Document HID mouse in README

This paves the way to add support for HID mouse initialization.

README.md

@@ -31,6 +31,8 @@ Its features include:
  - device screen [as a webcam (V4L2)](#v4l2loopback) (Linux-only)
  - [physical keyboard simulation (HID)](#physical-keyboard-simulation-hid)
    (Linux-only)
+ - [physical mouse simulation (HID)](#physical-mouse-simulation-hid)
+   (Linux-only)
  - and more…
 
 ## Requirements
@@ -815,6 +817,35 @@ a physical keyboard is connected).
 
 [Physical keyboard]: https://github.com/Genymobile/scrcpy/pull/2632#issuecomment-923756915
 
+#### Physical mouse simulation (HID)
+
+Similarly to the physical keyboard simulation, it is possible to simulate a
+physical mouse. Likewise, it only works if the device is connected by USB, and
+is currently only supported on Linux.
+
+By default, scrcpy uses Android mouse events injection, using absolute
+coordinates. By simulating a physical mouse, a mouse pointer appears on the
+Android device, and relative mouse motion, clicks and scrolls are injected.
+
+To enable this mode:
+
+```bash
+scrcpy --hid-mouse
+scrcpy -M  # short version
+```
+
+You could also add `--forward-all-clicks` to [forward all mouse
+buttons][forward_all_clicks].
+
+[forward_all_clicks]: #right-click-and-middle-click
+
+When this mode is enabled, the computer mouse is "captured" (the mouse pointer
+disappears from the computer and appears on the Android device instead).
+
+Special capture keys, either <kbd>Alt</kbd> or <kbd>Super</kbd>, toggle
+(disable or enable) the mouse capture. Use one of them to give the control of
+the mouse back to the computer.
+
 
 #### Text injection preference
 

app/scrcpy.1

@@ -96,6 +96,8 @@ The keyboard layout must be configured (once and for all) on the device, via Set
 
 However, the option is only available when the HID keyboard is enabled (or a physical keyboard is connected).
 
+Also see \fB\-\-hid\-mouse\fR.
+
 .TP
 .B \-\-legacy\-paste
 Inject computer clipboard text as a sequence of key events on Ctrl+v (like MOD+Shift+v).
@@ -120,6 +122,18 @@ Limit both the width and height of the video to \fIvalue\fR. The other dimension
 
 Default is 0 (unlimited).
 
+.TP
+.B \-M, \-\-hid\-mouse
+Simulate a physical mouse by using HID over AOAv2.
+
+In this mode, the computer mouse is captured to control the device directly (relative mouse mode).
+
+LAlt, LSuper or RSuper toggle the capture mode, to give control of the mouse back to the computer.
+
+It may only work over USB, and is currently only supported on Linux.
+
+Also see \fB\-\-hid\-keyboard\fR.
+
 .TP
 .B \-\-no\-clipboard\-autosync
 By default, scrcpy automatically synchronizes the computer clipboard to the device clipboard before injecting Ctrl+v, and the device clipboard to the computer clipboard whenever it changes.

app/src/cli.c

@@ -178,7 +178,8 @@ static const struct sc_option options[] = {
                 "directly: `adb shell am start -a "
                 "android.settings.HARD_KEYBOARD_SETTINGS`.\n"
                 "However, the option is only available when the HID keyboard "
-                "is enabled (or a physical keyboard is connected).",
+                "is enabled (or a physical keyboard is connected).\n"
+                "Also see --hid-mouse.",
     },
     {
         .shortopt = 'h',
@@ -223,7 +224,8 @@ static const struct sc_option options[] = {
                 "LAlt, LSuper or RSuper toggle the capture mode, to give "
                 "control of the mouse back to the computer.\n"
                 "It may only work over USB, and is currently only supported "
-                "on Linux.\n",
+                "on Linux.\n"
+                "Also see --hid-keyboard.",
     },
     {
         .shortopt = 'm',
@@ -406,8 +408,8 @@ static const struct sc_option options[] = {
                 "frames. This increases latency to compensate for jitter.\n"
                 "This option is similar to --display-buffer, but specific to "
                 "V4L2 sink.\n"
-                "This feature is only available on Linux.\n"
+                "Default is 0 (no buffering).\n"
-                "Default is 0 (no buffering).",
+                "This option is only available on Linux.",
     },
     {
         .shortopt = 'V',

