Add full-screen scan triggered by constant, untrusted damage reports

This goes further than commit cb122392 by forcing a whole screen
scan, looking for changes.

This improves the feel of using a session with mutter, which is
quite noticeable in a terminal window.

Acked-by: Frediano Ziglio <fziglio@redhat.com>

4 files changed, 94 insertions, 4 deletions

diff --git a/src/display.c b/src/display.c
index 8757c2f..5c54143 100644
--- a/src/display.c
+++ b/src/display.c
@@ -149,7 +149,7 @@ static void handle_damage_notify(display_t *display, xcb_damage_notify_event_t *
             scanner_push(&display->session->scanner, DAMAGE_SCAN_REPORT,
                          p[i].x1, p[i].y1, p[i].x2 - p[i].x1, p[i].y2 - p[i].y1);
     } else {
-        scanner_push(&display->session->scanner, PERIODIC_SCAN_REQUEST, 0, 0, 0, 0);
+        scanner_push(&display->session->scanner, FULLSCREEN_SCAN_REQUEST, 0, 0, 0, 0);
     }
 
     pixman_region_clear(damage_region);
@@ -601,6 +601,66 @@ void display_copy_image_into_fullscreen(display_t *d, shm_image_t *shmi, int x,
     }
 }
 
+int display_scan_whole_screen(display_t *d, int num_vertical_tiles, int num_horizontal_tiles,
+                              int tiles[][num_horizontal_tiles], int *tiles_changed_in_row)
+{
+    int ret;
+    int len;
+    int h_tile, v_tile, y;
+    shm_image_t *fullscreen_new;
+
+    memset(tiles, 0, sizeof(**tiles) * num_vertical_tiles * num_horizontal_tiles);
+    fullscreen_new = create_shm_image(d, 0, 0);
+    if (!fullscreen_new)
+        return 0;
+
+    ret = read_shm_image(d, fullscreen_new, 0, 0);
+    if (ret == 0) {
+        for (v_tile = 0; v_tile < num_vertical_tiles; v_tile++) {
+            /* Note that integer math and multiplying first is important;
+               especially in the case where our screen height is not a
+               multiple of 32 */
+            int ystart = (v_tile * d->fullscreen->h) / num_vertical_tiles;
+            int yend = ((v_tile + 1) * d->fullscreen->h) / num_vertical_tiles;
+            for (y = ystart; y < yend; y++) {
+                if (y >= d->fullscreen->h)
+                    continue;
+
+                uint32_t *old = ((uint32_t *) d->fullscreen->segment.shmaddr) +
+                    (y * d->fullscreen->w);
+                uint32_t *new = ((uint32_t *) fullscreen_new->segment.shmaddr) +
+                    (y * fullscreen_new->w);
+                if (memcmp(old, new, sizeof(*old) * d->fullscreen->w) == 0)
+                    continue;
+
+                len = d->fullscreen->w / num_horizontal_tiles;
+                for (h_tile = 0; h_tile < num_horizontal_tiles; h_tile++, old += len, new += len) {
+                    if (h_tile == num_horizontal_tiles - 1)
+                        len = d->fullscreen->w - (h_tile * len);
+                    if (memcmp(old, new, sizeof(*old) * len)) {
+                        ret++;
+                        tiles[v_tile][h_tile]++;
+                        tiles_changed_in_row[v_tile]++;
+                    }
+                }
+            }
+#if defined(DEBUG_SCANLINES)
+            fprintf(stderr, "%d: ", v_tile);
+            for (h_tile = 0; h_tile < num_horizontal_tiles; h_tile++)
+                fprintf(stderr, "%c", tiles[v_tile][h_tile] ? 'X' : '-');
+            fprintf(stderr, "\n");
+            fflush(stderr);
+#endif
+        }
+    }
+
+    /* We've just read the full screen; may as well use it */
+    destroy_shm_image(d, d->fullscreen);
+    d->fullscreen = fullscreen_new;
+
+    return ret;
+}
+
 
 void destroy_shm_image(display_t *d, shm_image_t *shmi)
 {
diff --git a/src/display.h b/src/display.h
index f4cabc0..9e5cdf4 100644
--- a/src/display.h
+++ b/src/display.h
@@ -86,6 +86,8 @@ int display_start_event_thread(display_t *d);
 void display_stop_event_thread(display_t *d);
 int display_find_changed_tiles(display_t *d, int row, int *tiles, int tiles_across);
 void display_copy_image_into_fullscreen(display_t *d, shm_image_t *shmi, int x, int y);
+int display_scan_whole_screen(display_t *d, int num_vertical_tiles, int num_horizontal_tiles,
+                              int tiles[][num_horizontal_tiles], int *tiles_changed_in_row);
 
 shm_image_t *create_shm_image(display_t *d, unsigned int w, unsigned int h);
 int read_shm_image(display_t *d, shm_image_t *shmi, int x, int y);
diff --git a/src/scan.c b/src/scan.c
index 1c5927e..fcd472d 100644
--- a/src/scan.c
+++ b/src/scan.c
@@ -348,6 +348,34 @@ static void scanner_periodic(scanner_t *scanner)
     g_mutex_unlock(scanner->session->lock);
 }
 
+static void scan_full_screen(scanner_t *scanner)
+{
+    int num_vertical_tiles;
+    int rc;
+
+    g_mutex_lock(scanner->session->lock);
+    num_vertical_tiles = scanner->session->display.fullscreen->h / NUM_SCANLINES;
+    if (scanner->session->display.fullscreen->h % NUM_SCANLINES)
+        num_vertical_tiles++;
+
+    int tiles_changed_in_row[num_vertical_tiles];
+    int tiles_changed[num_vertical_tiles][NUM_HORIZONTAL_TILES];
+
+    memset(tiles_changed_in_row, 0, sizeof(tiles_changed_in_row));
+
+    rc = display_scan_whole_screen(&scanner->session->display,
+                                   num_vertical_tiles, NUM_HORIZONTAL_TILES,
+                                   tiles_changed, tiles_changed_in_row);
+    if (rc < 0) {
+        g_mutex_unlock(scanner->session->lock);
+        return;
+    }
+
+    grow_changed_tiles(scanner, tiles_changed_in_row, tiles_changed, num_vertical_tiles);
+    push_changed_tiles(scanner, tiles_changed_in_row, tiles_changed, num_vertical_tiles);
+    g_mutex_unlock(scanner->session->lock);
+}
+
 #if ! GLIB_CHECK_VERSION(2, 31, 18)
 static gpointer g_async_queue_timeout_pop(GAsyncQueue *queue, guint64 t)
 {
@@ -370,9 +398,9 @@ static void *scanner_run(void *opaque)
             continue;
         }
 
-        if (r->type == PERIODIC_SCAN_REQUEST) {
+        if (r->type == FULLSCREEN_SCAN_REQUEST) {
             free_queue_item(r);
-            scanner_periodic(scanner);
+            scan_full_screen(scanner);
             continue;
         }
 
diff --git a/src/scan.h b/src/scan.h
index 69991fe..8d92ba3 100644
--- a/src/scan.h
+++ b/src/scan.h
@@ -30,7 +30,7 @@ typedef enum {
     DAMAGE_SCAN_REPORT,
     SCANLINE_SCAN_REPORT,
     EXIT_SCAN_REPORT,
-    PERIODIC_SCAN_REQUEST,
+    FULLSCREEN_SCAN_REQUEST,
 } scan_type_t;
 
 struct session_struct;