Correctly compute diffWidth and diffHeight.

The previous calculation was wrong and lead to less parallax than
expected in some cases. This is the OP part of the CL.

Also, this CL makes sure we scale by width if the crop is
proportionally taller than the screen: this way, the window will always
be filled with content (and could support vertical parallax).

Note that given our implementation of WallpaperCropper, the wallpaper
is always wide enough for the screen, so we always scale by height
(make the wallpaper match the screen height) and only have horizontal
parallax.

A honest alternative would be to remove (under flag) the whole logic
for vertical parallax.

Flag: aconfig com.android.window.flags.multi_crop DEVELOPMENT
Test: atest WallpaperControllerTest
Bug: 327042053
Change-Id: I8aac1b0d4b85fed0a446aed794fdb525b21d8e3a

1 files changed, 27 insertions, 15 deletions

diff --git a/services/core/java/com/android/server/wm/WallpaperController.java b/services/core/java/com/android/server/wm/WallpaperController.java
index 594043d380c9..9b19a707d7be 100644
--- a/services/core/java/com/android/server/wm/WallpaperController.java
+++ b/services/core/java/com/android/server/wm/WallpaperController.java
@@ -349,7 +349,7 @@ class WallpaperController {
         final Rect lastWallpaperBounds = wallpaperWin.getParentFrame();
         int screenWidth = lastWallpaperBounds.width();
         int screenHeight = lastWallpaperBounds.height();
-        float screenRatio = ((float) screenWidth) / screenHeight;
+        float screenRatio = (float) screenWidth / screenHeight;
         Point screenSize = new Point(screenWidth, screenHeight);
 
         WallpaperWindowToken token = wallpaperWin.mToken.asWallpaperToken();
@@ -399,20 +399,32 @@ class WallpaperController {
             Point bitmapSize = new Point(
                     wallpaperWin.mRequestedWidth, wallpaperWin.mRequestedHeight);
             SparseArray<Rect> cropHints = token.getCropHints();
-            wallpaperFrame = mWallpaperCropUtils.getCrop(
-                    screenSize, bitmapSize, cropHints, wallpaperWin.isRtl());
-
-            cropZoom = wallpaperFrame.isEmpty() ? 1f
-                    : ((float) screenHeight) / wallpaperFrame.height() / wallpaperWin.mVScale;
-
-            // A positive x / y offset shifts the wallpaper to the right / bottom respectively.
-            cropOffsetX = -wallpaperFrame.left
-                    + (int) ((cropZoom - 1f) * wallpaperFrame.height() * screenRatio / 2f);
-            cropOffsetY = -wallpaperFrame.top
-                    + (int) ((cropZoom - 1f) * wallpaperFrame.height() / 2f);
-
-            diffWidth = (int) (wallpaperFrame.width() * wallpaperWin.mHScale) - screenWidth;
-            diffHeight = (int) (wallpaperFrame.height() * wallpaperWin.mVScale) - screenHeight;
+            wallpaperFrame = bitmapSize.x <= 0 || bitmapSize.y <= 0 ? wallpaperWin.getFrame()
+                    : mWallpaperCropUtils.getCrop(screenSize, bitmapSize, cropHints,
+                            wallpaperWin.isRtl());
+            int frameWidth = wallpaperFrame.width();
+            int frameHeight = wallpaperFrame.height();
+            float frameRatio = (float) frameWidth / frameHeight;
+
+            // If the crop is proportionally wider/taller than the screen, scale it so that its
+            // height/width matches the screen height/width, and use the additional width/height
+            // for parallax (respectively).
+            boolean scaleHeight = frameRatio >= screenRatio;
+            cropZoom = wallpaperFrame.isEmpty() ? 1f : scaleHeight
+                    ? (float) screenHeight / frameHeight / wallpaperWin.mVScale
+                    : (float) screenWidth / frameWidth / wallpaperWin.mHScale;
+
+            // The dimensions of the frame, without the additional width or height for parallax.
+            float w = scaleHeight ? frameHeight * screenRatio : frameWidth;
+            float h = scaleHeight ? frameHeight : frameWidth / screenRatio;
+
+            // Note: a positive x/y offset shifts the wallpaper to the right/bottom respectively.
+            cropOffsetX = -wallpaperFrame.left + (int) ((cropZoom - 1f) * w / 2f);
+            cropOffsetY = -wallpaperFrame.top + (int) ((cropZoom - 1f) * h / 2f);
+
+            // Available width or height for parallax
+            diffWidth = (int) ((frameWidth - w) * wallpaperWin.mHScale);
+            diffHeight = (int) ((frameHeight - h) * wallpaperWin.mVScale);
         } else {
             wallpaperFrame = wallpaperWin.getFrame();
             cropZoom = 1f;