1 files changed, 93 insertions, 0 deletions
diff --git a/widget/ScrollbarDrawingAndroid.cpp b/widget/ScrollbarDrawingAndroid.cpp
new file mode 100644
index 0000000000..8b1adb3d9b
--- /dev/null
+++ b/widget/ScrollbarDrawingAndroid.cpp
@@ -0,0 +1,93 @@
+/* -*- Mode: C++; tab-width: 40; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "ScrollbarDrawingAndroid.h"
+
+#include "nsIFrame.h"
+#include "nsNativeTheme.h"
+#include "mozilla/StaticPrefs_widget.h"
+
+using namespace mozilla;
+using namespace mozilla::widget;
+
+LayoutDeviceIntSize ScrollbarDrawingAndroid::GetMinimumWidgetSize(
+    nsPresContext* aPresContext, StyleAppearance aAppearance,
+    nsIFrame* aFrame) {
+  MOZ_ASSERT(nsNativeTheme::IsWidgetScrollbarPart(aAppearance));
+
+  auto sizes =
+      GetScrollbarSizes(aPresContext, StyleScrollbarWidth::Auto, Overlay::Yes);
+  MOZ_ASSERT(sizes.mHorizontal == sizes.mVertical);
+
+  return LayoutDeviceIntSize{sizes.mHorizontal, sizes.mVertical};
+}
+
+auto ScrollbarDrawingAndroid::GetScrollbarSizes(nsPresContext* aPresContext,
+                                                StyleScrollbarWidth aWidth,
+                                                Overlay aOverlay)
+    -> ScrollbarSizes {
+  // We force auto-width scrollbars because scrollbars on android are already
+  // thin enough.
+  return ScrollbarDrawing::GetScrollbarSizes(
+      aPresContext, StyleScrollbarWidth::Auto, aOverlay);
+}
+
+template <typename PaintBackendData>
+void ScrollbarDrawingAndroid::DoPaintScrollbarThumb(
+    PaintBackendData& aPaintData, const LayoutDeviceRect& aRect,
+    ScrollbarKind aScrollbarKind, nsIFrame* aFrame, const ComputedStyle& aStyle,
+    const ElementState& aElementState, const DocumentState& aDocumentState,
+    const Colors& aColors, const DPIRatio& aDpiRatio) {
+  // TODO(emilio): Maybe do like macOS and draw a stroke?
+  const auto color = ComputeScrollbarThumbColor(aFrame, aStyle, aElementState,
+                                                aDocumentState, aColors);
+  const bool horizontal = aScrollbarKind == ScrollbarKind::Horizontal;
+
+  // Draw the thumb rect centered in the scrollbar.
+  LayoutDeviceRect thumbRect(aRect);
+  if (horizontal) {
+    thumbRect.height *= 0.5f;
+    thumbRect.y += thumbRect.height * 0.5f;
+  } else {
+    thumbRect.width *= 0.5f;
+    thumbRect.x += thumbRect.width * 0.5f;
+  }
+
+  const LayoutDeviceCoord radius =
+      (horizontal ? thumbRect.height : thumbRect.width) / 2.0f;
+  ThemeDrawing::PaintRoundedRectWithRadius(aPaintData, thumbRect, color,
+                                           sRGBColor::White(0.0f), 0.0f,
+                                           radius / aDpiRatio, aDpiRatio);
+}
+
+bool ScrollbarDrawingAndroid::PaintScrollbarThumb(
+    DrawTarget& aDt, const LayoutDeviceRect& aRect,
+    ScrollbarKind aScrollbarKind, nsIFrame* aFrame, const ComputedStyle& aStyle,
+    const ElementState& aElementState, const DocumentState& aDocumentState,
+    const Colors& aColors, const DPIRatio& aDpiRatio) {
+  DoPaintScrollbarThumb(aDt, aRect, aScrollbarKind, aFrame, aStyle,
+                        aElementState, aDocumentState, aColors, aDpiRatio);
+  return true;
+}
+
+bool ScrollbarDrawingAndroid::PaintScrollbarThumb(
+    WebRenderBackendData& aWrData, const LayoutDeviceRect& aRect,
+    ScrollbarKind aScrollbarKind, nsIFrame* aFrame, const ComputedStyle& aStyle,
+    const ElementState& aElementState, const DocumentState& aDocumentState,
+    const Colors& aColors, const DPIRatio& aDpiRatio) {
+  DoPaintScrollbarThumb(aWrData, aRect, aScrollbarKind, aFrame, aStyle,
+                        aElementState, aDocumentState, aColors, aDpiRatio);
+  return true;
+}
+
+void ScrollbarDrawingAndroid::RecomputeScrollbarParams() {
+  uint32_t defaultSize = 6;
+  uint32_t overrideSize =
+      StaticPrefs::widget_non_native_theme_scrollbar_size_override();
+  if (overrideSize > 0) {
+    defaultSize = overrideSize;
+  }
+  mHorizontalScrollbarHeight = mVerticalScrollbarWidth = defaultSize;
+}