Don't hardcode fps for fake screen

Currently, when main hardware screen is powered-off,
X server initializes fake screen's timer with
1 second update interval.

Streaming software like Nomachine or Vnc, as well as
desktop input automation suffers from it, since it
will forever be stuck on 1 fps until the display is
turned back on.

This commit adds command line option -fakescreenfps <int>
that allows the user to change the default fake screen
timer.

Signed-off-by: Baranin Alexander <ismailsiege@gmail.com>

man/Xserver.man

@@ -164,6 +164,9 @@ a list of accepted extension names is printed.
 .B \-f \fIvolume\fP
 sets beep (bell) volume (allowable range: 0-100).
 .TP 8
+.B \-fakescreenfps \fFps\fP
+sets fake presenter screen default fps (allowable range: 1-600).
+.TP 8
 .B \-fp \fIfontPath\fP
 sets the search path for fonts.  This path is a comma separated list
 of directories which the X server searches for font databases.

os/utils.c

@@ -112,6 +112,8 @@ __stdcall unsigned long GetTickCount(void);
 
 #include "miinitext.h"
 
+#include "present.h"
+
 Bool noTestExtensions;
 
 #ifdef COMPOSITE
@@ -534,6 +536,7 @@ UseMsg(void)
     ErrorF
         ("-deferglyphs [none|all|16] defer loading of [no|all|16-bit] glyphs\n");
     ErrorF("-f #                   bell base (0-100)\n");
+    ErrorF("-fakescreenfps #       fake screen default fps (1-600)\n");
     ErrorF("-fp string             default font path\n");
     ErrorF("-help                  prints message with these options\n");
     ErrorF("+iglx                  Allow creating indirect GLX contexts\n");
@@ -781,6 +784,15 @@ ProcessCommandLine(int argc, char *argv[])
             else
                 UseMsg();
         }
+        else if (strcmp(argv[i], "-fakescreenfps") == 0) {
+            if (++i < argc) {
+                FakeScreenFps = (uint32_t) atoi(argv[i]);
+                if (FakeScreenFps < 1 || FakeScreenFps > 600)
+                    FatalError("fakescreenfps must be an integer in [1;600] range\n");
+            }
+            else
+                UseMsg();
+        }
         else if (strcmp(argv[i], "-fp") == 0) {
             if (++i < argc) {
                 defaultFontPath = argv[i];

present/present.h

@@ -162,4 +162,6 @@ present_register_complete_notify(present_complete_notify_proc proc);
 extern _X_EXPORT Bool
 present_can_window_flip(WindowPtr window);
 
+extern _X_EXPORT uint32_t FakeScreenFps;
+
 #endif /* _PRESENT_H_ */

present/present_fake.c

@@ -113,21 +113,29 @@ present_fake_queue_vblank(ScreenPtr     screen,
     return Success;
 }
 
+uint32_t FakeScreenFps = 0;
+
 void
 present_fake_screen_init(ScreenPtr screen)
 {
+    uint32_t                fake_fps;
     present_screen_priv_ptr screen_priv = present_screen_priv(screen);
 
-    /* For screens with hardware vblank support, the fake code
-     * will be used for off-screen windows and while screens are blanked,
-     * in which case we want a slow interval here
-     *
-     * Otherwise, pretend that the screen runs at 60Hz
-     */
-    if (screen_priv->info && screen_priv->info->get_crtc)
-        screen_priv->fake_interval = 1000000;
-    else
-        screen_priv->fake_interval = 16667;
+    if (FakeScreenFps)
+        fake_fps = FakeScreenFps;
+    else {
+        /* For screens with hardware vblank support, the fake code
+        * will be used for off-screen windows and while screens are blanked,
+        * in which case we want a large interval here: 1Hz
+        *
+        * Otherwise, pretend that the screen runs at 60Hz
+        */
+        if (screen_priv->info && screen_priv->info->get_crtc)
+            fake_fps = 1;
+        else
+            fake_fps = 60;
+    }
+    screen_priv->fake_interval = 1000000 / fake_fps;
 }
 
 void