From f4a872bef4f048ea2bce0d273317dc93e30f881a Mon Sep 17 00:00:00 2001
From: Romain Vimont <rom@rom1v.com>
Date: Fri, 17 Apr 2026 18:17:57 +0200
Subject: [PATCH] Fix aspect ratio accuracy

The window aspect ratio was previously enforced by calling
`SDL_SetWindowAspectRatio()` before explicitly setting the window size,
using the width/height ratio of the new size.

However, this size may already be a scaled version of the actual content
size, subject to integer rounding. Using this derived size instead of
the actual content size could result in an inaccurate ratio, causing a
mismatch between the content and window aspect ratios, which may result
in a thin row or column of black pixels.

To avoid this issue, always set the aspect ratio based on the content
size.

Refs 1b4fd672869dcaa7f0ba8f11b722b731488d690d
Refs #6761 <https://github.com/Genymobile/scrcpy/pull/6761>
PR #6774 <https://github.com/Genymobile/scrcpy/pull/6774>
---
 app/src/screen.c | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/app/src/screen.c b/app/src/screen.c
index b1bcdf3a..683d3e5f 100644
--- a/app/src/screen.c
+++ b/app/src/screen.c
@@ -15,18 +15,16 @@
 #define DOWNCAST(SINK) container_of(SINK, struct sc_screen, frame_sink)
 
 static void
-set_window_size_ar(struct sc_screen *screen, struct sc_size window_size) {
-    assert(window_size.width && window_size.height);
+set_aspect_ratio(struct sc_screen *screen, struct sc_size content_size) {
+    assert(content_size.width && content_size.height);
 
     if (screen->window_aspect_ratio_lock) {
-        float ar = (float) window_size.width / window_size.height;
+        float ar = (float) content_size.width / content_size.height;
         bool ok = SDL_SetWindowAspectRatio(screen->window, ar, ar);
         if (!ok) {
             LOGW("Could not set window aspect ratio: %s", SDL_GetError());
         }
     }
-
-    sc_sdl_set_window_size(screen->window, window_size);
 }
 
 static inline struct sc_size
@@ -625,7 +623,8 @@ sc_screen_show_initial_window(struct sc_screen *screen) {
                                                        screen->req.height);
 
     assert(is_windowed(screen));
-    set_window_size_ar(screen, window_size);
+    set_aspect_ratio(screen, screen->content_size);
+    sc_sdl_set_window_size(screen->window, window_size);
     sc_sdl_set_window_position(screen->window, position);
 
     if (screen->req.fullscreen) {
@@ -711,7 +710,8 @@ resize_for_content(struct sc_screen *screen, struct sc_size old_content_size,
     };
     target_size = get_optimal_size(target_size, new_content_size, true);
     assert(is_windowed(screen));
-    set_window_size_ar(screen, target_size);
+    set_aspect_ratio(screen, new_content_size);
+    sc_sdl_set_window_size(screen->window, target_size);
 }
 
 static void
@@ -887,7 +887,8 @@ sc_screen_resize_to_fit(struct sc_screen *screen) {
         .y = point.y + (window_size.height - optimal_size.height) / 2,
     };
 
-    set_window_size_ar(screen, optimal_size);
+    set_aspect_ratio(screen, screen->content_size);
+    sc_sdl_set_window_size(screen->window, optimal_size);
     sc_sdl_set_window_position(screen->window, new_position);
     LOGD("Resized to optimal size: %ux%u", optimal_size.width,
                                            optimal_size.height);
@@ -902,7 +903,8 @@ sc_screen_resize_to_pixel_perfect(struct sc_screen *screen) {
     }
 
     struct sc_size content_size = screen->content_size;
-    set_window_size_ar(screen, content_size);
+    set_aspect_ratio(screen, content_size);
+    sc_sdl_set_window_size(screen->window, content_size);
     LOGD("Resized to pixel-perfect: %ux%u", content_size.width,
                                             content_size.height);
 }