Change Aura desktop background behavior.

ash/desktop_background/desktop_background_view.cc

Index: ash/desktop_background/desktop_background_view.cc
diff --git a/ash/desktop_background/desktop_background_view.cc b/ash/desktop_background/desktop_background_view.cc
index bd535a8a23811006d8ed01759a4749986972e26b..948bb38702823b385e29200fb75257d587d67b58 100644
--- a/ash/desktop_background/desktop_background_view.cc
+++ b/ash/desktop_background/desktop_background_view.cc
@@ -33,10 +33,45 @@ DesktopBackgroundView::~DesktopBackgroundView() {
 // DesktopBackgroundView, views::View overrides:
 
 void DesktopBackgroundView::OnPaint(gfx::Canvas* canvas) {
-  canvas->DrawBitmapInt(wallpaper_,
-      0, 0, wallpaper_.width(), wallpaper_.height(),
-      0, 0, width(), height(),
-      true);
+  // Scale the image while maintaining the aspect ratio, cropping as
+  // necessary to fill the background. Ideally the image should be larger
+  // than the largest display supported, if not we will center it rather than
+  // streching to avoid upsampling artifacts (Note that we could tile too, but
+  // decided not to do this at the moment).
+  gfx::Rect wallpaper_rect(0, 0, wallpaper_.width(), wallpaper_.height());
+  if (wallpaper_.width() > width() && wallpaper_.height() > height()) {
+    // The dimension with the smallest ratio must be cropped, the other one
+    // is preserved. Both are set in gfx::Size cropped_size.
+    double horizontal_ratio = static_cast<double>(width()) /
+        static_cast<double>(wallpaper_.width());
+    double vertical_ratio = static_cast<double>(height()) /
+        static_cast<double>(wallpaper_.height());
+
+    gfx::Size cropped_size;
+    if (vertical_ratio > horizontal_ratio) {
+      cropped_size = gfx::Size(
+          static_cast<int>(static_cast<double>(width()) / vertical_ratio),
+          wallpaper_.height());
+    } else {
+      cropped_size = gfx::Size(wallpaper_.width(),
+          static_cast<int>(static_cast<double>(height()) / horizontal_ratio));
+    }
+
+    gfx::Rect wallpaper_cropped_rect = wallpaper_rect.Center(cropped_size);
+    canvas->DrawBitmapInt(wallpaper_,
+       wallpaper_cropped_rect.x(), wallpaper_cropped_rect.y(),
+       wallpaper_cropped_rect.width(), wallpaper_cropped_rect.height(),
+       0, 0, width(), height(),
+       true);
+  }
+  else {
+    // Center the wallpaper and crop to the destination rectangle.
+    gfx::Rect wallpaper_centered_rect = wallpaper_rect.Center(gfx::Size(

[Daniel Erat, 2012/02/29 22:10:40]

you don't need this anymore

[Emmanuel Saint-loubert-Bié, 2012/02/29 22:32:58]

Done.

+        std::min(wallpaper_.width(), width()),
+        std::min(wallpaper_.height(), height())));
+    canvas->DrawBitmapInt(wallpaper_, (width() - wallpaper_.width()) / 2,
+        (height() - wallpaper_.height()) / 2);
+  }
 }
 
 bool DesktopBackgroundView::OnMousePressed(const views::MouseEvent& event) {