[gtk/ngl-tiling-experiment] ngl: Tiled rendering experiment

[Matthias Clasen <matthiasc src gnome org>]

commit b23a03a44b37831f7ae0aaae805382d46129dc11
Author: Matthias Clasen <mclasen redhat com>
Date:   Sun Apr 11 18:05:41 2021 -0400

    ngl: Tiled rendering experiment
    
    Render the tree 4 times, with clips to cut out one quarter
    of the window. Not pushing things into threads yet. The
    speedups are moderate at best, and there are some rendering
    artifacts at tile boundaries.

 gsk/ngl/gsknglrenderer.c | 71 +++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 70 insertions(+), 1 deletion(-)
---
diff --git a/gsk/ngl/gsknglrenderer.c b/gsk/ngl/gsknglrenderer.c
index 66edc98d5d..bd9fb03220 100644
--- a/gsk/ngl/gsknglrenderer.c
+++ b/gsk/ngl/gsknglrenderer.c
@@ -196,6 +196,7 @@ gsk_ngl_renderer_render (GskRenderer          *renderer,
   GskNglRenderJob *job;
   GdkSurface *surface;
   float scale_factor;
+  gint64 start_time, end_time;
 
   g_assert (GSK_IS_NGL_RENDERER (renderer));
   g_assert (root != NULL);
@@ -215,15 +216,83 @@ gsk_ngl_renderer_render (GskRenderer          *renderer,
   render_region = get_render_region (surface, self->context);
 
   gsk_ngl_driver_begin_frame (self->driver, self->command_queue);
+
+  start_time = g_get_monotonic_time ();
+  g_print ("tiled:");
+  end_time = start_time;
+
+  for (int i = 0; i < 4; i++)
+    {
+      cairo_region_t *region;
+      gint64 st = end_time;
+
+      int w = gdk_surface_get_width (surface);
+      int h = gdk_surface_get_height (surface);
+
+      if (render_region)
+        region = cairo_region_copy (render_region);
+      else
+        region = cairo_region_create_rectangle (&(GdkRectangle){ 0, 0, w, h });
+
+      switch (i)
+        {
+        case 0:
+          cairo_region_intersect_rectangle (region,
+                &(cairo_rectangle_int_t) { 0, 0, w/2, h/2 });
+          break;
+        case 1:
+          cairo_region_intersect_rectangle (region,
+                &(cairo_rectangle_int_t) { w/2, 0, w - w/2, h/2 });
+          break;
+        case 2:
+          cairo_region_intersect_rectangle (region,
+                &(cairo_rectangle_int_t) { 0, h/2, w/2, h - h/2 });
+          break;
+        case 3:
+          cairo_region_intersect_rectangle (region,
+                &(cairo_rectangle_int_t) { w/2, h/2, w - w/2, h - h/2 });
+          break;
+        default:
+          g_assert_not_reached ();
+          break;
+        }
+
+      if (cairo_region_num_rectangles (region) == 0)
+        continue;
+
+      job = gsk_ngl_render_job_new (self->driver, &viewport, scale_factor, region, 0);
+#ifdef G_ENABLE_DEBUG
+      if (GSK_RENDERER_DEBUG_CHECK (GSK_RENDERER (self), FALLBACK))
+        gsk_ngl_render_job_set_debug_fallback (job, TRUE);
+#endif
+      gsk_ngl_render_job_render (job, root);
+      gsk_ngl_render_job_free (job);
+
+      cairo_region_destroy (region);
+
+      end_time = g_get_monotonic_time ();
+
+      g_print ("%s %.2f", i > 0 ? " /" : "", (end_time - st) / 1000.0);
+    }
+
+  g_print (" ms");
+
+  start_time = g_get_monotonic_time ();
+
   job = gsk_ngl_render_job_new (self->driver, &viewport, scale_factor, render_region, 0);
 #ifdef G_ENABLE_DEBUG
   if (GSK_RENDERER_DEBUG_CHECK (GSK_RENDERER (self), FALLBACK))
     gsk_ngl_render_job_set_debug_fallback (job, TRUE);
 #endif
   gsk_ngl_render_job_render (job, root);
-  gsk_ngl_driver_end_frame (self->driver);
   gsk_ngl_render_job_free (job);
 
+  end_time = g_get_monotonic_time ();
+
+  g_print ("    non-tiled: %.2fms\n", (end_time - start_time) / 1000.0);
+
+  gsk_ngl_driver_end_frame (self->driver);
+
   gdk_gl_context_make_current (self->context);
   gdk_draw_context_end_frame (GDK_DRAW_CONTEXT (self->context));