[Qemu-devel] [PATCH] smoother sdl display & mouse

[Jindrich Makovicka <makovick@gmail.com>]

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Hi,

the attached patch modifies the SDL display refresh code so the mouse
and keyboard events are processed each 10 ms instead of 30. This causes
much better mouse behavior due to lower latency.

By default, display is still refreshed only each 30 ms to prevent the
increase of the cpu load, but it is possible to tune the refresh rate
via the -sdl-decimate option.

Please cc:, I am not a subscriber.

Regards,
-- 
Jindrich Makovicka

[-- Attachment #2: refresh.diff --]
[-- Type: text/x-patch, Size: 3893 bytes --]

diff -ur kvm-27.orig/qemu/sdl.c kvm-27/qemu/sdl.c
--- kvm-27.orig/qemu/sdl.c	2007-06-03 10:27:40.000000000 +0200
+++ kvm-27/qemu/sdl.c	2007-06-05 22:28:19.000000000 +0200
@@ -43,6 +43,7 @@
 static SDL_Cursor *sdl_cursor_normal;
 static SDL_Cursor *sdl_cursor_hidden;
 static int absolute_enabled = 0;
+static int decimate_counter = 0;
 
 static void sdl_update(DisplayState *ds, int x, int y, int w, int h)
 {
@@ -321,7 +322,10 @@
         sdl_update_caption();
     }
 
-    vga_hw_update();
+    if (decimate_counter == 0)
+	vga_hw_update();
+
+    decimate_counter = (decimate_counter + 1) % sdl_decimate;
 
     while (SDL_PollEvent(ev)) {
         switch (ev->type) {
@@ -504,6 +508,7 @@
     ds->dpy_update = sdl_update;
     ds->dpy_resize = sdl_resize;
     ds->dpy_refresh = sdl_refresh;
+    ds->refresh_interval = 10;
 
     sdl_resize(ds, 640, 400);
     sdl_update_caption();
diff -ur kvm-27.orig/qemu/vl.c kvm-27/qemu/vl.c
--- kvm-27.orig/qemu/vl.c	2007-06-03 10:27:40.000000000 +0200
+++ kvm-27/qemu/vl.c	2007-06-05 22:34:29.000000000 +0200
@@ -110,7 +110,7 @@
 #define DEFAULT_RAM_SIZE 128
 #endif
 /* in ms */
-#define GUI_REFRESH_INTERVAL 30
+#define DEFAULT_GUI_REFRESH_INTERVAL 30
 
 /* Max number of USB devices that can be specified on the commandline.  */
 #define MAX_USB_CMDLINE 8
@@ -133,6 +133,7 @@
 static DisplayState display_state;
 int nographic;
 const char* keyboard_layout = NULL;
+int sdl_decimate = 3;
 int64_t ticks_per_sec;
 int boot_device = 'c';
 int ram_size;
@@ -4137,6 +4138,7 @@
     ds->dpy_update = dumb_update;
     ds->dpy_resize = dumb_resize;
     ds->dpy_refresh = dumb_refresh;
+    ds->refresh_interval = DEFAULT_GUI_REFRESH_INTERVAL;
 }
 
 /***********************************************************/
@@ -5989,7 +5991,7 @@
 void gui_update(void *opaque)
 {
     display_state.dpy_refresh(&display_state);
-    qemu_mod_timer(gui_timer, GUI_REFRESH_INTERVAL + qemu_get_clock(rt_clock));
+    qemu_mod_timer(gui_timer, display_state.refresh_interval + qemu_get_clock(rt_clock));
 }
 
 struct vm_change_state_entry {
@@ -6342,6 +6344,7 @@
            "-snapshot       write to temporary files instead of disk image files\n"
 #ifdef CONFIG_SDL
            "-no-quit        disable SDL window close capability\n"
+           "-sdl-decimate n refresh display every n*10 milliseconds (default n=3)\n"
 #endif
 #ifdef TARGET_I386
            "-no-fd-bootchk  disable boot signature checking for floppy disks\n"
@@ -6541,6 +6544,9 @@
     QEMU_OPTION_no_rtc,
 #endif
     QEMU_OPTION_cpu_vendor,
+#ifdef CONFIG_SDL
+    QEMU_OPTION_sdl_decimate,
+#endif
 };
 
 typedef struct QEMUOption {
@@ -6616,6 +6622,7 @@
     { "full-screen", 0, QEMU_OPTION_full_screen },
 #ifdef CONFIG_SDL
     { "no-quit", 0, QEMU_OPTION_no_quit },
+    { "sdl-decimate", HAS_ARG, QEMU_OPTION_sdl_decimate },
 #endif
     { "pidfile", HAS_ARG, QEMU_OPTION_pidfile },
     { "win2k-hack", 0, QEMU_OPTION_win2k_hack },
@@ -7189,6 +7196,11 @@
 	    case QEMU_OPTION_k:
 		keyboard_layout = optarg;
 		break;
+	    case QEMU_OPTION_sdl_decimate:
+		sdl_decimate = atoi(optarg);
+		if (sdl_decimate <= 0 || sdl_decimate > 5)
+		    help();
+		break;
             case QEMU_OPTION_localtime:
                 rtc_utc = 0;
                 break;
diff -ur kvm-27.orig/qemu/vl.h kvm-27/qemu/vl.h
--- kvm-27.orig/qemu/vl.h	2007-06-03 10:27:40.000000000 +0200
+++ kvm-27/qemu/vl.h	2007-06-05 22:20:45.000000000 +0200
@@ -156,6 +156,7 @@
 extern int graphic_height;
 extern int graphic_depth;
 extern const char *keyboard_layout;
+extern int sdl_decimate;
 extern int kqemu_allowed;
 extern int kvm_allowed;
 extern int win2k_install_hack;
@@ -901,6 +902,7 @@
     int width;
     int height;
     void *opaque;
+    int refresh_interval;
 
     void (*dpy_update)(struct DisplayState *s, int x, int y, int w, int h);
     void (*dpy_resize)(struct DisplayState *s, int w, int h);