From 829707057e53950650b8a704f8bd77f3da6b3c24 Mon Sep 17 00:00:00 2001
From: Romain Vimont <rom@rom1v.com>
Date: Sun, 10 Nov 2024 09:11:57 +0100
Subject: [PATCH] Split computeVideoSize() into limit() and round8()

Expose two methods on Size directly:
 - limit() to downscale a size;
 - round8() to round both dimensions to multiples of 8.

This will allow to remove ScreenInfo completely.
---
 .../com/genymobile/scrcpy/device/Size.java    | 51 +++++++++++++++++++
 .../scrcpy/video/NewDisplayCapture.java       |  2 +-
 .../genymobile/scrcpy/video/ScreenInfo.java   | 30 +----------
 3 files changed, 53 insertions(+), 30 deletions(-)

diff --git a/server/src/main/java/com/genymobile/scrcpy/device/Size.java b/server/src/main/java/com/genymobile/scrcpy/device/Size.java
index 558deb00..3baa1bdd 100644
--- a/server/src/main/java/com/genymobile/scrcpy/device/Size.java
+++ b/server/src/main/java/com/genymobile/scrcpy/device/Size.java
@@ -29,6 +29,57 @@ public final class Size {
         return new Size(height, width);
     }
 
+    public Size limit(int maxSize) {
+        assert maxSize >= 0 : "Max size may not be negative";
+        assert maxSize % 8 == 0 : "Max size must be a multiple of 8";
+
+        if (maxSize == 0) {
+            // No limit
+            return this;
+        }
+
+        boolean portrait = height > width;
+        int major = portrait ? height : width;
+        if (major <= maxSize) {
+            return this;
+        }
+
+        int minor = portrait ? width : height;
+
+        int newMajor = maxSize;
+        int newMinor = maxSize * minor / major;
+
+        int w = portrait ? newMinor : newMajor;
+        int h = portrait ? newMajor : newMinor;
+        return new Size(w, h);
+    }
+
+    /**
+     * Round both dimensions of this size to be a multiple of 8 (as required by many encoders).
+     *
+     * @return The current size rounded.
+     */
+    public Size round8() {
+        if ((width & 7) == 0 && (height & 7) == 0) {
+            // Already a multiple of 8
+            return this;
+        }
+
+        boolean portrait = height > width;
+        int major = portrait ? height : width;
+        int minor = portrait ? width : height;
+
+        major &= ~7; // round down to not exceed the initial size
+        minor = (minor + 4) & ~7; // round to the nearest to minimize aspect ratio distortion
+        if (minor > major) {
+            minor = major;
+        }
+
+        int w = portrait ? minor : major;
+        int h = portrait ? major : minor;
+        return new Size(w, h);
+    }
+
     public Rect toRect() {
         return new Rect(0, 0, width, height);
     }
diff --git a/server/src/main/java/com/genymobile/scrcpy/video/NewDisplayCapture.java b/server/src/main/java/com/genymobile/scrcpy/video/NewDisplayCapture.java
index 9b1c9933..b9cecbe4 100644
--- a/server/src/main/java/com/genymobile/scrcpy/video/NewDisplayCapture.java
+++ b/server/src/main/java/com/genymobile/scrcpy/video/NewDisplayCapture.java
@@ -71,7 +71,7 @@ public class NewDisplayCapture extends SurfaceCapture {
     @Override
     public void prepare() {
         if (!newDisplay.hasExplicitSize()) {
-            size = ScreenInfo.computeVideoSize(mainDisplaySize.getWidth(), mainDisplaySize.getHeight(), maxSize);
+            size = mainDisplaySize.limit(maxSize).round8();
         }
         if (!newDisplay.hasExplicitDpi()) {
             dpi = scaleDpi(mainDisplaySize, mainDisplayDpi, size);
diff --git a/server/src/main/java/com/genymobile/scrcpy/video/ScreenInfo.java b/server/src/main/java/com/genymobile/scrcpy/video/ScreenInfo.java
index cc82a654..010ab59a 100644
--- a/server/src/main/java/com/genymobile/scrcpy/video/ScreenInfo.java
+++ b/server/src/main/java/com/genymobile/scrcpy/video/ScreenInfo.java
@@ -1,6 +1,5 @@
 package com.genymobile.scrcpy.video;
 
-import com.genymobile.scrcpy.BuildConfig;
 import com.genymobile.scrcpy.device.Device;
 import com.genymobile.scrcpy.device.Size;
 import com.genymobile.scrcpy.util.Ln;
@@ -82,7 +81,7 @@ public final class ScreenInfo {
             }
         }
 
-        Size videoSize = computeVideoSize(contentRect.width(), contentRect.height(), maxSize);
+        Size videoSize = new Size(contentRect.width(), contentRect.height()).limit(maxSize).round8();
         return new ScreenInfo(contentRect, videoSize, rotation, lockedVideoOrientation);
     }
 
@@ -90,33 +89,6 @@ public final class ScreenInfo {
         return rect.width() + ":" + rect.height() + ":" + rect.left + ":" + rect.top;
     }
 
-    public static Size computeVideoSize(int w, int h, int maxSize) {
-        // Compute the video size and the padding of the content inside this video.
-        // Principle:
-        // - scale down the great side of the screen to maxSize (if necessary);
-        // - scale down the other side so that the aspect ratio is preserved;
-        // - round this value to the nearest multiple of 8 (H.264 only accepts multiples of 8)
-        w &= ~7; // in case it's not a multiple of 8
-        h &= ~7;
-        if (maxSize > 0) {
-            if (BuildConfig.DEBUG && maxSize % 8 != 0) {
-                throw new AssertionError("Max size must be a multiple of 8");
-            }
-            boolean portrait = h > w;
-            int major = portrait ? h : w;
-            int minor = portrait ? w : h;
-            if (major > maxSize) {
-                int minorExact = minor * maxSize / major;
-                // +4 to round the value to the nearest multiple of 8
-                minor = (minorExact + 4) & ~7;
-                major = maxSize;
-            }
-            w = portrait ? minor : major;
-            h = portrait ? major : minor;
-        }
-        return new Size(w, h);
-    }
-
     private static Rect flipRect(Rect crop) {
         return new Rect(crop.top, crop.left, crop.bottom, crop.right);
     }