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Fix secondary monitor windows not handling DPI changes #29

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Fix secondary monitor windows not handling DPI changes #29

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13 changes: 13 additions & 0 deletions WindowsEdgeLight/MainWindow.xaml.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1147,6 +1147,19 @@ private MonitorWindowContext CreateMonitorWindow(Screen screen)
}
};

window.DpiChanged += (s, dpiArgs) =>
{
ctx.DpiScaleX = dpiArgs.NewDpi.DpiScaleX;
ctx.DpiScaleY = dpiArgs.NewDpi.DpiScaleY;

window.Left = screen.WorkingArea.X / ctx.DpiScaleX;
window.Top = screen.WorkingArea.Y / ctx.DpiScaleY;
window.Width = screen.WorkingArea.Width / ctx.DpiScaleX;
window.Height = screen.WorkingArea.Height / ctx.DpiScaleY;
Comment on lines +1155 to +1158
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Copilot AI Feb 12, 2026

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The DpiChanged handler captures the screen parameter in a closure, which can become stale after monitor configuration changes. When monitors are hot-plugged or DPI settings change, the Screen objects from Screen.AllScreens can be outdated.

The main window's OnDpiChanged method (lines 585-619) handles this by calling UpdateCurrentMonitorIndex() to refresh the monitor list and get a fresh screen object before using screen.WorkingArea.

Consider storing the screen's index or device name instead of the Screen object itself, then retrieve the current Screen from a refreshed Screen.AllScreens within the DpiChanged handler. This ensures the WorkingArea values are current.

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UpdateMonitorGeometry(ctx);
Comment on lines +1152 to +1160
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Copilot AI Feb 12, 2026

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The DpiChanged handler unconditionally updates window position and size without checking if the change is significant. This could potentially cause update loops or unnecessary geometry recalculations.

The main window's OnDpiChanged method (lines 609-616) includes a threshold check to only update if the difference is greater than 1 pixel, which helps avoid infinite update loops.

Consider adding a similar threshold check before updating the window properties and calling UpdateMonitorGeometry.

Suggested change
ctx.DpiScaleX = dpiArgs.NewDpi.DpiScaleX;
ctx.DpiScaleY = dpiArgs.NewDpi.DpiScaleY;
window.Left = screen.WorkingArea.X / ctx.DpiScaleX;
window.Top = screen.WorkingArea.Y / ctx.DpiScaleY;
window.Width = screen.WorkingArea.Width / ctx.DpiScaleX;
window.Height = screen.WorkingArea.Height / ctx.DpiScaleY;
UpdateMonitorGeometry(ctx);
double newDpiX = dpiArgs.NewDpi.DpiScaleX;
double newDpiY = dpiArgs.NewDpi.DpiScaleY;
double newLeft = screen.WorkingArea.X / newDpiX;
double newTop = screen.WorkingArea.Y / newDpiY;
double newWidth = screen.WorkingArea.Width / newDpiX;
double newHeight = screen.WorkingArea.Height / newDpiY;
// Only update if the resulting geometry change is significant (more than 1 pixel)
if (Math.Abs(window.Left - newLeft) > 1.0 ||
Math.Abs(window.Top - newTop) > 1.0 ||
Math.Abs(window.Width - newWidth) > 1.0 ||
Math.Abs(window.Height - newHeight) > 1.0)
{
ctx.DpiScaleX = newDpiX;
ctx.DpiScaleY = newDpiY;
window.Left = newLeft;
window.Top = newTop;
window.Width = newWidth;
window.Height = newHeight;
UpdateMonitorGeometry(ctx);
}

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};

return ctx;
}

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