diff --git a/example/imageviewer/imageviewer.cc b/example/imageviewer/imageviewer.cc
index 9e33474..26a5cf9 100644
--- a/example/imageviewer/imageviewer.cc
+++ b/example/imageviewer/imageviewer.cc
@@ -35,6 +35,8 @@
 The '1' to '8' keys change the magnification zoom (or minification zoom with
 the shift key). The '0' key toggles nearest neighbor and bilinear filtering.
 
+The arrow keys (or hjkl keys) scroll the image. The '`' key resets.
+
 The Escape key quits.
 */
 
@@ -108,6 +110,8 @@
 wuffs_base__pixel_buffer g_pixbuf = {0};
 uint32_t g_background_color_index = 0;
 int32_t g_zoom = 0;
+int32_t g_pos_x = 0;
+int32_t g_pos_y = 0;
 bool g_filter = false;
 
 struct {
@@ -160,6 +164,16 @@
   return NULL;
 }
 
+static int32_t  //
+i32_min(int32_t a, int32_t b) {
+  return (a < b) ? a : b;
+}
+
+static int32_t  //
+i32_max(int32_t a, int32_t b) {
+  return (a > b) ? a : b;
+}
+
 class MyDecodeImageCallbacks : public wuffs_aux::DecodeImageCallbacks {
  public:
   MyDecodeImageCallbacks() : m_combined_gamma(1.0) {}
@@ -308,6 +322,10 @@
 #define XK_BackSpace 0xFF08
 #define XK_Escape 0xFF1B
 #define XK_Return 0xFF0D
+#define XK_Left 0xFF51
+#define XK_Up 0xFF52
+#define XK_Right 0xFF53
+#define XK_Down 0xFF54
 
 uint32_t g_maximum_request_length = 0;  // Measured in 4-byte units.
 xcb_atom_t g_atom_net_wm_name = XCB_NONE;
@@ -335,7 +353,10 @@
   uint32_t value_mask = XCB_CW_BACK_PIXEL | XCB_CW_EVENT_MASK;
   uint32_t value_list[2];
   value_list[0] = s->black_pixel;
-  value_list[1] = XCB_EVENT_MASK_EXPOSURE | XCB_EVENT_MASK_KEY_PRESS;
+  value_list[1] = XCB_EVENT_MASK_KEY_PRESS |        //
+                  XCB_EVENT_MASK_BUTTON_PRESS |     //
+                  XCB_EVENT_MASK_BUTTON_1_MOTION |  //
+                  XCB_EVENT_MASK_EXPOSURE;
   xcb_create_window(c, 0, w, s->root, 0, 0, 1024, 768, 0,
                     XCB_WINDOW_CLASS_INPUT_OUTPUT, s->root_visual, value_mask,
                     value_list);
@@ -407,6 +428,16 @@
   return (b < M) ? b : M;
 }
 
+int32_t  //
+calculate_delta(uint16_t state) {
+  if (state & XCB_MOD_MASK_SHIFT) {
+    return 256;
+  } else if (state & XCB_MOD_MASK_CONTROL) {
+    return 1;
+  }
+  return 16;
+}
+
 bool  //
 load(xcb_connection_t* c, xcb_window_t w, const char* filename) {
   if (g_pixmap != XCB_NONE) {
@@ -469,6 +500,44 @@
   return true;
 }
 
+// clear_area clears the L-shaped difference between old and new rectangles (of
+// equal width and height). It does this in up to two xcb_clear_area calls,
+// labeled A and B in the example below (with old_x=0, old_y=0, width=5,
+// height=4, new_x=2, new_y=2).
+//
+// AAAAA
+// AAAAA
+// BB+---+
+// BB|   |
+//   |   |
+//   +---+
+void  //
+clear_area(xcb_connection_t* c,
+           xcb_window_t w,
+           int32_t old_x,
+           int32_t old_y,
+           int32_t width,
+           int32_t height,
+           int32_t new_x,
+           int32_t new_y) {
+  int32_t dy = new_y - old_y;
+  if (dy < 0) {
+    xcb_clear_area(c, 1, w, old_x, old_y + height + dy, width, -dy);
+  } else if (dy > 0) {
+    xcb_clear_area(c, 1, w, old_x, old_y, width, dy);
+  }
+
+  int32_t y0 = i32_max(old_y, new_y);
+  int32_t y1 = i32_min(old_y + height, new_y + height);
+
+  int32_t dx = new_x - old_x;
+  if (dx < 0) {
+    xcb_clear_area(c, 1, w, old_x + width + dx, y0, -dx, y1 - y0);
+  } else if (dx > 0) {
+    xcb_clear_area(c, 1, w, old_x, y0, dx, y1 - y0);
+  }
+}
+
 int  //
 main(int argc, char** argv) {
   const char* status = parse_flags(argc, argv);
@@ -532,6 +601,9 @@
   g_pixmap_gc = xcb_generate_id(c);
   g_pixmap_picture = xcb_generate_id(c);
 
