DesktopConfiguration: shared mode

This teaches the DesktopConfiguration command about a new option:
shared.  When in this mode, a shared state means that's there one set of
desktops (defined via the `DesktopName` command), but these desks are
global to all monitors, yet monitors may independently selected which
desktop to show at that time.

If a request to move to a particular desktop matches one already shown
on a different monitors, these two desks are exchanged between those
monitors.

Fixes #260

dev-docs/DESKTOPS.md

@@ -0,0 +1,66 @@
+Desktop Thoughts
+================
+
+Fvwm3 has two modes for handling desktops:
+
+* `global` -- all connected monitors share the same desktop
+* `per-monitor` -- all desktops defined by `DesktopName` are separate from one
+  another.
+
+A third mode is suggested:  `shared`.
+
+
+Shared would operate much like spectrwm does now:
+
+So for example, let's say you had the following number of desktops:
+
+```
+0     1      2      3     4
+```
+
+... and let's say that you have two monitors.  You might have this:
+
+```
+[0]     1      2      <3>     4
+```
+
+Where `[]` is monitor1 and `<>` is monitor2.
+
+You could move monitor1 (`[]`) all the way along to desktop 2, without changing where monitor2 (`<>`) is, as in:
+
+```
+0     1     [2]      <3>     4
+```
+
+If you were to then continue to move monitor1 (`[]`) to desktop 3, what would happen is this:
+
+```
+0     1     <2>      [3]     4
+```
+
+So that now, the desktops have switched over from each monitor.
+
+FVWM3 Changes
+=============
+
+In order to provide this feature, fvwm3 needs to try and structure things such
+that existing `DesktopConfiguration` modes are not broken by this
+implementation.  Unlike with other modes, this `shared` mode is not a
+structure suited to isolation per-monitor, thus this breaks the conceptual
+model.
+
+In order for `fvwm3` to sustain all three models, the following should be
+true:
+
+* When setting `shared`:
+
+1. Initialise the shared desktop environment.
+2. Existing windows per desktop should be migrated to the share env.
+3. All monitors should be scanned.  They need to be placed on different desktops.
+4. On a switch to a new desktop (regardless of page) if a desktop:
+   * Is mapped:
+     * Swap the desktop:
+       * Mark the windows on the current monitor
+       * Move the windows on the *other* monitor to this monitor's desk
+       * Switch desktops
+       * Move the marked windows from this monitor to the other monitor.

dev-docs/shareddesks

@@ -0,0 +1,101 @@
+DesktopConfiguration per-monitor
+SetEnv RXVT "urxvt -b 5 -bd '#333333'"
+
+ModuleTimeout 1
+EdgeResistance 800 1
+EdgeThickness 2
+IgnoreModifiers L25
+
+DesktopName 0 0
+DesktopName 1 1
+DesktopName 2 2
+DesktopName 3 3
+DesktopName 4 4
+DesktopName 5 5
+
+DesktopSize 1x1
+
+Key Right   A C GotoDesk next
+Key Left    A C GotoDesk -1 0 0 5
+
+# Window key-bindings
+Key i       A   4   Iconify
+
+Key Left    A   4   Direction West (CurrentDesk, AcceptsFocus, Visible) Focus
+Key Right   A   4   Direction East (CurrentDesk, AcceptsFocus, Visible) Focus
+Key Up      A   4   Direction North (CurrentDesk, AcceptsFocus, Visible) Focus
+Key Down    A   4   Direction South (CurrentDesk, AcceptsFocus, Visible) Focus
+
+Key Return   A   4  Exec exec $[RXVT] -ls 
+Key Return   A   C  Maximize grow grow
+Key A        W   S4  Close
+Key Down     W   M   Lower
+Key Up       W   M Raise
+Key m	     W   4 Maximize
+
+Key L	A CM  Exec exec i3lock -c '#2000FF'
+Key S   A 4   Stick
+
+Key F12 A 4   Module FvwmConsole
+#Key F12 A 4   Exec exec $[RXVT] -bg '#004103' -e FvwmPrompt 
+
+Key Up      WTSF    CM  PackUp
+Key Down    WTSF    CM  PackDown
+Key Left    WTSF    CM  PackLeft
+Key Right   WTSF    CM  PackRight
+
+Key p 	    A       C4  Exec exec rofi-pass
+Key slash   A       M4	Exec exec rofi \
+				-levenshtein-sort \
+				-show window \
+				-bg '#66ba66' \
+				-fg black \
+				-hlbg white \
+				-hlfg black \
+				-bc 'blue' \
+				-bw 4 \
+				-columns 1 \
+				-lines 5 \
+				-fixed-num-lines 1 \
+				-width 40 \
+				-terminal xterm \
+				-hide-scrollbar \
+				-font "Monospace 12"
+
+Key question   A       MS	Exec exec rofi \
+				-levenshtein-sort \
+				-show run \
+				-bg '#66ba66' \
+				-fg black \
+				-hlbg white \
+				-hlfg black \
+				-bc 'blue' \
+				-bw 4 \
+				-columns 1 \
+				-lines 5 \
+				-fixed-num-lines 1 \
+				-width 40 \
+				-terminal xterm \
+				-hide-scrollbar \
+				-font "Monospace 12"
+
+KillModule FvwmPager FP1
+DestroyModuleConfig FP1: *
+*FP1: Monitor DP1-8
+
+Style FP1 StartsOnScreen DP1-8, Sticky, CirculateSkip
+Module FvwmPager FP1 0 5
+
+KillModule FvwmPager FP2
+DestroyModuleConfig FP2: *
+*FP2: Monitor DP1-1-8
+
+Style FP2 StartsOnScreen DP1-1-8, Sticky, CirculateSkip
+Module FvwmPager FP2 0 5
+
+KillModule FvwmPager FP3
+DestroyModuleConfig FP3: *
+*FP3: Monitor HDMI2
+
+Style FP3 StartsOnScreen HDMI2, Sticky, CirculateSkip
+Module FvwmPager FP3 0 5

doc/fvwm3/fvwm3.adoc

@@ -7468,7 +7468,7 @@ Specifying an invalid decor results in all windows being updated.
 	names starting from desktop 0 are defined, then these names can be
 	used by any EWMH compliant application (as a pager).
 
-*DesktopConfiguration* global | per-monitor::
+*DesktopConfiguration* global | per-monitor | shared::
 	This command controls the behaviour of how desktops should be managed
 	by FVWM. By default, for all screens detected by FVWM through RandR
 	support, the option of global means that all windows on the same desk
@@ -7478,6 +7478,28 @@ Specifying an invalid decor results in all windows being updated.
 With per-monitor , each RandR monitor has a separate copy of desktops,
 and hence function independently of one another when switching
 desks/pages.
++
+When __shared__ is set, the desktops are shared amongst all monitors.  So for
+example, with the following number of desktops defined with two monitors
+(__[]__ is monitor1, and __<>__ is monitor2):
++
+....
+[0]     1      2      <3>     4
+....
++
+
+Moving between desktops would still honor the monitor the desktop is being
+requested on.  If __monitor1__ wanted to switch to desktop 3, then that
+desktop is exchanged with __monitor2__ such that the following showed the
+active desktop on both monitors:
++
+....
+<0>     1      2      [3]     4
+....
++
+This concept is similar to how spectrwm or xmonad handles desktops.
++
+**Note:** these each *DesktopConfiguration* mode can be changed on-the-fly.
 
 *DesktopSize* __Horizontal__x_Vertical_::
 	Defines the virtual desktop size in units of the physical screen size.

fvwm/add_window.c

@@ -58,6 +58,7 @@
 #include "libs/Grab.h"
 #include "libs/Strings.h"
 #include "libs/XResource.h"
+#include "libs/safemalloc.h"
 #include "fvwm.h"
 #include "externs.h"
 #include "cursor.h"
@@ -89,6 +90,7 @@
 #include "functions.h"
 #include "virtual.h"
 #include "builtins.h"
+#include "expand.h"
 
 /* ---------------------------- local definitions -------------------------- */
 
@@ -2489,7 +2491,12 @@ FvwmWindow *AddWindow(
 	{
 		struct monitor	*tm = (fw && fw->m) ? fw->m :
 			monitor_get_current();
-		goto_desk(fw->Desk, tm);
+
+		char *cmd;
+
+		xasprintf(&cmd, "GotoDesk %s 0 %d", tm->si->name, fw->Desk);
+		execute_function_override_window(NULL, NULL, cmd, 0, fw);
+		free(cmd);
 
 		/* read the requested absolute geometry */
 		gravity_translate_to_northwest_geometry_no_bw(
@@ -2630,7 +2637,6 @@ FvwmWindow *AddWindow(
 	setup_key_and_button_grabs(fw);
 
 	/****** inform modules of new window ******/
-	UPDATE_FVWM_SCREEN(fw);
 	BroadcastConfig(M_ADD_WINDOW,fw);
 	BroadcastWindowIconNames(fw, True, False);
 
@@ -2808,6 +2814,19 @@ FvwmWindow *AddWindow(
 		fw = NULL;
 	}
 
+	if (is_tracking_shared && fw != NULL) {
+		/* If we're in `DesktopConfiguration shared` mode, reposition
+		 * the window, for scenarios involving StartsOn{Screen,Desk}.
+		 * In this cases, the window won't have been placed due to
+		 * XGetGeometry() not knowing about the window.
+		 *
+		 * All other styles will have been applied.
+		 *
+		 * So now just adjust for StartsOn{Screen,Desk}
+		 */
+		adjust_for_shared_placement(fw, exc);
+	}
+
 	return fw;
 }
 

fvwm/builtins.c

@@ -148,8 +148,14 @@ status_send(void)
 	m_cur = monitor_get_current();
 
 	bson_init(&msg);
-	BSON_APPEND_INT64(&msg, "version", 1);
+	BSON_APPEND_INT64(&msg, "version", 2);
 	BSON_APPEND_UTF8(&msg, "current_screen", m_cur->si->name);
+	BSON_APPEND_UTF8(&msg, "desktop_mode",
+	    monitor_mode == MONITOR_TRACKING_G && is_tracking_shared ? "shared" :
+	    monitor_mode == MONITOR_TRACKING_G ? "global" :
+	    monitor_mode == MONITOR_TRACKING_M ? "per-monitor" :
+	    "unknown");
+
 	BSON_APPEND_DOCUMENT_BEGIN(&msg, "screens", &screens);
 
 	d_count = 0;

fvwm/events.c

@@ -3163,7 +3163,6 @@ void HandleMapRequestKeepRaised(
 			}
 			MyXUngrabServer(dpy);
 
-			UPDATE_FVWM_SCREEN(fw);
 			break;
 
 		case IconicState:

fvwm/fvwm3.c

@@ -2442,6 +2442,7 @@ int main(int argc, char **argv)
 	fvwm_debug(__func__, "Loading window states via %s", state_filename);
 	LoadWindowStates(state_filename);
 
+	is_tracking_shared = false;
 	TAILQ_FOREACH(m, &monitor_q, entry)
 		EWMH_Init(m);