Bug 869314 - Fix missing dropmarkers in non-native styled combobox controls when overlay scrollbars are used. r=roc

gfx/src/nsThemeConstants.h

@@ -157,6 +157,9 @@
 #define NS_THEME_SCROLLBAR_THUMB_HORIZONTAL                88
 #define NS_THEME_SCROLLBAR_THUMB_VERTICAL                  89
 
+// A non-disappearing scrollbar.
+#define NS_THEME_SCROLLBAR_NON_DISAPPEARING                90
+
 // A textfield or text area
 #define NS_THEME_TEXTFIELD                                 95
 

layout/forms/nsComboboxControlFrame.cpp

@@ -56,6 +56,7 @@
 #include "mozilla/Likely.h"
 #include <algorithm>
 #include "nsTextNode.h"
+#include "mozilla/LookAndFeel.h"
 
 using namespace mozilla;
 
@@ -738,8 +739,8 @@ nsComboboxControlFrame::GetIntrinsicWidth(nsRenderingContext* aRenderingContext,
   if (mListControlFrame) {
     nsIScrollableFrame* scrollable = do_QueryFrame(mListControlFrame);
     NS_ASSERTION(scrollable, "List must be a scrollable frame");
-    scrollbarWidth =
-      scrollable->GetDesiredScrollbarSizes(presContext, aRenderingContext).LeftRight();
+    scrollbarWidth = scrollable->GetNondisappearingScrollbarWidth(
+      presContext, aRenderingContext);
   }
 
   nscoord displayWidth = 0;
@@ -751,11 +752,19 @@ nsComboboxControlFrame::GetIntrinsicWidth(nsRenderingContext* aRenderingContext,
 
   if (mDropdownFrame) {
     nscoord dropdownContentWidth;
+    bool isUsingOverlayScrollbars =
+      LookAndFeel::GetInt(LookAndFeel::eIntID_UseOverlayScrollbars) != 0;
     if (aType == nsLayoutUtils::MIN_WIDTH) {
       dropdownContentWidth = mDropdownFrame->GetMinWidth(aRenderingContext);
+      if (isUsingOverlayScrollbars) {
+        dropdownContentWidth += scrollbarWidth;
+      }
     } else {
       NS_ASSERTION(aType == nsLayoutUtils::PREF_WIDTH, "Unexpected type");
       dropdownContentWidth = mDropdownFrame->GetPrefWidth(aRenderingContext);
+      if (isUsingOverlayScrollbars) {
+        dropdownContentWidth += scrollbarWidth;
+      }
     }
     dropdownContentWidth = NSCoordSaturatingSubtract(dropdownContentWidth,
                                                      scrollbarWidth,
@@ -850,9 +859,8 @@ nsComboboxControlFrame::Reflow(nsPresContext*          aPresContext,
   else {
     nsIScrollableFrame* scrollable = do_QueryFrame(mListControlFrame);
     NS_ASSERTION(scrollable, "List must be a scrollable frame");
-    buttonWidth =
-      scrollable->GetDesiredScrollbarSizes(PresContext(),
-                                           aReflowState.rendContext).LeftRight();
+    buttonWidth = scrollable->GetNondisappearingScrollbarWidth(
+      PresContext(), aReflowState.rendContext);
     if (buttonWidth > aReflowState.ComputedWidth()) {
       buttonWidth = 0;
     }

layout/generic/nsGfxScrollFrame.cpp

@@ -932,6 +932,40 @@ nsGfxScrollFrameInner::GetDesiredScrollbarSizes(nsBoxLayoutState* aState)
   return result;
 }
 
