Refactor and optimize --scale and --rotation-offset

app/src/cli.c

@@ -845,28 +845,30 @@ static const struct sc_option options[] = {
         .longopt_id = OPT_ROTATION_OFFSET,
         .longopt = "rotation-offset",
         .argdesc = "value",
-        .text = "Set the initial display rotation offset.\n"
+        .text = "Set the display rotation offset in degrees.\n"
+                "Positive values rotate clockwise, negative values "
+                "rotate counter-clockwise.\n"
                 "Default is 0 (automatic).",
     },
     {
         .longopt_id = OPT_SCALE,
         .longopt = "scale",
         .argdesc = "value",
-        .text = "Set the initial display scale.\n"
+        .text = "Set the display scale in integer percentage.\n"
                 "Default is 100 (automatic).",
     },
     {
         .longopt_id = OPT_POSITION_X_OFFSET,
         .longopt = "position-x-offset",
         .argdesc = "value",
-        .text = "Set the initial display horizontal position offset.\n"
+        .text = "Set the display horizontal position offset.\n"
                 "Default is 0 (automatic).",
     },
     {
         .longopt_id = OPT_POSITION_Y_OFFSET,
         .longopt = "position-y-offset",
         .argdesc = "value",
-        .text = "Set the initial display vertical position offset.\n"
+        .text = "Set the display vertical position offset.\n"
                 "Default is 0 (automatic).",
     },
 };

app/src/display.c

@@ -262,8 +262,8 @@ sc_display_render(struct sc_display *display, const SDL_Rect *geometry,
     rect.y = geometry->y + transform_offsets->position.y;
 
     if (transform_offsets->scale != 100) {
-        rect.w = (int)(geometry->w * (float32_t)transform_offsets->scale / 100);
-        rect.h = (int)(geometry->h * (float32_t)transform_offsets->scale / 100);
+        rect.w = geometry->w * transform_offsets->scale / 100;
+        rect.h = geometry->h * transform_offsets->scale / 100;
     } else {
         rect.w = geometry->w;
         rect.h = geometry->h;

app/src/screen.c

@@ -850,7 +850,8 @@ static void
 sc_rotate_point(struct sc_point *point,
                 struct sc_point *pivot,
                 int16_t angle_in_degrees) {
-    float32_t angle_in_radians = (float32_t)angle_in_degrees * M_PI / 180.0;
+    const double deg_to_rad = M_PI / 180.0;
+    float32_t angle_in_radians = (float32_t)angle_in_degrees * deg_to_rad;
     float32_t cosine = (float32_t)cos(angle_in_radians);
     float32_t sine = (float32_t)sin(angle_in_radians);
 
@@ -870,20 +871,20 @@ sc_screen_convert_drawable_to_frame_coords(struct sc_screen *screen,
 
     int32_t w = screen->content_size.width;
     int32_t h = screen->content_size.height;
-    int32_t w_half = (int32_t) w * 0.5;
-    int32_t h_half = (int32_t) h * 0.5;
+    int32_t w_half = w >> 1;
+    int32_t h_half = h >> 1;
     struct sc_point pivot = {
         .x = w_half,
         .y = h_half,
     };
     int8_t flip_factor = -1;
-    float32_t scale_factor = 100 / (float32_t)screen->transform_offsets.scale;
+    float32_t scale_factor = 100.0 / screen->transform_offsets.scale;
 
     // screen->rect must be initialized to avoid a division by zero
     assert(screen->rect.w && screen->rect.h);
 
-    float32_t w_factor = (float32_t)w / screen->rect.w;
-    float32_t h_factor = (float32_t)h / screen->rect.h;
+    float32_t w_factor = w / (float32_t)screen->rect.w;
+    float32_t h_factor = h / (float32_t)screen->rect.h;
     x = (int64_t) (x - screen->rect.x) * w_factor;
     y = (int64_t) (y - screen->rect.y) * h_factor;
     int32_t x_offset = screen->transform_offsets.position.x * w_factor;

doc/video.md

@@ -143,7 +143,8 @@ values are allowed when recording.
 
 ## Rotation offset
 
-Rotation offset to be applied (positive values will rotate clockwise):
+Rotation offset in degrees to be applied (positive values rotate clockwise,
+negative values rotate counter-clockwise):
 
 ```bash
 scrcpy --rotation-offset=45
@@ -152,18 +153,23 @@ scrcpy --rotation-offset=45
 This is useful for Meta Quest 3 tilted screen setup:
 
 ```bash
-scrcpy --crop=2064:2208:0:0 --rotation-offset=21
+scrcpy --crop=2064:2208:0:0 --rotation-offset=22
 ```
 
+This is not supported when recording.
+
 
 ## Scale
 
-Scale to be applied (default is 100):
+Scale in integer percentage to be applied (default is 100):
 
 ```bash
 scrcpy --scale=150 # 150% scale
 ```
 
+This is not supported when recording.
+
+
 ## Position offset
 
 Position offset to be applied both horizontally and/or vertically
@@ -174,6 +180,9 @@ scrcpy --position-x-offset=150
 scrcpy --position-y-offset=150
 ```
 
+This is not supported when recording.
+
+
 ## Crop
 
 The device screen may be cropped to mirror only part of the screen.