From b23a03a44b37831f7ae0aaae805382d46129dc11 Mon Sep 17 00:00:00 2001
From: Matthias Clasen <mclasen@redhat.com>
Date: Sun, 11 Apr 2021 18:05:41 -0400
Subject: [PATCH] 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));