Add --display-orientation

Deprecate the option --rotation and introduce a new option
--display-orientation with the 8 possible orientations (0, 90, 180, 270,
flip0, flip90, flip180 and flip270).

New shortcuts MOD+Shift+(arrow) dynamically change the display
(horizontal or vertical) flip.

Fixes #1380 <https://github.com/Genymobile/scrcpy/issues/1380>
Fixes #3819 <https://github.com/Genymobile/scrcpy/issues/3819>
PR #4441 <https://github.com/Genymobile/scrcpy/pull/4441>

app/data/bash-completion/scrcpy

@@ -21,6 +21,7 @@ _scrcpy() {
         --disable-screensaver
         --display-buffer=
         --display-id=
+        --display-orientation=
         -e --select-tcpip
         -f --fullscreen
         --force-adb-forward
@@ -112,6 +113,10 @@ _scrcpy() {
             COMPREPLY=($(compgen -W 'front back external' -- "$cur"))
             return
             ;;
+        --display-orientation)
+            COMPREPLY=($(compgen -> '0 90 180 270 flip0 flip90 flip180 flip270' -- "$cur"))
+            return
+            ;;
         --lock-video-orientation)
             COMPREPLY=($(compgen -W 'unlocked initial 0 1 2 3' -- "$cur"))
             return
@@ -132,10 +137,6 @@ _scrcpy() {
             COMPREPLY=($(compgen -W 'direct3d opengl opengles2 opengles metal software' -- "$cur"))
             return
             ;;
-        --rotation)
-            COMPREPLY=($(compgen -W '0 1 2 3' -- "$cur"))
-            return
-            ;;
         --shortcut-mod)
             # Only auto-complete a single key
             COMPREPLY=($(compgen -W 'lctrl rctrl lalt ralt lsuper rsuper' -- "$cur"))

app/data/zsh-completion/_scrcpy

@@ -28,6 +28,7 @@ arguments=(
     '--disable-screensaver[Disable screensaver while scrcpy is running]'
     '--display-buffer=[Add a buffering delay \(in milliseconds\) before displaying]'
     '--display-id=[Specify the display id to mirror]'
+    '--display-orientation=[Set the initial display orientation]:orientation values:(0 90 180 270 flip0 flip90 flip180 flip270)'
     {-e,--select-tcpip}'[Use TCP/IP device]'
     {-f,--fullscreen}'[Start in fullscreen]'
     '--force-adb-forward[Do not attempt to use \"adb reverse\" to connect to the device]'
@@ -68,7 +69,6 @@ arguments=(
     '--record-format=[Force recording format]:format:(mp4 mkv m4a mka opus aac flac wav)'
     '--render-driver=[Request SDL to use the given render driver]:driver name:(direct3d opengl opengles2 opengles metal software)'
     '--require-audio=[Make scrcpy fail if audio is enabled but does not work]'
-    '--rotation=[Set the initial display rotation]:rotation values:(0 1 2 3)'
     {-s,--serial=}'[The device serial number \(mandatory for multiple devices only\)]:serial:($("${ADB-adb}" devices | awk '\''$2 == "device" {print $1}'\''))'
     {-S,--turn-screen-off}'[Turn the device screen off immediately]'
     '--shortcut-mod=[\[key1,key2+key3,...\] Specify the modifiers to use for scrcpy shortcuts]:shortcut mod:(lctrl rctrl lalt ralt lsuper rsuper)'

app/meson.build

@@ -289,6 +289,10 @@ if get_option('buildtype') == 'debug'
             'tests/test_device_msg_deserialize.c',
             'src/device_msg.c',
         ]],
+        ['test_orientation', [
+            'tests/test_orientation.c',
+            'src/options.c',
+        ]],
         ['test_strbuf', [
             'tests/test_strbuf.c',
             'src/util/strbuf.c',

app/scrcpy.1

@@ -141,6 +141,14 @@ The available display ids can be listed by \fB\-\-list\-displays\fR.
 
 Default is 0.
 
+.TP
+.BI "\-\-display\-orientation " value
+Set the initial display orientation.
+
+Possible values are 0, 90, 180, 270, flip0, flip90, flip180 and flip270. The number represents the clockwise rotation in degrees; the "flip" keyword applies a horizontal flip before the rotation.
+
+Default is 0.
+
 .TP
 .B \-e, \-\-select\-tcpip
 Use TCP/IP device (if there is exactly one, like adb -e).
@@ -369,10 +377,6 @@ Supported names are currently "direct3d", "opengl", "opengles2", "opengles", "me
 .B \-\-require\-audio
 By default, scrcpy mirrors only the video if audio capture fails on the device. This option makes scrcpy fail if audio is enabled but does not work.
 
