@@ -262,7 +262,7 @@ // Window title changed
         if (at == server.atom._NET_WM_VISIBLE_NAME || at == server.atom._NET_WM_NAME || at == server.atom.WM_NAME) {
             if (task_update_title(task)) {
                 if (g_tooltip.mapped && (g_tooltip.area == (Area *)task)) {
-                    tooltip_copy_text((Area *)task);
+                    tooltip_update_contents_for((Area *)task);
                     tooltip_update();
                 }
                 if (taskbar_sort_method == TASKBAR_SORT_TITLE)

@@ -47,6 +47,12 @@ Task *t = (Task *)obj;
     return strdup(t->title);
 }
 
+cairo_surface_t *task_get_thumbnail(void *obj)
+{
+    Task *t = (Task *)obj;
+    return t->thumbnail;
+}
+
 Task *add_task(Window win)
 {
     if (!win)
@@ -122,8 +128,10 @@ // fprintf(stderr, "tint2: %s %d: win = %ld hiding task: another desktop\n", __func__, __LINE__, win);
             task_instance->area.on_screen = always_show_all_desktop_tasks;
         }
         task_instance->title = task_template.title;
-        if (panels[monitor].g_task.tooltip_enabled)
+        if (panels[monitor].g_task.tooltip_enabled) {
             task_instance->area._get_tooltip_text = task_get_tooltip;
+            task_instance->area._get_tooltip_image = task_get_thumbnail;
+        }
         for (int k = 0; k < TASK_STATE_COUNT; ++k) {
             task_instance->icon[k] = task_template.icon[k];
             task_instance->icon_hover[k] = task_template.icon_hover[k];
@@ -201,6 +209,8 @@ // even with task_on_all_desktop and with task_on_all_panel
     // fprintf(stderr, "tint2: remove_task %s %d\n", task->title, task->desktop);
     if (task->title)
         free(task->title);
+    if (task->thumbnail)
+        cairo_surface_destroy(task->thumbnail);
     task_remove_icon(task);
 
     GPtrArray *task_buttons = g_hash_table_lookup(win_to_task, &win);
@@ -212,6 +222,8 @@ if (task2 == task_drag)
             task_drag = 0;
         if (g_slist_find(urgent_list, task2))
             del_urgent(task2);
+        if (g_tooltip.area == &task2->area)
+            tooltip_hide(NULL);
         remove_area((Area *)task2);
         free(task2);
     }
@@ -603,10 +615,24 @@ set_task_state((active_task = get_task(w1)), TASK_ACTIVE);
     }
 }
 
+void task_refresh_thumbnail(Task *task)
+{
+    cairo_surface_t *thumbnail = get_window_thumbnail(task->win);
+    if (!thumbnail)
+        return;
+    if (task->thumbnail)
+        cairo_surface_destroy(task->thumbnail);
+    task->thumbnail = thumbnail;
+}
+
 void set_task_state(Task *task, TaskState state)
 {
     if (!task || state == TASK_UNDEFINED || state >= TASK_STATE_COUNT)
         return;
+
+    if (state != TASK_ICONIFIED) {
+        task_refresh_thumbnail(task);
+    }
 
     if (state == TASK_ACTIVE && task->current_state != state) {
         clock_gettime(CLOCK_MONOTONIC, &task->last_activation_time);

@@ -74,6 +74,7 @@ int _text_height;
     double _text_posy;
     int _icon_x;
     int _icon_y;
+    cairo_surface_t *thumbnail;
 } Task;
 
 extern timeout *urgent_timeout;

@@ -55,7 +55,7 @@ void cleanup_tooltip()
 {
     stop_tooltip_timeout();
     tooltip_hide(NULL);
-    tooltip_copy_text(NULL);
+    tooltip_update_contents_for(NULL);
     if (g_tooltip.window)
         XDestroyWindow(server.display, g_tooltip.window);
     g_tooltip.window = 0;
@@ -118,7 +118,7 @@ y = area->posy + area->height / 2 + e->xmotion.y_root - e->xmotion.y;
     just_shown = TRUE;
     g_tooltip.panel = p;
     if (g_tooltip.mapped && g_tooltip.area != area) {
-        tooltip_copy_text(area);
+        tooltip_update_contents_for(area);
         tooltip_update();
         stop_tooltip_timeout();
     } else if (!g_tooltip.mapped) {
@@ -133,7 +133,7 @@ Window w;
     XTranslateCoordinates(server.display, server.root_win, g_tooltip.panel->main_win, x, y, &mx, &my, &w);
     Area *area = find_area_under_mouse(g_tooltip.panel, mx, my);
     if (!g_tooltip.mapped && area->_get_tooltip_text) {
-        tooltip_copy_text(area);
+        tooltip_update_contents_for(area);
         g_tooltip.mapped = True;
         XMapWindow(server.display, g_tooltip.window);
         tooltip_update();
@@ -162,6 +162,12 @@ pango_layout_set_wrap(layout, PANGO_WRAP_WORD);
     pango_layout_get_pixel_extents(layout, &r1, &r2);
     width = left_right_bg_border_width(g_tooltip.bg) + 2 * g_tooltip.paddingx + r2.width;
     height = top_bottom_bg_border_width(g_tooltip.bg) + 2 * g_tooltip.paddingy + r2.height;
+    if (g_tooltip.image) {
+        width = MAX(width,
+                    left_right_bg_border_width(g_tooltip.bg) + 2 * g_tooltip.paddingx +
+                        cairo_image_surface_get_width(g_tooltip.image));
+        height += g_tooltip.paddingy + cairo_image_surface_get_height(g_tooltip.image);
+    }
 
     if (panel_horizontal && panel_position & BOTTOM)
         y = panel->posy - height;
@@ -278,8 +284,16 @@ cairo_move_to(c,
                   -r1.x / 2 + left_bg_border_width(g_tooltip.bg) + g_tooltip.paddingx,
                   -r1.y / 2 + 1 + top_bg_border_width(g_tooltip.bg) + g_tooltip.paddingy);
     pango_cairo_show_layout(c, layout);
+    g_object_unref(layout);
 
-    g_object_unref(layout);
+    if (g_tooltip.image) {
+        cairo_translate(c,
+                        g_tooltip.paddingx,
+                        height - g_tooltip.paddingy - cairo_image_surface_get_height(g_tooltip.image));
+        cairo_set_source_surface(c, g_tooltip.image, 0, 0);
+        cairo_paint(c);
+    }
+
     cairo_destroy(c);
     cairo_surface_destroy(cs);
 }
@@ -287,7 +301,7 @@ 
 void tooltip_trigger_hide()
 {
     if (g_tooltip.mapped) {
-        tooltip_copy_text(0);
+        tooltip_update_contents_for(NULL);
         start_hide_timeout();
     } else {
         // tooltip not visible yet, but maybe a timeout is still pending
@@ -319,12 +333,23 @@ {
     stop_timeout(g_tooltip.timeout);
 }
 
-void tooltip_copy_text(Area *area)
+void tooltip_update_contents_for(Area *area)
 {
     free(g_tooltip.tooltip_text);
     if (area && area->_get_tooltip_text)
         g_tooltip.tooltip_text = area->_get_tooltip_text(area);
     else
         g_tooltip.tooltip_text = NULL;
+    if (area && area->_get_tooltip_image) {
+        if (g_tooltip.image)
+            cairo_surface_destroy(g_tooltip.image);
+        g_tooltip.image = area->_get_tooltip_image(area);
+        if (g_tooltip.image)
+            cairo_surface_reference(g_tooltip.image);
+    } else {
+        if (g_tooltip.image)
+            cairo_surface_destroy(g_tooltip.image);
+        g_tooltip.image = NULL;
+    }
     g_tooltip.area = area;
 }

@@ -37,6 +37,7 @@ PangoFontDescription *font_desc;
     Color font_color;
     Background *bg;
     timeout *timeout;
+    cairo_surface_t *image;
 } Tooltip;
 
 extern Tooltip g_tooltip;
@@ -53,7 +54,7 @@ void tooltip_show(void * /*arg*/);
 void tooltip_update();
 void tooltip_trigger_hide();
 void tooltip_hide(void * /*arg*/);
-void tooltip_copy_text(Area *area);
+void tooltip_update_contents_for(Area *area);
 void tooltip_default_font_changed();
 
 #endif // TOOLTIP_H

@@ -233,6 +233,7 @@ 
     // Returns a copy of the tooltip to be displayed for this widget.
     // The caller takes ownership of the pointer.
     char *(*_get_tooltip_text)(void *obj);
+    cairo_surface_t *(*_get_tooltip_image)(void *obj);
 
     // Returns true if the Area handles a mouse event at the given x, y coordinates relative to the window.
     // Leave this to NULL to use a default implementation.

@@ -157,7 +157,8 @@ }
 
     if (best_match < 0)
         best_match = 0;
-    // fprintf(stderr, "tint2: window %lx %s : viewport %d, (%d, %d)\n", win, get_task(win) ? get_task(win)->title : "??",
+    // fprintf(stderr, "tint2: window %lx %s : viewport %d, (%d, %d)\n", win, get_task(win) ? get_task(win)->title :
+    // "??",
     // best_match+1, x, y);
     return best_match;
 }
@@ -190,15 +191,18 @@ // get_task(win) ? get_task(win)->title : "??", best_match+1, x, y);
     return best_match;
 }
 
-void get_window_coordinates(Window win, int *x, int *y, int *w, int *h)
+gboolean get_window_coordinates(Window win, int *x, int *y, int *w, int *h)
 {
     int dummy_int;
     unsigned ww, wh, bw, bh;
     Window src;
-    XTranslateCoordinates(server.display, win, server.root_win, 0, 0, x, y, &src);
-    XGetGeometry(server.display, win, &src, &dummy_int, &dummy_int, &ww, &wh, &bw, &bh);
+    if (!XTranslateCoordinates(server.display, win, server.root_win, 0, 0, x, y, &src))
+        return FALSE;
+    if (!XGetGeometry(server.display, win, &src, &dummy_int, &dummy_int, &ww, &wh, &bw, &bh))
+        return FALSE;
     *w = ww + bw;
     *h = wh + bh;
+    return TRUE;
 }
 
 gboolean window_is_iconified(Window win)
@@ -352,3 +356,39 @@ XFreeStringList(name_list);
     XFree(text_property.value);
     return result;
 }
+
+cairo_surface_t *get_window_thumbnail(Window win)
+{
+    int x, y, w, h;
+    if (!get_window_coordinates(win, &x, &y, &w, &h))
+        return NULL;
+
+    int tw, th;
+    th = 128;
+    tw = w * th / h;
+
+    cairo_surface_t *x11_surface =
+        cairo_xlib_surface_create(server.display, win, DefaultVisual(server.display, server.screen), w, h);
+    cairo_surface_t *image_surface = cairo_surface_create_similar_image(x11_surface, CAIRO_FORMAT_ARGB32, tw, th);
+
+    cairo_t *cr = cairo_create(image_surface);
+    cairo_scale(cr, tw/(double)w, th/(double)h);
+    cairo_set_source_surface(cr, x11_surface, 0, 0);
+    cairo_pattern_set_filter(cairo_get_source(cr), CAIRO_FILTER_BEST);
+    cairo_paint(cr);
+    cairo_destroy(cr);
+    cairo_surface_destroy(x11_surface);
+
+    uint32_t *pixels = (uint32_t *)cairo_image_surface_get_data(image_surface);
+    gboolean empty = TRUE;
+    for (int i = 0; empty && i < tw * th; i += 4) {
+        if (pixels[i] & 0xffFFff)
+            empty = FALSE;
+    }
+    if (empty) {
+        cairo_surface_destroy(image_surface);
+        return NULL;
+    }
+
+    return image_surface;
+}

@@ -25,7 +25,7 @@ int get_window_monitor(Window win);
 
 void activate_window(Window win);
 void close_window(Window win);
-void get_window_coordinates(Window win, int *x, int *y, int *w, int *h);
+gboolean get_window_coordinates(Window win, int *x, int *y, int *w, int *h);
 void toggle_window_maximized(Window win);
 void toggle_window_shade(Window win);
 void change_window_desktop(Window win, int desktop);
@@ -34,5 +34,6 @@ int get_icon_count(gulong *data, int num);
 gulong *get_best_icon(gulong *data, int icon_count, int num, int *iw, int *ih, int best_icon_size);
 
 char *get_window_name(Window win);
+cairo_surface_t *get_window_thumbnail(Window win);
 
 #endif