Add damage presentation and reduce CPU surface latency

Add yasl_cpu_present_damage to submit partial damage rectangles.
Skip commit timers for CPU surfaces to prevent display delay.
Remove frame callback gating in surface_draw_frame when free buffers exist.
Flush the display immediately on CPU present.
Forward tearing option to window specifications.

1 files changed, 1 insertions, 0 deletions

diff --git a/src/common/backend.h b/src/common/backend.h
index e26f9d2..b111d3e 100644
--- a/src/common/backend.h
+++ b/src/common/backend.h
@@ -38,6 +38,7 @@ struct yasl_surface {
     /* CPU canvas returned by yasl_cpu_pixels and copied into each drawn frame. */
     uint32_t *canvas;
     int canvas_width, canvas_height;
+    struct yasl_private_damage_list cpu_damage;
     /* Window values last reported through public WINDOW events. */
     struct yasl_private_vector2i reported_size;
     uint32_t reported_scale_120, reported_state;