Simplify the public event and CPU API

Applications now need far less ceremony: hello.c is a 20-line loop that
handles REFRESH, CLOSE and QUIT and draws into the surface's own pixels.

- Fold GEOMETRY, STATE and FOCUS into one WINDOW event carrying size,
  scale and state; unchanged values send nothing.
- Guarantee REFRESH once a window has a size and after every resize,
  never at size zero.
- Merge DROP_HOVER into DROP with over/leave/data actions and give drag
  and drop actions enums.
- Keep event strings valid until the next wait and drop
  yasl_event_release; empty or failed waits report NONE.
- Replace copy-in presentation with a lent pixel buffer:
  yasl_cpu_pixels and yasl_cpu_present.
- Remove yasl_poll_event, yasl_cpu_read_pixels, unused event fields and
  comments that restated names.
- Wayland: resize floating windows in request_size instead of reporting
  it unsupported, and stop marking new GPU surfaces as Vulkan so
  yasl_vulkan_create_surface no longer fails with NATIVE_WINDOW_IN_USE.

Also includes the in-progress public API refactor that was uncommitted
in the tree (removal of the app/loop layer, new surface, GL and Vulkan
entry points).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 56 insertions, 0 deletions

diff --git a/src/common/private_timing.h b/src/common/private_timing.h
new file mode 100644
index 0000000..308765c
--- /dev/null
+++ b/src/common/private_timing.h
@@ -0,0 +1,56 @@
+/**
+ * @file
+ * Timing provenance, refresh estimates, and buffer-resize statistics.
+ * All timestamps are monotonic nanoseconds, not wall-clock dates.
+ */
+#ifndef YASL_PRIVATE_TIMING_H
+#define YASL_PRIVATE_TIMING_H
+
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/** Cumulative backend buffer-resize measurements; unavailable counters are zero. */
+struct yasl_private_resize_stats {
+    /** Number of measured buffer resizes. */
+    uint64_t count;
+    /** Mean measured resize duration in microseconds. */
+    double avg_us;
+    /** Maximum measured resize duration in microseconds. */
+    double max_us;
+    /** Backend minor page-fault counter, if collected. */
+    long minflt;
+};
+
+/* Describes last_present_ns, not merely availability of an extension. */
+/** Provenance of last_present_ns; only PRESENTATION confirms compositor presentation. */
+enum yasl_private_timing_source {
+    YASL_PRIVATE_TIMING_UNKNOWN = 0, /**< No timing sample yet. */
+    YASL_PRIVATE_TIMING_SUBMISSION, /**< CPU submission time, not scanout confirmation. */
+    YASL_PRIVATE_TIMING_FRAME_CALLBACK, /**< Compositor pacing callback, not scanout confirmation. */
+    YASL_PRIVATE_TIMING_PRESENTATION, /**< Compositor-confirmed presentation. */
+};
+
+/** Snapshot of estimates and timing provenance. Zero timestamps mean no sample yet. */
+struct yasl_private_timing {
+    /** Estimated refresh interval in nanoseconds; zero if unavailable. */
+    double refresh_ns;
+    /** Last timestamp, whose meaning is specified by source. */
+    uint64_t last_present_ns;
+    /** Estimated next presentation time, or zero without a prior sample. */
+    uint64_t next_present_ns;
+    /** Backend skipped-frame counter; not comparable across backends. */
+    uint64_t frames_skipped;
+    /** Provenance of last_present_ns. */
+    enum yasl_private_timing_source source;
+    /** Cumulative backend resize statistics. */
+    struct yasl_private_resize_stats resize;
+};
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* YASL_PRIVATE_TIMING_H */