Simplify non-client hit testing in NCIslandWindow to fix doubleclick (#…

…3024)

It turns out that our WM_LBUTTONDOWN handler wasn't even necessary, as
our NCHITTEST tells win32 that all of the titlebar is actually
non-client area. This brings the code in line with
NonNonClientIslandWindow.

Fixes #2513

src/cascadia/WindowsTerminal/NonClientIslandWindow.cpp

@@ -263,22 +263,14 @@ void NonClientIslandWindow::_UpdateDragRegion()
 // - Hit test the frame for resizing and moving.
 // Arguments:
 // - ptMouse: the mouse point being tested, in absolute (NOT WINDOW) coordinates.
-// - titlebarIsCaption: If true, we want to treat the titlebar area as
-//   HTCAPTION, otherwise we'll return HTNOWHERE for the titlebar.
 // Return Value:
 // - one of the values from
 //  https://docs.microsoft.com/en-us/windows/desktop/inputdev/wm-nchittest#return-value
 //   corresponding to the area of the window that was hit
 // NOTE:
 // - Largely taken from code on:
 // https://docs.microsoft.com/en-us/windows/desktop/dwm/customframe
-// NOTE[2]: Concerning `titlebarIsCaption`
-// - We want HTNOWHERE as the return value for WM_NCHITTEST, so that we can get
-//   mouse presses in the titlebar area. If we return HTCAPTION there, we won't
-//   get any mouse WMs. However, when we're handling the mouse events, we need
-//   to know if the mouse was in that are or not, so we'll return HTCAPTION in
-//   that handler, to differentiate from the rest of the window.
-[[nodiscard]] LRESULT NonClientIslandWindow::HitTestNCA(POINT ptMouse, const bool titlebarIsCaption) const noexcept
+[[nodiscard]] LRESULT NonClientIslandWindow::HitTestNCA(POINT ptMouse) const noexcept
 {
     // Get the window rectangle.
     RECT rcWindow = BaseWindow::GetWindowRect();
@@ -319,7 +311,7 @@ void NonClientIslandWindow::_UpdateDragRegion()
 
     // clang-format off
     // Hit test (HTTOPLEFT, ... HTBOTTOMRIGHT)
-    const auto topHt = fOnResizeBorder ? HTTOP : (titlebarIsCaption ? HTCAPTION : HTNOWHERE);
+    const auto topHt = fOnResizeBorder ? HTTOP : HTCAPTION;
     LRESULT hitTests[3][3] = {
         { HTTOPLEFT,    topHt,      HTTOPRIGHT },
         { HTLEFT,       HTNOWHERE,  HTRIGHT },
@@ -520,7 +512,7 @@ RECT NonClientIslandWindow::GetMaxWindowRectInPixels(const RECT* const prcSugges
         // Handle hit testing in the NCA if not handled by DwmDefWindowProc.
         if (lRet == 0)
         {
-            lRet = HitTestNCA({ GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam) }, false);
+            lRet = HitTestNCA({ GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam) });
             if (lRet != HTNOWHERE)
             {
                 return lRet;
@@ -598,22 +590,18 @@ RECT NonClientIslandWindow::GetMaxWindowRectInPixels(const RECT* const prcSugges
         return 0;
     }
 
-    case WM_LBUTTONDOWN:
+    case WM_NCLBUTTONDOWN:
+    case WM_NCLBUTTONUP:
+    case WM_NCMBUTTONDOWN:
+    case WM_NCMBUTTONUP:
+    case WM_NCRBUTTONDOWN:
+    case WM_NCRBUTTONUP:
+    case WM_NCXBUTTONDOWN:
+    case WM_NCXBUTTONUP:
     {
-        POINT point1 = {};
-        ::GetCursorPos(&point1);
-
-        const auto region = HitTestNCA(point1, true);
-        if (region == HTCAPTION)
-        {
-            // If we clicked in the titlebar, raise an event so the app host can
-            // dispatch an appropriate event.
-            _DragRegionClickedHandlers();
-
-            const auto longParam = MAKELPARAM(point1.x, point1.y);
-            ::SetActiveWindow(_window.get());
-            ::PostMessage(_window.get(), WM_SYSCOMMAND, SC_MOVE | HTCAPTION, longParam);
-        }
+        // If we clicked in the titlebar, raise an event so the app host can
+        // dispatch an appropriate event.
+        _DragRegionClickedHandlers();
         break;
     }
 

src/cascadia/WindowsTerminal/NonClientIslandWindow.h

@@ -55,7 +55,7 @@ class NonClientIslandWindow : public IslandWindow
 
     RECT GetDragAreaRect() const noexcept;
 
-    [[nodiscard]] LRESULT HitTestNCA(POINT ptMouse, const bool titlebarIsCaption) const noexcept;
+    [[nodiscard]] LRESULT HitTestNCA(POINT ptMouse) const noexcept;
 
     [[nodiscard]] HRESULT _UpdateFrameMargins() const noexcept;