
// island's coordinate space with correct DPI awareness (matches
// ReactNativeWindow::ContentSiteBridge initialization order).
m_bridge.ResizePolicy(winrt::Microsoft::UI::Content::ContentSizePolicy::ResizeContentToParentWindow);

auto island = m_compRootView.Island();
m_compRootView.ScaleFactor(ScaleFactor());
bridge.ResizePolicy(winrt::Microsoft::UI::Content::ContentSizePolicy::ResizeContentToParentWindow);

m_bridge.Connect(island);
m_bridge.Show();

m_compRootView.ReactViewHost(std::move(m_reactViewHost));
m_compRootView.ScaleFactor(ScaleFactor());
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2 changes: 2 additions & 0 deletions vnext/Microsoft.ReactNative/Fabric/Composition/CompositionHwndHost.h
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Expand Up @@ -5,6 +5,7 @@
#include "CompositionHwndHost.g.h"

#include <windows.ui.composition.interop.h>
#include <winrt/Microsoft.UI.Content.h>
#include <winrt/Windows.UI.Composition.Desktop.h>
#include "ReactHost/React.h"

Expand Down Expand Up @@ -34,6 +35,7 @@ struct CompositionHwndHost : CompositionHwndHostT<CompositionHwndHost> {

HWND m_hwnd;
winrt::Microsoft::ReactNative::ReactNativeIsland m_compRootView{nullptr};
winrt::Microsoft::UI::Content::DesktopChildSiteBridge m_bridge{nullptr};
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@acoates-ms acoates-ms May 18, 2026

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And now we dont need to store the DesktopChildSiteBridge...

LONG m_height{0};
LONG m_width{0};

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