app/src/input_events.h

@@ -54,7 +54,6 @@ enum sc_mod {
 
     SC_MOD_NUM = KMOD_NUM,
     SC_MOD_CAPS = KMOD_CAPS,
-    SC_MOD_SCROLL = KMOD_SCROLL,
 };
 
 enum sc_action {

app/src/input_manager.c

@@ -171,7 +171,6 @@ send_keycode(struct controller *controller, enum android_keycode keycode,
 
     if (!controller_push_msg(controller, &msg)) {
         LOGW("Could not request 'inject %s'", name);
-        return;
     }
 }
 
@@ -223,7 +222,6 @@ press_back_or_turn_screen_on(struct controller *controller,
 
     if (!controller_push_msg(controller, &msg)) {
         LOGW("Could not request 'press back or turn screen on'");
-        return;
     }
 }
 
@@ -634,14 +632,6 @@ static void
 input_manager_process_mouse_motion(struct input_manager *im,
                                    const SDL_MouseMotionEvent *event) {
 
-    uint32_t mask = SDL_BUTTON_LMASK;
-    if (im->forward_all_clicks) {
-        mask |= SDL_BUTTON_MMASK | SDL_BUTTON_RMASK;
-    }
-    //if (!(event->state & mask)) {
-    //    // do not send motion events when no click is pressed
-    //    return;
-    //}
     if (event->which == SDL_TOUCH_MOUSEID) {
         // simulated from touch events, so it's a duplicate
         return;
@@ -663,7 +653,11 @@ input_manager_process_mouse_motion(struct input_manager *im,
     assert(im->mp->ops->process_mouse_motion);
     im->mp->ops->process_mouse_motion(im->mp, &evt);
 
+    // vfinger must never be used in relative mode
+    assert(!im->mp->relative_mode || !im->vfinger_down);
+
     if (im->vfinger_down) {
+        assert(!im->mp->relative_mode); // assert one more time
         struct sc_point mouse =
             screen_convert_window_to_frame_coords(im->screen, event->x,
                                                   event->y);
@@ -792,8 +786,9 @@ input_manager_process_mouse_button(struct input_manager *im,
     // In other words, the center of the rotation/scaling is the center of the
     // screen.
 #define CTRL_PRESSED (SDL_GetModState() & (KMOD_LCTRL | KMOD_RCTRL))
-    if ((down && !im->vfinger_down && CTRL_PRESSED)
+    if (event->button == SDL_BUTTON_LEFT &&
-            || (!down && im->vfinger_down)) {
+            ((down && !im->vfinger_down && CTRL_PRESSED) ||
+             (!down && im->vfinger_down))) {
         struct sc_point mouse =
             screen_convert_window_to_frame_coords(im->screen, event->x,
                                                               event->y);

app/src/input_manager.h

@@ -13,8 +13,6 @@
 #include "trait/key_processor.h"
 #include "trait/mouse_processor.h"
 
-struct screen; // forward declaration to avoid cycle
-
 struct input_manager {
     struct controller *controller;
     struct screen *screen;

app/src/mouse_inject.c

@@ -58,6 +58,11 @@ convert_touch_action(enum sc_touch_action action) {
 static void
 sc_mouse_processor_process_mouse_motion(struct sc_mouse_processor *mp,
                                     const struct sc_mouse_motion_event *event) {
+    if (!event->buttons_state) {
+        // Do not send motion events when no click is pressed
+        return;
+    }
+
     struct sc_mouse_inject *mi = DOWNCAST(mp);
 
     struct control_msg msg = {

app/src/util/net.c

@@ -83,6 +83,7 @@ unwrap(sc_socket socket) {
 #endif
 }
 
+#ifndef HAVE_SOCK_CLOEXEC // avoid unused-function warning
 static inline bool
 sc_raw_socket_close(sc_raw_socket raw_sock) {
 #ifndef _WIN32
@@ -91,6 +92,7 @@ sc_raw_socket_close(sc_raw_socket raw_sock) {
     return !closesocket(raw_sock);
 #endif
 }
+#endif
 
 #ifndef HAVE_SOCK_CLOEXEC
 // If SOCK_CLOEXEC does not exist, the flag must be set manually once the