Fix rendering on Retina displays

Since the QWindow returned by the RWHV delegates was always 0 we never
actually propagated a valid WebScreenInfo to chromium.
Additionally the painting and scrolling in the backing store had to be
fixed so that the device pixel ratio is taken into account.

Change-Id: I22dc135e8e090362201292863ed911464b9fc133
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>

1 files changed, 34 insertions, 10 deletions

diff --git a/lib/backing_store_qt.cpp b/lib/backing_store_qt.cpp
index bd33a0a4b..e16e9ab03 100644
--- a/lib/backing_store_qt.cpp
+++ b/lib/backing_store_qt.cpp
@@ -44,14 +44,21 @@
 #include "content/public/browser/render_process_host.h"
 #include "ui/gfx/rect.h"
 #include "ui/gfx/rect_conversions.h"
+#include "ui/gfx/vector2d_conversions.h"
 #include "skia/ext/platform_canvas.h"
 
 #include <QPainter>
+#include <QScreen>
+#include <QSizeF>
+#include <QWindow>
 
 BackingStoreQt::BackingStoreQt(content::RenderWidgetHost *host, const gfx::Size &size, QWindow* parent)
     : content::BackingStore(host, size)
-    , m_pixelBuffer(size.width(), size.height())
+    , m_deviceScaleFactor((parent && parent->screen()) ? parent->screen()->devicePixelRatio() : 1)
+    , m_pixelBuffer(size.width() * m_deviceScaleFactor, size.height() * m_deviceScaleFactor)
 {
+    Q_ASSERT(parent);
+    Q_ASSERT(parent->screen());
 }
 
 BackingStoreQt::~BackingStoreQt()
@@ -62,7 +69,14 @@ void BackingStoreQt::paintToTarget(QPainter* painter, const QRectF& rect)
 {
     if (m_pixelBuffer.isNull())
         return;
-    painter->drawPixmap(rect, m_pixelBuffer, rect);
+
+    qreal x = rect.x() * m_deviceScaleFactor;
+    qreal y = rect.y() * m_deviceScaleFactor;
+    qreal w = rect.width() * m_deviceScaleFactor;
+    qreal h = rect.height() * m_deviceScaleFactor;
+
+    QRectF source(x, y, w, h);
+    painter->drawPixmap(rect, m_pixelBuffer, source);
 }
 
 void BackingStoreQt::PaintToBackingStore(content::RenderProcessHost *process,
@@ -81,25 +95,26 @@ void BackingStoreQt::PaintToBackingStore(content::RenderProcessHost *process,
     if (!dib)
       return;
 
-    gfx::Rect pixel_bitmap_rect = bitmap_rect;
+    gfx::Rect pixel_bitmap_rect = gfx::ToEnclosingRect(gfx::ScaleRect(bitmap_rect, scale_factor));
 
     uint8_t* bitmapData = static_cast<uint8_t*>(dib->memory());
     const QImage img(bitmapData, pixel_bitmap_rect.width(), pixel_bitmap_rect.height(), QImage::Format_ARGB32);
 
     QPainter painter(&m_pixelBuffer);
-
     for (size_t i = 0; i < copy_rects.size(); ++i) {
-        gfx::Rect copy_rect = gfx::ToEnclosedRect(gfx::ScaleRect(copy_rects[i], scale_factor));
+        gfx::Rect copy_rect = gfx::ToEnclosingRect(gfx::ScaleRect(copy_rects[i], scale_factor));
 
         QRect source = QRect( copy_rect.x() - pixel_bitmap_rect.x()
                             , copy_rect.y() - pixel_bitmap_rect.y()
                             , copy_rect.width()
                             , copy_rect.height());
 
-        QRect destination = QRect( copy_rect.x()
-                                 , copy_rect.y()
-                                 , copy_rect.width()
-                                 , copy_rect.height());
+        gfx::Rect copy_rect_dst = gfx::ToEnclosingRect(gfx::ScaleRect(copy_rects[i], m_deviceScaleFactor));
+
+        QRect destination = QRect( copy_rect_dst.x()
+                                 , copy_rect_dst.y()
+                                 , copy_rect_dst.width()
+                                 , copy_rect_dst.height());
 
         painter.drawImage(destination, img, source);
     }
@@ -109,7 +124,16 @@ void BackingStoreQt::ScrollBackingStore(const gfx::Vector2d &delta, const gfx::R
 {
     DCHECK(delta.x() == 0 || delta.y() == 0);
 
-    m_pixelBuffer.scroll(delta.x(), delta.y(), clip_rect.x(), clip_rect.y(), clip_rect.width(), clip_rect.height());
+    gfx::Rect pixel_rect = gfx::ToEnclosingRect(gfx::ScaleRect(clip_rect, m_deviceScaleFactor));
+    gfx::Vector2d pixel_delta = gfx::ToFlooredVector2d(gfx::ScaleVector2d(delta, m_deviceScaleFactor));
+
+    m_pixelBuffer.scroll(pixel_delta.x()
+                         , pixel_delta.y()
+                         , pixel_rect.x()
+                         , pixel_rect.y()
+                         , pixel_rect.width()
+                         , pixel_rect.height());
+
 }
 
 bool BackingStoreQt::CopyFromBackingStore(const gfx::Rect &rect, skia::PlatformBitmap *output)