[v2] ui/sdl: Mouse event optimization

Commit Message

Lei Huang Oct. 30, 2024, 3:43 a.m. UTC

Use a convergence factor to make the VM's input
global coordinates more closely approach the global
coordinates of host.

Change-Id: I2c3f12f1fe7dfb9306d1fc40c4fd4d299937f4c6
Signed-off-by: Lei Huang <[e-mail]>
---
 ui/sdl2.c | 32 ++++++++++++++++++++++++++++++--
 1 file changed, 30 insertions(+), 2 deletions(-)

Patch

diff --git a/ui/sdl2.c b/ui/sdl2.c
index bd4f5a9da14..ea3fd74dd63 100644
--- a/ui/sdl2.c
+++ b/ui/sdl2.c
@@ -303,6 +303,34 @@  static void sdl_mouse_mode_change(Notifier *notify, void *data)
     }
 }
 
+/*
+ * guest_x and guest_y represent the global coordinates on the VM side,
+ * while x and y represent the global coordinates on the host side.
+ * The goal of this entire process is to align the global coordinates of
+ * the VM with those of host using dx and dy. The current approach aims
+ * for precise calibration in once attempt; however, because guest_x
+ * and guest_y are non-zero values, they are not accurate values when
+ * they are counted out to become negative. Therefore, achieving perfect
+ * alignment in one attempt is impossible. Since the same calibration method
+ * is used each time, repeated attempts cannot achieve alignment either.
+ * By introducing a convergence factor, guest_x and guest_y can be made to
+ * approach host x and y indefinitely.
+ *
+ *                   QEMU                       (dx,dy)  VM
+ * calculates dx and dy using guest_x and guest_y ---->  input driver
+ *            ^                                            |
+ *            |                                            |
+ *            |                                            V
+ *            |     update
+ *            | guest_x,guest_y              input dispatcher ---> WindowManager
+ *            |                                            |                 |
+ *            |                                            |                 |
+ *            |                 libdrm                     V                 |
+ *    display device  <------ drmModeMoveCursor <------ compositor <-------  |
+ *                            (guest_x,guest_y)   calculates guest_x and
+ *                                                guest_y dy using dx and dy
+ */
+#define CONVERGENCE_FACTOR 3
 static void sdl_send_mouse_event(struct sdl2_console *scon, int dx, int dy,
                                  int x, int y, int state)
 {
@@ -331,8 +359,8 @@  static void sdl_send_mouse_event(struct sdl2_console *scon, int dx, int dy,
             y -= guest_y;
             guest_x += x;
             guest_y += y;
-            dx = x;
-            dy = y;
+            dx = x / CONVERGENCE_FACTOR;
+            dy = y / CONVERGENCE_FACTOR;
         }
         qemu_input_queue_rel(scon->dcl.con, INPUT_AXIS_X, dx);
         qemu_input_queue_rel(scon->dcl.con, INPUT_AXIS_Y, dy);