+  int32_t button_x = 0;
+  int32_t button_y = 0;
+
   bool loaded = load(
       c, w, (g_flags.remaining_argc > 0) ? g_flags.remaining_argv[0] : NULL);
   int arg = 0;
@@ -544,12 +616,14 @@
     }
 
     bool reload = false;
+    int32_t old_pos_x = g_pos_x;
+    int32_t old_pos_y = g_pos_y;
     switch (event->response_type & 0x7F) {
       case XCB_EXPOSE: {
         xcb_expose_event_t* e = (xcb_expose_event_t*)event;
         if (loaded && (e->count == 0)) {
           xcb_render_composite(c, XCB_RENDER_PICT_OP_SRC, g_pixmap_picture,
-                               XCB_NONE, p, 0, 0, 0, 0, 0, 0,
+                               XCB_NONE, p, 0, 0, 0, 0, g_pos_x, g_pos_y,
                                zoom_shift(g_width), zoom_shift(g_height));
           xcb_flush(c);
         }
@@ -589,6 +663,31 @@
               reload = true;
               break;
 
+            case '`':
+              g_pos_x = 0;
+              g_pos_y = 0;
+              break;
+
+            case XK_Left:
+            case 'h':
+              g_pos_x += calculate_delta(e->state);
+              break;
+
+            case XK_Down:
+            case 'j':
+              g_pos_y -= calculate_delta(e->state);
+              break;
+
+            case XK_Up:
+            case 'k':
+              g_pos_y += calculate_delta(e->state);
+              break;
+
+            case XK_Right:
+            case 'l':
+              g_pos_x -= calculate_delta(e->state);
+              break;
+
             case '0':
             case '1':
             case '2':
@@ -619,6 +718,38 @@
         break;
       }
 
+      case XCB_BUTTON_PRESS: {
+        xcb_button_press_event_t* e = (xcb_button_press_event_t*)event;
+        switch (e->detail) {
+          case 1:
+            button_x = e->event_x;
+            button_y = e->event_y;
+            break;
+          case 4:
+            g_pos_y += calculate_delta(e->state);
+            break;
+          case 5:
+            g_pos_y -= calculate_delta(e->state);
+            break;
+          case 6:
+            g_pos_x += calculate_delta(e->state);
+            break;
+          case 7:
+            g_pos_x -= calculate_delta(e->state);
+            break;
+        }
+        break;
+      }
+
+      case XCB_MOTION_NOTIFY: {
+        xcb_motion_notify_event_t* e = (xcb_motion_notify_event_t*)event;
+        g_pos_x += e->event_x - button_x;
+        g_pos_y += e->event_y - button_y;
+        button_x = e->event_x;
+        button_y = e->event_y;
+        break;
+      }
+
       case XCB_CLIENT_MESSAGE: {
         xcb_client_message_event_t* e = (xcb_client_message_event_t*)event;
         if (e->data.data32[0] == g_atom_wm_delete_window) {
@@ -634,6 +765,14 @@
       loaded = load(c, w, g_flags.remaining_argv[arg]);
       xcb_clear_area(c, 1, w, 0, 0, 0xFFFF, 0xFFFF);
       xcb_flush(c);
+    } else if (loaded &&  //
+               ((old_pos_x != g_pos_x) || (old_pos_y != g_pos_y))) {
+      clear_area(c, w, old_pos_x, old_pos_y, zoom_shift(g_width),
+                 zoom_shift(g_height), g_pos_x, g_pos_y);
+      xcb_render_composite(c, XCB_RENDER_PICT_OP_SRC, g_pixmap_picture,
+                           XCB_NONE, p, 0, 0, 0, 0, g_pos_x, g_pos_y,
+                           zoom_shift(g_width), zoom_shift(g_height));
+      xcb_flush(c);
     }
   }
   return 0;