-.TP
-.BI "\-\-rotation " value
-Set the initial display rotation. Possibles values are 0, 1, 2 and 3. Each increment adds a 90 degrees rotation counterclockwise.
-
 .TP
 .BI "\-s, \-\-serial " number
 The device serial number. Mandatory only if several devices are connected to adb.
@@ -534,6 +538,14 @@ Rotate display left
 .B MOD+Right
 Rotate display right
 
+.TP
+.B MOD+Shift+Left, MOD+Shift+Right
+Flip display horizontally
+
+.TP
+.B MOD+Shift+Up, MOD+Shift+Down
+Flip display vertically
+
 .TP
 .B MOD+g
 Resize window to 1:1 (pixel\-perfect)

app/src/cli.c

@@ -90,6 +90,7 @@ enum {
     OPT_CAMERA_AR,
     OPT_CAMERA_FPS,
     OPT_CAMERA_HIGH_SPEED,
+    OPT_DISPLAY_ORIENTATION,
 };
 
 struct sc_option {
@@ -309,6 +310,17 @@ static const struct sc_option options[] = {
                 "    scrcpy --list-displays\n"
                 "Default is 0.",
     },
+    {
+        .longopt_id = OPT_DISPLAY_ORIENTATION,
+        .longopt = "display-orientation",
+        .argdesc = "value",
+        .text = "Set the initial display orientation.\n"
+                "Possible values are 0, 90, 180, 270, flip0, flip90, flip180 "
+                "and flip270. The number represents the clockwise rotation "
+                "in degrees; the \"flip\" keyword applies a horizontal flip "
+                "before the rotation.\n"
+                "Default is 0.",
+    },
     {
         .shortopt = 'e',
         .longopt = "select-tcpip",
@@ -615,12 +627,10 @@ static const struct sc_option options[] = {
                 "is enabled but does not work."
     },
     {
+        // deprecated
         .longopt_id = OPT_ROTATION,
         .longopt = "rotation",
         .argdesc = "value",
-        .text = "Set the initial display rotation.\n"
-                "Possible values are 0, 1, 2 and 3. Each increment adds a 90 "
-                "degrees rotation counterclockwise.",
     },
     {
         .shortopt = 's',
@@ -824,6 +834,14 @@ static const struct sc_shortcut shortcuts[] = {
         .shortcuts = { "MOD+Right" },
         .text = "Rotate display right",
     },
+    {
+        .shortcuts = { "MOD+Shift+Left", "MOD+Shift+Right" },
+        .text = "Flip display horizontally",
+    },
+    {
+        .shortcuts = { "MOD+Shift+Up", "MOD+Shift+Down" },
+        .text = "Flip display vertically",
+    },
     {
         .shortcuts = { "MOD+g" },
         .text = "Resize window to 1:1 (pixel-perfect)",
@@ -1405,6 +1423,45 @@ parse_rotation(const char *s, uint8_t *rotation) {
     return true;
 }
 
+static bool
+parse_orientation(const char *s, enum sc_orientation *orientation) {
+    if (!strcmp(s, "0")) {
+        *orientation = SC_ORIENTATION_0;
+        return true;
+    }
+    if (!strcmp(s, "90")) {
+        *orientation = SC_ORIENTATION_90;
+        return true;
+    }
+    if (!strcmp(s, "180")) {
+        *orientation = SC_ORIENTATION_180;
+        return true;
+    }
+    if (!strcmp(s, "270")) {
+        *orientation = SC_ORIENTATION_270;
+        return true;
+    }
+    if (!strcmp(s, "flip0")) {
+        *orientation = SC_ORIENTATION_FLIP_0;
+        return true;
+    }
+    if (!strcmp(s, "flip90")) {
+        *orientation = SC_ORIENTATION_FLIP_90;
+        return true;
+    }
+    if (!strcmp(s, "flip180")) {
+        *orientation = SC_ORIENTATION_FLIP_180;
+        return true;
+    }
+    if (!strcmp(s, "flip270")) {
+        *orientation = SC_ORIENTATION_FLIP_270;
+        return true;
+    }
+    LOGE("Unsupported orientation: %s (expected 0, 90, 180, 270, flip0, "
+         "flip90, flip180 or flip270)", optarg);
+    return false;
+}
+
 static bool
 parse_window_position(const char *s, int16_t *position) {
     // special value for "auto"
@@ -2008,7 +2065,34 @@ parse_args_with_getopt(struct scrcpy_cli_args *args, int argc, char *argv[],
                 opts->key_inject_mode = SC_KEY_INJECT_MODE_RAW;
                 break;
             case OPT_ROTATION:
-                if (!parse_rotation(optarg, &opts->rotation)) {
+                LOGW("--rotation is deprecated, use --display-orientation "
+                     "instead.");
+                uint8_t rotation;
+                if (!parse_rotation(optarg, &rotation)) {
+                    return false;
+                }
+                assert(rotation <= 3);
+                switch (rotation) {
+                    case 0:
+                        opts->display_orientation = SC_ORIENTATION_0;
+                        break;
+                    case 1:
+                        // rotation 1 was 90° counterclockwise, but orientation
+                        // is expressed clockwise
+                        opts->display_orientation = SC_ORIENTATION_270;
+                        break;
+                    case 2:
+                        opts->display_orientation = SC_ORIENTATION_180;
+                        break;
+                    case 3:
+                        // rotation 3 was 270° counterclockwise, but orientation
+                        // is expressed clockwise
+                        opts->display_orientation = SC_ORIENTATION_90;
+                        break;
+                }
+                break;
+            case OPT_DISPLAY_ORIENTATION:
+                if (!parse_orientation(optarg, &opts->display_orientation)) {
                     return false;
                 }
                 break;

app/src/display.c

@@ -234,7 +234,7 @@ sc_display_update_texture(struct sc_display *display, const AVFrame *frame) {
 
 enum sc_display_result
 sc_display_render(struct sc_display *display, const SDL_Rect *geometry,
-                  unsigned rotation) {
+                  enum sc_orientation orientation) {
     SDL_RenderClear(display->renderer);
 
     if (display->pending.flags) {
@@ -247,33 +247,33 @@ sc_display_render(struct sc_display *display, const SDL_Rect *geometry,
     SDL_Renderer *renderer = display->renderer;
     SDL_Texture *texture = display->texture;
 
-    if (rotation == 0) {
+    if (orientation == SC_ORIENTATION_0) {
         int ret = SDL_RenderCopy(renderer, texture, NULL, geometry);
         if (ret) {
             LOGE("Could not render texture: %s", SDL_GetError());
             return SC_DISPLAY_RESULT_ERROR;
         }
     } else {
-        // rotation in RenderCopyEx() is clockwise, while screen->rotation is
+        unsigned cw_rotation = sc_orientation_get_rotation(orientation);
-        // counterclockwise (to be consistent with --lock-video-orientation)
-        int cw_rotation = (4 - rotation) % 4;
         double angle = 90 * cw_rotation;
 
         const SDL_Rect *dstrect = NULL;
         SDL_Rect rect;
-        if (rotation & 1) {
+        if (sc_orientation_is_swap(orientation)) {
             rect.x = geometry->x + (geometry->w - geometry->h) / 2;
             rect.y = geometry->y + (geometry->h - geometry->w) / 2;
             rect.w = geometry->h;
             rect.h = geometry->w;
             dstrect = ▭
         } else {
-            assert(rotation == 2);
             dstrect = geometry;
         }
 
+        SDL_RendererFlip flip = sc_orientation_is_mirror(orientation)
+                              ? SDL_FLIP_HORIZONTAL : 0;
+
         int ret = SDL_RenderCopyEx(renderer, texture, NULL, dstrect, angle,
-                                   NULL, 0);
+                                   NULL, flip);
         if (ret) {
             LOGE("Could not render texture: %s", SDL_GetError());
             return SC_DISPLAY_RESULT_ERROR;

app/src/display.h

@@ -9,6 +9,7 @@
 
 #include "coords.h"
 #include "opengl.h"
+#include "options.h"
 
 #ifdef __APPLE__
 # define SC_DISPLAY_FORCE_OPENGL_CORE_PROFILE
@@ -54,6 +55,6 @@ sc_display_update_texture(struct sc_display *display, const AVFrame *frame);
 
 enum sc_display_result
 sc_display_render(struct sc_display *display, const SDL_Rect *geometry,
-                  unsigned rotation);
+                  enum sc_orientation orientation);
 
 #endif

app/src/input_manager.c

@@ -293,15 +293,11 @@ rotate_device(struct sc_controller *controller) {
 }
 
 static void
-rotate_client_left(struct sc_screen *screen) {
+apply_orientation_transform(struct sc_screen *screen,
-    unsigned new_rotation = (screen->rotation + 1) % 4;
+                            enum sc_orientation transform) {
-    sc_screen_set_rotation(screen, new_rotation);
+    enum sc_orientation new_orientation =
-}
+        sc_orientation_apply(screen->orientation, transform);
-
+    sc_screen_set_orientation(screen, new_orientation);
-static void
-rotate_client_right(struct sc_screen *screen) {
-    unsigned new_rotation = (screen->rotation + 3) % 4;
-    sc_screen_set_rotation(screen, new_rotation);
 }
 
 static void
@@ -421,25 +417,47 @@ sc_input_manager_process_key(struct sc_input_manager *im,
                 }
                 return;
             case SDLK_DOWN:
-                if (controller && !shift) {
+                if (shift) {
+                    if (!repeat & down) {
+                        apply_orientation_transform(im->screen,
+                                                    SC_ORIENTATION_FLIP_180);
+                    }
+                } else if (controller) {
                     // forward repeated events
                     action_volume_down(controller, action);
                 }
                 return;
             case SDLK_UP:
-                if (controller && !shift) {
+                if (shift) {
+                    if (!repeat & down) {
+                        apply_orientation_transform(im->screen,
+                                                    SC_ORIENTATION_FLIP_180);
+                    }
+                } else if (controller) {
                     // forward repeated events
                     action_volume_up(controller, action);
                 }
                 return;
             case SDLK_LEFT:
-                if (!shift && !repeat && down) {
+                if (!repeat && down) {
-                    rotate_client_left(im->screen);
+                    if (shift) {
+                        apply_orientation_transform(im->screen,
+                                                    SC_ORIENTATION_FLIP_0);
+                    } else {
+                        apply_orientation_transform(im->screen,
+                                                    SC_ORIENTATION_270);
+                    }
                 }
                 return;
             case SDLK_RIGHT:
-                if (!shift && !repeat && down) {
+                if (!repeat && down) {
-                    rotate_client_right(im->screen);
+                    if (shift) {
+                        apply_orientation_transform(im->screen,
+                                                    SC_ORIENTATION_FLIP_0);
+                    } else {
+                        apply_orientation_transform(im->screen,
+                                                    SC_ORIENTATION_90);
+                    }
                 }
                 return;
             case SDLK_c:

app/src/options.c

@@ -39,7 +39,7 @@ const struct scrcpy_options scrcpy_options_default = {
     .audio_bit_rate = 0,
     .max_fps = 0,
     .lock_video_orientation = SC_LOCK_VIDEO_ORIENTATION_UNLOCKED,
-    .rotation = 0,
+    .display_orientation = SC_ORIENTATION_0,
     .window_x = SC_WINDOW_POSITION_UNDEFINED,
     .window_y = SC_WINDOW_POSITION_UNDEFINED,
     .window_width = 0,
@@ -89,3 +89,39 @@ const struct scrcpy_options scrcpy_options_default = {
     .camera_high_speed = false,
     .list = 0,
 };
+
+enum sc_orientation
+sc_orientation_apply(enum sc_orientation src, enum sc_orientation transform) {
+    assert(!(src & ~7));
+    assert(!(transform & ~7));
+
+    unsigned transform_hflip = transform & 4;
+    unsigned transform_rotation = transform & 3;
+    unsigned src_hflip = src & 4;
+    unsigned src_rotation = src & 3;
+    unsigned src_swap = src & 1;
+    if (src_swap && transform_hflip) {
+        // If the src is rotated by 90 or 270 degrees, applying a flipped
+        // transformation requires an additional 180 degrees rotation to
+        // compensate for the inversion of the order of multiplication:
+        //
+        //     hflip1 × rotate1 × hflip2 × rotate2
+        //     `--------------'   `--------------'
+        //           src             transform
+        //
+        // In the final result, we want all the hflips then all the rotations,
+        // so we must move hflip2 to the left:
+        //
+        //     hflip1 × hflip2 × rotate1' × rotate2
+        //
+        // with rotate1' = | rotate1           if src is 0° or 180°
+        //                 | rotate1 + 180°    if src is 90° or 270°
+
+        src_rotation += 2;
+    }
+
+    unsigned result_hflip = src_hflip ^ transform_hflip;
+    unsigned result_rotation = (transform_rotation + src_rotation) % 4;
+    enum sc_orientation result = result_hflip | result_rotation;
+    return result;
+}

app/src/options.h

@@ -3,6 +3,7 @@
 
 #include "common.h"
 
+#include <assert.h>
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
@@ -67,6 +68,67 @@ enum sc_camera_facing {
     SC_CAMERA_FACING_EXTERNAL,
 };
 
+                              // ,----- hflip (applied before the rotation)
+                              // | ,--- 180°
+                              // | | ,- 90° clockwise
+                              // | | |
+enum sc_orientation {         // v v v
+    SC_ORIENTATION_0,         // 0 0 0
+    SC_ORIENTATION_90,        // 0 0 1
+    SC_ORIENTATION_180,       // 0 1 0
+    SC_ORIENTATION_270,       // 0 1 1
+    SC_ORIENTATION_FLIP_0,    // 1 0 0
+    SC_ORIENTATION_FLIP_90,   // 1 0 1
+    SC_ORIENTATION_FLIP_180,  // 1 1 0
+    SC_ORIENTATION_FLIP_270,  // 1 1 1
+};
+
+static inline bool
+sc_orientation_is_mirror(enum sc_orientation orientation) {
+    assert(!(orientation & ~7));
+    return orientation & 4;
+}
+
+// Does the orientation swap width and height?
+static inline bool
+sc_orientation_is_swap(enum sc_orientation orientation) {
+    assert(!(orientation & ~7));
+    return orientation & 1;
+}
+
+static inline enum sc_orientation
+sc_orientation_get_rotation(enum sc_orientation orientation) {
+    assert(!(orientation & ~7));
+    return orientation & 3;
+}
+
+enum sc_orientation
+sc_orientation_apply(enum sc_orientation src, enum sc_orientation transform);
+
+static inline const char *
+sc_orientation_get_name(enum sc_orientation orientation) {
+    switch (orientation) {
+        case SC_ORIENTATION_0:
+            return "0";
+        case SC_ORIENTATION_90:
+            return "90";
+        case SC_ORIENTATION_180:
+            return "180";
+        case SC_ORIENTATION_270:
+            return "270";
+        case SC_ORIENTATION_FLIP_0:
+            return "flip0";
+        case SC_ORIENTATION_FLIP_90:
+            return "flip90";
+        case SC_ORIENTATION_FLIP_180:
+            return "flip180";
+        case SC_ORIENTATION_FLIP_270:
+            return "flip270";
+        default:
+            return "(unknown)";
+    }
+}
+
 enum sc_lock_video_orientation {
     SC_LOCK_VIDEO_ORIENTATION_UNLOCKED = -1,
     // lock the current orientation when scrcpy starts
@@ -157,7 +219,7 @@ struct scrcpy_options {
     uint32_t audio_bit_rate;
     uint16_t max_fps;
     enum sc_lock_video_orientation lock_video_orientation;
-    uint8_t rotation;
+    enum sc_orientation display_orientation;
     int16_t window_x; // SC_WINDOW_POSITION_UNDEFINED for "auto"
     int16_t window_y; // SC_WINDOW_POSITION_UNDEFINED for "auto"
     uint16_t window_width;

app/src/scrcpy.c

@@ -691,7 +691,7 @@ aoa_hid_end:
             .window_width = options->window_width,
             .window_height = options->window_height,
             .window_borderless = options->window_borderless,
-            .rotation = options->rotation,
+            .orientation = options->display_orientation,
             .mipmaps = options->mipmaps,
             .fullscreen = options->fullscreen,
             .start_fps_counter = options->start_fps_counter,

app/src/screen.c

@@ -14,16 +14,16 @@
 #define DOWNCAST(SINK) container_of(SINK, struct sc_screen, frame_sink)
 
 static inline struct sc_size
-get_rotated_size(struct sc_size size, int rotation) {
+get_oriented_size(struct sc_size size, enum sc_orientation orientation) {
-    struct sc_size rotated_size;
+    struct sc_size oriented_size;
-    if (rotation & 1) {
+    if (sc_orientation_is_swap(orientation)) {
-        rotated_size.width = size.height;
+        oriented_size.width = size.height;
-        rotated_size.height = size.width;
+        oriented_size.height = size.width;
     } else {
-        rotated_size.width = size.width;
+        oriented_size.width = size.width;
-        rotated_size.height = size.height;
+        oriented_size.height = size.height;
     }
-    return rotated_size;
+    return oriented_size;
 }
 
 // get the window size in a struct sc_size
@@ -251,7 +251,7 @@ sc_screen_render(struct sc_screen *screen, bool update_content_rect) {
     }
 
     enum sc_display_result res =
-        sc_display_render(&screen->display, &screen->rect, screen->rotation);
+        sc_display_render(&screen->display, &screen->rect, screen->orientation);
     (void) res; // any error already logged
 }
 
@@ -379,9 +379,10 @@ sc_screen_init(struct sc_screen *screen,
         goto error_destroy_frame_buffer;
     }
 
-    screen->rotation = params->rotation;
+    screen->orientation = params->orientation;
-    if (screen->rotation) {
+    if (screen->orientation != SC_ORIENTATION_0) {
-        LOGI("Initial display rotation set to %u", screen->rotation);
+        LOGI("Initial display orientation set to %s",
+             sc_orientation_get_name(screen->orientation));
     }
 
     uint32_t window_flags = SDL_WINDOW_HIDDEN
@@ -559,19 +560,19 @@ apply_pending_resize(struct sc_screen *screen) {
 }
 
 void
-sc_screen_set_rotation(struct sc_screen *screen, unsigned rotation) {
+sc_screen_set_orientation(struct sc_screen *screen,
-    assert(rotation < 4);
+                          enum sc_orientation orientation) {
-    if (rotation == screen->rotation) {
+    if (orientation == screen->orientation) {
         return;
     }
 
     struct sc_size new_content_size =
-        get_rotated_size(screen->frame_size, rotation);
+        get_oriented_size(screen->frame_size, orientation);
 
     set_content_size(screen, new_content_size);
 
-    screen->rotation = rotation;
+    screen->orientation = orientation;
-    LOGI("Display rotation set to %u", rotation);
+    LOGI("Display orientation set to %s", sc_orientation_get_name(orientation));
 
     sc_screen_render(screen, true);
 }
@@ -584,7 +585,7 @@ sc_screen_init_size(struct sc_screen *screen) {
     // The requested size is passed via screen->frame_size
 
     struct sc_size content_size =
-        get_rotated_size(screen->frame_size, screen->rotation);
+        get_oriented_size(screen->frame_size, screen->orientation);
     screen->content_size = content_size;
 
     enum sc_display_result res =
@@ -604,7 +605,7 @@ prepare_for_frame(struct sc_screen *screen, struct sc_size new_frame_size) {
     screen->frame_size = new_frame_size;
 
     struct sc_size new_content_size =
-        get_rotated_size(new_frame_size, screen->rotation);
+        get_oriented_size(new_frame_size, screen->orientation);
     set_content_size(screen, new_content_size);
 
     sc_screen_update_content_rect(screen);
@@ -843,8 +844,7 @@ sc_screen_handle_event(struct sc_screen *screen, const SDL_Event *event) {
 struct sc_point
 sc_screen_convert_drawable_to_frame_coords(struct sc_screen *screen,
                                            int32_t x, int32_t y) {
-    unsigned rotation = screen->rotation;
+    enum sc_orientation orientation = screen->orientation;
-    assert(rotation < 4);
 
     int32_t w = screen->content_size.width;
     int32_t h = screen->content_size.height;
@@ -855,27 +855,43 @@ sc_screen_convert_drawable_to_frame_coords(struct sc_screen *screen,
     x = (int64_t) (x - screen->rect.x) * w / screen->rect.w;
     y = (int64_t) (y - screen->rect.y) * h / screen->rect.h;
 
-    // rotate
     struct sc_point result;
-    switch (rotation) {
+    switch (orientation) {
-        case 0:
+        case SC_ORIENTATION_0:
             result.x = x;
             result.y = y;
             break;
-        case 1:
+        case SC_ORIENTATION_90:
-            result.x = h - y;
-            result.y = x;
-            break;
-        case 2:
-            result.x = w - x;
-            result.y = h - y;
-            break;
-        default:
-            assert(rotation == 3);
             result.x = y;
             result.y = w - x;
             break;
+        case SC_ORIENTATION_180:
+            result.x = w - x;
+            result.y = h - y;
+            break;
+        case SC_ORIENTATION_270:
+            result.x = h - y;
+            result.y = x;
+            break;
+        case SC_ORIENTATION_FLIP_0:
+            result.x = w - x;
+            result.y = y;
+            break;
+        case SC_ORIENTATION_FLIP_90:
+            result.x = h - y;
+            result.y = w - x;
+            break;
+        case SC_ORIENTATION_FLIP_180:
+            result.x = x;
+            result.y = h - y;
+            break;
+        default:
+            assert(orientation == SC_ORIENTATION_FLIP_270);
+            result.x = y;
+            result.y = x;
+            break;
     }
+
     return result;
 }
 

app/src/screen.h

@@ -14,6 +14,7 @@
 #include "frame_buffer.h"
 #include "input_manager.h"
 #include "opengl.h"
+#include "options.h"
 #include "trait/key_processor.h"
 #include "trait/frame_sink.h"
 #include "trait/mouse_processor.h"
@@ -49,8 +50,8 @@ struct sc_screen {
     // fullscreen (meaningful only when resize_pending is true)
     struct sc_size windowed_content_size;
 
-    // client rotation: 0, 1, 2 or 3 (x90 degrees counterclockwise)
+    // client orientation
-    unsigned rotation;
+    enum sc_orientation orientation;
     // rectangle of the content (excluding black borders)
     struct SDL_Rect rect;
     bool has_frame;
@@ -86,7 +87,7 @@ struct sc_screen_params {
 
     bool window_borderless;
 
-    uint8_t rotation;
+    enum sc_orientation orientation;
     bool mipmaps;
 
     bool fullscreen;
@@ -129,9 +130,10 @@ sc_screen_resize_to_fit(struct sc_screen *screen);
 void
 sc_screen_resize_to_pixel_perfect(struct sc_screen *screen);
 
-// set the display rotation (0, 1, 2 or 3, x90 degrees counterclockwise)
+// set the display orientation
 void
-sc_screen_set_rotation(struct sc_screen *screen, unsigned rotation);
+sc_screen_set_orientation(struct sc_screen *screen,
+                          enum sc_orientation orientation);
 
 // react to SDL events
 // If this function returns false, scrcpy must exit with an error.

app/tests/test_orientation.c

@@ -0,0 +1,91 @@
+#include "common.h"
+
+#include <assert.h>
+
+#include "options.h"
+
+static void test_transforms(void) {
+    #define O(X) SC_ORIENTATION_ ## X
+    #define ASSERT_TRANSFORM(SRC, TR, RES) \
+        assert(sc_orientation_apply(O(SRC), O(TR)) == O(RES));
+
+    ASSERT_TRANSFORM(0, 0, 0);
+    ASSERT_TRANSFORM(0, 90, 90);
+    ASSERT_TRANSFORM(0, 180, 180);
+    ASSERT_TRANSFORM(0, 270, 270);
+    ASSERT_TRANSFORM(0, FLIP_0, FLIP_0);
+    ASSERT_TRANSFORM(0, FLIP_90, FLIP_90);
+    ASSERT_TRANSFORM(0, FLIP_180, FLIP_180);
+    ASSERT_TRANSFORM(0, FLIP_270, FLIP_270);
+
+    ASSERT_TRANSFORM(90, 0, 90);
+    ASSERT_TRANSFORM(90, 90, 180);
+    ASSERT_TRANSFORM(90, 180, 270);
+    ASSERT_TRANSFORM(90, 270, 0);
+    ASSERT_TRANSFORM(90, FLIP_0, FLIP_270);
+    ASSERT_TRANSFORM(90, FLIP_90, FLIP_0);
+    ASSERT_TRANSFORM(90, FLIP_180, FLIP_90);
+    ASSERT_TRANSFORM(90, FLIP_270, FLIP_180);
+
+    ASSERT_TRANSFORM(180, 0, 180);
+    ASSERT_TRANSFORM(180, 90, 270);
+    ASSERT_TRANSFORM(180, 180, 0);
+    ASSERT_TRANSFORM(180, 270, 90);
+    ASSERT_TRANSFORM(180, FLIP_0, FLIP_180);
+    ASSERT_TRANSFORM(180, FLIP_90, FLIP_270);
+    ASSERT_TRANSFORM(180, FLIP_180, FLIP_0);
+    ASSERT_TRANSFORM(180, FLIP_270, FLIP_90);
+
+    ASSERT_TRANSFORM(270, 0, 270);
+    ASSERT_TRANSFORM(270, 90, 0);
+    ASSERT_TRANSFORM(270, 180, 90);
+    ASSERT_TRANSFORM(270, 270, 180);
+    ASSERT_TRANSFORM(270, FLIP_0, FLIP_90);
+    ASSERT_TRANSFORM(270, FLIP_90, FLIP_180);
+    ASSERT_TRANSFORM(270, FLIP_180, FLIP_270);
+    ASSERT_TRANSFORM(270, FLIP_270, FLIP_0);
+
+    ASSERT_TRANSFORM(FLIP_0, 0, FLIP_0);
+    ASSERT_TRANSFORM(FLIP_0, 90, FLIP_90);
+    ASSERT_TRANSFORM(FLIP_0, 180, FLIP_180);
+    ASSERT_TRANSFORM(FLIP_0, 270, FLIP_270);
+    ASSERT_TRANSFORM(FLIP_0, FLIP_0, 0);
+    ASSERT_TRANSFORM(FLIP_0, FLIP_90, 90);
+    ASSERT_TRANSFORM(FLIP_0, FLIP_180, 180);
+    ASSERT_TRANSFORM(FLIP_0, FLIP_270, 270);
+
+    ASSERT_TRANSFORM(FLIP_90, 0, FLIP_90);
+    ASSERT_TRANSFORM(FLIP_90, 90, FLIP_180);
+    ASSERT_TRANSFORM(FLIP_90, 180, FLIP_270);
+    ASSERT_TRANSFORM(FLIP_90, 270, FLIP_0);
+    ASSERT_TRANSFORM(FLIP_90, FLIP_0, 270);
+    ASSERT_TRANSFORM(FLIP_90, FLIP_90, 0);
+    ASSERT_TRANSFORM(FLIP_90, FLIP_180, 90);
+    ASSERT_TRANSFORM(FLIP_90, FLIP_270, 180);
+
+    ASSERT_TRANSFORM(FLIP_180, 0, FLIP_180);
+    ASSERT_TRANSFORM(FLIP_180, 90, FLIP_270);
+    ASSERT_TRANSFORM(FLIP_180, 180, FLIP_0);
+    ASSERT_TRANSFORM(FLIP_180, 270, FLIP_90);
+    ASSERT_TRANSFORM(FLIP_180, FLIP_0, 180);
+    ASSERT_TRANSFORM(FLIP_180, FLIP_90, 270);
+    ASSERT_TRANSFORM(FLIP_180, FLIP_180, 0);
+    ASSERT_TRANSFORM(FLIP_180, FLIP_270, 90);
+
+    ASSERT_TRANSFORM(FLIP_270, 0, FLIP_270);
+    ASSERT_TRANSFORM(FLIP_270, 90, FLIP_0);
+    ASSERT_TRANSFORM(FLIP_270, 180, FLIP_90);
+    ASSERT_TRANSFORM(FLIP_270, 270, FLIP_180);
+    ASSERT_TRANSFORM(FLIP_270, FLIP_0, 90);
+    ASSERT_TRANSFORM(FLIP_270, FLIP_90, 180);
+    ASSERT_TRANSFORM(FLIP_270, FLIP_180, 270);
+    ASSERT_TRANSFORM(FLIP_270, FLIP_270, 0);
+}
+
+int main(int argc, char *argv[]) {
+    (void) argc;
+    (void) argv;
+
+    test_transforms();
+    return 0;
+}

doc/shortcuts.md

@@ -26,6 +26,8 @@ _<kbd>[Super]</kbd> is typically the <kbd>Windows</kbd> or <kbd>Cmd</kbd> key._
  | Switch fullscreen mode                      | <kbd>MOD</kbd>+<kbd>f</kbd>
  | Rotate display left                         | <kbd>MOD</kbd>+<kbd>←</kbd> _(left)_
  | Rotate display right                        | <kbd>MOD</kbd>+<kbd>→</kbd> _(right)_
+ | Flip display horizontally                   | <kbd>MOD</kbd>+<kbd>Shift</kbd>+<kbd>←</kbd> _(left)_ \| <kbd>MOD</kbd>+<kbd>Shift</kbd>+<kbd>→</kbd> _(right)_
+ | Flip display vertically                     | <kbd>MOD</kbd>+<kbd>Shift</kbd>+<kbd>↑</kbd> _(up)_ \| <kbd>MOD</kbd>+<kbd>Shift</kbd>+<kbd>↓</kbd> _(down)_
  | Resize window to 1:1 (pixel-perfect)        | <kbd>MOD</kbd>+<kbd>g</kbd>
  | Resize window to remove black borders       | <kbd>MOD</kbd>+<kbd>w</kbd> \| _Double-left-click¹_
  | Click on `HOME`                             | <kbd>MOD</kbd>+<kbd>h</kbd> \| _Middle-click_