+nscoord
+nsGfxScrollFrameInner::GetNondisappearingScrollbarWidth(nsBoxLayoutState* aState)
+{
+  NS_ASSERTION(aState && aState->GetRenderingContext(),
+               "Must have rendering context in layout state for size "
+               "computations");
+
+  if (LookAndFeel::GetInt(LookAndFeel::eIntID_UseOverlayScrollbars) != 0) {
+    // We're using overlay scrollbars, so we need to get the width that
+    // non-disappearing scrollbars would have.
+    nsITheme* theme = aState->PresContext()->GetTheme();
+    if (theme &&
+        theme->ThemeSupportsWidget(aState->PresContext(),
+                                   mVScrollbarBox,
+                                   NS_THEME_SCROLLBAR_NON_DISAPPEARING)) {
+      nsIntSize size;
+      nsRenderingContext* rendContext = aState->GetRenderingContext();
+      if (rendContext) {
+        bool canOverride = true;
+        theme->GetMinimumWidgetSize(rendContext,
+                                    mVScrollbarBox,
+                                    NS_THEME_SCROLLBAR_NON_DISAPPEARING,
+                                    &size,
+                                    &canOverride);
+        if (size.width) {
+          return aState->PresContext()->DevPixelsToAppUnits(size.width);
+        }
+      }
+    }
+  }
+
+  return GetDesiredScrollbarSizes(aState).LeftRight();
+}
+
 nsresult
 nsXULScrollFrame::CreateAnonymousContent(nsTArray<ContentInfo>& aElements)
 {

layout/generic/nsGfxScrollFrame.h

@@ -235,6 +235,7 @@ public:
   }
   nsMargin GetActualScrollbarSizes() const;
   nsMargin GetDesiredScrollbarSizes(nsBoxLayoutState* aState);
+  nscoord GetNondisappearingScrollbarWidth(nsBoxLayoutState* aState);
   bool IsLTR() const;
   bool IsScrollbarOnRight() const;
   bool IsScrollingActive() const { return mScrollingActive || ShouldBuildLayer(); }
@@ -486,6 +487,11 @@ public:
     nsBoxLayoutState bls(aPresContext, aRC, 0);
     return GetDesiredScrollbarSizes(&bls);
   }
+  virtual nscoord GetNondisappearingScrollbarWidth(nsPresContext* aPresContext,
+          nsRenderingContext* aRC) MOZ_OVERRIDE {
+    nsBoxLayoutState bls(aPresContext, aRC, 0);
+    return mInner.GetNondisappearingScrollbarWidth(&bls);
+  }
   virtual nsRect GetScrollPortRect() const MOZ_OVERRIDE {
     return mInner.GetScrollPortRect();
   }
@@ -744,6 +750,11 @@ public:
     nsBoxLayoutState bls(aPresContext, aRC, 0);
     return GetDesiredScrollbarSizes(&bls);
   }
+  virtual nscoord GetNondisappearingScrollbarWidth(nsPresContext* aPresContext,
+          nsRenderingContext* aRC) MOZ_OVERRIDE {
+    nsBoxLayoutState bls(aPresContext, aRC, 0);
+    return mInner.GetNondisappearingScrollbarWidth(&bls);
+  }
   virtual nsRect GetScrollPortRect() const MOZ_OVERRIDE {
     return mInner.GetScrollPortRect();
   }

layout/generic/nsIScrollableFrame.h

@@ -81,7 +81,11 @@ public:
    */
   virtual nsMargin GetDesiredScrollbarSizes(nsPresContext* aPresContext,
                                             nsRenderingContext* aRC) = 0;
-
+  /**
+   * Return the width for non-disappearing scrollbars.
+   */
+  virtual nscoord GetNondisappearingScrollbarWidth(nsPresContext* aPresContext,
+                                                   nsRenderingContext* aRC) = 0;
   /**
    * Get the area of the scrollport relative to the origin of this frame's
    * border-box.

widget/cocoa/nsNativeThemeCocoa.mm

@@ -2811,7 +2811,11 @@ nsNativeThemeCocoa::GetMinimumWidgetSize(nsRenderingContext* aContext,
         aResult->SizeTo(16, 16);
         break;
       }
+      // Intentional fallthrough to next case.
+    }
 
+    case NS_THEME_SCROLLBAR_NON_DISAPPEARING:
+    {
       // yeah, i know i'm cheating a little here, but i figure that it
       // really doesn't matter if the scrollbar is vertical or horizontal
       // and the width metric is a really good metric for every piece
@@ -3020,6 +3024,7 @@ nsNativeThemeCocoa::ThemeSupportsWidget(nsPresContext* aPresContext, nsIFrame* a
     case NS_THEME_SCROLLBAR_THUMB_VERTICAL:
     case NS_THEME_SCROLLBAR_TRACK_VERTICAL:
     case NS_THEME_SCROLLBAR_TRACK_HORIZONTAL:
+    case NS_THEME_SCROLLBAR_NON_DISAPPEARING:
 
     case NS_THEME_DROPDOWN:
     case NS_THEME_DROPDOWN_BUTTON: