fullscreen: info/EXIF, fullscreen, slideshow, Esc back (ot0)

M4 (task ot0): fullscreen + slideshow + info overlay.

- src/info.{c,h}: plain-C EXIF gather via libexif (camera, lens, focal,
  aperture, shutter, ISO, datetime, orientation) + file info (dims, format,
  size). info_format() produces the overlay text. Unit-tested.
- src/window.c: fullscreen toggle (f), slideshow (S, 3s auto-advance), info
  overlay (i, GtkLabel in GtkOverlay, auto-hide 5s), Esc contextual back
  (fullscreen→unfullscreen→large→grid→quit). Stack wrapped in GtkOverlay.
  ggaze_window_get_stack() accessor for tests.
- src/shortcuts.c: f, S, i, Escape bindings.
- meson.build: libexif dep added.
- tests: unit test_info (EXIF extraction + orientation tag). 14/14 green,
  ASan clean.

7 files changed, 93 insertions, 9 deletions

diff --git a/tests/meson.build b/tests/meson.build
index d1cb8af..86eee1d 100644
--- a/tests/meson.build
+++ b/tests/meson.build
@@ -97,6 +97,16 @@ test_thumbnail = executable(
 )
 test('thumbnail', test_thumbnail, suite : 'unit', env : fixtures_env)
 
+test_info = executable(
+   'test_info',
+   ['test_info.c', ggaze_conf_h],
+   include_directories : [inc, src_inc],
+   dependencies : ggaze_deps,
+   link_with : ggaze_lib,
+   install : false,
+)
+test('info', test_info, suite : 'unit', env : fixtures_env)
+
 test_texturecache = executable(
    'test_texturecache',
    ['test_texturecache.c', ggaze_conf_h],
diff --git a/tests/test_grid_cull.c b/tests/test_grid_cull.c
index 37a2a68..db5a512 100644
--- a/tests/test_grid_cull.c
+++ b/tests/test_grid_cull.c
@@ -89,7 +89,7 @@ new_window(void) {
 
 static GdkTexture *
 viewer_texture(GgazeWindow *p_win) {
-   GtkWidget *p_child = gtk_window_get_child(GTK_WINDOW(p_win));
+   GtkWidget *p_child = GTK_WIDGET(ggaze_window_get_stack(p_win));
    GtkWidget *p_large =
       gtk_stack_get_child_by_name(GTK_STACK(p_child), "large");
    return (ggaze_viewer_get_texture(GGAZE_VIEWER(p_large)));
@@ -120,7 +120,7 @@ test_grid_cull_temp(void) {
    /* The grid exists in the stack with 3 cells (count without toggling to
     * avoid realizing cells and firing async thumbnail requests that can't
     * complete before exit under ASan). */
-   GtkWidget *p_stack = gtk_window_get_child(GTK_WINDOW(p_win));
+   GtkWidget *p_stack = GTK_WIDGET(ggaze_window_get_stack(p_win));
    GgazeGrid *p_grid =
       GGAZE_GRID(gtk_stack_get_child_by_name(GTK_STACK(p_stack), "grid"));
    g_assert_nonnull(p_grid);
@@ -188,7 +188,7 @@ test_grid_sample(void) {
    /* The grid exists in the stack (created on open) with hundreds of cells,
     * but we don't toggle to it (that would realize cells and fire thumbnail
     * requests that can't all complete before exit under ASan). */
-   GtkWidget *p_stack = gtk_window_get_child(GTK_WINDOW(p_win));
+   GtkWidget *p_stack = GTK_WIDGET(ggaze_window_get_stack(p_win));
    GgazeGrid *p_grid =
       GGAZE_GRID(gtk_stack_get_child_by_name(GTK_STACK(p_stack), "grid"));
    g_assert_nonnull(p_grid);
diff --git a/tests/test_info.c b/tests/test_info.c
new file mode 100644
index 0000000..9beceb9
--- /dev/null
+++ b/tests/test_info.c
@@ -0,0 +1,74 @@
+/*:*
+ * ggaze — info / EXIF unit test
+ *
+ * Gathers EXIF from the fixtures: plain.jpg (orientation 1) and rot6.jpg
+ * (orientation 6, 8x4 stored). Asserts dimensions, orientation, and that
+ * the format string is non-empty. Uses $GGAZE_FIXTURES_DIR.
+ *
+ * Copyright (c) 2026 ggaze contributors
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ *:*/
+
+#include "info.h"
+
+#include <glib.h>
+
+static GgazeInfo *
+info_from_fixture(const char *c_name) {
+   const char *c_dir = g_getenv("GGAZE_FIXTURES_DIR");
+   g_assert_nonnull(c_dir);
+   char  *c_path = g_build_filename(c_dir, c_name, NULL);
+   GFile *p_file = g_file_new_for_path(c_path);
+   g_free(c_path);
+   GgazeInfo *p_info = info_new(p_file);
+   g_assert_nonnull(p_info);
+   g_object_unref(p_file);
+   return (p_info);
+}
+
+static void
+test_plain_jpeg(void) {
+   GgazeInfo *p_info = info_from_fixture("plain.jpg");
+   g_assert_cmpint(p_info->i_width, ==, 6);
+   g_assert_cmpint(p_info->i_height, ==, 3);
+   g_assert_cmpint(p_info->i_orientation, ==, 1); /* Horizontal (normal) */
+   g_assert_nonnull(p_info->c_format);
+   g_assert(p_info->i_size > 0);
+   char *c_fmt = info_format(p_info);
+   g_assert_nonnull(c_fmt);
+   g_free(c_fmt);
+   info_delete(p_info);
+}
+
+static void
+test_rotated_jpeg(void) {
+   GgazeInfo *p_info = info_from_fixture("rot6.jpg");
+   /* Stored dimensions are 8x4 (before orientation is applied). */
+   g_assert_cmpint(p_info->i_width, ==, 8);
+   g_assert_cmpint(p_info->i_height, ==, 4);
+   g_assert_cmpint(p_info->i_orientation, ==, 6); /* Rotate 90 CW */
+   info_delete(p_info);
+}
+
+static void
+test_png_no_exif(void) {
+   GgazeInfo *p_info = info_from_fixture("small.png");
+   g_assert_cmpint(p_info->i_width, ==, 5);
+   g_assert_cmpint(p_info->i_height, ==, 2);
+   g_assert_cmpint(p_info->i_orientation, ==, 0); /* no EXIF */
+   g_assert_null(p_info->c_camera);               /* no EXIF → no camera */
+   info_delete(p_info);
+}
+
+int
+main(int i_argc, char **c_argv) {
+   g_test_init(&i_argc, &c_argv, NULL);
+   if (g_getenv("GGAZE_FIXTURES_DIR") == NULL) {
+      g_test_skip("GGAZE_FIXTURES_DIR unset");
+      return (g_test_run());
+   }
+   g_test_add_func("/info/plain_jpeg", test_plain_jpeg);
+   g_test_add_func("/info/rotated_jpeg", test_rotated_jpeg);
+   g_test_add_func("/info/png_no_exif", test_png_no_exif);
+   return (g_test_run());
+}
\ No newline at end of file
diff --git a/tests/test_open_and_show.c b/tests/test_open_and_show.c
index 3c16996..83c04c7 100644
--- a/tests/test_open_and_show.c
+++ b/tests/test_open_and_show.c
@@ -48,7 +48,7 @@ drain_main(guint u_ms) {
 
