From c0f14567f349a44b732221662beb3a62ca49e1f4 Mon Sep 17 00:00:00 2001
From: Mike Griese <migrie@microsoft.com>
Date: Tue, 4 Apr 2023 09:21:43 -0500
Subject: [PATCH] Use DIPs for the window bounds when tearing out (#15094)

Fixes a bug where you'd drag across the boundary and the new window
would be at the wrong size

related to #14957
---
 src/cascadia/TerminalApp/TerminalWindow.cpp |  8 ++++----
 src/cascadia/WindowsTerminal/AppHost.cpp    | 12 ++++++------
 src/inc/til/size.h                          |  4 ++--
 src/til/ut_til/SizeTests.cpp                |  4 ++--
 4 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/src/cascadia/TerminalApp/TerminalWindow.cpp b/src/cascadia/TerminalApp/TerminalWindow.cpp
index dd984c6c126..07cc41274ee 100644
--- a/src/cascadia/TerminalApp/TerminalWindow.cpp
+++ b/src/cascadia/TerminalApp/TerminalWindow.cpp
@@ -613,11 +613,11 @@ namespace winrt::TerminalApp::implementation
         if (_contentBounds)
         {
             // If we've been created as a torn-out window, then we'll need to
-            // use that size instead. _contentBounds is in raw pixels. Huzzah!
-            // Just return that.
+            // use that size instead. _contentBounds is in DIPs. Scale
+            // accordingly to the new pixel size.
             return {
-                _contentBounds.Value().Width,
-                _contentBounds.Value().Height
+                _contentBounds.Value().Width * scale,
+                _contentBounds.Value().Height * scale
             };
         }
 
diff --git a/src/cascadia/WindowsTerminal/AppHost.cpp b/src/cascadia/WindowsTerminal/AppHost.cpp
index 3776017f25e..df55bfa7e0f 100644
--- a/src/cascadia/WindowsTerminal/AppHost.cpp
+++ b/src/cascadia/WindowsTerminal/AppHost.cpp
@@ -1231,7 +1231,6 @@ winrt::TerminalApp::TerminalWindow AppHost::Logic()
 void AppHost::_handleMoveContent(const winrt::Windows::Foundation::IInspectable& /*sender*/,
                                  winrt::TerminalApp::RequestMoveContentArgs args)
 {
-    winrt::Windows::Foundation::Rect rect{};
     winrt::Windows::Foundation::IReference<winrt::Windows::Foundation::Rect> windowBoundsReference{ nullptr };
 
     if (args.WindowPosition() && _window)
@@ -1280,12 +1279,13 @@ void AppHost::_handleMoveContent(const winrt::Windows::Foundation::IInspectable&
         dragPositionInPixels.y -= nonClientFrame.top;
         windowSize = windowSize - nonClientFrame.size();
 
+        // Convert to DIPs for the size, so that dragging across a DPI boundary
+        // retains the correct dimensions.
+        const auto sizeInDips = windowSize.scale(til::math::rounding, 1.0f / scale);
+        til::rect inDips{ dragPositionInPixels, sizeInDips };
+
         // Use the drag event as the new position, and the size of the actual window.
-        rect = winrt::Windows::Foundation::Rect{ static_cast<float>(dragPositionInPixels.x),
-                                                 static_cast<float>(dragPositionInPixels.y),
-                                                 static_cast<float>(windowSize.width),
-                                                 static_cast<float>(windowSize.height) };
-        windowBoundsReference = rect;
+        windowBoundsReference = inDips.to_winrt_rect();
     }
 
     _windowManager.RequestMoveContent(args.Window(), args.Content(), args.TabIndex(), windowBoundsReference);
diff --git a/src/inc/til/size.h b/src/inc/til/size.h
index cf91a08a0d7..72dbb602852 100644
--- a/src/inc/til/size.h
+++ b/src/inc/til/size.h
@@ -75,7 +75,7 @@ namespace til // Terminal Implementation Library. Also: "Today I Learned"
         }
 
         template<typename TilMath, typename T, typename = std::enable_if_t<std::is_floating_point_v<T>>>
-        constexpr size scale(TilMath math, const T scale) const
+        [[nodiscard]] constexpr size scale(TilMath math, const T scale) const
         {
             return {
                 math,
@@ -84,7 +84,7 @@ namespace til // Terminal Implementation Library. Also: "Today I Learned"
             };
         }
 
-        constexpr size divide_ceil(const size other) const
+        [[nodiscard]] constexpr size divide_ceil(const size other) const
         {
             // The integer ceil division `((a - 1) / b) + 1` only works for numbers >0.
             // Support for negative numbers wasn't deemed useful at this point.
diff --git a/src/til/ut_til/SizeTests.cpp b/src/til/ut_til/SizeTests.cpp
index 357ab300785..a75b48922a2 100644
--- a/src/til/ut_til/SizeTests.cpp
+++ b/src/til/ut_til/SizeTests.cpp
@@ -306,7 +306,7 @@ class SizeTests
             constexpr auto scale = 1e12f;
 
             auto fn = [&]() {
-                sz.scale(til::math::ceiling, scale);
+                std::ignore = sz.scale(til::math::ceiling, scale);
             };
 
             VERIFY_THROWS(fn(), gsl::narrowing_error);
@@ -359,7 +359,7 @@ class SizeTests
             const til::size divisor{ 3, 2 };
 
             auto fn = [&]() {
-                sz.divide_ceil(divisor);
+                std::ignore = sz.divide_ceil(divisor);
             };
 
             VERIFY_THROWS(fn(), std::invalid_argument);