ui/sdl: Consider scaling in mouse event handling

When using sdl display backend, if the window is scaled, incorrect mouse
positions will be reported since scaling is not properly handled. Fix it
by transforming the positions from window coordinate to guest buffer
coordinate.

Signed-off-by: Weifeng Liu <weifeng.liu@intel.com>
Message-ID: <20250511073337.876650-6-weifeng.liu.z@gmail.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Marc-André Lureau <marcandre.lureau@redhat.com>

1 files changed, 15 insertions, 5 deletions

diff --git a/ui/sdl2.c b/ui/sdl2.c
index cda4293a53..b00e421f7f 100644
--- a/ui/sdl2.c
+++ b/ui/sdl2.c
@@ -488,14 +488,14 @@ static void handle_mousemotion(SDL_Event *ev)
 {
     int max_x, max_y;
     struct sdl2_console *scon = get_scon_from_window(ev->motion.windowID);
+    int scr_w, scr_h, surf_w, surf_h, x, y, dx, dy;
 
     if (!scon || !qemu_console_is_graphic(scon->dcl.con)) {
         return;
     }
 
+    SDL_GetWindowSize(scon->real_window, &scr_w, &scr_h);
     if (qemu_input_is_absolute(scon->dcl.con) || absolute_enabled) {
-        int scr_w, scr_h;
-        SDL_GetWindowSize(scon->real_window, &scr_w, &scr_h);
         max_x = scr_w - 1;
         max_y = scr_h - 1;
         if (gui_grab && !gui_fullscreen
@@ -509,9 +509,14 @@ static void handle_mousemotion(SDL_Event *ev)
             sdl_grab_start(scon);
         }
     }
+    surf_w = surface_width(scon->surface);
+    surf_h = surface_height(scon->surface);
+    x = (int64_t)ev->motion.x * surf_w / scr_w;
+    y = (int64_t)ev->motion.y * surf_h / scr_h;
+    dx = (int64_t)ev->motion.xrel * surf_w / scr_w;
+    dy = (int64_t)ev->motion.yrel * surf_h / scr_h;
     if (gui_grab || qemu_input_is_absolute(scon->dcl.con) || absolute_enabled) {
-        sdl_send_mouse_event(scon, ev->motion.xrel, ev->motion.yrel,
-                             ev->motion.x, ev->motion.y, ev->motion.state);
+        sdl_send_mouse_event(scon, dx, dy, x, y, ev->motion.state);
     }
 }
 
@@ -520,12 +525,17 @@ static void handle_mousebutton(SDL_Event *ev)
     int buttonstate = SDL_GetMouseState(NULL, NULL);
     SDL_MouseButtonEvent *bev;
     struct sdl2_console *scon = get_scon_from_window(ev->button.windowID);
+    int scr_w, scr_h, x, y;
 
     if (!scon || !qemu_console_is_graphic(scon->dcl.con)) {
         return;
     }
 
     bev = &ev->button;
+    SDL_GetWindowSize(scon->real_window, &scr_w, &scr_h);
+    x = (int64_t)bev->x * surface_width(scon->surface) / scr_w;
+    y = (int64_t)bev->y * surface_height(scon->surface) / scr_h;
+
     if (!gui_grab && !qemu_input_is_absolute(scon->dcl.con)) {
         if (ev->type == SDL_MOUSEBUTTONUP && bev->button == SDL_BUTTON_LEFT) {
             /* start grabbing all events */
@@ -537,7 +547,7 @@ static void handle_mousebutton(SDL_Event *ev)
         } else {
             buttonstate &= ~SDL_BUTTON(bev->button);
         }
-        sdl_send_mouse_event(scon, 0, 0, bev->x, bev->y, buttonstate);
+        sdl_send_mouse_event(scon, 0, 0, x, y, buttonstate);
     }
 }