From 0ffe5948a53ca6681ff95ef6d703870f04fabb5a Mon Sep 17 00:00:00 2001
From: reuk <reuk@users.noreply.github.com>
Date: Tue, 30 Jul 2024 12:29:12 +0100
Subject: [PATCH] Windows: Fix issue where maximised windows with non-native
 titlebars could slightly exceed the screen bounds

When handling WM_NCCALCSIZE, we reduce the size of the client area when
the window is maximised. If we don't do this, then the client area
matches the top-level window area, which is larger than the display's
safe area. As a result, the window appears too large, and the edges are
obscured under the edges of the display.

After reducing the client area in WM_NCCALCSIZE, the client area is no
longer equal to the top-level window area, so getBounds() must be
updated to return the window's *client* area rather than the top-level
window area.
---
 .../native/juce_Windowing_windows.cpp         | 73 ++++++++++++-------
 1 file changed, 48 insertions(+), 25 deletions(-)

diff --git a/modules/juce_gui_basics/native/juce_Windowing_windows.cpp b/modules/juce_gui_basics/native/juce_Windowing_windows.cpp
index c5aa812ced..314e00a40e 100644
--- a/modules/juce_gui_basics/native/juce_Windowing_windows.cpp
+++ b/modules/juce_gui_basics/native/juce_Windowing_windows.cpp
@@ -1662,20 +1662,32 @@ public:
     {
         if (parentToAddTo == nullptr)
         {
-            // Depending on the desktop scale factor, the physical size of the window may not map to
-            // an integral client-area size.
-            // In this case, we always round the width and height of the client area up to the next
-            // integer.
-            // This means that we may end up clipping off up to one logical pixel under the physical
-            // window border, but this is preferable to displaying an uninitialised/unpainted
-            // region of the client area.
-            const auto physicalBorder = findPhysicalBorderSize();
+            if (hasTitleBar())
+            {
+                // Depending on the desktop scale factor, the physical size of the window may not map to
+                // an integral client-area size.
+                // In this case, we always round the width and height of the client area up to the next
+                // integer.
+                // This means that we may end up clipping off up to one logical pixel under the physical
+                // window border, but this is preferable to displaying an uninitialised/unpainted
+                // region of the client area.
+                const auto physicalBorder = findPhysicalBorderSize();
 
-            const auto physicalBounds = D2DUtilities::toRectangle (getWindowScreenRect (hwnd));
-            const auto physicalClient = physicalBorder.subtractedFrom (physicalBounds);
-            const auto logicalClient = convertPhysicalScreenRectangleToLogical (physicalClient.toFloat(), hwnd);
-            const auto snapped = logicalClient.withPosition (logicalClient.getPosition().roundToInt().toFloat()).getSmallestIntegerContainer();
-            return snapped;
+                const auto physicalBounds = D2DUtilities::toRectangle (getWindowScreenRect (hwnd));
+                const auto physicalClient = physicalBorder.subtractedFrom (physicalBounds);
+                const auto logicalClient = convertPhysicalScreenRectangleToLogical (physicalClient.toFloat(), hwnd);
+                const auto snapped = logicalClient.withPosition (logicalClient.getPosition().roundToInt().toFloat()).getSmallestIntegerContainer();
+                return snapped;
+            }
+
+            RECT rect{};
+            GetClientRect (hwnd, &rect);
+            auto points = readUnaligned<std::array<POINT, 2>> (&rect);
+            MapWindowPoints (hwnd, nullptr, points.data(), (UINT) points.size());
+
+            const auto mappedRect = readUnaligned<RECT> (points.data());
+            const auto logicalClient = convertPhysicalScreenRectangleToLogical (D2DUtilities::toRectangle (mappedRect), hwnd);
+            return logicalClient;
         }
 
         auto localBounds = D2DUtilities::toRectangle (getWindowClientRect (hwnd));
@@ -3481,6 +3493,7 @@ private:
                 return true;
         }
 
+        updateBorderSize();
         handleMovedOrResized();
         updateCurrentMonitorAndRefreshVBlankDispatcher();
 
@@ -3876,18 +3889,29 @@ private:
 
             case WM_NCCALCSIZE:
             {
-                auto* rect = (RECT*) lParam;
-
-                if (renderContext != nullptr)
-                    renderContext->setSize (rect->right - rect->left, rect->bottom - rect->top);
-
-                if (! wParam)
+                // If we're using the native titlebar, then the default window proc behaviour will
+                // do the right thing.
+                if (hasTitleBar())
                     break;
 
-                if (! hasTitleBar() && windowUsesNativeShadow())
-                    return 0;
+                auto* param = (RECT*) lParam;
 
-                break;
+                // If we're not using a native titlebar, and the window is maximised, then the
+                // proposed window may be a bit bigger than the available space. Remove the padding
+                // so that the client area exactly fills the available space.
+                if (isFullScreen())
+                {
+                    const auto padX = -param->left;
+                    const auto padY = -param->top;
+
+                    param->left  += padX;
+                    param->right -= padX;
+
+                    param->top    += padY;
+                    param->bottom -= padY;
+                }
+
+                return 0;
             }
 
             //==============================================================================
@@ -3978,9 +4002,8 @@ private:
 
                 if ((wPos.flags & SWP_NOMOVE) != 0 && (wPos.flags & SWP_NOSIZE) != 0)
                     startTimer (100);
-                else
-                    if (handlePositionChanged())
-                        return 0;
+                else if (handlePositionChanged())
+                    return 0;
             }
             break;