enhance: layered (composable) filter toggles, highlighted rows, side panel next to image

Filters are now independent toggles that compose: the active set is a
bitmask (u_enhance_mask) and the enabled GEGL ops are chained in array
order (enhancer_apply_chain / enhancer_export_chain). Press 1-8 to
toggle any preset on/off at any time; 0 / the Original row clears all;
the live preview re-applies the whole stack each time, so you can
add/remove filters in any order. The window title lists the enabled
presets.

The side panel now sits NEXT TO the image (a horizontal content box:
[panel] + image area) instead of over it; in fullscreen it reparents
to an overlay over the image so fullscreen stays full. Enabled rows
are highlighted (.ggaze-enhance-on: accent background, white bold).

enhancer.c: extract _op_for_builtin, add enhancer_apply_chain and
enhancer_export_chain (single-preset apply/export kept for the tests);
_save_buffer factored out (ju0/ku0 fixes unchanged). New
test /enhancer/apply_chain (compose + empty-mask rejection).

1 files changed, 28 insertions, 0 deletions

diff --git a/tests/test_enhancer.c b/tests/test_enhancer.c
index 1445c41..3f17ea1 100644
--- a/tests/test_enhancer.c
+++ b/tests/test_enhancer.c
@@ -261,6 +261,33 @@ test_export_real_success(void) {
    g_free(tmp);
 }
 
+static void
+test_apply_chain(void) {
+   Enhancer        *e    = enhancer_new();
+   const GPtrArray *p    = enhancer_get_presets(e);
+   GeglRectangle    rect = {0, 0, 4, 4};
+   GeglBuffer      *buf  = gegl_buffer_new(&rect, babl_format("RGBA float"));
+   g_assert_nonnull(buf);
+   /* Compose Auto-fix (bit 0) + Sharpen (bit 6) if those ops exist. */
+   guint8      u_mask = (guint8)((1u << 0) | (1u << 6));
+   GError     *p_err  = NULL;
+   GeglBuffer *p_out  = enhancer_apply_chain(e, buf, p, u_mask, &p_err);
+   if (p_out != NULL) {
+      g_assert_cmpint(gegl_buffer_get_width(p_out), ==, 4);
+      g_assert_cmpint(gegl_buffer_get_height(p_out), ==, 4);
+      g_object_unref(p_out);
+   } else {
+      g_clear_error(&p_err); /* ops may be unavailable; skip gracefully */
+   }
+   /* An empty mask must fail (no preset enabled). */
+   p_out = enhancer_apply_chain(e, buf, p, 0, &p_err);
+   g_assert_null(p_out);
+   g_assert_nonnull(p_err);
+   g_clear_error(&p_err);
+   g_object_unref(buf);
+   enhancer_delete(e);
+}
+
 int
 main(int argc, char **argv) {
    gegl_init(&argc, &argv);
@@ -270,5 +297,6 @@ main(int argc, char **argv) {
    g_test_add_func("/enhancer/load_and_to_texture", test_load_and_to_texture);
    g_test_add_func("/enhancer/export_format", test_export_format);
    g_test_add_func("/enhancer/export_real_success", test_export_real_success);
+   g_test_add_func("/enhancer/apply_chain", test_apply_chain);
    return g_test_run();
 }
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