Merge pull request #608 from bebehei/xrandr-dpi

XRandR DPI Online Changes

src/draw.c

@@ -237,7 +237,7 @@ static PangoLayout *layout_create(cairo_t *c)
         struct screen_info *screen = get_active_screen();
 
         PangoContext *context = pango_cairo_create_context(c);
-        pango_cairo_context_set_resolution(context, get_dpi_for_screen(screen));
+        pango_cairo_context_set_resolution(context, screen_dpi_get(screen));
 
         PangoLayout *layout = pango_layout_new(context);
 

src/x11/screen.c

@@ -25,8 +25,6 @@ int screens_len;
 
 bool dunst_follow_errored = false;
 
-int randr_event_base = 0;
-
 static int randr_major_version = 0;
 static int randr_minor_version = 0;
 
@@ -39,59 +37,84 @@ static int x_follow_tear_down_error_handler(void);
 static int FollowXErrorHandler(Display *display, XErrorEvent *e);
 static Window get_focused_window(void);
 
-static double get_xft_dpi_value(void)
+
+/**
+ * A cache variable to cache the Xft.dpi xrdb values.
+ * We do not expect to change xrdb often, but there's much
+ * overhead to query it once.
+ *
+ * @retval -DBL_MAX: uncached
+ * @retval     <=0: Invalid and unusable value
+ * @retval      >0: valid
+ */
+double screen_dpi_xft_cache = -DBL_MAX;
+
+void screen_dpi_xft_cache_purge(void)
 {
-        static double dpi = -1;
-        //Only run this once, we don't expect dpi changes during runtime
-        if (dpi <= -1) {
-                XrmInitialize();
-                char *xRMS = XResourceManagerString(xctx.dpy);
+        screen_dpi_xft_cache = -DBL_MAX;
+}
 
-                if (!xRMS) {
-                        dpi = 0;
-                        return 0;
-                }
+static double screen_dpi_get_from_xft(void)
+{
+        if (screen_dpi_xft_cache == -DBL_MAX) {
+                screen_dpi_xft_cache = 0;
 
-                XrmDatabase xDB = XrmGetStringDatabase(xRMS);
                 char *xrmType;
                 XrmValue xrmValue;
-
-                if (XrmGetResource(xDB, "Xft.dpi", "Xft.dpi", &xrmType, &xrmValue)) {
-                        dpi = strtod(xrmValue.addr, NULL);
-                } else {
-                        dpi = 0;
-                }
-                XrmDestroyDatabase(xDB);
+                XrmDatabase db = XrmGetDatabase(xctx.dpy);
+                ASSERT_OR_RET(db, screen_dpi_xft_cache);
+                if (XrmGetResource(db, "Xft.dpi", "Xft.dpi", &xrmType, &xrmValue))
+                        screen_dpi_xft_cache = strtod(xrmValue.addr, NULL);
         }
-        return dpi;
+        return screen_dpi_xft_cache;
+}
+
+static double screen_dpi_get_from_monitor(struct screen_info *scr)
+{
+        return (double)scr->h * 25.4 / (double)scr->mmh;
+}
+
+double screen_dpi_get(struct screen_info *scr)
+{
+        if (  ! settings.force_xinerama
+             && settings.per_monitor_dpi)
+                return screen_dpi_get_from_monitor(scr);
+
+        if (screen_dpi_get_from_xft() > 0)
+                return screen_dpi_get_from_xft();
+
+        // Calculate the DPI on the overall screen size.
+        // xrandr --dpi <DPI> does only change the overall screen's millimeters,
+        // but not the physical screen's sizes.
+        //
+        // The screen parameter is XDefaultScreen(), as our scr->id references
+        // the xrandr monitor and not the xrandr screen
+        return ((((double)DisplayWidth  (xctx.dpy, XDefaultScreen(xctx.dpy))) * 25.4) /
+                 ((double)DisplayWidthMM(xctx.dpy, XDefaultScreen(xctx.dpy))));
 }
 
 void init_screens(void)
 {
-        if (!settings.force_xinerama) {
+        if (settings.force_xinerama) {
+                xinerama_update();
+        } else {
                 randr_init();
                 randr_update();
-        } else {
-                xinerama_update();
         }
 }
 
 void alloc_screen_ar(int n)
 {
         assert(n > 0);
-        if (n <= screens_len) return;
-
-        screens = g_realloc(screens, n * sizeof(struct screen_info));
-
-        memset(screens, 0, n * sizeof(struct screen_info));
-
+        g_free(screens);
+        screens = g_malloc0(n * sizeof(struct screen_info));
         screens_len = n;
 }
 
 void randr_init(void)
 {
-        int randr_error_base = 0;
-        if (!XRRQueryExtension(xctx.dpy, &randr_event_base, &randr_error_base)) {
+        int ignored;
+        if (!XRRQueryExtension(xctx.dpy, &ignored, &ignored)) {
                 LOG_W("Could not initialize the RandR extension. "
                       "Falling back to single monitor mode.");
                 return;
@@ -138,20 +161,15 @@ void randr_update(void)
         XRRFreeMonitors(m);
 }
 
-static int autodetect_dpi(struct screen_info *scr)
+bool screen_check_event(XEvent *ev)
 {
-        return (double)scr->h * 25.4 / (double)scr->mmh;
-}
-
-void screen_check_event(XEvent event)
-{
-        if (event.type == randr_event_base + RRScreenChangeNotify) {
+        if (XRRUpdateConfiguration(ev)) {
                 LOG_D("XEvent: processing 'RRScreenChangeNotify'");
                 randr_update();
 
-        } else {
-                LOG_D("XEvent: Ignoring '%d'", event.type);
+                return true;
         }
+        return false;
 }
 
 void xinerama_update(void)
@@ -355,18 +373,6 @@ sc_cleanup:
         return &screens[ret];
 }
 
