[sysprof/wip/chergert/mem-preload] memprof: use pixbuf drawing

[Christian Hergert <chergert src gnome org>]

commit 7f8c9f7efcc7615d8d58803885050ddbb4f17684
Author: Christian Hergert <chergert redhat com>
Date:   Thu Feb 6 13:16:51 2020 -0800

    memprof: use pixbuf drawing
    
    We will have to draw a lot of these, so by reducing this to pixel drawing
    we can save quite a bit of overhead and memory from storing paths for
    eventual filling.
    
    Also, we should have enough pixels to draw that you'll still get the idea
    of allocations without having to draw lines.

 src/libsysprof-ui/sysprof-memprof-visualizer.c | 81 +++++++++++++++++---------
 1 file changed, 52 insertions(+), 29 deletions(-)
---
diff --git a/src/libsysprof-ui/sysprof-memprof-visualizer.c b/src/libsysprof-ui/sysprof-memprof-visualizer.c
index 1c2209d..9137d77 100644
--- a/src/libsysprof-ui/sysprof-memprof-visualizer.c
+++ b/src/libsysprof-ui/sysprof-memprof-visualizer.c
@@ -99,23 +99,6 @@ sysprof_memprof_visualizer_new (void)
   return g_object_new (SYSPROF_TYPE_MEMPROF_VISUALIZER, NULL);
 }
 
-static void
-draw_context_add (cairo_t                        *cr,
-                  DrawContext                    *draw,
-                  const SysprofCaptureAllocation *ev)
-{
-  gint x;
-  gint y;
-
-  g_assert (draw != NULL);
-  g_assert (ev != NULL);
-
-  x = (ev->frame.time - draw->begin_time) / (gdouble)draw->duration * draw->alloc.width;
-  y = 0;
-
-  cairo_rectangle (cr, x, y, 1, 1);
-}
-
 static void
 sysprof_memprof_visualizer_draw_worker (GTask        *task,
                                         gpointer      source_object,
@@ -125,7 +108,10 @@ sysprof_memprof_visualizer_draw_worker (GTask        *task,
   DrawContext *draw = task_data;
   SysprofCaptureFrameType type;
   cairo_t *cr;
+  guint8 *data;
   guint counter = 0;
+  gint stride;
+  gint r, g, b;
 
   g_assert (G_IS_TASK (task));
   g_assert (draw != NULL);
@@ -133,26 +119,42 @@ sysprof_memprof_visualizer_draw_worker (GTask        *task,
   g_assert (draw->reader != NULL);
   g_assert (!cancellable || G_IS_CANCELLABLE (cancellable));
 
-  cr = cairo_create (draw->surface);
-
   /* Fill background first */
+  cr = cairo_create (draw->surface);
   gdk_cairo_rectangle (cr, &draw->alloc);
   gdk_cairo_set_source_rgba (cr, &draw->bg);
   cairo_fill (cr);
+  cairo_destroy (cr);
+
+  stride = cairo_image_surface_get_stride (draw->surface);
+  data = cairo_image_surface_get_data (draw->surface);
+
+  if (data == NULL)
+    {
+      g_task_return_new_error (task,
+                               G_IO_ERROR,
+                               G_IO_ERROR_INVALID_DATA,
+                               "No data from image surface to access");
+      return;
+    }
+
+  r = draw->fg.red * 255;
+  g = draw->fg.green * 255;
+  b = draw->fg.blue * 255;
 
   /* Now draw data points */
   while (sysprof_capture_reader_peek_type (draw->reader, &type))
     {
       const SysprofCaptureAllocation *ev;
+      guint8 *pptr;
+      gint x;
+      gint y;
 
       /* Cancellation check every 1000 frames */
       if G_UNLIKELY (++counter == 1000)
         {
           if (g_task_return_error_if_cancelled (task))
-            {
-              cairo_destroy (cr);
-              return;
-            }
+            return;
 
           counter = 0;
         }
@@ -174,13 +176,14 @@ sysprof_memprof_visualizer_draw_worker (GTask        *task,
       if (ev == NULL)
         break;
 
-      draw_context_add (cr, draw, ev);
-    }
+      x = (ev->frame.time - draw->begin_time) / (gdouble)draw->duration * draw->alloc.width;
+      y = 0;
 
-  /* Now fill our draw paths */
-  gdk_cairo_set_source_rgba (cr, &draw->fg);
-  cairo_fill (cr);
-  cairo_destroy (cr);
+      pptr = data + ((stride * y) + (x * 3));
+      pptr[0] = r;
+      pptr[1] = g;
+      pptr[2] = b;
+    }
 
   g_task_return_boolean (task, TRUE);
 }
@@ -363,7 +366,27 @@ sysprof_memprof_visualizer_class_init (SysprofMemprofVisualizerClass *klass)
   visualizer_class->set_reader = sysprof_memprof_visualizer_set_reader;
 }
 
+static void
+on_style_changed_cb (SysprofMemprofVisualizer *self,
+                     GtkStyleContext          *style_context)
+{
+  g_assert (SYSPROF_IS_MEMPROF_VISUALIZER (self));
+  g_assert (GTK_IS_STYLE_CONTEXT (style_context));
+
+  /* Style changing means we might look odd (dark on light, etc) so
+   * we just invalidate immediately instead of skewing the result
+   * until it has drawn.
+   */
+  g_clear_pointer (&self->surface, cairo_surface_destroy);
+  sysprof_memprof_visualizer_queue_redraw (self);
+}
+
 static void
 sysprof_memprof_visualizer_init (SysprofMemprofVisualizer *self)
 {
+  g_signal_connect_object (gtk_widget_get_style_context (GTK_WIDGET (self)),
+                           "changed",
+                           G_CALLBACK (on_style_changed_cb),
+                           self,
+                           G_CONNECT_SWAPPED);
 }