Bug 1700148, add an appearance type that forces a dropshadow on menus on Windows, and uses SetWindowRgn to clip the popup to the border radius, r=tnikkel

Differential Revision: https://phabricator.services.mozilla.com/D109833

layout/base/nsLayoutUtils.cpp

@@ -6658,6 +6658,27 @@ bool nsLayoutUtils::HasNonZeroCornerOnSide(const BorderRadius& aCorners,
   return false;
 }
 
+/* static */
+LayoutDeviceIntSize nsLayoutUtils::GetBorderRadiusForMenuDropShadow(
+    const nsIFrame* aFrame) {
+  if (aFrame->StyleUIReset()->mWindowShadow == StyleWindowShadow::Cliprounded) {
+    const auto& corners = aFrame->StyleBorder()->mBorderRadius;
+
+    // Get the width and height of the top-left corner.
+    const LengthPercentage& cornerX = corners.Get(eCornerTopLeftX);
+    const LengthPercentage& cornerY = corners.Get(eCornerTopLeftY);
+    nscoord lengthX = (cornerX.IsLength() ? cornerX.ToLength() : 0);
+    nscoord lengthY = (cornerY.IsLength() ? cornerY.ToLength() : 0);
+    if (lengthX || lengthY) {
+      const nsPresContext* presContext = aFrame->PresContext();
+      return LayoutDeviceIntSize(presContext->AppUnitsToDevPixels(lengthX),
+                                 presContext->AppUnitsToDevPixels(lengthY));
+    }
+  }
+
+  return LayoutDeviceIntSize();
+}
+
 /* static */
 nsTransparencyMode nsLayoutUtils::GetFrameTransparency(
     nsIFrame* aBackgroundFrame, nsIFrame* aCSSRootFrame) {

layout/base/nsLayoutUtils.h

@@ -2011,6 +2011,15 @@ class nsLayoutUtils {
   static bool HasNonZeroCornerOnSide(const mozilla::BorderRadius& aCorners,
                                      mozilla::Side aSide);
 
+  /**
+   * Return the border radius size (width, height) based only on the top-left
+   * corner. This is a special case used for drawing the Windows 10 drop-shadow,
+   * and only supports a specified length (not percentages) on the top-left
+   * corner.
+   */
+  static LayoutDeviceIntSize GetBorderRadiusForMenuDropShadow(
+      const nsIFrame* aFrame);
+
   /**
    * Determine if a widget is likely to require transparency or translucency.
    *   @param aBackgroundFrame The frame that the background is set on. For

layout/style/nsStyleConsts.h

@@ -640,6 +640,7 @@ enum class StyleWindowShadow : uint8_t {
   Menu,
   Tooltip,
   Sheet,
+  Cliprounded,  // clip border to popup border-radius
 };
 
 // dominant-baseline

layout/style/test/property_database.js

@@ -12943,7 +12943,7 @@ if (false) {
     inherited: false,
     type: CSS_TYPE_LONGHAND,
     initial_values: ["default"],
-    other_values: ["none", "menu", "tooltip", "sheet"],
+    other_values: ["none", "menu", "tooltip", "sheet", "cliprounded"],
     invalid_values: [],
   };
 

layout/xul/nsMenuPopupFrame.cpp

@@ -315,10 +315,14 @@ nsresult nsMenuPopupFrame::CreateWidgetForView(nsView* aView) {
     tag = parentContent->NodeInfo()->NameAtom();
   widgetData.mHasRemoteContent = remote;
   widgetData.mSupportTranslucency = mode == eTransparencyTransparent;
-  widgetData.mDropShadow =
-      !(mode == eTransparencyTransparent || tag == nsGkAtoms::menulist);
   widgetData.mPopupLevel = PopupLevel(widgetData.mNoAutoHide);
 
+  // The special cases are menulists and handling the Windows 10
+  // drop-shadow on menus with rounded borders.
+  widgetData.mDropShadow =
+      !(mode == eTransparencyTransparent || tag == nsGkAtoms::menulist) ||
+      StyleUIReset()->mWindowShadow == StyleWindowShadow::Cliprounded;
+
   // panels which have a parent level need a parent widget. This allows them to
   // always appear in front of the parent window but behind other windows that
   // should be in front of it.