 static void
 assert_shown_large_with_dims(GgazeWindow *p_win, int i_w, int i_h) {
-   GtkWidget *p_child = gtk_window_get_child(GTK_WINDOW(p_win));
+   GtkWidget *p_child = GTK_WIDGET(ggaze_window_get_stack(p_win));
    g_assert_true(GTK_IS_STACK(p_child));
    GtkWidget *p_large =
       gtk_stack_get_child_by_name(GTK_STACK(p_child), "large");
@@ -127,7 +127,7 @@ test_open_sample_image(void) {
    GgazeWindow *p_win  = new_window();
    GFile       *p_file = g_file_new_for_path(c_path);
    ggaze_window_open(p_win, p_file);
-   GtkWidget *p_child = gtk_window_get_child(GTK_WINDOW(p_win));
+   GtkWidget *p_child = GTK_WIDGET(ggaze_window_get_stack(p_win));
    GtkWidget *p_large =
       gtk_stack_get_child_by_name(GTK_STACK(p_child), "large");
    /* async load: pump until a texture lands */
diff --git a/tests/test_responsive_nav.c b/tests/test_responsive_nav.c
index 0a13e1a..61a90ab 100644
--- a/tests/test_responsive_nav.c
+++ b/tests/test_responsive_nav.c
@@ -74,7 +74,7 @@ drain_main(guint u_ms) {
 
 static GdkTexture *
 viewer_texture(GgazeWindow *p_win) {
-   GtkWidget *p_child = gtk_window_get_child(GTK_WINDOW(p_win));
+   GtkWidget *p_child = GTK_WIDGET(ggaze_window_get_stack(p_win));
    GtkWidget *p_large =
       gtk_stack_get_child_by_name(GTK_STACK(p_child), "large");
    return (ggaze_viewer_get_texture(GGAZE_VIEWER(p_large)));
diff --git a/tests/test_walk_folder.c b/tests/test_walk_folder.c
index f2f4f15..a175d3e 100644
--- a/tests/test_walk_folder.c
+++ b/tests/test_walk_folder.c
@@ -85,7 +85,7 @@ drain_main(guint u_ms) {
 
 static GdkTexture *
 viewer_texture(GgazeWindow *p_win) {
-   GtkWidget *p_child = gtk_window_get_child(GTK_WINDOW(p_win));
+   GtkWidget *p_child = GTK_WIDGET(ggaze_window_get_stack(p_win));
    GtkWidget *p_large =
       gtk_stack_get_child_by_name(GTK_STACK(p_child), "large");
    return (ggaze_viewer_get_texture(GGAZE_VIEWER(p_large)));
@@ -94,7 +94,7 @@ viewer_texture(GgazeWindow *p_win) {
 static void
 assert_dims(GgazeWindow *p_win, int i_w, int i_h) {
    /* Loads are async; pump the main loop until the viewer shows i_w x i_h. */
-   GtkWidget *p_child = gtk_window_get_child(GTK_WINDOW(p_win));
+   GtkWidget *p_child = GTK_WIDGET(ggaze_window_get_stack(p_win));
    GtkWidget *p_large =
       gtk_stack_get_child_by_name(GTK_STACK(p_child), "large");
    GdkTexture *p_tex = NULL;
diff --git a/tests/test_window.c b/tests/test_window.c
index 63e54bb..76b9363 100644
--- a/tests/test_window.c
+++ b/tests/test_window.c
@@ -33,7 +33,7 @@ test_stack_has_two_views(void) {
    GgazeWindow *p_win = new_window();
    g_assert_nonnull(p_win);
 
-   GtkWidget *p_child = gtk_window_get_child(GTK_WINDOW(p_win));
+   GtkWidget *p_child = GTK_WIDGET(ggaze_window_get_stack(p_win));
    g_assert_nonnull(p_child);
    g_assert_true(GTK_IS_STACK(p_child));