From 3ee3f8dc027fe4e2d21ef144df4c29acbd709ee7 Mon Sep 17 00:00:00 2001
From: Romain Vimont <rom@rom1v.com>
Date: Thu, 17 Feb 2022 21:46:13 +0100
Subject: [PATCH] Work around mouse capture SDL bug on macOS

On macOS, SDL relative mouse mode does not work correctly when the
cursor is outside the window.

As a workaround, move the cursor inside the window before setting the
relative mouse mode.

Refs SDL/#5340 <https://github.com/libsdl-org/SDL/issues/5340>
PR #3031 <https://github.com/Genymobile/scrcpy/pull/3031>
---
 app/src/screen.c         | 19 +++++++++++++++++++
 app/src/usb/screen_otg.c | 19 +++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/app/src/screen.c b/app/src/screen.c
index 7ca9bfb7..ae28e6e6 100644
--- a/app/src/screen.c
+++ b/app/src/screen.c
@@ -164,7 +164,26 @@ sc_screen_is_relative_mode(struct sc_screen *screen) {
 
 static void
 sc_screen_set_mouse_capture(struct sc_screen *screen, bool capture) {
+#ifdef __APPLE__
+    // Workaround for SDL bug on macOS:
+    // <https://github.com/libsdl-org/SDL/issues/5340>
+    if (capture) {
+        int mouse_x, mouse_y;
+        SDL_GetGlobalMouseState(&mouse_x, &mouse_y);
+
+        int x, y, w, h;
+        SDL_GetWindowPosition(screen->window, &x, &y);
+        SDL_GetWindowSize(screen->window, &w, &h);
+
+        bool outside_window = mouse_x < x || mouse_x >= x + w
+                           || mouse_y < y || mouse_y >= y + h;
+        if (outside_window) {
+            SDL_WarpMouseInWindow(screen->window, w / 2, h / 2);
+        }
+    }
+#else
     (void) screen;
+#endif
     if (SDL_SetRelativeMouseMode(capture)) {
         LOGE("Could not set relative mouse mode to %s: %s",
              capture ? "true" : "false", SDL_GetError());
diff --git a/app/src/usb/screen_otg.c b/app/src/usb/screen_otg.c
index 96d7eaff..561a84ca 100644
--- a/app/src/usb/screen_otg.c
+++ b/app/src/usb/screen_otg.c
@@ -6,7 +6,26 @@
 
 static void
 sc_screen_otg_set_mouse_capture(struct sc_screen_otg *screen, bool capture) {
+#ifdef __APPLE__
+    // Workaround for SDL bug on macOS:
+    // <https://github.com/libsdl-org/SDL/issues/5340>
+    if (capture) {
+        int mouse_x, mouse_y;
+        SDL_GetGlobalMouseState(&mouse_x, &mouse_y);
+
+        int x, y, w, h;
+        SDL_GetWindowPosition(screen->window, &x, &y);
+        SDL_GetWindowSize(screen->window, &w, &h);
+
+        bool outside_window = mouse_x < x || mouse_x >= x + w
+                           || mouse_y < y || mouse_y >= y + h;
+        if (outside_window) {
+            SDL_WarpMouseInWindow(screen->window, w / 2, h / 2);
+        }
+    }
+#else
     (void) screen;
+#endif
     if (SDL_SetRelativeMouseMode(capture)) {
         LOGE("Could not set relative mouse mode to %s: %s",
              capture ? "true" : "false", SDL_GetError());