servo/components/style/properties/longhands/ui.mako.rs

@@ -53,7 +53,7 @@ ${helpers.single_keyword(
 
 ${helpers.single_keyword(
     "-moz-window-shadow",
-    "default none menu tooltip sheet",
+    "default none menu tooltip sheet cliprounded",
     engines="gecko",
     gecko_ffi_name="mWindowShadow",
     gecko_enum_prefix="StyleWindowShadow",

widget/cocoa/nsCocoaWindow.mm

@@ -3899,6 +3899,7 @@ static const NSUInteger kWindowShadowOptionsTooltipMojaveOrLater = 4;
     case StyleWindowShadow::Default:  // we treat "default" as "default panel"
     case StyleWindowShadow::Menu:
     case StyleWindowShadow::Sheet:
+    case StyleWindowShadow::Cliprounded:  // this is a Windows-only value.
       return kWindowShadowOptionsMenu;
 
     case StyleWindowShadow::Tooltip:

widget/windows/nsWindow.cpp

@@ -1757,28 +1757,60 @@ bool nsWindow::IsVisible() const { return mIsVisible; }
  *
  **************************************************************/
 
+static bool ShouldHaveRoundedMenuDropShadow(nsWindow* aWindow) {
+  nsView* view = nsView::GetViewFor(aWindow);
+  return view && view->GetFrame() &&
+         view->GetFrame()->StyleUIReset()->mWindowShadow ==
+             StyleWindowShadow::Cliprounded;
+}
+
 // XP and Vista visual styles sometimes require window clipping regions to be
 // applied for proper transparency. These routines are called on size and move
 // operations.
 // XXX this is apparently still needed in Windows 7 and later
 void nsWindow::ClearThemeRegion() {
-  if (!HasGlass() &&
-      (mWindowType == eWindowType_popup && !IsPopupWithTitleBar() &&
-       (mPopupType == ePopupTypeTooltip || mPopupType == ePopupTypePanel))) {
+  if (mWindowType == eWindowType_popup && mPopupType == ePopupTypeMenu &&
+      ShouldHaveRoundedMenuDropShadow(this)) {
+    SetWindowRgn(mWnd, nullptr, false);
+  } else if (!HasGlass() &&
+             (mWindowType == eWindowType_popup && !IsPopupWithTitleBar() &&
+              (mPopupType == ePopupTypeTooltip ||
+               mPopupType == ePopupTypePanel))) {
     SetWindowRgn(mWnd, nullptr, false);
   }
 }
 
 void nsWindow::SetThemeRegion() {
+  // Clip the window to the rounded rect area of the popup if needed.
+  if (mWindowType == eWindowType_popup && mPopupType == ePopupTypeMenu) {
+    nsView* view = nsView::GetViewFor(this);
+    if (view) {
+      LayoutDeviceIntSize size =
+          nsLayoutUtils::GetBorderRadiusForMenuDropShadow(view->GetFrame());
+      if (size.width || size.height) {
+        int32_t width =
+            NSToIntRound(size.width * GetDesktopToDeviceScale().scale);
+        int32_t height =
+            NSToIntRound(size.height * GetDesktopToDeviceScale().scale);
+        HRGN region = CreateRoundRectRgn(0, 0, mBounds.Width(),
+                                         mBounds.Height(), width, height);
+        if (!SetWindowRgn(mWnd, region, false)) {
+          DeleteObject(region);  // region setting failed so delete the region.
+        }
+      }
+    }
+  }
+
   // Popup types that have a visual styles region applied (bug 376408). This can
   // be expanded for other window types as needed. The regions are applied
   // generically to the base window so default constants are used for part and
   // state. At some point we might need part and state values from
   // nsNativeThemeWin's GetThemePartAndState, but currently windows that change
   // shape based on state haven't come up.
-  if (!HasGlass() &&
-      (mWindowType == eWindowType_popup && !IsPopupWithTitleBar() &&
-       (mPopupType == ePopupTypeTooltip || mPopupType == ePopupTypePanel))) {
+  else if (!HasGlass() &&
+           (mWindowType == eWindowType_popup && !IsPopupWithTitleBar() &&
+            (mPopupType == ePopupTypeTooltip ||
+             mPopupType == ePopupTypePanel))) {
     HRGN hRgn = nullptr;
     RECT rect = {0, 0, mBounds.Width(), mBounds.Height()};