-double get_dpi_for_screen(struct screen_info *scr)
-{
-        double dpi = 0;
-        if ((!settings.force_xinerama && settings.per_monitor_dpi &&
-                (dpi = autodetect_dpi(scr))))
-                return dpi;
-        else if ((dpi = get_xft_dpi_value()))
-                return dpi;
-        else
-                return 96;
-}
-
 /*
  * Return the window that currently has
  * the keyboard focus.

src/x11/screen.h

@@ -17,10 +17,11 @@ struct screen_info {
 };
 
 void init_screens(void);
-void screen_check_event(XEvent event);
+void screen_dpi_xft_cache_purge(void);
+bool screen_check_event(XEvent *ev);
 
 struct screen_info *get_active_screen(void);
-double get_dpi_for_screen(struct screen_info *scr);
+double screen_dpi_get(struct screen_info *scr);
 
 /**
  * Find the currently focused window and check if it's in

src/x11/x.c

@@ -17,6 +17,7 @@
 #include <X11/X.h>
 #include <X11/XKBlib.h>
 #include <X11/Xlib.h>
+#include <X11/Xresource.h>
 #include <X11/Xutil.h>
 
 #include "../dbus.h"
@@ -55,6 +56,8 @@ bool dunst_grab_errored = false;
 
 static bool fullscreen_last = false;
 
+static void XRM_update_db(void);
+
 static void x_shortcut_init(struct keyboard_shortcut *ks);
 static int x_shortcut_grab(struct keyboard_shortcut *ks);
 static void x_shortcut_ungrab(struct keyboard_shortcut *ks);
@@ -333,9 +336,18 @@ gboolean x_mainloop_fd_dispatch(GSource *source, GSourceFunc callback, gpointer
                             ev.xcreatewindow.override_redirect == 0)
                                 XRaiseWindow(xctx.dpy, win->xwin);
                         break;
+                case PropertyNotify:
+                        if (ev.xproperty.atom == XA_RESOURCE_MANAGER) {
+                                LOG_D("XEvent: processing PropertyNotify for Resource manager");
+                                XRM_update_db();
+                                screen_dpi_xft_cache_purge();
+                                draw();
+                                break;
+                        }
+                        /* Explicitly fallthrough. Other PropertyNotify events, e.g. catching
+                         * _NET_WM get handled in the Focus(In|Out) section */
                 case FocusIn:
                 case FocusOut:
-                case PropertyNotify:
                         LOG_D("XEvent: Checking for active screen changes");
                         fullscreen_now = have_fullscreen_window();
                         scr = get_active_screen();
@@ -355,7 +367,10 @@ gboolean x_mainloop_fd_dispatch(GSource *source, GSourceFunc callback, gpointer
                         }
                         break;
                 default:
-                        screen_check_event(ev);
+                        if (!screen_check_event(&ev)) {
+                                LOG_D("XEvent: Ignoring '%d'", ev.type);
+                        }
+
                         break;
                 }
         }
@@ -437,6 +452,47 @@ void x_free(void)
                 XCloseDisplay(xctx.dpy);
 }
 
+static int XErrorHandlerDB(Display *display, XErrorEvent *e)
+{
+        char err_buf[BUFSIZ];
+        XGetErrorText(display, e->error_code, err_buf, BUFSIZ);
+        LOG_W("%s", err_buf);
+        return 0;
+}
+
+static void XRM_update_db(void)
+{
+        XrmDatabase db;
+        XTextProperty prop;
+        Window root;
+        // We shouldn't destroy the first DB coming
+        // from the display object itself
+        static bool runonce = false;
+
+        XFlush(xctx.dpy);
+        XSetErrorHandler(XErrorHandlerDB);
+
+        root = RootWindow(xctx.dpy, DefaultScreen(xctx.dpy));
+
+        XLockDisplay(xctx.dpy);
+        if (XGetTextProperty(xctx.dpy, root, &prop, XA_RESOURCE_MANAGER)) {
+                if (runonce) {
+                        db = XrmGetDatabase(xctx.dpy);
+                        XrmDestroyDatabase(db);
+                }
+
+                db = XrmGetStringDatabase((const char*)prop.value);
+                XrmSetDatabase(xctx.dpy, db);
+        }
+        XUnlockDisplay(xctx.dpy);
+
+        runonce = true;
+
+        XFlush(xctx.dpy);
+        XSync(xctx.dpy, false);
+        XSetErrorHandler(NULL);
+}
+
 /*
  * Setup X11 stuff
  */
@@ -468,6 +524,8 @@ void x_setup(void)
 
         init_screens();
         x_shortcut_grab(&settings.history_ks);
+
+        XrmInitialize();
 }
 
 struct geometry x_parse_geometry(const char *geom_str)
@@ -616,9 +674,17 @@ struct window_x11 *x_win_create(void)
 
         win->esrc = x_win_reg_source(win);
 
-        long root_event_mask = SubstructureNotifyMask;
+        /* SubstructureNotifyMask is required for receiving CreateNotify events
+         * in order to raise the window when something covers us. See #160
+         *
+         * PropertyChangeMask is requred for getting screen change events when follow_mode != none
+         *                    and it's also needed to receive
+         *                    XA_RESOURCE_MANAGER events to update the dpi when
+         *                    the xresource value is updated
+         */
+        long root_event_mask = SubstructureNotifyMask | PropertyChangeMask;
         if (settings.f_mode != FOLLOW_NONE) {
-                root_event_mask |= FocusChangeMask | PropertyChangeMask;
+                root_event_mask |= FocusChangeMask;
         }
         XSelectInput(xctx.dpy, root, root_event_mask);